An Evaluation of Sonochemical Surface Modification for ... · PDF fileAn Evaluation of Sonochemical Surface Modification for Electronic Manufacture. ... Epoxy. 5. Other materials

An Evaluation of Sonochemical

Surface Modification for Electronic Manufacture

Dr Andy Cobley

Prof. Tim Mason

The Sonochemistry

Centre at Coventry University

IeMRC

2nd

Annual Conference

5th

September 2007

Sonochemistry Centre at Coventry University “The Home of Sound Science”

AgendaAgenda1.Surface Modification in Electronic Manufacturing

Problems associated with traditional methods

2.What is SonochemistryAcoustic cavitation

Advantages for surface modification

3.Sonochemical Surface Modification of a High Tg

EpoxyWeight loss

Contact Angle

Roughness

Gloss

Adhesion SEM

4. Conclusions for High Tg

Epoxy

5. Other materials tested

6. Lean, Green and Clean Processing?


Traditional Traditional ‘‘WetWet’’

Surface ModificationSurface Modification

Chemistry Time / min Temp / ºCSolvent Swell 5-15 65-85Rinse 2-6Rinse 2-6Permanganate Etch 5-15 75-85Rinse 2-6Rinse 2-6Neutralizer 3 RT-50Rinse 1-2Rinse 1-2

•Relatively long dwell times

•3 stage process

•High Temperatures required

•High energy costs

•Copious rinsing

•High water costs

Example Example --

DesmearingDesmearing

of PCBof PCB’’s or Adhesion Promotion of s or Adhesion Promotion of MIDsMIDs



Surface ModificationSurface Modification

Substrates Chemistry HazardsPCBs, MIDs

other polymersSolvent Swell VOC, flammable

PCBs, MIDs other polymersAlkaline Permanganate

Highly caustic, strong oxidant

ABS Chromic acid Carcinogenic, highly acidic

Ceramics, glass Hydrofluoric acid Causes burns, targets bone

•Hazardous Chemistry

•VOC’s, carcinogens, corrosive

•Environmental and health and safety legislation

•High Waste Treatment costs



Surface ModificationSurface Modification SummarySummary

Traditional surface modification processes characterised by…..

•Long process times

•High temperature baths

•High water usage

•Hazardous chemistry

CAN SONOCHEMISTRY HELP ?


SonochemistrySonochemistryThe effect of sound on the chemistry of a solution

I I I I I I I I 0 10 10 10 10 10 10 10

2 3 4 5 6 7

Human hearing 16Hz - 18kHz

Conventional power ultrasound 20kHz - 100kHz

Extended range for sonochemistry 20kHz - 2MHz

Diagnostic ultrasound 5MHz - 10MHz

THE FREQUENCY RANGES OF SOUND

I I I I I I I I 0 10 10 10 10 10 10 10

2 3 4 5 6 7

Human hearing 16Hz - 18kHz

Conventional power ultrasound 20kHz - 100kHz

Extended range for sonochemistry 20kHz - 2MHz

Diagnostic ultrasound 5MHz - 10MHz

THE FREQUENCY RANGES OF SOUND


Sonochemical Surface ModificationSonochemical Surface Modification Acoustic Acoustic CavitationCavitation

5000 oC2000 ats

bubbleforms

bubble grows in successive cycles

reachesunstable size

undergoesviolent collapse

compression compression

rarefactionrarefaction rarefaction rarefaction rarefaction


5000 oC2000 ats5000 oC2000 ats

bubbleforms

bubble grows in successive cycles

reachesunstable size

undergoesviolent collapse



compression compressioncompression compression




Sonochemical Surface ModificationSonochemical Surface Modification MicrojettingMicrojetting at a solid surfaceat a solid surface

surface cleaningdestruction of boundary layersurface activationimproved mass and heat transfer

boundary layer

solid surface

Collapse at or near a solid surfaceInrush of liquid from one side of the collapsing bubble

produces powerful jet of liquid targeted at surface



boundary layer

solid surface

Collapse at or near a solid surfaceInrush of liquid from one side of the collapsing bubble

produces powerful jet of liquid targeted at surface


Sonochemical Surface ModificationSonochemical Surface Modification MicrojettingMicrojetting

at a solid surfaceat a solid surface

Prof. L.A. Crum, University of Seattle


Sonochemical Surface ModificationSonochemical Surface Modification Generation of Oxidizing Species

