Cleanroom Technology

2

Editorial

3

Changes in industrial produc-tion have also resulted inchanges in the prevailingenvironmental conditions. Thedemand for quality has risenand the reduction of costs hasnow become the essentialcriterion. Cleanroom productionoffers considerable potentialhere – as long as it is usedproperly.

The more sensitive the item tobe produced, the “cleaner” theproduction method required.Production in cleanrooms orusing cleanroom technologyhas become increasinglypopular. However, it is notalways immediately obviouswhat is actually behind it, nevermind how it should be used.Even the concepts used todescribe it are often difficult tounderstand and unclear. Let us start with the concept ofthe cleanroom. The onlypossible method of cleanroomcomparison is based on thenumber of airborne particlesrelative to a volume equivalent.The VDI Guideline 2083 and theUS Federal Standard 209E havemade a start by defining inter-national standards for cleanli-ness classes.

One of the main factors thatinfluences air cleanliness is theequipment installed in a clean-room. As a supplier of auto-mation expertise Festo hasbeen concerned with this sub-ject for over ten years. Backthen the number of customersin this specialized area wassmall. That has since changed.The propagation of high-techchip development facilities, forexample, has resulted in a clearincrease in cleanroom produc-tion.

The purpose of this manual isto provide solutions to specificproblems in the area of clean-room technology. Our aim wasto produce a comprehensivework containing all relevantinformation to serve as avaluable reference source.

We are grateful to the Institutefor Production Technology andAutomation (IPA) at theFraunhofer Institute in Stuttgartfor its support in technicalmatters and Wiley & Sonswhich kindly allowed us toquote from its reference book“Cleanroom Design” by W.Whyte (ISBN 0 472 94204 9).

Festo SingaporeJiang Hong, Christian Burdin,Edward Gasper

Festo GermanyRobert Strommer

4

Contents

Chapter 1 – Introduction of Cleanroom

1.1 Introduction of Cleanroom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

1.2 Definition of Cleanroom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

1.3 Classification of Cleanrooms . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 – 11

1.4 Cleanrooms for Different Industries . . . . . . . . . . . . . . . . . . . . . . . . . 12

1.5 Types of Clean Areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 – 19

Chapter 2 – Cleanroom Design and Technology

2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

2.2. Tasks of Cleanroom Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

2.3 Design Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 – 32

Chapter 3 –Design Principles of Cleanroom Equipment

3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

3.2 The Importance of Equipment Design . . . . . . . . . . . . . . . . . . . . . . . 35

3.3 Influence on Air Flow Pattern . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

3.4 Suitable Materials for Equipment Design . . . . . . . . . . . . . . . 37 – 39

3.5 Cleaning Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

3.6 Basic Principles of Equipment Design . . . . . . . . . . . . . . . . . . . . . . . 41

3.7 Contamination Control of Cleanroom Equipment . . . . . . . . 42 –45

3.8 Qualification of Cleanroom Equipment . . . . . . . . . . . . . . . . . . . . . . 46

3.9 Cleanroom and Cleanliness Suitability . . . . . . . . . . . . . . . . . . . . . . 47

5

Contents

Chapter 4 – Cleanroom Garment System

4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

4.2 Cleanroom Garments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

4.3 Entry and Exit Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 – 54

Chapter 5 – International Standard for Cleanrooms

5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

5.2 Cleanroom Classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

5.3 Present Engineering Classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

5.4 Federal Standard 209E, and its Four Early Editions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 – 60

5.5 German Standard: VDI 2083 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

5.6 British Standard: BS 5295 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

5.7 Japanese Industrial Standard: JIS B 9920 . . . . . . . . . . . . . . . . . . . . 63

5.8 Australian Standard: AS 1386 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

5.9 French Standard: AFNOR X 44101 . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

5.10 Dutch Standard: VCCN-RL-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

5.11 Russian Standard: GOST R 50766-95 . . . . . . . . . . . . . . . . . . . . . . . . 67

5.12 ISO Classification Standard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 – 71

5.13 Summary of FS 209E and ISO 14644-1 and -2 . . . . . . . . . . 72 – 73

5.14 Biocontamination and Pharmaceutical Classes . . . . . . . . . 74 – 76

5.15 ISO Biocontamination Standards: 14698 . . . . . . . . . . . . . . . 77 – 78

5.16 The Containment Classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

6

Contents

Chapter 6 – Airborne Particle Emission Measurements

6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

6.2 Sources of Particles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

6.3 Optical Particle Counters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 – 84

6.4 LASAIR 210 Optical Particle Counter . . . . . . . . . . . . . . . . . . . . . . . . 85

6.5 Setting Up of Optical Counters . . . . . . . . . . . . . . . . . . . . . . . . . 86 – 87

6.6 Test Environment Measurements . . . . . . . . . . . . . . . . . . . . . . . 88 – 89

Chapter 7 – Festo Cleanroom Project

7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

7.2 Festo’s Cooperation with Fraunhofer and Nanyang Polytechnic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 – 93

7.3 Test Environment and Test Conditions . . . . . . . . . . . . . . . . . . 94 – 97

7.4 Standard Operating Procedures . . . . . . . . . . . . . . . . . . . . . . . 98 – 100

Chapter 8 – Cleanroom Products

8.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102

8.2 Reasons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

8.3 Basic Principles for Cleanroom Products . . . . . . . . . . . . . . . . . . . 104

8.4 Production Sequence for Cleanroom Products . . . . . . . . . . . . . 105

8.5 Performance of Cleanroom Products . . . . . . . . . . . . . . . . . . . . . . . 106

8.6 Precautions in Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

Keyword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .108

1.0 Introduction to Cleanroom

8

1.1 Introduction of Cleanroom

The term “Cleanroom” is some-thing you associate with inmodern industries. However,the roots of cleanroom designgoes back more than a century.Think of the need to controlcontamination in hospitals andyou would be able to imaginethe first cleanroom.

At present, the need for clean-rooms is a requirement ofmodern industries. The use ofcleanrooms is diverse. Table 1.1below shows you the needs ofdifferent industries.

It can be seen that the require-ment for cleanrooms can bebroadly divided into two areas.

• That in which inanimate particles are a problem and where their presence may prevent a product functioningor reduce its useful life.

• To ensure the absence of microbe carrying particles whose growth could lead to human infection.

Electronics

Semiconductors

Micromechanics

Optics

Biotechnology

Pharmacy

Medical Devices

Food and Drink

Hospital

Computers, TV tubes, flat screens,magnetic tape production

Production of integrated circuits used incomputer memory and control

Gyroscopes, miniature bearings, computerdisc players

Lenses, photographic film, laserequipment

Antibiotic production, genetic engineering

Sterile pharmaceuticals

Heart valves, cardiac by-pass systems

Disease-free food and drink

Immunodeficiency therapy, isolation ofcontagious patients, operating rooms

The table will be continuouslyincreased to include futureinnovations requiringcleanrooms. The demand forcleanrooms will definitely grow.

Table 1.1

9

1.2 Definition of Cleanroom

A cleanroom must certainly be“clean”. However, a cleanroomnow has a special meaning andit is defined in US FederalStandard 209E as:

“A room in which the concen-tration of airborne particles iscontrolled and which containsone or more clean zones.”

And in ISO 14644-1 as:

“A room in which the concen-tration of airborne particles iscontrolled, and which is con-structed and used in a mannerto minimize the introduction,generation and retention ofparticles inside the room and inwhich other relevant particlesinside the room and in whichother relevant parameters, e.g.temperature, humidity andpressure, are controlled asnecessary.”

10

Cleanrooms are classified bythe cleanliness of their air. Themethod most easily understoodand universally applied is theone suggested in versions ofUS Federal Standard 209 up toedition “D”.

To classify cleanrooms, thenumber of particles equal toand greater than 0.5 µm ismeasured in one cubic foot ofair and this count is used toidentify the Cleanroom Class.

Table 1.2 shows the simplifiedclassification of CleanroomClass according to the older USFederal Standard 209D. Thisstandard has now been super-seded by the metric version; USFederal Standard 209E whichwas published in 1992.

However, because of the simpli-city and universal usage of theUS Federal Standard 209D, it isunlikely to be forgotten or re-moved. It is also likely that theUS Federal Standard 209E willnot supersede it but by the newInternational Standard Organi-zation’s (ISO) standard 14644-1.

We will go into details later.

Class

1

10

100

1000

10000

100000

Measured Particle Size (µm)0.1

35

350

NA

NA

NA

NA

0.2

7.5

75

750

NA

NA

NA

0.3

3

30

300

NA

NA

NA

0.5

1

10

100

1000

10000

100000

5.0

NA

NA

NA

7

70

7000

US Federal Standard 209D Cleanroom Class Limits

Table 1.2

1.3 Classification of Cleanrooms

11

The basic unit of measurementwithin a cleanroom is a micron(µm) which is one millionth of ametre. Table 1.3 gives a betterunderstanding of just howsmall a submicron particle is.

The human eye is capable ofseeing particles down toapproximately 25 µm. Humanstypically emit 100,000 to300,000 particles per minutesized 0.3 µm and larger.

It should also be noted that theairborne contamination level incleanrooms is dependent onthe particle generating activi-ties going on in these rooms.Which means low particle con-centration for an empty roomand high particle concentrationfor a room in full production.

Objects

Human hair

Rubbing or abrading an ordinary paintedsurface

Sliding metal surfaces (non-lubricated)

Crumpling or folding paper

Rubbing an epoxy-painted surface

Belt drive (conveyor)

Dust

Writing with ball pen on ordinary paper

Abrading of the skin

Oil smoke particles

Approximatesize (microns)

100

90

75

65

40

30

25

20

0.4

0.1

The different conditions forclassifying the cleanroom

As built:Condition where theinstallation is complete with all services connected andfunctioning but with no pro-duction equipment, materialsor personnel present.

At rest:Condition where theinstallation is complete withequipment installed andoperating in a manner agreedupon by the customer andsupplier, but with no personnelpresent.

Operational:Condition where theinstallation is functioning in thespecified manner, with thespecified number of personneland working in the manneragreed upon.

Table 1.3

1.3 Classification of Cleanrooms

12

1.4 Cleanrooms for Different Industries

The required standard of clean-liness of a room is dependenton the task performed in it; themore susceptible the product isto contamination, the betterthe standard. Table 1.4 showsthe possible cleanroom require-ments for various tasks.

Class1

10

100

1000

10000

100000

Integrated circuit manufacturersmanufacturing submicron geometries onlyuse these rooms.

Semiconductor manufacturers producingintegrated circuits with line widths below2 µm use these rooms.

Used with a bacteria-free or particulate-free environment is required in themanufacture of aseptically producedinjectable medicines. Required for implantor transplant surgical operations.

Manufacture of high quality opticalequipment. Assembly and testing ofprecision gyroscopes. Assembly andtesting of precision gyroscopes. Assembly of miniaturized bearings.

Assembly of precision of hydraulic orpneumatic equipment, servo-controlvalves, precision timing devices, high-grade gearing.

General optical work, assembly ofelectronic components, hydraulic andpneumatic assembly.

Table 1.4

13

1.5 Types of Clean Areas

Clean areas can be divided intofour main types:• Conventional• Unidirectional flow• Mixed flow• Isolators or minienvironment

1.5.1 Conventionally ventilatedcleanrooms

These cleanrooms are alsoknown as turbulently ventilatedor non-unidirectional flow andare distinguished by theirmethod of air supply.

As shown in Figure 1.1, airsupply diffusers or filters in theceiling supply the air.

Figure 1.2 is a diagram of asimple conventionally venti-lated cleanroom. The generalmethod of ventilation used inthis type of cleanroom is similarto that found in offices, shops,etc. in that air supplied by anair-conditioning plant throughdiffusers in the ceiling.

High efficiencyair filter

Air extract

Productionequipment

Changearea

Pass-through grilles

Cleanroom

Pressurestabilizers

plant

Freshair

Passoverbench

Recirculatedair

Air conditioning

Figure 1.1

Figure 1.2

14

1.5 Types of Clean Areas

However, a cleanroom differsfrom an ordinary ventilatedroom in a number of ways:

• Increased air supply – An office or shop will be sup-plied with sufficient air to achieve comfort conditions; this may be in the region of 2 to 10 air change per hour. A conventionally ventilated cleanroom is likely to have between 20 to 60 air changes per hour. This additional air supply is mainly produced to dilute to an acceptable con-centration the contamination produced in the room.

• High-efficiency filters – A cleanroom uses filters that are much more efficient. Cleanroom filters would normally be 99.97 % more efficient in removing particles greater than 0.3 mm from the room air supply. These filters are known as High Efficiency Particle Air (HEPA) filters, although Ultra Low Particle Air(ULPA) filters, which have a higher efficiency, are used in microelectronic fabrication areas.

• Terminal air filters – The high-efficiency filters used in cleanrooms are installed at the point of discharge into the room. In airconditioning systems used in offices, etc. the filters will be placed directly after the ventilation plant but particles may be induced into the air supply ducts or come off duct surfaces and hence pass into the room.

• Room pressurization and pass-through grilles – To ensure that air does not pass from dirtier adjacent areas into the cleanroom is positively pressurized with respect to these dirtier areas to prevent infiltration by wind.This is done by extracting lessair from the room that is

supplied to it, or by extractingthe supplied air in adjacent areas. To achieve the correct pressure and allow a designed movement of air from the cleanest to the less cleanrooms is a suite, pass-through grilles or dampers will usually be seen at a low level on walls or doors.

Another indication that theroom is a cleanroom is the typeof surface finish in a room. Theroom will be of materials, whichdo not generate particles andare easy to clean. Surfaces willbe constructed so that they areaccessible to cleaning and donot harbour dirt in cracks, e.g.covered flooring and recessedlighting.

The airborne cleanliness of aconventionally ventilatedcleanroom is dependent on theamount and quality of airsupplied to the room and theefficiency of mixing of the air.

Generally speaking, a clean-room will have sufficient airsupply to achieve good mixingand the air quality of the roomwill therefore only depend onthe air supply quantity andquality. It is important to under-stand that the cleanliness isdependent on the volume of airsupplied per unit of time andnot the air change rate.

The cleanliness is also depen-dent on the generation ofcontamination with the room,i.e. from machinery and indi-viduals working in the room.The more people in the clean-room, the greater their activityand the poorer their cleanroomgarments the more airbornecontamination is generated.

15

1.5 Types of Clean Areas

1.5.2 Unidirectional airflowcleanrooms

Unidirectional airflow is usedwhen low airborne concen-tration of particles of bacteria isrequired. This type of clean-room was previously known as“laminar flow”, usually horizon-tal or vertical, at a uniformspeed of between 0.3 and 0.45 m/s and throughout theentire air space.

The air velocity suggested issufficient to remove relativelylarge particles before theysettle onto surfaces. Any con-taminant generated into the aircan therefore be immediatelybe removed by this flow of air,whereas the conventionalturbulently ventilated systemrelies on mixing and dilution toremove contamination.

For these cleanrooms, you mustensure that the velocity issufficient to overcome obstruc-tions from the machines andpeople moving about. The dis-rupted unidirectional flow mustbe quickly reinstated and thecontamination around theobstructions is adequatelydiluted.

Unidirectional airflow is correct-ly defined in terms of air veloc-ity, the cleanliness of a uni-directional room being directlyproportional to the air velocity.The air volumes supplied tounidirectional flow rooms aremany times (10 to 100) greaterthan those supplied to a con-ventionally ventilated room.They are therefore very muchmore expensive in capital andrunning costs.

There are generally two typesof unidirectional flow rooms:• Horizontal – the air flow is

from wall to wall• Vertical – the airflow is from

ceiling to ceiling.

16

1.5 Types of Clean Areas

Figure 1.3 and 1.4 show a typi-cal vertical flow type of clean-room. Air is supplied from acomplete bank of HEPA filtersin the roof and this flowsvertically through the room andout though open grilledflooring.

An alternative is to have theairflow out through the lowerlevels of the floor. The exhaustair is recirculated, mixed withsome fresh make-up air, andsupplied to the room throughthe HEPA filters in the ceiling.

Most unidirectional cleanroomsare built in a vertical manner, asparticles generated within theroom will be quickly sweptdown and out of the room. Lesspopular is the horizontal typeof cleanroom. Figure 1.5 showsa typical example.

This type is not so popular asany contamination generatedclose to the filters will be sweptdown the room and couldcontaminate work processesdownwind. However, as thearea of a wall in a room isusually much smaller than theceiling, the capital and runningcosts is less.

High-efficiency filters

Air extract

Productionequipment

Supply plenum

Hepa ceiling

Fan Fan

Return plenum

Protectivescreen

Supplyplenum

LightingRecirculatingair

Hepa filterbankAir-exhaust grill

Figure 1.3

Figure 1.4

Figure 1.5

17

1.5 Types of Clean Areas

1.5.3 Mixed flow cleanrooms

This type of room is a con-ventional flow room in whichthe critical manufacturingoperations are carried out with-in a higher quality of air pro-vided by a unidirectional flowsystem, e.g. bench. This mixedtype of system is very popularas the best conditions areprovided only where they areneeded and considerable costsavings are available for use inthis room. (Figure 1.6)

Figure 1.7 shows a horizontalflow cabinet, this being one ofthe simplest and most effectivemethods of controlling conta-mination. In this bench theoperator’s contamination iskept downwind of the criticalprocess.

High-efficiencyair filter

Air extract

Productionequipment

Hepafilters

Plenumcontainingfans

Figure 1.6

Figure 1.7

18

1.5 Types of Clean Areas

1.5.4 Isolator or minienviron-ment

Hazardous work with toxicchemicals or dangerous bac-teria has been carried out formany years in glove boxes.These contaminant-retainingand contaminant-excludingsystems do not principallydepend on airflow for isolationbut uses walls of metal andplastic. This principle of isola-tion clearly has excellentbarrier properties and it hasnow been developed for use inmodern classroom technology.(Figure 1.8)

In the pharmaceutical manu-facturing area, this technologyis generally known as isolatoror barrier technology, whereasin the semiconductor industry itis generally known as minienvi-ronments.

Figure 1.9 shows a system ofinterlocked plastic film isola-tors of the type used in pharma-ceutical manufacturing. It maybe seen that the plastic sheetacts as a barrier to outsidecontamination, and personneleither enter into half suits oruse gauntlets to work at theclean processes within theisolators.

The air within the isolator issterile and particle-free havingbeen filtered by HEPA and thisair is also used to pressurizedthe system and prevent ingressof outside contamination.

High-efficiencyair filter

Air extract

Productionequipment

Figure 1.8

Figure 1.9

Sterilizingtunnel

Liquid fillingline isolator

Inspectionisolator

Connect-ing tunnel

Cappingmachineisolator

Sortingisolator

Freeze dryer

19

1.5 Types of Clean Areas

In the semiconductor indus-tries, minienvironments arecommonly used; they are notcalled isolators.

Minienvironments are used toisolate the product or operationfrom contamination. The mini-environment has the capabilityof delivering clean filtered air inthe vertical or horizontal direc-tion. The minienvironment doesnot have to be fully enclosedlike an isolator but could bejust an enclosed space in thecleanroom.

The minienvironment rapidlysweeps away all particles fromthe space surrounding theequipment. A ballroom clean-room does not flush this criticalarea nearly as effective or asrapidly. And it is these particles,right next to the equipment andpresent in high concentrationsin a ballroom but largely absentin a minienvironment.

Another system, which is usedin semiconductor manufactur-ing, is the SMIF (StandardMechanical Interface Format)system. In this system, siliconwafers are transported be-tween machines in specialcontainers, which prevent thewafers being contaminated bythe air outside (Figure 1.11).These containers which containthe wafers, are slotted into themachine interface, the wafersprocesses and then loadedonto another container whichcan be taken to anothermachine and loaded into itsinterface.

Figure 1.10

Figure 1.11

2.0 Cleanroom Design and Technology

21

2.1 Introduction

As earlier stated, cleanroomsare a reaction to ever more demanding clean productionprocesses. They have beendeveloped to establish mini-mum contamination to adefined task whether in theform of pharmaceutical work orin the semiconductor industry.

Contamination can be con-sidered in many ways with oneparticular definition coveringairborne particulate matter. The principles for air treatmentdesign must recognize contain-ment and elimination, to definestandards, of airborne contami-nation.

22

2.2 Tasks of Cleanroom Technology

Before we start on the designof cleanrooms, we mustunderstand the required tasksof cleanroom technology. Thereare basically two parts toconsider:• Personnel protection• Product protection

2.2.1 Personnel protection

Personnel must be protectedagainst harmful dust particlesor microorganisms.

2.2.2 Product protection

Products must be protectedagainst contamination from thesurroundings, productionfacilities or from personnel.

2.3.1 Layout

The design of semiconductorcleanrooms has evolved overseveral years. The design of a cleanroom that has beenpopular for a number of years.

The air flows in an unidirection-al way from a complete ceilingof high-efficiency filters downthrough the floor of the clean-room. The design shown isoften called the “ballroom”type because there is one largecleanroom. Typically it is over1,000m2 in floor area. It isexpensive to run but it is veryadaptable.

In the “ballroom” type of clean-room, a ceiling of high-efficien-cy filters provides clean airthroughout the whole roomirrespective of need. It is clearthat the best quality air isnecessary where the product isexposed to airborne contamina-tion, but that lesser qualitywould be acceptable in otherareas. (Figure 2.1)

Silencer

Flex

VibrationisolatorFan +

system

R.A.plenum

R.A. = Return air

R.A.space

Supply plenum

Optical floor

Hepa ceiling

Fan +system

Silencer

Figure 2.1

23

2.3 Design Features

Using this concept, lessexpensive cleanrooms havebeen designed in which servicechases with lower environmen-tal cleanliness standards areinterdispersed with cleanroomtunnels. Figure 2.2 shows this.

It is also in the ballroom type ofdesign to divide up the ball-room with prefabricated wallsand provide clean tunnel andservice chases; these walls canbe dismantled and reassem-bled with different configura-tion should the need arise.

Figure 2.3 and 2.4 show twotypical designs of tunnel andservice chase. These aredesigns which have been usedin the past but are stillapplicable in manufacturingareas or laboratories whereless than state-of-the-artcomponents are produced.

(a) (b) (c)

Service areaCleanroom

Service areawith chases

Cleanroom

Service areaCleanroom

Minienvironment

ISO 3 (Class 1) or better ISO 6 (Class 1,000) or worse

Supply air from fans

Class 1/100

Returnair

Ducted orceiling fan

Utility andequipmentchase

Perforated floor

100 % Hepa ceiling

Supply air from fans

Ceilingreturn

Electrical

Utilityprocesspiping

Returnair

Class 1000

30 % ceilingcoverage

Class 100Equipmentchase

Class 100

Hepa

Hepa

Hepa

Figure 2.2

Figure 2.3

Figure 2.4

24

2.3 Design Features

Reducing the capital andrunning costs of a semicon-ductor cleanroom is alwaysrequired. There has thereforebeen much interest in whathave been variously called“isolators”, “barrier technolo-gy” and “minienvironments”.Minienvironments is the termcommonly used in the semi-conductor industry.

A minienvironment uses a phys-ical barrier (usually a plasticfilm, plastic sheet or glass) toisolate the susceptible orcritical part of the manufac-turing process from the rest ofthe room. The critical manu-facturing area is kept within theminienvironment and providedwith large quantities of the verybest quality air, the rest of theroom being provided with lowerquantities of air.

Figure 2.5 shows the traditionalway and Figure 2.6 is thedesign using minienviron-ments. The total air supplyvolume can be seen to be muchless when minienvironmentsare used.

As well as using minienviron-ment to isolate the area wherethe critical components areexposed, they can also betransported between pro-cessing machines in speciallydesigned carriers, which inter-face, with machines through aStandard Mechanical Interface(SMIF). The components arethen laded by a SMIF arm intothe processing machine whereit is contained within a minien-vironment. After processing,the components are loadedback into the carrier and takento the next machine.

Class 190 ft/min

Class 1,00020 ft/min

Figure 2.5

a

a = SMIF Pod b = SMIF Arm

Class 190 ft/min

Class 1,00020 ft/min

Class 1,00020 ft/minb

Figure 2.6

25

2.3 Design Features

2.3.2 Air flow patterns

The type of air flow patternemployed most often describescleanroom air flow. Selection ofan air flow pattern should bebased on cleanliness require-ments and layout of the pro-cess equipment.

Cleanroom air flow patterns areeither:• Unidirectional• Nonunidirectional• Mixed air flow

Air flow patterns for cleanroomclass M3.5 (Class 100) orcleaner are typically unidirec-tional while nonunidirectionalare mixed flow are used forClass M4 and M4.5 (Class1,000) or less cleanrooms.

horizontalvertical

Supply air

Returnair

Returnair

Supplyair

a) Unidirectional Air flow

Air flow in unidirectionalcleanrooms is often vertical. Airflows downwards throughHEPA/ULPA filters located inthe ceiling and returns throughsidewall returns or perforatedflooring. (Figure 2.7)

Air flow in unidirectional clean-rooms may also be horizontalwhen the air flow horizontallythrough a full wall of filters andflows through sidewall returnslocated in the opposite wall.Figure 2.8 shows this.

In general, unidirectional airflow has a degree of turbulenceof between 5 and 20. It is highlyrecommended to have laminarairflow in the system. Laminarairflow is much better as thedegree of turbulence is lessthan 5. Mainly used in clean-room as the most relevant andwe must try to achieve this atall times.

Figure 2.7 Figure 2.8

26

2.3 Design Features

b) Nonunidirectional air flow(Figure 2.9)

In nonunidirectional airflowcleanrooms, air flows throughHEPA/ULPA filters located invarious positions and is re-turned through opposite loca-tions. Filters may be distributedat equal intervals throughoutthe cleanroom or grouped overcritical process areas. Becauseof the distribution of the filters,air flow may be turbulent innature. The degree of turbu-lence is usually greater than 20.

c) Mixed air flow(Figure 2.10)

Mixed air flow cleanroomscombine both unidirectionaland nonunidirectional air flowin the same room.

DisplacementTurbulent

Supply air

Returnair

Supplyair

Return air

Supplyair

Supplyair

Returnair

Supplyair

Returnair

Figure 2.9

Figure 2.10

27

2.3 Design Features

2.3.3 Cleanroom layoutdetermines air flow patterns

The layout of the cleanroomcan determine the air flow thatis needed to maintain a speci-fied level of room cleanliness.For example, it may take lessair flow to achieve a desiredlevel of cleanliness if the clean-room layout has taken intoaccount the uniformity of airflow patterns.

Unidirectional air flow clean-rooms rely on the air flow tomove particles in the directionof the air flow. Layouts thatwould interrupt the path of airflow should be avoided;resulting dead air spaces andzones would be likely to trapparticles, creating areas of highparticulate concentration.

The layout of mixed air flowcleanrooms should be con-sidered even more carefully.Mixed air flow cleanroomsmaintain cleanliness primarilyby dilution, rather than by airflow. As a result, areas withinthe cleanroom that are isolatedfrom the air path are most likelyto develop high concentrationof contamination.

Internal surfaces, in contactwith the air flow, should besmooth and free from cracks,ledges and cavities. Irregularsurfaces and similar featuresthat might collect contaminantsshould be minimized.

In vertical unidirectional airflow cleanrooms, space shouldbe provided to accommodatereturn air flow. The return airpath may be in the service area,duct work, or space adjacent tothe cleanroom.

The quantity and resultingvelocity of the air supplied by a central system may berestricted by the architecturalconfiguration of the building.As the quantity of centrallysupplied air increases, so toodo the requirements formechanical space to house airhandling equipment. Typically,the mechanical space allocatedfor air-handling equipment isplaced either on a separatelevel or adjacent to it.

The flexibility of a cleanroommay be either enhanced ordetracted from by additional air flow, depending on howflexibility is defined. If definedas the ability to rearrange andrelocate equipment within thecleanroom, flexibility may beenhanced by additional air flow.

The additional air flow makesthe cleanroom more capable ofrecovering from transientepisodes of particle generationdue to activity within it. If flexi-bility is defined as the ability tomodify the entire cleanroom,then fan hoods or modulescapable of being easily rear-ranged may be used in lieu of a central recirculating system.

28

2.3 Design Features

2.3.4 Air Velocity

Relating a cleanliness classlevel to a specific air velocity isa complex task because anumber of variables that maybe involved. Operating proto-col, flow direction, and filterquality all have an impact onthe potential cleanliness levelfor a given velocity. Air velocityis a determining factor inachieving air flow uniformityunder unidirectional air flowdevices. Air velocities in thosecases may vary with the con-figuration of the equipmentdownstream of the air filters.

Air velocity can be specified byone of two methods:• Average air velocity (metres

per second or feet per minute)

• Number of air changes per hour.

Table 2.1 provides somegeneral rules for selection of airvelocity in cleanrooms. The airvelocity shown is based onaverage room cross-sectionvelocity as opposed to filter-face velocity.

Class Air flow Average air flow velocity2 Air changes per hour3

Type1

M7 & M6.5 (Class 100,000) N M .005 - .041 m/s (1-8 ft/min) 4 – 48

M6 & M5.5 (Class 10,000) N M .051 - .076 m/s (10-15 ft/min) 60 – 90

M5 & M4.5 (Class 1,000) N M .127 - .203 m/s (25-40 ft/min) 150 – 240

M4 & M3.5 (Class 100) U N M .203 - .406 m/s (40-80 ft/min) 240 – 480

M3 & M2.5 (Class 10) U .254 - .457 m/s (50-90 ft/min) 300 – 540

M2 & M1.5 (Class 1) U .305 - .457 m/s (60-90 ft/min) 360 – 540

M1 & Cleaner U .305 - .508 m/s (60-100 ft/min) 360 – 600

Air velocity in cleanrooms

1 When air flow type is listed, it re-

presents the more common airflow

characteristics for cleanrooms of

that class: U = unidirectional;

N = nonunidirectional; M = mixed

2 Average air flow velocity is the

way that air flow is standard dimen-

sion cleanrooms (i.e. those that

typically have a ceiling height of 10

feet or 3 metres) usually is speci-

fied. This term is commonly used to

refer to unidirectional air flow.

3 Air changes per hour are the way

that nonunidirectional and mixed

air flow in nonstandard, high bay, or

unusually configured cleanrooms

usually is specified. Air flow velocity

and air changes per hour are mathe-

matically equivalent methods, the

conversion formula being:

air changes p/hr =average air flow velocity x room area x 60 min/hr

room volume

Table 2.1

29

2.3 Design Features

Selection of the air velocityshould be based on such con-siderations as product cleanli-ness criteria, the contaminationrate expected from the pro-cesses and operating equip-ment, the anticipated use of thecleanroom for processing orstorage, and the influence ofpersonnel on the contamina-tion load.

Take note that the selection ofair flow patterns and velocitiesaffect the cleanroom capitaland operating costs. Highervelocities increase capital costas a result of the cost of largerfans and air conditioningequipment. Operating costsalso increase with high velo-cities because of the increasedcosts of energy required for airmovement and cooling.

Figure 2.11 shows air flowpatterns at air flow velocity of0.45 m/s.

Figure 2.11

Air flow velocityof 0.45 m/s

Undirectionalair flow

Nonundirectionalair flow

30

2.3 Design Features

2.3.5 Filters

Filters are used to ensure thatthe supply air is removed ofparticles that would contami-nate the process being carriedout in the room. Until the early1980s, the air was filtered withHigh Efficiency Particulate Air(HEPA) filters, which were themost efficient air filters avail-able.

Today, HEPA filters are still usedin many types of cleanroomsbut one cleanroom application,the production of integratedcircuits, has evolved to a levelwhere more efficient filters arerequired. These are known asUltra Low Penetration Air(ULPA) filters.

In cleanrooms, high-efficiencyfilters are used for the dualpurpose of removing smallparticles and, in unidirectionalflow cleanrooms, straighteningthe air flow. The arrangementand spacing of high-efficiencyfilters, as well as the velocity ofair, affect both the concentra-tion of airborne particles and

the formation of turbulentzones and pathways in whichparticles can accumulate andmigrate throughout the clean-room. The combination of ahigh-efficiency filter and a fanonly initiates the unidirectionalflow process. A balance of theentire air flow path is requiredto ensure good unidirectionalflow.

It is generally accepted that forcleanrooms of ISO 6 (Class1,000) and higher, HEPA filtersare sufficient to meet the roomclassification, and traditionalventilation techniques, such asthe use of terminal filter unitsor filters installed in the airsupply ducting, are adequate.

For ISO 5 (Class 100), HEPAfilters should completely coverthe ceiling, supplying unidirec-tional flow down through thecleanroom. For ISO 4 (Class 10)or lower, ULPA filters should beused in a unidirectional flowcleanroom.

Figure 2.11 Samplers of HEPAand ULPA filters Fa. Freuden-

Figure 2.11

31

2.3 Design Features

a) High-efficiency filters

High-efficiency filters areusually constructed in twoways, i.e. deep pleated or mini-pleated. Both methods areused to ensure that a largesurface area of filter paper iscompactly and safely assem-bled into a frame so that thereis no leakage of unfiltered airthrough it.

b) HEPA filters

Its particle removal efficiencyand its pressure drop at a ratedair flow define a HEPA filter.

A HEPA filter is defined ashaving a minimum efficiencyin removing small particles(approximately equal to 0.3 mm) from air of 99.97 %(i.e. only three out of 10,000particles, 0.3 mm in size, canpenetrate through the filter).

The traditional size of a deep-pleated type of HEPA filter is 2 ft x 2 ft x 12 in. (0.6 m x 0.6 mx 0.3 m), which has a rated flowof 1,000 ft3/min (0.47 m3/s). Atthis rated flow, the air velocitywould be between 3.6 ft/min(1.8 cm/s) and 5.9 ft/min (3.0 cm/s). This velocity is im-portant, because it determinesthe removal efficiency of thefilter medium and if the airvelocity is increased ordecreased the efficiency willchange. It is possible, byincreasing the amount offiltering medium in a filter, notonly to decrease the pressuredrop across it but also toincrease its efficiency.

32

2.3 Design Features

c) ULPA filters

The category of ULPA filter wascreated to define filters thathave efficiencies higher thanstandard HEPA filters.

An ULPA filter will haveefficiency greater than 99.999 % against 0.1-0.2 mm particles.

They differ in that the filtermedium used has a higherproportion of smaller fibres andthe pressure drop is slightlyhigher. For a filter with thesame amount of medium, anULPA filter will have a higherresistance than a HEPA filter.Because of the higher efficiencyof removal of smaller particles,the methods used for testingHEPA filters are not appropriateand other methods using laseroptical particle counters orcondensation nuclei countersare applied.

d) Filters remove upstreamcontamination

It is important to note thatfilters can remove a portion ofupstream contamination andnot reduce the amount of con-tamination introduced down-stream of the filter. Filtersensure that the air coming intothe cleanroom is removed ofcontaminants and we mustkeep in mind of the internalcontamination of the clean-room.

Recommended ceiling filter coverage:Class (FS 209E) Ceiling CoverageM7 and M6.5 (Class 100,000) 5 – 15%M6 and M5.5 (Class 10,000) 15 – 20%M5 and M4.5 (Class 1,000) 25 – 40%M4 and M3.5 (Class 100) 35 – 70%M3 and M2.5 (Class 10) 50 – 90%M2 and M1.5 (Class 1) 60 – 100%M1 and Cleaner 80 – 100%

Actual average velocity and air changes required may vary depending on

application and floor plan.

3.0 Design Principles of Cleanroom Equipment

34

3.1 Introduction

The design of cleanroomequipment plays an importantrole in cleanroom technology. Itwould be wasteful to design astate-of-the-art cleanroom anddo not place any importance onthe equipment used in thecleanroom.

35

3.2 The Importance of Equipment Design

When designing cleanroomequipment, care must be takenright from the initial stage. Thefollowing chart shows a typicalequipment developmentprocedure:

Optimizing a pieceof production equip-ment

➔

➔

New development ofa piece of productionequipment

Drawing up a require-ment profile

Conception/Construction phase

Realization phase

Checking contamina-tion levels

Modification

Qualification

➔

When designing cleanroomequipment, we must rememberthat• If there is a design fault in

one part, it will affect the whole equipment

• If there is a fault in concep-tion stage and it is not taken care of, it will spread and, accumulate down the equipment development procedure. Faults at this stage must be rectified immediately.

• Reworking of existing equip-ment is expensive and time-consuming.

As can be seen, the importanceof equipment design isconstantly increasing. This isdue to the following reasons:• Larger substrates• Smaller structures• Higher throughput• Higher costs per substrate• Higher reject losses

36

3.3 Influence on air flow pattern

One of the points to note is theway air flow patterns areinfluenced during the designstage.

3.3.1 Influence of operatingmaterials on air flow patterns

There are some guidelines onhow the choice of operatingmaterials affects the air flowpatterns. The basic require-ments are:• Air must be able to flow

through the operating material.

• Operating materials must ensure well-directed transportation of any contamination generated.

•Wherever possible first air flow should be used.

Things to avoid include:• Counterdrafts• Stagnant areas• Areas where air rises• Turbulent areas• Cross currents

3.3.2 Influence of individualcomponents on air flowpatterns

The geometrical profile of thecomponent will affect the airflow pattern and should beconsidered when designingequipment.

Unsuitable geometric profile

Suitable geometric profile

Ideal geometric profile

37

3.4 Suitable Materials for Equipment Design

When choosing materials forthe equipment, importantfactors to take into account arefriction and combination ofmaterials.

You should keep operatingmaterial friction elements to aminimum. If friction is unavoid-able:• Employ lubricants suitable for

cleanroom use.• Encapsulate materials

rubbing against each other.• Extract particles using a

vacuum.• Keep materials rubbing

against each other as far apart from the product as possible and place them “downstream”.

Stainlesssteel

Aluminum

Steel

Polypropylene(PP)

Polyvinyl chloride (PVC)

Polyethylene(PE)

Polyvenylidenefluoride (PVDF)

Polyfluoralcoxy(PFA)

Polytetrafluor-ethylene (PTFE)

Material Treatment Properties Application UsageElectro-static Abrasion

electro-polished

polished

eloxed

coated

–

–

–

–

–

–

good

good

good

neutral

bad

bad

bad

bad

bad

bad

good

good

neutral

bad

good

neutral

good

good

neutral

bad

Process chambertool surface

tool surface

handling tool

Tool Surface

process chamber tool surface means of transp.

process chamber tool surface

process chambertool surface

process chambermeans of transp.

process chamber

process chamber

very often

very often

seldom

often

very often

often

often

often

often

often

Material overview for equipment design

With regard to combination ofmaterials, it must be noted thatmaterial combination is adeciding factor affecting par-ticle emission concentrations.

Factors to consider are:• Surface structure/Surface

roughness•Contact pressure between

materials

38

3.4 Suitable Materials for Equipment Design

3.4.1 Surface structure/Surface roughness

•There should be minimal surface roughness of all surfaces. This would equip the surface with easy cleaningproperties.

•It has to be resistant to cleaning agents and not change its properties after cleaning.

•Wherever possible, there should be no gaps or edges, this would avoid contamina-tion from collecting in areas, which cannot be cleaned.

•However, the surface should have sufficient roughness for handling equipment such as grippers. There should be adequate adherence achievedbetween the gripper and the product.

Technical surface Surface roughnessRa (µm) Rmax (µm)

Stainless steel, electro-polished 0.40 3.46

Stainless steel, polished (V2A) 0.65 5.61

Polypropylene (PP) 0.02 0.24

Silicon Wafer 0.001 0.005

Surface roughness of materials

39

3.4.2 Treatment of materials

When choosing the suitablematerials to be used, there area few points to note:•When manufacturing the

material, try to have as few cutting and material-abrading processes as possible. The reason for this is that abrasives can be found on theproducts, which needs to be kept clean. This will also lead to the contamination of the product.

•Ideally, no further processing of the material is made. If further processing is un-avoidable, then the material needs to be further cleaned. You can clean by:– ultrasonic, megasonic baths– ionized, compressed ultra-

pure air– wiping– carbon dioxide cleaning– laser cleaning

3.4.3 Recommended materialsfor process tools

Requirements:•Product fabrication•Low contamination

– direct contact with product– indirect contact with prod-

uct

Materials:•Stainless steel•Conductive plastic plates•Ceramics•Glass•Plastics (PTFE, PFA, PVDF,

PP…)

3.4.4 Recommended materialsfor handling and transportsystems

Requirements:•Low abrasive behaviour

– moving parts generate particles

– no outgassing of such items as transport boxes or lubri-cants

Materials:•Stainless steel

– chemically or electrochemi-cally polished

– pickled roughness Ra ‹5 µm•Eloxed aluminum (thickness ›20 µm)

•Stoved finished quartz•Glass•Plastics

– no outgassing of additives– no out-diffusion of softener:

PTFE, PFA, PVDF, PP

3.4 Suitable Materials for Equipment Design

40

3.5 Cleaning Methods

When cleaning the equipment,care must be taken to ensurethe following:•Avoidance of cross

contamination •Awareness of chemical

incompatibility •Prevention of mechanical

destruction

The following are the commonlyused cleaning methods:•Cleaning blasts, e.g.

compressed air, CO2

•Thermal cleaning, e.g. steam cleaning

•Flow technology, e.g. ultrasound, megasound

•Plasma-jet cleaning•Chemical, solvent cleaning

41

3.6 Basic Principles of Equipment Design

The following principles areused as a guide for equipmentdesign; these are used tominimize faults in the finalequipment.

3.6.1 Using rotary movingelements

Whenever possible rotarymovements should beemployed, as lesser particlesare generated by rotary movingelements. Furthermore, it iseasier to seal rotating elementsfrom the clean environment.

3.6.2 Minimizing slidingfriction

The design should minimizesliding friction. Do not usesliding tracks, it is better if youcould use roller tracking. Lipsealing is also not allowed andtries to avoid unnecessaryfunctional contact.

3.6.3 Principle of arrangingtask integration

Reduce the number of compo-nents used to a minimum, ifpossible make use of singlecomponents which can assumeseveral functions.

3.6.4 Analyzing of ways ofgripping products

If you need to use a gripper inthe production, avoid grippingin the same direction as thedirection of the first air flow.Keep the product contact to a minimum either by theequipment or the operator.

If you grip either from the sideor from beneath the product,the gripper does not affect theair flow around the product andthe air flow obstruction causedby the gripper is kept to aminimum.

If the gripper can only be usedabove the product, then keepmoving elements next to theproduct and select the shape ofthe gripper and its distanceaway from the product in sucha way that stagnant areas donot reach the product

3.6.5 Choice of materials/Surface finish

With regard to the choice ofmaterials, the following arerecommended:•Use materials with low

electrostatic charge proper-ties

•Combination of materials: plastic – metal: avoid insulated partial systems

•Surfaces should be smooth where possible, no sharp edges:– easier to clean, minimizing

influence on air flow•In semiconductor industry:

– no moving elements made of copper of brass

– better: special steel, alumi-num

3.6.6 Secondary measures/alternatives

The above five principles arerequired but however, if you arenot available to meet theserequirements.

The following are someguidelines, which should beconsidered:•Encapsulating components•All moving parts enclosed•Vacuum suction•Accurately aimed local air flow

direction

42

3.7 Contamination Control of Cleanroom Equipment

Besides knowing the basicprinciples behind the designingof cleanroom equipment, wemust also know what type ofcontamination control isrequired for this equipment.

3.7.1 Types of contamination

Contamination is defined as“Any unwanted substancepresent in or on a material orany surface within a cleanzone”. This presumes that oneis working in an area wherecleanliness is regulated.

Contaminants are particulate,liquid, gaseous, film orbiological. Other authoritiesalso include radiation andelectromagnetic interference(EMI) as contaminants.

Particles can be solids orliquids and can be solid-solid,solid-liquid, solid-gas, liquid-liquid or liquid-gas as long asthey are discrete entities. Filmsare typically dried liquidscontaining solids or gasses andare often only molecules thick.A trace amount of gas withinanother gas may be considereda contaminant.

3.7.2 Reason for contaminationcontrol

In all cleanrooms, threeparameters influence theproduction area:•Cleanroom class•Personnel•Equipment

We need to define the threeparameters, but here we areconcentrating only on theequipment. Contaminationcharacteristics of equipmenthave major influence on cleanli-ness level of the productionarea.

43

3.7 Contamination Control of Cleanroom Equipment

3.7.3 Sources of contamination

There are many sources ofcontamination. The atmospherecontains dusts, microorganisms,condensates, and gases.People in clean environments,are the greatest contributors tocontamination emitting bodyvapours, dead skin, microorga-nisms, skin oils, and, if smokingor wearing cosmetics, thefumes and particles from thesematerials.

Industrial processes producethe widest variety of contami-nants. Wherever there is aprocess which grinds, corrodes,fumes, heats, sprays, turns,etc., particles and fumes areemitted and will contaminatetheir surroundings. Finallyplants and soils contributeparticulate and biological con-taminants.

Airborne contaminants may beorganic, inorganic, or aerosols,the latter being composites ofany number of components.Organic contaminants includehydrocarbons such as hexanes,benzene, alcohol, ketones, andother volatile organic solvents.

Inorganic contaminants aremainly composed of gases suchas carbon dioxide, chlorine,hydrogen sulphide, sulphuroxides, ammonia, etc. Aerosolscan entrain any of the aboveinto liquid or particle agglom-erations containing dusts,pollens, small organisms suchas mites, microorganisms, etc.

In addition to dust and otherparticles, surface contamina-tion can be any one of thefollowing – reaction layers ofchemical compounds, absorbedlayers of mostly hydrocarbonsand moisture, or variablecomposition contaminants dueto preferential diffusion of onecomponent through a sub-strate.

44

3.7 Contamination Control of Cleanroom Equipment

a) ESD Behaviour of operatingmaterials

ESD stands for ElectrostaticDischarge. It is the rapidtransfer from static chargedbodies of materials to or fromElectrostatic DischargeSensitive Electronic Devices.

Virtually all electronic devicesare ESD sensitive; thesensitivity is based on productand design. ESD occurs whencharge is generated, stored onan object and rapidlytransferred.

Materials become charged via:•First air flowing onto them•Particles generated are not

removed by the first air flow•Contamination adheres to

charged materials•Formation of larger agglom-

erates•Sporadic, intermittent detach-

ment of very large forms of contamination

As shown, ESD is harmful to thesystem and must be removed.Recommended ways ofremoving of electrostaticcharges are:•Equipping with various

ionizers – nuclear or x-ray ionizers:

ionizing radiation– corona discharge: electronic– emission of particles

(approx. 5 P/cbf, P = 0.03 µm)

•Grounding (earthing) the equipment

45

3.7 Contamination Control of Cleanroom Equipment

b) Magnetic influences

When handling components,which are subject to magneticinfluences, care must be takento ensure that they are shieldedfrom the electromagneticeffects.

Another option would bekeeping critical products awayfrom electromotors, permanentmagnets, coils andelectromagnetic fields.

c) Properties of materials

The properties of the materialsused in the equipment affectsthe level of contamination. Ifthe wrong choice were madethere would be more particlesemitted and would greatlyaffect the cleanroom.

Take note of the followingpoints when choosing the rightmaterial:•Know the emission of par-

ticles from the material in use•Constantly•Sporadically•Which size of particle,

critical/uncritical?•Which combinations of

materials emit particles•Know the life span of material•Correlation between the wear

and tear of materials used and tool life

d) Outgassing

When the equipment is underextremes of temperature, thereis the likely occurrence of“Outgassing” which is simplythe release of gases or volatilesubstances from a materialother than a change of state ofthe material.

Make sure that the emissionlevels of volatile substances donot exceed limits. They mustnot be harmful to either theproduct or the personnelworking the area. The materialschosen must pass tests atextremes of temperature.

46

3.8 Qualification of Cleanroom Equipment

Qualification tests are carriedout to assess the cleanroomsuitability of operatingmaterials that include equip-ment.

It is very important to note herethat “No operating materialmay be allocated to a clean-room class”. It is thereforewrong to say that “Our producthas the Cleanroom Class 100”.

The reasons are:•Cleanroom classes were

drawn up only for the accept-ance and classification of cleanrooms.

•Operating materials do not fulfil these fundamental conditions.

•Missing of specifications for the classification of operating materials.

It might be easy to say that wecould just transfer the clean-room classifications to operat-ing materials, but there areproblems in doing so.

•Correlation of cleanroom classification/air volume– air volume– defined degree of cleanli-

ness per volume of air •Procedures for classification

standards are related to cleanrooms

A possible solution is to drawup and use standardized pro-cedures for classification ofcleanroom products. This iscovered in German standardVDI 2083 Part 8. However, it isimportant to note that the USFederal Standard and ISOstandard does not cover this.

➔

➔

➔

47

3.9 Cleanroom and Cleanliness Suitability

When using operatingmaterials, there is a need todifferentiate on the differencebetween cleanroom suitabilityand cleanliness suitability.

As shown in Figure 3.1, youwould be able to see that thecleanroom suitability of theoperating material will dependon the cleanliness suitabilityand the examination of theairborne particulatecontamination.

To summarize, cleanlinesssuitability would consider allcontamination, relevant to thespecific product whilecleanroom suitability wouldonly consider airborneparticulate contamination.

3.9.1 Parameters ofcleanliness suitability

The following lists out theparameters that affect thecleanliness suitability.•Airflow patterns•Airborne particulate

contamination•Finding optimization

potentials•ESD behaviour•Quality of surfaces•Sedimented particle emission

behaviour•Cleanroom suitability of

material used•Conception of the operating

materials•Molecular contamination•Upholding constructional

device standards (e.g. SEMI)•Upholding national and

international regulations/ guidelines for cleanliness

Difference between cleanroom and cleanliness suitability

Figure 3.1

Assessment of suitability of operatingmaterials for use under clean conditions

Cleanliness suitability

Examination of all kindsof contaminantsemitted by the product

Assessment:for which products theoperating materialsmay be used

Cleanroom suitability

Examination of airborneparticulatecontaminants emittedby the product

Assessment:in which cleanroomclasses the operatingmaterials may be used

4.0 Cleanroom Garment System

49

4.1 Introduction

The largest cause of contamina-tion in a cleanroom is person-nel. To illustrate this, let us lookas some statistics:

Personnel working in clean-rooms disperse large quantitiesof particles from their skin andclothing. It is therefore neces-sary for personnel workingwithin a cleanroom to useclothing that will minimize thisdispersion. Cleanroom clothingis made from fabrics that do notlint or disperse particles andact as a filter against particlesdispersed from the person’sskin and indoor, or factory,clothing.

Particles generated/minute (0.3 µm or larger)

100,000

500,000

1,000,000

2,500,000

5,000,000

7,500,000

10,000,000

10,000,000

Action

Standing or sitting with nomovement

Sitting or standing, light head,hand and forearm movements

Sitting or standing, averagebody or arm movement, toetapping

Changing positions, sitting tostanding

Slow walking (2 mph)

Average walking (3.5 mph)

Fast walking (5 mph)

Climbing stairs

The type of clothing used in acleanroom varies according tothe type of cleanroom. In clean-rooms where contaminationcontrol is very important, per-sonnel wear clothing that com-pletely envelops them to en-sure that particles and bacteriaare not dispersed into the air.Whatever the choice of fabric orstyle of clothing, garments willhave to be put on prior to enter-ing the cleanroom. This shouldbe done in such a manner thatoutside of the clothing is notcontaminated.

The majority of cleanroomsrequire that a garment be usedmore than once. It is thereforenecessary to devise a methodthat ensures garments areremoved and then stored insuch a way to ensure that theminimum of contamination isdeposited onto them.

50

4.2 Cleanroom Garments

The garments used in clean-rooms are:•Coverall or overall•Hood•Face mask•Knee-length boots•Gloves

In cleanrooms where contami-nation is not as critical, then asmock, cap and shoe cover maybe sufficient.

51

4.3 Entry and Exit Procedures

4.3.1 Entry procedure

It is necessary to change intocleanroom garments beforeentering a cleanroom. Themethod outlined here can beused in a typical cleanroom. Itshould be noted that there arealternatives to the proposedmethod and these are quiteacceptable as long as they givean appropriate level of contam-ination control. It is common tofind that the change area isdivided into three zones, orareas. These zones are pre-change zone, changing zone,and cleanroom entrance.Personnel move through thezones carrying out the changingprocedure in the followingmanner:

4.3.2 Prechange zone

Before changing clothing, it isbest to go to the bathroom. If itis necessary to come out of thecleanroom to go to the bath-room this is likely to entailchanging in and out of clean-room clothing. In cleanroomswhere outdoor shoes are notremoved or fully covered, shoecleaners should be used. Theseshoe cleaners are speciallymade for cleanrooms.Cleanroom mats or flooring areoften used in the approachroute to the prechange room.The shoes should be applied toa mat three times to ensure theremoval of practically all foot-wear contamination. Cleanroomflooring should be of sufficientsize for the correct number ofsteps (a minimum of three).Within the prechange zone, thefollowing tasks may be carriedout:•Personnel should remove

sufficient street or factory clothes to feel comfortable in the cleanroom. If the company

provides dedicated cleanroomgarments for wearing under the cleanroom garments, thenall street clothing should be removed and replaced.

•Watches and rings should be removed. Wedding rings that are smooth may be accept-able if the ring (and under the ring) is kept clean. Rings that are not smooth can be taped over. Along with other items, such as cigarettes and lighters, wallets and any othervaluables should be securely stored.

•Remove cosmetics and, if required, apply a suitable skinlotion. Don a disposable bouffant hat or hairnet to ensure that hair will not stick out from under the cleanroom hood.

•Put on a pair of disposable footwear coverings, or changeinto cleanroom-dedicated footwear.

• If a hand washing system is located in this area, then wash the hands, dry and apply a suitable hand lotion. However, it is probably best that the hands be washed within the change area just before the clean garments are put on.

•Cross over from the preentry area into the changing area or zone. The demarcation

between these two zones maybe a door or a crossover bench, or both. The bench willnormally be built between the zones to ensure that person-nel cannot walk round it but must cross over it. If a bench is used, it may be best to attend to footwear as one crosses over it. If a bench is not used, then a cleanroom mat or flooring can be used.

52

4.3 Entry and Exit Procedures

4.3.3 Changing zone

The outer cleanroom garmentsare put on in this area. Severalmethods can be used but thefollowing one is used in manycleanrooms. This methodassumes that a face mask,hood, coverall and overbootsare used but it can be adaptedfor use with a cap, gown andovershoes. This methodrequires that the garments bedonned from the top down.

• The garments to be worn areselected. If a fresh garment isused then it should bechecked for size and thepackaging checked to seethat it is free from tears andfaulty heat seals. The packag-ing is then opened.

• If a hand washing system isinstalled in this area, then thehands should now be washed(and disinfected if required).This is probably the best timeto wash hands; temporarygloves known as “donninggloves” are sometimes used.Use of these gloves is con-fined to the highest quality ofcleanroom. These should beput on, if required.

• A face mask and hood (or cap)should be put on. It appearsto make little differencewhether the mask is putunder, or over, the hood.However, the mask should notbe placed under the nose.

• The coverall (or gown) shouldbe unfolded without touchingthe floor. The garment shouldthen be put on ensuring thatit does not touch the floor.

• The garment should then bezipped all the way up to thetop, with the yoke of the hood(if used) being tucked insidethe collar.

• If the garment has snaps atthe ankles and wrists, thenthese should be snappedshut.

53

4.3 Entry and Exit Procedures

4.3.4 Cleanroom entrance

If a crossover bench is avail-able, it should be crossed overnow. This bench is used todemarcate the slightly soiledchanging zone from the cleanerentrance zone and allowscleanroom footwear (overshoesor overboots) to be correctlyput on.

• Personnel should sit on thebench. One leg should beraised, the cleanroomfootwear put on, the legtransferred over the benchand placed on the floor of theentrance zone. Footwearshould be put on the otherfoot and the leg taken overthe bench. While still sittingon the bench, the legs of thecleanroom garment and thefootwear should be adjustedfor comfort and security.Personnel should now standup.

• If donning gloves have beenused they can be dispensedwith now; if deemednecessary, the hands canagain be washed (ordisinfected).

• Powder-free cleanroom glovesshould now be put on. Amethod should be employedto prevent the outside ofthem from becomingcontaminated when being puton. This usually entailsholding the glove at the cuff.

• Protective eyeglasses, ifrequired, may be put on.

• The garment should bechecked in a full-length mirrorto see that it is being worncorrectly.

• Personnel may now proceedinto the cleanroom. This maybe over a cleanroom mat.

54

4.3 Entry and Exit Procedures

4.3.5 Exit changing procedures

When leaving a cleanroom,personnel will either:• Discard all their garments and

disposable items; on reentrythey will use a freshly pro-cessed set of garments (thismethod is normally only usedin a pharmaceutical clean-room) or

• Discard their disposableitems, such as their mask andgloves, but reuse their gar-ments on reentry. If a com-plete change of clothing isrequired on reentry, then thedisposable bouffant hat,gloves, face mask and (if dis-posable) shoe covers will beplaced in a container for dis-posal. The remainder of thegarments that are not dis-posable should be placed in a separate container for dis-patch to the cleanroom laun-dry for processing.

If the garments are to be usedagain on reentry, they shouldbe removed in such a way thatthe outside of the garment iscontaminated as little aspossible. The cleanroom foot-wear should be removed at thecrossover bench, one at a time,and the inner shoe (with orwithout the covering of a plas-tic shoe cover) placed in theless clean zone.

The coverall should be un-zipped and removed using thehands within the garment toremove it over the shoulder anddown to the waist. In a sittingposition, one leg is now re-moved from the garment.

The empty arm and leg of thegarment should be held so thatthey do not touch the floor. Theother leg can now be removed.The face mask and hood cannow be removed.

Garments to be used again onreentry should be correctlystored. This can be done inseveral ways. These are asfollows:• Each item of clothing can be

rolled up ensuring the insidedoes not touch the outside. Inthe case of cleanroom foot-wear, this should be done sothat the dirty soles are to theoutside. The footwear cannow be placed in one opencompartment and the hoodand coverall (or cap andgown) in another. If thoughtnecessary, the items ofclothing can be placed intobags before being put in anopen compartment.

• The hood (or cap) can beattached to the outside of thecoverall (or gown) by meansof a snap, and hung in a cabi-net. The cleanroom footwearcan be placed at the bottomof the cabinet. Garments canalso be hung up in the roombut they should not touch thewall, or each other. In higher-grade cleanrooms, clothing isoften hung up in unidirection-al flow cabinets (normallyvertical flow type), specificallymade to ensure that garmentsare not contaminated.

• Garment bags, which can behung up, can be used. Thesewill have separate pockets forthe various clothing items andshould be regularly laundered.

If the entry described aboveand exit changing methods areused in a cleanroom facilitythen contamination of gar-ments during donning will beminimized. However, becausethe layout of particular changeareas, it may be necessary tomodify the method suggestedabove. If an alternative methodcan be devised to minimizingcontamination then no harmwill be done to the product.

5.0 International Standard for Cleanrooms

56

5.1 Introduction

The US Federal Standard 209Ehave long been the only defi-nition of cleanroom classifica-tion available from a standardorganization. It is from the U.S.General Service Administrationand approved for use by all U.S.Agencies. In the absence of aninternational standard, FS 209Ewas broadly used internation-ally.

The need for a new internation-al standard that covered morecleanroom environmental para-meters and practices led to theformation of a technical com-mittee of the InternationalStandards Organization. Thetechnical committee is namedTC 209 Cleanrooms and Asso-ciated Controlled Environ-ments.

The goal of TC 209 is “standard-ization of equipment, facilitiesand operational methods forcleanrooms and associatedcontrolled environments. Thisincludes procedural limits andtesting procedures to achievedesired attributes to minimizemicrocontamination.”

The ISO committee will produce10 new standards documentsthat relate to cleanrooms orclean zones.

National and internationalstandards will be introduced inthis chapter with emphasisgiven to the above two.

57

5.2 Cleanroom Classes

Cleanroom classificationstandards can be divided intothe following subgroups:

Engineering classes

Biocontamination(pharmacy) classes

Containment classes

These originate from Federal Standard209 and are based on inanimateparticles in air.

These were originally based on FederalStandard 209 but developed to includeliving microorganisms. These standardsare required for hygienic or sterileproduction.

These are for areas where hazardouscontaminants are used or can occur.

Table 5.1

58

5.3 The Present Engineering Classes

These classes are used mainlyin rooms where electronic andengineering items are manu-factured. Most of these stan-dards are based on one of the

various editions of the USFederal Standard 209.Some countries completelyadopted FS 209, while othersmade their own national ver-

Australia

France

Germany

Holland

Japan

Russia

UK

US

Country Standard Year Description

AS 1386

AFNOR X44101

VDI 2083.3

VCCN 1

JIS-B-9920

Gost-R 50766

BS 5295

FS 209E

1989

1981

1993

1992

1989

1995

1989

1992

Cleanrooms and clean workstations

Definition of cleanroom levels

Contamination control measuringtechnique for clean air rooms

Dust and microorganismclassification of air

Measuring methods for airborneparticles in cleanroom andevaluating methods, etc.

Cleanroom classification, generalrequirements

Environmental cleanliness inenclosed spaces

Airborne particulate cleanlinessclasses in cleanrooms and cleanzones

Major national standards

sion, similar to FS 209. Somemade minor changes of theclasses to comply with the met-ric system, but all changed thedenomination of the classes.

1

10

100

1,000

10,000

100,000

USA ISO Japan France Germany UK Australia209E 14644-1 B 9920 X44101 VDI 2083 BS 5295 AS 13861992 1997 1989 1981 1990 1989 1989

A comparison of major engineering cleanroom classes in the world

ISO Class 1

ISO Class 2

ISO Class 3

ISO Class 4

ISO Class 5

ISO Class 6

ISO Class 7

ISO Class 8

ISO Class 9

1

2

3

4

5

6

7

8

4,000

–

40,0000

4,000,000

0

1

2

3

4

5

6

7

C

D

E, F

G, H

J

K

L

0.035

0.35

3.5

35

350

3500

Note: The M values for FS 209E (and

the ISO values) are in metric units.

The M figures are therefore ele-

vated above the line of the others,

which are given in cubic feet.

FS 209E class 100 therefore corre-

sponds to M class 3.5 and ISO 5.

M1

M2

M3

M4

M5

M6

M7

59

5.4 Federal Standard 209E, and its Four Early Editions

The following table shows asummary of the FederalStandard 209.

Federal Standard209

209A

209B

209C

209D

209E

Year1963

1966

1973

1987

1988

1992

CommentsInitial standard

First revision

Mixture of information advises and rules. Helpedpeople enter the new field of contamination controland building cleanrooms.

Revision of 209B but had printing errors

Proper revision of 209C

Present version

1

10

100

1,000

10,000

100,000

Class Messured particle size (µm)

Federal Standard 209 (A to D) Class Limits

The following table shows thecleanroom classification priorto version 209E.

0.1

35

350

NA

NA

NA

NA

0.2

7.5

75

750

NA

NA

NA

0.3

3

30

300

NA

NA

NA

0.5

1

10

100

1,000

10,000

100,000

5.0

NA

NA

NA

7

70

700

Table 5.4

Table 5.5

60

5.4 Federal Standard 209E, and its Four Early Editions

5.4.1 Federal Standard 209 –Version E

A substantially changed versionE was published in 1992, with a more precise title: “Airborneparticulate cleanliness classesfor cleanrooms and cleanzones.“

Version E differs from theprevious editions as follows:• The cleanroom classes are

metric.• It has seven classes of

cleanliness: M1-M7.• It gives a method for

measuring air cleanliness.• It demands a plan for

monitoring air cleanliness.• It gives a rational for the

statistical rules used.• Ultrafine particles are con-

sidered, i.e. particles ‹0.02 mm.

• It considers iso-anisokinetic sampling.

• It describes sequential sampling for low concentra-

tions of particles.Table shows the class limits ofthe classroom in terms of theparticle concentration in bothmetric and the original Englishunits. This table does notnecessarily represent the sizedistribution to be found in anyparticular situation.

Concentration limits can be calculated for intermediateclasses, approximately, fromthe equation:

particles/m3 = 10M (0.5/d)2.2

Where “M” is the numericaldesignation of the class basedon SI units and “d” is the

Class Class limits (µm)

Federal Standard 209E Airborne Particle Cleanliness Classes

0.1 0.2 0.3 0.5

SI

M1

M1.5

M2

M2.5

M3

M3.5

M4

M4.5

M5

M5.5

M6

M6.5

M7

English

1

10

100

1,000

100,000

(m3)

350

1,240

3,500

12,400

35,000

(ft3)

9.91

35.0

99.1

350

991

Table 5.6

(m3)

75.7

265

757

2,650

7,570

26,500

75,700

(ft3)

2.14

7.50

21.4

75.0

214

750

2,140

(m3)

30.9

106

309

1,060

3,090

10,600

30,900

(ft3)

0.875

3.00

8.75

30.0

87.5

300

(m3)

10.0

35.3

100

353

1,000

3,530

10,000

35,300

100,000

353,000

1,000,000

3,530,000

10,000,000

(ft3)

0.283

1.00

2.83

10.0

28.3

100

283

1,000

2,830

10,000

28,300

100,000

283,000

(m3)

247

618

2,470

6,180

24,700

61,800

(ft3)

7.00

17.5

70.0

175

700

61

5.5 German Standard: VDI 2083

The German EngineeringAssociation, known in Germanyas Vereinigte Deutsche Ingeni-eure (VDI), has a group workingin the field of contaminationcontrol. In 1976, the VDI pub-lished VDI 2083 as their “Clean-room Engineering” standardwith a metric system used inthe classification. It was thenrevised from 1987 onwards andconsists (in 1998) of elevenparts.

Part 1

Part 2

Part 3

Part 4

Part 5

Part 6

Part 7

Part 8

Part 9

Part 10

Part 11

Fundamentals, definitions anddetermination of classes

Construction, operation andmaintenance

Measuring technique for clean airrooms

Surface cleanliness

Criterion on comfort

Personnel in cleanroom work area

Cleanliness of process media(liquids, gasses, etc.)

Suitability of products for cleanroom

Quality, production and distributionof superpure water

Media distribution

Quality assurance

issued 1991

issued 1991

issued 1993

issued 1991

issued 1989

issued 1991

issued 1991

issued 2000

issued 1991

issued 1998

under develop-ment

VDI 2083: Part 3 gives theGerman cleanroom classifica-tion. It is a metric standard anduses a size ≥1.0 µm as a basisof its nomenclature, instead ofthe ≥0.5 µm used by FS 209E.

Table 5.7

62

5.6 British Standard: BS 5295

This standard, which is entitled“Environmental cleanliness inenclosed spaces”, was firstpublished in 1976 and revisedand published in 1989. It issimilar to FS 209B in that itgives useful information tothose designing and using a cleanroom. It is divided into 5 sections.

Part 0

Part 1

Part 2

Part 3

Part 4

General introduction, terms and definitions forcleanrooms and clean air devices.

Specification for cleanrooms and clean air devices.

Methods for specifying the design, construction andcommissioning of cleanrooms and clean air devices.

Guide to operational procedures and disciplinesapplicable to cleanrooms and clean air devices.

Specification for monitoring cleanrooms and cleanair devices.

C

D

E

F

G

H

J

K

L

M

Class of environ. Maximum permitted number of particles per m3

cleanliness

BS 5295: Environmental cleanliness classes

0.3 µm

100

1,000

10,000

NS

100,000

NS

NS

NS

NS

NS

0.5 µm

35

350

3,500

3,500

35,000

35,000

350,000

3,500,000

NS

NS

5 µm

0

0

0

0

200

200

2,000

20,000

200,000

NS

10 µm

NS

NS

NS

NS

0

0

450

4,500

45,000

450,000

25 µm

NS

NS

NS

NS

NS

NS

0

500

5,000

50,000NS – No specified limit

Table 5.8

Table 5.9

63

5.7 Japanese Industrial Standard: JIS B 9920

FS 209B to D were translatedinto Japanese and were used bythe Japanese until the late1980s. The JIS B 9920 waspublished in 1989 and itdeviates from the FS 209E inthe following ways:• It is metric and has a denomi-

nation system based on the exponent of particle concentration.

• It uses particles ≥ 0.1 µm as the reference size, instead of ≥ 0.5 µm used in FS 209E.

• It has two cleaner classes than FS 209E.

However, it is similar to the ISO 14644-1, as the ISO clean-room classification is alsobased on particles ≥ 0.1 µm,that method being derived fromthis standard.

64

5.8 Australian Standard: AS 1386

This was first published in 1976and is now revised and wasrepublished in 1989. It consistsof seven parts. The Australiansclassify cleanrooms using ametric system.

65

5.8 French Standard: AFNOR X 44101

In France, the French cleanroomassociation (ASPEC) has de-veloped many “Recommenda-tions” for cleanrooms since1972. Their main cleanroomclassification was taken overand published in 1981 by theFrench Organization for Stan-dards (AFNOR) and given thenumber X 44101.

66

5.10 Dutch Standard: VCCN-RL-1

In the Netherlands, their clean-room association, VCCN, hasissued contamination control“Guidelines”. They have issuedsix contamination controlstandards since then, the firstbeing VCCN-RL-1 that considersthe “Particle and microorganismclassification” of cleanrooms.VCCN-RL-2 is about “Buildingand maintenance of clean-rooms”.

67

5.11 Russian Standard: GOST R 50766-95

In the 1970s, the Soviet Unionpublished a cleanroom classifi-cation standard with five classi-fications. It was based on FS 209E. During the 1980s asimilar COMECON standard waspublished in the Soviet Union.In 1991, a Soviet CleanroomAssociation (ASENMCO) wasformed acting for internationalcooperation and standardiza-tion. The first Russian classifi-cation, GOST R 50766-95,“Cleanroom classifications.Methods of certification.General Requirements”, wasdeveloped by ASENMCO andapproved by Gosstandard inJanuary, 1986.

68

5.12 ISO Classification Standard

Because of the large number ofcleanroom standards producedby individual countries, it isvery desirable that one world-wide standard of cleanroomclassification is produced. ISOhas setup a technical com-mittee (TC 209) and will pro-duce 10 new standards docu-ments that relate to cleanroomsor clean zones. The first twostandards have been pub-lished: ISO 14644-1 and –2.

ISO DocumentISO 14644-1

ISO 14644-2

ISO 14644-3

ISO 14644-4

ISO 14644-5

ISO 14644-6

ISO 14644-7

ISO 14698-1

ISO 14698-2

ISO 14698-3

TitleClassification of Air Cleanliness

Cleanroom Testing for Compliance

Methods for Evaluating & Measuring Clean-rooms & Associated Controlled Environments

Cleanroom Design & Construction

Cleanroom Operations

Terms, Definitions & Units

Enhanced Clean Devices

Biocontamination: Control General Principles

Biocontamination: Evaluation &Interpretation of Data

Biocontamination: Methodology for Measur-ing Efficiency of Cleaning Inert Surfaces

Table 5.10 shows the 10 differ-ent documents which will makeup the cleanroom standards.Many of these documents areat the final voting stage andcan be legally used in trade.

Table 5.10

69

5.12 ISO Classification Standard

5.12.1 ISO 14644-1 classifica-tion of air cleanliness

Cleanliness class designationsand quantity have changedfrom FS 209E. Along with theobvious change to metric mea-sure of air volume, ISO 14644-1adds three additional classes –two cleaner than Class 10 andone dirtier than Class 100,000.

ISO 1

ISO 2

ISO 3

ISO 4

ISO 5

ISO 6

ISO 7

ISO 8

ISO 9

Class Number of particles per cubic meter by micrometer size

Airborne particulate cleanliness classes

0.1 µm

10

100

1,000

10,000

100,000

1,000,000

0.2 µm

2

24

237

2,370

23,700

237,000

0.3 µm

10

102

1,020

10,200

102,000

1 µm

8

83

832

8,320

83,200

832,000

8,320,000

83,200,000

5 µm

29

293

2,930

29,300

293,000

0.5 µm

4

35

352

3,520

35,200

352,000

3,520,000

35,200,000

Table 5.11

70

5.12 ISO Classification Standard

5.12.2 ISO 14644-2 cleanroomtesting for compliance

ISO 14644-2 determines thetype and frequency of testingrequired conforming to thestandard. Table 5.12 indicateswhich tests are mandatory andTable 5.13 indicates which testsare optional.

Particle counttest

Air pressure test

Air flow

Test Class Maximum Test parameter time interval procedure

Schedule of Tests to Demonstrate Continuing Compliance

≤ ISO 5› ISO 5

all classes

all classes

6 month 12 month

12 month

12 month

ISO 14644-1Annex A

ISO 14644-1Annex A

ISO 14644-1Annex B4

Installed filterleakage

Containmentleakage

Recovery

Air flowvisualization

Test Class Maximum Test Parameter time interval procedure

Schedule of additional optional tests

all classes

all classes

all classes

all classes

24 month

24 month

24 month

24 month

ISO 14644-3Annex B6

ISO 14644-3Annex B4

ISO 14644-3Annex B13

ISO 14644-3Annex B7

Table 5.12

Table 5.13

71

5.12 ISO Classification Standard

5.12.3 Status of other ISO 14644 Standards

The development stages aregiven the following prefixes:• WD – Working Draft.

Circulation of developing within the Working Group setup by the ISO/TC209 committee.

• CD – Committee Draft. Circulation of approved Working Draft within ISO/TC209 for approval and/ or comments by the National Technical Bodies of the participating countries.

• DIS – Draft International Standard. Circulation of the ISO-ap-proved Committee Draft by ISO for public enquiry in all ISO member countries.

• FDIS – Final Draft Internation-al Standard. Circulation of approved DIS for final vote.

ISO 14644-3

ISO 14644-4

ISO 14644-5

ISO 14644-6

ISO 14644-7

Document Title Status

Status of ISO 14644 Standards

Methods for evaluating & mea-suring cleanrooms & associ-ated controlled environments

Cleanroom design & Cconstruction

Cleanroom operations

Terms, definitions & units

Enhanced clean devices

CD 14644-3DIS in 2001

DIS 14644-4

CD 14644-5

CD 14644-6DIS in 2001

CD 14644-7

Table 5.14

72

5.13 Summary of FS 209E and ISO 14644-1 and -2

The cleanliness classificationlevels defined by FS 209E andISO 14644-1 are approximatelyequal, except the new ISO Stan-dard uses new class designa-tions, a metric measure of airvolume and adds threeadditional classes – two cleanerthan Class 10 and one dirtierthan Class 100,000.

The second new ISO Standard,ISO 14644-2, gives require-ments for monitoring a clean-room or clean zone to provideevidence of its continuedcompliance with ISO 14644-1.The following table comparesthe FS 209E to the new ISO 14644-1 classifications.

ISO 14644-1ISO Class

123456789

FED STD 209EEnglish

––1101001,00010,000100,000–

Metric

––M1.5M2.5M3.5M4.5M5.5M6.5–

The ISO Standard also requiresfewer sample locations,especially as the cleanroom/area size increases; however,the ISO Standard does requireminimum one minute samples,whereas the Federal Standardallows shorter samples,especially at smaller particlesizes. For example, to certify anFS Class 10 cleanroom (ISOClass 4), with 250 square feet(7.08 square meters), classifiedat 0.3 micron with a 1 ft3/mflow rate particle counter, therequired number of samplelocations, sample volumes, andsample times would be asfollows:• FS 209E requires 10 sample

locations, 19.6 litre minimumsample volume (0.85 ft3), anda sample time of 51 seconds.This yields a total minimumsample time of 510 secondsand 10 equipment moves.

• ISO 14644-1 requires threesample locations, 19.6 litreminimum sample volume(0.85 cft3), but also a minimumsample time of one minuteyielding three samples of onecubic foot. This yields a totalsample time of 180 secondsand three equipment moves.

Table 5.15

73

5.13 Summary of FS 209E and ISO 14644-1 and -2

Disposition

Particle range

Classification

Formula for classes

Reference for particle size

Number of classes

Occupancy states orconditions

Occupational states at test

Requirement of particle sizesfor classification

Minimum sample volume

Minimum counts/test

Sampling locations

Number of samples/location

Measurement methods

Ultrafine particles

Macroparticles ≥ 5 µm

Confidence level needed

Sequential sampling

Isokinetic sampling

Regarding FED STD 209E ISO 14644

according to federal regulations

0.1 – 10 µm

according to table, equationgiven

C = (0.5/D)2.2 x 10N

0.5 µm

M1 to M7

at built, at rest, operational

not given

1 or more

2.83 litres

20

according to three givenequations

1 or more

DPC (=OPC, CNC) + opticalmicroscopy

considers particles ≤ 0.02 µm

not considered

95 % UCL for ≤ 9 samplelocations

included

included

according to ISO

0.1 – 5 µm

according to equation

C = (0.1/D)2.08 x 10N

0.1 = a constant

ISO 1 to 9 (expandable)

at built, at rest, operational

1 or more states

1 or more, where diameter ofone is 1.5 x diameter of nextsmaller particle

2 litres

20

number of locations =√ area of room

1 but 3 if one location

DPC for 0.1 – 5 mm particles,CNC for ultrafines; opticalmicroscope for macroparticles

considers particles ≤ 0.1 µm

information on particles ≥ 5 µm

95 % UCL for ≤ 9 sample locations

included

not included

Comparison between FS 209E and ISO Standard 14644-1

Table 5.16

74

5.14 Biocontamination and Pharmaceutical Classes

In the early 1960s, the pharma-ceutical industry developedcleanroom standards tocounteract contaminationproblems of sterile productswhich had caused sickness anddeath in patients.

It had been realized that asonly a small sample of drugscould be tested, a final test ofsterility could never determinethe safety of sterile products. Itwas necessary therefore to relyon proper manufacturing, i.e.good manufacturing practice(GMP).

These standards are known asGuides to Good ManufacturingPractice (GGMP). They werebased on experience of thethen new FS 209, BS 5295 andother engineering standards, aswell as the experience in themanufacture of pharmaceuticalproducts.

The goal of GGMPs is to care-fully specify the proper methodof manufacture of sterile prod-ucts by eliminating microbialand particle contamination andhence creating the correctquality assurance (QA).

The GMP guides deals largelywith the methods of goodmanufacturing but also specifythe building design, buildingmaterial, care of personnel, etc.They also give figures for thecleanliness classes of clean-rooms: particles, microorgan-is-ms, as well as the type of airfilters and number of airchanges per hour.

The GMP guides, produced bythe various countries, areadvisory rather than legal andconsider that there is morethan one way to achieve therecommended standards. Tocheck that the GMP is beingapplied correctly, each countryhas government inspectors.They will interpret the generallyexpressed statements of theguides. A pharmaceuticalmanufacturer must also complywith the GMP guides of thecountries receiving theirproducts.

75

5.14 Biocontamination and Pharmaceutical Classes

Year1963

1966

1969

19721983198919921995

19891992

1997

1992

ByFood and Drug Administration (FDA)

Swedish Regulation

World Health Organization (WHO)

European Pharmaceutical InspectionConvention (PIC)This guide is accepted in most WesternEuropean countries and a few EasternEuropean countries and Australia

EEC Guide to Good ManufacturingPractices for Medicinal Products (produced by Commission of theEuropean Communities)

EU GMP Annex 1

GMP, LD 64-125-91from Russia

Some of the produced GMPs

Remarksfirst GMP

made official

first guide published

first publishedrevisedrevisedrevisedrevised (document PH 5/92)

first issuereprinted with new AnnexesIt came into legal use and supersededall other GMP guides produced in EECcountries.

revised with a new cleanroomclassification method

first GMP issued in Eastern Europe

Year1995

1987

1997

ByPIC: GMP and Guidelines

FDA cGMP

EU GGMP

Most used GMP Guides

Remarksvalid in European countries outside theEU and Australia

valid for the United States

valid for the EU area

Table 5.17

Table 5.18

76

5.14 Biocontamination and Pharmaceutical Classes

Table 5.19 shows the com-parison of major GMP guidesregarding working conditionsand classes. Unfortunately,these GMPs are not harmon-ized. The conditions for testing(at rest, or operational) aredifferent and the letters for thelevel, or grade do not mean thesame in different countries.

A revised classification schemewas developed and issued foruse in 1997.

Condition

Grade A

Grade B

Grade C

Grade D

GMP PIC EU-GMP FDA Transfer of classes, all operationalGMP 1992 1987

Comparison of Major Pharmacy GMP Guides regarding working conditions and classes

at rest

100

100

10,000

100,000

operational

100

10,000

100,000

–

operational

critical area

–

–

controlledarea

209D

100

100

10,000

100,000

209E

M3.5

M3.5

M5.5

M6.5

ISO

ISO 5

ISO 5

ISO 7

ISO 8

A

B (a)

C (a)

D (a)

Grade Maximum permitted number of particles per m3 equal to or aboveat rest (b) in operation

EU GMP Guide 1997, air particle classification system for the manufacture of sterile products

0.5 µm

3,500

3,500

350,000

3,500,000

5 µm

0

0

2,000

20,000

0.5 µm

3,500

350,000

3,500,000

not defined (c)

5 µm

0

2,000

20,000

not defined (c)

(a) In order to reach the B, C and D

air grades, the number of air

changes should be related to the

size of the room and the equipment

and personnel present in the room.

The air system should be provided

with appropriate filters such as

HEPA for grades A, B and C.

(b) At rest should be received in the

unmanned state after the 15-20 min

“clean-up” period.

(C) Appropriate alert and action

limits should be set for the results

of particulate and microbiological

monitoring. If these limits are

exceeded, operating procedures

should prescribe corrective action.

Table 5.19

Table 5.20

77

5.15 ISO Biocontamination Standards: 14698

Originally, the ISO/TC 209committee created a packageof three standards on biocon-tamination control. This hasbeen subsequently revised totwo standards and one tech-nical report.

5.15.1 ISO 14698-1

a) TitleCleanrooms and associatedcontrolled environments –Biocontamination control. Part 1 – General Principles andMethods.

b) ScopeDescribes the principles andbasic methodology for a formalsystem to assess and controlbiocontamination in clean-rooms.

c) StatusFDIS (Final Draft InternationalStandard) document is awaitingissue by ISO Geneva for an FDISvote by all member ISO nations.

d) RemarksISO 14698-1 is concerned onlywith a formal system to addressmicrobiological hazards incleanrooms. Such a systemmust have the means toidentify potential hazards,determine the resultant likeli-hood of occurrence, designaterisk zones, establish measuresof prevention or control, estab-lish control limits, establishmonitoring and observationschedules, establish correctiveactions, establish trainingprocedures, and provide properdocumentation.

It also provides detailedguidance on how to measureairborne biocontamination,how to validate air samples andhow to measure biocontamina-tion of surfaces, liquids andtextiles used in cleanrooms; italso provides guidance forvalidating laundering processesand how to provide proper per-sonnel training.

78

5.15 ISO Biocontamination Standards: 14698

5.15.2 ISO 14698-2

a) TitleCleanrooms and associatedcontrolled environments –Biocontamination control. Part 2 – Evaluation and Inter-pretation of BiocontaminationData.

b) ScopeGives guidance on basicprinciples and methodologyrequirements for all microbio-logical data evaluationobtained from sampling forviable particles in specified riskzones in cleanrooms.

c) StatusFDIS (Final Draft InternationalStandard) document is awaitingissue by ISO Geneva for an FDISvote by all member ISO nations.

5.15.3 ISO 14698-3

a) TitleCleanrooms and associatedcontrolled environments –Biocontamination control. Part 3 – Measurement of theEfficiency of Processes ofCleaning and/or Disinfection ofInert Surfaces Bearing Bio-contamination Wet Soiling orBiofilms.

b) ScopeDescribes guidance for alaboratory method formeasuring the efficiency ofcleaning an inert surface.

c) StatusPassed an ISO DIS (DraftInternational Standard) vote inJuly, 1999. Has beensubsequently determined to betoo limiting to be issued as anISO standard.

79

5.16 The Containment Classes

The handling of toxic or patho-genic material, as well asgenetic engineering work, mustbe performed in specialpremises using containmentequipment. Premises, equip-ment, and working techniquesare regulated by these“Standards”.

In the United States, guides onbiosafety, which have beendeveloped by the NationalInstitute of Health, are con-tained DNA research – actionsunder the Guidelines: FederalRegister 56" (1961). In Europe,the designer must meet thestandards given in the ECDirective 90/912/EEC of 1990when designing facilities forgenetically modified organisms.

A European standard “EN 1620:Biotechnology – Large-scaleprocesses and production –Plant building according todegree of hazard”, was issuedin 1997.

Biological risks, and themeasures are directed towardthese are classified in fourclasses. Four laboratories withrisks levels of BL1 to BL4 areused.

ClassBL1BL2BL3BL4

ExplanationNormal laboratory standardSpecial training and routines toprevent lab infections Appropriate waste handling

Special lab with negative pressureAir locks for people and materialAutoclave in the roomAll work done in safety cabinetSpecial decontamination of waste

Special labs with total separation be-tween humans and microorganismsin every aspect, negative pressure,sterilization

Four Classes BL1- BL4 of Biosafety Laboratories

ExampleOrdinary biochemistry labs School and university labsDiagnostic labsHealth labs

Special safety labsTuberculosis labs

High-risks labs

Table 5.21

6.0 Airborne Particle Emission Measurements

81

6.1 Introduction

When we talk about clean-rooms, airborne particleemission measurement is animportant factor. In thischapter, we will discuss on thesource of particles, the meth-ods for measuring particles andthe LASAIR optical particlecounter.

82

Diameter (µm)

0.001 0.01 0.1 1 10 100

Collec-tivemethod

bothcom-bined

In-Situ

Particledetec-tion

Sizeselec-tion

Condensation nucleuscounter

Aerosol electrometer

Diffusion battery

Electrical mobility analysis

Aerodyn. sensor

Optical counter

Light optical microscope

Electron microscope

Methods for measuring particles

6.2 Sources of Particles

As stated in the earlier chapter,one of the sources of contami-nation is operating materials.Contamination caused byoperating materials can beeither:• Chemical• Physical• Biological• Radiological• Ionic

Particle contamination fallsunder the umbrella of physicalcontamination. Particles arecaused by:• Leakage• Abrasion• Vibration

6.2.1 Leakage

Leakage from the pneumaticcomponents will lead toparticle contamination. The air,which leaks, might bring alongparticles with it.

6.2.2 Abrasion

When operating materials comeinto contact with one another,there is bound to be abrasion,make sure that the abrasion isto a minimum as particles aregenerated.

6.2.3 Vibration

When the pneumatic compo-nents move from end to end,there tend to be knocking atthe end position, this will leadto minor vibration and alsocause particles to be released.

There are a few methods tomeasure particles. Table 6.1shows the recommendedmethods for measuringparticles of different sizes.

Table 6.1

83

6.3 Optical Particle Counters

6.3.1 A basic particle counter

Airborne particle counters aresophisticated instruments thatmeasure airborne particles in a number of size ranges whichare far too small to be seen, butmay have a serious impact onair quality.

Although they come in a widevariety of sizes from heavybench top units designed forsemipermanent installation tohand-held counters weighingless than half a kilogram, allcounters have the same basiccomponents of sensor, vacuumsource (for sample flow) andcontrol electronics.

Display, printer and datainterface is available on manycounters as shown in Figure6.1. The vacuum pump pullsthe sample through the sensorwhere any particles present aredetected. The countingelectronics collect, report andstore the information for use bythe operator. The countedparticles are trapped in anexhaust filter and not returnedto the environment from whichthe sample was taken.

Sensor

0,3 2408

PrinterDisplay

Control electronics

Serialdataout

FilterPumpFlowmonitor

Sample inlet

Sampleexhaust

Counting particles

Figure 6.1

The most important part of aparticle counter is its sensor,which uses collected lightscattered from particles. Thesensor contains a laser lightsource that illuminates an areacalled the “view volume” withintense light. Particles in thesample pass through the viewvolume and scatter the laserlight; just as dust motes orsmoke particles do in asunbeam.

The light is then collected andfocused onto a photo detector.The photo detector convertsthe light signal to electricalpulses, the height of which isdirectly proportional to theparticle size.

The counting electronics cate-gorize and count the pulsesaccording to size, then storesthe count data in a buffer andformats it for use by the display,printer and remote communi-cations. For those countersequipped with an internalpump, sample flow control isachieved by operating a vacu-um pump under control of thecounting electronics and usinga flow meter to monitor for thecorrect flow rate. Automatic ormanual controls are then em-ployed to correct any unaccept-able variations.

In addition to discrete particlecounters, there are facility-monitoring systems that useremote sensors, externalvacuum pumps and PC work-stations to complete the basicparticle counter concept.

84

6.3 Optical Particle Counters

6.3.2 Technical characteristicsof particle counters

Analyzing unit

Detection volumes –measuring cell

Sensor-light source

Distribution of intensityof the incoming light ray

Signal processing

Size and position of registeringrange (light collector) e.g. 90° orforward areaShape and size of the measuring cellIn-situ sensors, volumetric

White lightGas laserSolid matter laser

MonitorsSpectrometers

6.3.3 General characteristics of particle counters

Individual particledetection

Indirect measuringmethod

Sample-feeding

Single particles in motionStatistical statement (samplingrange, sample taking techniques)

No recognition of particular materialNo recognition of the measuringmediumNo recognition of particle shape(killer particle)Classification of a latex-equivalent,optical particle diameterLimited comparability of differentmeasuring devices

Defined volume flowConstant volume flow

Table 6.2

Table 6.3

85

6.4 LASAIR 210 Optical Particle Counter

The LASAIR particle counter is amicroprocessor-based instru-ment that detects airborneparticles, analyses and storesthe data in eight size classes,and produces reports. It dis-plays real-time data on a 5-inchCRT and contains a printer,which can be used to producehard copies of reports.

6.4.1 Working Principle

The LASAIR sizes and countsparticles by measuring theamount of light scattered fromeach particle. The source ofillumination is a 10-milliwattHeNe laser. The patentedpassive optical cavity is definedby the laser output couplermirror and a mirror-coatedquartz which is part of anoscillator.

The vibration of the crystalshifts the wavelength of thereflected light to maximize thetransfer of power into theexternal passive cavity whileminimizing reflection ofcoherent light back into thelaser.

The cavity has a resonant Q ofapproximately 100. When it isdriven with 10-milliwatt HeNelaser, a one-watt beam is avail-able to illuminate particles.

The LASAIR flow system (Figure6.2) provides a sample flow.The system includes a pump,filters, flow meter, inlet jet andoutlet jet. The jet tip definesthe size, shape, and position ofthe sample stream in relation tothe laser beam. A purge flow isdrawn across the sample cavitymirrors to keep the laser opticsclean while sampling.

The collecting optics includesfour Mangin mirrors and asolid-state photodetector. Themirrors are anti-reflective A-Rcoated for minimal light loss.One set of mirrors is located oneach side of the laser opticalbench. The collecting opticsprovides one-to-one magnifi-cation of scattered light to thedetector.

The amplified signal from thephotodiode is proportional tothe size of the particle and thebrightness of the illumination.This signal is compared to thereference voltage derived fromthe laser light leaked throughthe crystal mirror to provideautomatic gain control.

The data system tallies theparticles in each size bin, pro-cesses and displays the data.

Sampleblock

Sampleinlet

Plumbingblock

Pump

Filter

FilterCarbonfilter

Outlet

Bypass valveto set flow

Lasair 110 only

Purgeinlet

Differentialpressure sensorfor flow meter

Figure 6.2

6.4.2 Flow volume

The flow volume for this counteris 1 ft3/min (cubic foot per min-ute) or 28.3 litres per minute.

6.4.3 Size range

The counter is able to detectparticle size from 0.2 µm to 5.0 µm.

86

6.5 Setting Up of Optical Counters

When setting up an opticalcounter, there are certainfeatures, which needs to benoted. The following are someof the important ones.

6.5.1 Flow rate

The flow rate through thecounters can either is fullstream or partial stream. Thereare of course advantages anddisadvantages of both.

a) Full-stream flow rate

• Statistically good as all the air flow passes the probe

• Poor detection of particle sizes

b) Partial stream

• Statistically poor as not all the air flow passes the probe

• Good detection of particle sizes

Full stream Near full streamPartial stream

Probevolume

Sampleflow rate 100 % 5 – 10 % >80 %

Cellwalls

Figure 6.3

87

6.5.2 Condition for Sampling

When particles are sampledfrom a flowing air stream, a difference between the airvelocity in the stream and theair velocity entering the probeinlet can cause a change inconcentration because ofparticle inertia. When thesevelocities are the same, thesampling is isokinetic; other-wise, the sampling is aniso-kinetic.

a) Anisokinetic

The condition of anisokineticsampling is when the meanvelocity of the flowing airstream differs from the meanvelocity of the air entering theinlet of the sampling probe.

Because of particle inertia,anisokinetic sampling cancause the concentration ofparticles in the sample to differfrom the concentration ofparticles in the air beingsampled.

b) Isokinetic

Isokinetic sampling is achievedwhen the probe inlet is pointedinto the direction from whichthe flow is coming and isparallel with that flow, andwhen the mean velocity into theinlet matches the mean flowvelocity of the air at thatlocation.

6.5.3 OPC parameters

During the airborne particleemission measurements, theoperating parameters of theOPC are set as follows:• Air volume: 1.0 ft3/min• Sampling time: 60 seconds• Delay time: 1 second• Measurement time: 5 minutes

6.5 Setting Up of Optical Counters

88

6.6 Test Environment Measurements

6.6.1 Purpose

In order to get correct particlecount results, the test environ-ment, in which the tests arecarried out should have little orno influence on the particlemeasurements. The para-meters, which influence theparticle count, are the particlecount in the:• Environment • Air velocity • Degree of turbulence • Relative humidity

The purpose of measuring thetest environment is to deter-mine whether the givenenvironment is suitable forparticle measurement.

Therefore, the “ground contam-ination level” of the testenvironment has to bemeasured for the cleanroom aswell as the Minienvironment(MENV). The lower the “groundcontamination level”, the moreaccurate the particle measure-ments will be.

6.6.2 Zero-count measurement

Before any test is done, a zero-count measurement is made.When doing a zero-countmeasurement, it is a functionaltest. For this test, a zero-filter isattached to the OPC and thecounter takes measurement forabout 3 minutes. The readingobtained should be zero. Thenthe environment is ready foruse.

89

6.6.3 Base measurement ofairborne particulate in MENV(Figure 6.4)

Similar to the zero-countmeasurement, which is used forthe OPC, the base measure-ment is used for the Mini-environment. The measurementtime is 3 minutes, 1.0 ft3 and atmaximum air flow velocity ofthe MENV. The measurementpoint used is the centre ofMENV on operational level ofcomponent.

6.6.4 VTH measurement(Figure 6.5)

Three major environmentparameters:• Air velocity• Air temperature• Relative humidityare measured in the cleanroomand MENV to ensure the meetthe requirements. We obtainthese readings by using theKanomax Climomaster. This is a precision measuring instru-ment, which has velocity,temperature and humiditysensors.

Simultaneous measurements ofair velocity air temperature andrelative humidity can beobtained with a single probe ofthis instrument.

The Climomaster is set up asfollows:• Data sampling time:

60 seconds• Data sampling interval:

1 second• Number of sampling data: 1• VTH measurement time:

3 minutes

Upon completion of the test,the readings must be within theparameters:• First air flow velocity:

0.45 ±0.05 m/s• Temperature: 20.0 ±2.0 °C• Relative humidity: 55 ±10 %

6.6 Test Environment Measurements

Figure 6.4

Figure 6.5

7.0 Festo Cleanroom Project

91

7.1 Introduction

The objective of the project isto accumulate sufficient know-how in the field of cleanroomapplications, especially for theelectronic industry.

First we had to develop and toset up a suitable test processfor the “Cleanroom Products”.With this procedure we wereable to define the cleanliness ofthe pneumatic products.

92

7.2 Festo’s Collaboration with Fraunhofer and Nanyang Polytechnic

The cleanroom project initiatedby Festo has a collaborationwith Fraunhofer Institute forManufacturing Engineering andAutomation of Germany andNanyang Polytechnic (NYP) ofSingapore.

Festo’s objective is to measurethe particle emission of itsproducts, in order to establishhow far selected products canbe used inside of clean rooms.Furthermore, it is Festo’sintention to gain experience inthe field of particle measure-ments, contamination controlas well as cleanroom applica-tions in general.

Nanyang Polytechnic’s objec-tive is to develop capabilities tosupport the industry’s needs inequipment building for use inclean zones. Furthermore, it isNYP’s intention to gainexperience in the field ofparticle measurements, con-tamination control as well ascleanrooms in general.

Fraunhofer Institute for Manu-facturing Engineering andAutomation department of“Cleanroom Manufacturing”will train Festo and NYP staff oncleanroom technology. Theywill also help to measure someFesto standard products.

93

7.2.1 Scope of cooperation

Festo and NYP will setup aparticle test rig inside thecleanroom at NYP. This test rigwill be suitable for particletesting according to US FEDSTD 209E.

To obtain the necessary know-how, the Fraunhofer Institutefor Production Technology andAutomation will be invited totrain NYP and Festo staff onhow to do particle measure-ments on industrial compo-nents.

Festo will test several of itsproducts in order to establishtheir cleanroom class suita-bility. NYP staff and studentsare invited to participate in thetesting process.

NYP is also allowed to do theirown tests and train their staffand students with the equip-ment.

Festo and NYP will in the futuredo particle testing for thirdparties on a commercial basisbut not in the area of industrialpneumatics.

7.2 Festo’s Collaboration with Fraunhofer and Nanyang Polytechnic

94

7.3 Test Environment and Test Conditions

7.3.1 Cleanroom environment

The cleanroom environment inNanyang Polytechnic is Class1,000 cleanroom (according toUS FED STD 209E). The designof this cleanroom is shown asFigure 7.1, and the layout is acleanroom typical layout.

This is a “ballroom” type clean-room with the area of 120 m2.The air flows in a unidirectionalway from a ceiling of High-Efficiency Particular Air (HEPA)filters down to the floor of thecleanroom. The return airpasses through a return airplenum in the Grey Roomshown in Figure 7.1. The GreyRoom, which is located justbeside the cleanroom, is usedfor service.

Supply air from fans

Ceiling

Hepa

Floor

CleanroomGrey room

Returnair

Utility andequipmentchase

Return airplenum

Windowpanel

Layout of the cleanroom

Figure 7.1

95

7.3.2 Minienvironment

A Class 1 clean Minienviron-ment (MENV) is used within acleanroom to provide the highlevel of protection to productsagainst contamination and ESDevents. This MENV is acleanroom test cabinet withone clear antistatic front paneland three side panels (Figure7.2). The dimension of MENV is1.2 m x 0.6 m internal area andwith 2.2 m height. In order toachieve high cleanliness class,Ultra-low Penetration Air (ULPA)Fan Filter Unit (99.9995 %efficiency on 0.12 micron) isinstalled on the ceiling of theMENV. The unidirectionalsupply of air flows verticallyfrom the Fan Filter Unit (FFU),and the air velocity can beadjusted up from 0.2 m/s to 0.6 m/s.

In accordance with the US FEDSTD 209E, a cleanroom isclassified to be of Class 1 if onlyone particle of the size of 0.5µm or larger can be found in areference volume of 1 cubicfoot (ft3) of the first air (filteredair supplied).

7.3 Test Environment and Test Conditions

Figure 7.2

96

7.3 Test Environment and Test Conditions

7.3.3 Test conditions

Before any test is done, thecomponents need to be pre-pared. The preparation for thecleanroom suitability assess-ment involves the cleaning ofthese components according tothe Festo-SG guidelines“Operating Conditions forCleanroom Tests”. The cleaningsequence is outlined below:• Precleaning by blowing

component surface with ultra-pure compressed dry air.

• Cleaning of component surface using presaturated wipers containing a blend of

isopropyl alcohol.• Final cleaning by blowing

component surface with ultra-pure compressed dry air.

Figure 7.3

It is also important to note thateach time before the tests aremade the required instrumentand environment tests arecarried out as stated in theearlier chapter.

The component is mounted ona test support fixture as shownin Figure 7.3.

97

7.3.4 Measurement technique

During the test, the airborneparticle generated by the com-ponent is measured using adiscrete particle counter (DPC).The measuring range of particlesize is >0.2 µm, >0.7 µm, >1.0 µm, >2.0 µm, >3.0µm, and >5.0 µm areselected.

Figure 7.4 shows the measuringpoint used for checking thecylinders. All cylinders arechecked at this exact point toensure that the measurementsobtained are consistent.

7.3 Test Environment and Test Conditions

Figure 7.4

98

7.4 Standard Operating Procedure

7.4.1 Inward transfer of testsamples

• Decontamination of test samples (inner and outer parts) with isopropanol saturated wipers and ultra-pure compressed dry air.Sequence:1st: cleaning with dry compressed air, 2nd: isopropanol wipers, 3rd: cleaning with dry compressed air

• Bringing the test samples intothe CR environment and MENV

• Arranging the test samples (with gloves, intermediate decontamination, cleaning)

7.4.2 Instrumentation test

Before every measurementchecking following items:• Bringing the test samples into

the CR-environment and MENV

• OPC air flow• OPC laser reference• OPC zero-particle count

(measurement time: 3 minutes, with zero filter attached)

• MENV air flow velocity (maximum power of FFU)

• Relative humidity (measurement time: 3 times for 1 minute with measure-ment intervals of 1 second)

• Air flow velocity (measure-ment time: 3 times for 1 minute with measurement intervals of 1 second)

• Temperature (measurement time: 3 times for 1 minute with measurement intervals of 1 second)

• Base measurements of MENV,airborne particulate contami-nation (measurement time 3 minutes, 1.0 ft3, at maxi-mum air flow velocity of MENV, measurement point in the centre of MENV on opera-tional level of component).

99

7.4.3 Adjustment of theoperating parameters for thetest sample

• Adjustment of operating parameters

• Statement about performed duty cycles at the time of testing

• Documentation of adjustment(sketch or photograph)

7.4.4 Localization measure-ments

Determination of points ofhighest concentrations ofparticle emission (according toVDI 2083 part 8)

• Coarse localization measure-ment

• Localization measurement

7.4.5 Classification measure-ments

• Measurement time:– standard-classification:

100 minutes (according to VDI 2083 part 8) at the measurement points that were found during the localization measurements

– lifecycle test: several days, up to months

• Documentation of measure-ments points (sketch or photograph)

7.4.6 Statistical evaluation

Evaluation according toguideline VDI 2083 part 8

7.4.7 Visual inspection

Visual inspection of testedcomponents (e.g. wear andtear, deposition of lubricantsand particles, product failure …)

7.4.8 Classification

Classification according tostatistical evaluation and visualinspection (see guideline VDI 2083 part 8)

VDI 2083

7.4 Standard Operating Procedure

100

7.4 Standard Operating Procedure

7.4.9 Documentation

Documentation should containfollowing information:• Title• Date• Place• Person responsible• Test environment

– operating parameters– temperature– relative humidity– air flow velocity– particulate concentration in

test environment• Measurement technology

– type – model– detection limits– air flow– description of sample

technique• Sample characteristics

– type– supplier– serial number– component description

• Operating parameters of components– break-in load– running-in time– mounting position– operating frequency– attached load– supply (air power supply,

etc.)

• Description of measurement points– sketches or photographs

• References to applied standards and guidelines

• Documentation – particle concentration at

measurement points– graphical visualisation of

particle emission• Interpretation of results and

conclusion – classification related to

applied standards/guide-lines

– general assessment– potential for optimization

8.0 Cleanroom Products

102

8.1 Introduction

Cleanrooms are essential inindustries, be it electronics orpharmaceutical manufacturing.Products have to be manufac-tured to be used in cleanrooms.With the rapid development ofelectronic industries, more andmore pneumatic products arerequired for cleanrooms.

103

8.2 Reasons

In all automation processes,pneumatics plays an importantrole. This is the same forcleanrooms, pneumatics areused in cleanrooms for thefollowing reasons:• Automation of production

sequence with pneumatics• Lower space requirements

with pneumatics• Lower levels of contamination

with pneumatics• Laminar flow virtually

unimpaired by pneumatics

8.2.1 Benefits

• Avoidance or reduction of particle emissions both with stationary components and inan operating sequences

• Minimization of disturbance factors affecting laminar flow

• Counter measures against possible environmental influences (e.g. acids, aggressive media)

8.2.2 Difference in comparisonwith standard products

The following list is thedifference between thestandard products and thoseused in cleanrooms.

• Generally suitable for unlubri-cated operation

• Cleanroom compatible greaseused when necessary

• Cleanroom compatible markings

• Ducted exhaust ports and connections for air breather ports

• Extraction by means of vacuum where necessary

104

8.3 Basic Principles for Cleanroom Products

It is known that there isn’t a standard or guideline forcleanroom product designavailable.

In order to develop products forcleanroom application, wemainly base on the principle of“avoiding cleanroom contami-nation by preventing particlesgenerated from the compo-nents”.

Products

Cylinders

Valves

Noncontaminant releasing• Air leakage from the piston

rod is sucked back and extracted by vacuum via a additional vacuum suction port on the front cap or barrel (housing)

• Leak-free design principle

• Exhaust air from both mainvalve and pilot valve are released via common exhaust ports

• Breather air from under-side of piston is removed via exhaust ports

• Leak-free design principle

This principle includes thefollowing three aspects:• Noncontaminant release –

very low leakage construc-tion

• Noncontaminant generation –special material, surface treatment and special lubri-cation specification

• Noncontaminant in produc-tion processes – component cleaning and double bag packaging

Noncontaminant generating• Piston rod is made

of corrosion-resistant steel

Noncontaminant in productionprocess

• Cleaning individual compo-nents by ultrasonic cleaning bath

• All components are cleaned and assembled in a cleanroom

• Functional test in a clean-room

• Double-packed in plastic bags in a cleanroom

The above three aspects can beachieved for cleanroom com-patibility by modifying our stan-dard products to cleanroomproducts with some specialfeatures. The general principleis to design an additionalvacuum suction port so that airleakage during operation canbe sucked back and extractedby vacuum.

Products

Air serviceunits

Grippers

Vacuumequipmentothers

Noncontaminant releasing• Regulator: vent air in the

bonnet is sucked through a vacuum connection on an additional ring

• Air filter: drain is discharg-ed from cleanroom via drain guide port

• Air leakage is extracted viavacuum suction port

• Exhaust air is ported to theoutside of cleanroom

• Shock absorber: replace-ment of a new housing with a vacuum port

• Fittings & tubing: air leakage is minimized by using the barbed fittings

Noncontaminant generating

Noncontaminant in productionprocess

• Cleaning individual compo-nents by ultrasonic cleaning bath

• All components are cleaned and assembled in a clean-room

• Functional test in a clean-room

• Double-packed in plastic bags in a cleanroom

Table 8.1 and 8.2 show the basic

principles for pneumatic products in

the cleanroom product range.

Table 8.1

Table 8.2

105

8.4 Production Sequence for Cleanroom Products

This section describes thesequence, how cleanroomproducts are designed andproduced. Basically, themanufacturing of clean roompneumatics is not any differentfrom the design of any otherpneumatic component. It isjust, that special care is taken,to avoid any kind ofcontamination caused by theproduct.

8.4.1 Design 0ffice

Firstly the design of a standardproduct is modified with a viewto cleanroom compatibility.How this is done, was dis-cussed in Chapter 3 of this text-book already.

8.4.2 Assembly

All products are assembledoutside the cleanroom,according to the standardassembly procedures. In veryspecial cases, cleanroomgrease is applied instead of thestandard lubricant.

8.4.3 Testing

Just as any standard product,cleanroom products are tested,concerning their functionality.There is no particle emissiontest conducted for everyproduct.

8.4.4 Cleaning

Before packing all products arecleaned under cleanroomcondition of Class 10,000according to US FED STD 209E.The cleaning is done either bymeans of an ultrasonic bath orwith isopropanol wipers.

8.4.5 Packaging

Packaging is done in antistaticplastic bags. Whereby eachproduct is double packed andsealed. Just as the cleaning, thepackaging takes place undercleanroom condition of Class10,000.

106

8.5 Performance of Cleanroom Products

At present our standard prod-ucts are suitable to be used incleanrooms with CleanroomClass 10.000, with the changeor modification on the design,we can achieve CleanroomClasses up 10 or 100.

107

8.6 Precautions in Operation

8.6.1 Purification of supply air

For the cleanliness of anapplication clean dry air isextremely important. To supplyclean air, we have set up the airsupply as follows:

➔ Absorption dryerAir supply

Grey Room

Regulator(Type: LR)

Filter combina.(Type: LFMBA)

Cleanroom

Solenoid on-offvalve (Type: HEE)➔ ➔ ➔

8.6.2 Piping

Pipes and fitting have a largeinfluence on the cleanliness ofan application. Generallybarbed fitting should beapplied whenever possible.Push-pull fitting are notsuitable for cleanroomapplications, as they tend toleak. Also, the way, how tubesare laid, is important for cleanapplications of pneumatics. Itshould be avoided that tubesrub on any surface.

8.6.3 Notes of set up

The way, how pneumaticcomponents are mounted doesnot directly influence theparticle emission. However, it isan important factor to avoidcross contamination. Meaning,contamination caused byparticles, which are carried bythe air from a less sensitivelocation to a sensitive location.

8.6.4 Operating piston speed

Piston speed and thus theimpact the piston generateswhen touching the end cap of a cylinder, is the most crucialparameter concerning particleemission. The piston speedshould not exceed 0.2 m/s inorder to archive a goodcleanliness.

8.6.5 Solenoid valve manifold

Whenever possible valvesshould not be used in the directvicinity of any sensitiveproduct, although, valves ingeneral only emits littleparticle. It is best to installvalves directly above the floor.

Figure 8.1

108

Festo AG & Co.

Ruiter Strasse 82D-73734 Esslingen

Keyword

What are the points to bear in mind when using Festocomponents?

The specified values for pres-sures, speeds, loads, lateralforces, actuating forces,voltages, magnetic fields andtemperatures should beadhered to at all times and atany operational note observedby the user to ensure thecorrect functioning of theequipment.

All texts, representations,illustrations and drawingsincluded in this publication arethe intellectual property ofFesto AG & Co., and are pro-tected by copyright law.

All rights reserved, includingtranslation rights. No part ofthis publication may bereproduced or transmitted inany form or by any means,electronic, mechanical,photocopying or otherwise,without the prior writtenpermission of Festo AG & Co.All technical data subject tochange according to technicalupdate.