Chemicals break down in the cavitation bubble

Sonochemical decomposition of water

H2 O →

Ho

+ OHo

Ho

+ O2

→

HO2o

HO2o

+ HO2

o →

H2 O2 + O2

OHo

+ OHo →

H2 O2

OHo

(Hydroxyl radical) –

short lived

HO2o (Perhydroxyl

radical) –

short lived

H2 O2 (Hydrogen Peroxide)


Sonochemical Surface ModificationSonochemical Surface Modification

• Microjetting– Mechanical/physical attack of surface– Scrubbing/cleaning action– Destruction of boundary layers– Movement of reactants to, and products/debris away

from, the surface• Extreme temperatures and pressures

– Chemical/oxidative attack of the surface due to oxidative species

– Breaking of bonds on surface of material– Chemical reactions on surface


Sonochemical Surface ModificationSonochemical Surface Modification of a High of a High TgTg

EpoxyEpoxy

IsolaIsola

370HR370HR

Tg (ºC)By DSC

180

Dielectric Constant (10 GHz)

3.92

Dissipation Factor (10 GHz)

0.0025

NB Values collected from from Isola

Data sheet


SonochemicalSonochemical

Experimental SetExperimental Set--upup20 kHz Ultrasonic probe

Water in

Water out

Water Jacket

Solution

Sample holder

Sample

Thermostat

•All experiments performed at 40 ºC

•Sonication

carried out in DI water


Process FlowsProcess FlowsSonochemical1. Sonication40 ºC, 4,8,15,30 and 60 minutes2. Cold water rinse, 5 minutes3. DI water rinse, 1 minute4. Dry

Total process time –

10-

66 minutes

Swell and Etch(Rohm and Haas Electronic Materials Products)

1. Sweller

(Circuposit

3302)85 ºC, 10 minutes2. Cold water rinse, 5 minutes3. Cold water rinse, 5 minutes4. Etch (Circuposit

Promoter 3310)85 ºC, 10 minutes5. Cold water rinse, 5 minutes6. Cold water rinse, 5 minutes7. Neutraliser (3% H2

O2

, 3% H2

SO4

)RT, 3 minutes8. Cold water rinse, 3 minutes9. DI water rinse, 1 minute10. Dry

Total process time –

47 minutes


ResponsesWeight lossMaterial removed from substrate

SEMVisual examination of the surface after surface modification

Contact Angle

A measure of the wettability

of a surfaceRelated to surface energy of substrate

AdhesionTape test after electroless

copper

platingGrade 10 –

no metal removed by tapeGrade 0 –

all metal removed by tape

Gloss MeterMeasures % light reflected from a surface.Rougher the surface less light reflected

RoughnessStylus profilometerRa -

the arithmetic departure of the

roughness profile from the mean line


0 4 8 15 30 600.0000

0.1000

0.2000

0.3000

Wei

ght L

oss

(mg/

cm2 )

Time (minutes)


Surface Modification of Surface Modification of IsolaIsola

370HR370HR DI Water, 40DI Water, 40ººCC

Effect of Effect of SonicationSonication

Time on Weight LossTime on Weight Loss

•Weight loss increases with sonication

time –

ultrasound is removing material•Extended sonication

times produces weight loss approximately 50% of swell and etch technique

Swell and Etch -

0.6059 mg/cm2


0 4 8 15 30 6060.0

70.0

80.0

90.0

Con

tact

Ang

le (θ)

Time (minutes)





Time on Contact AngleTime on Contact Angle

•Contact angle decreases with sonication

time –

suggests surface activation•Swell and Etch gives contact angle value of around 70º

-

surface activation similar to 30 minutes sonication

Swell and Etch -

71.6 º


0 4 8 15 30 600.3

0.4

0.5

Rou

ghne

ss (µ

m)

Time (minutes)





Time on RoughnessTime on Roughness

• After 30 minutes sonication

a value of 0.5 is reached which appears to be a maximum•Swell and Etch process produced a relatively low value for roughness

Swell and Etch -

0.3977


0 4 8 15 30 600.5

1.0

1.5

2.0

Glo

ss (%

)

Time (minutes)





Time on GlossTime on Gloss

•Gloss meter results are all very low •Gloss meter readings tended to drop with sonication

time -

minimum at 30 minutes•Swell and Etch sample had a reading of 1.9% suggesting a smoother topography.

Swell and Etch -

1.9%


0 4 8 15 30 605.0

6.0

7.0

8.0

9.0

10.0

Adh

esio

n (G

rade

)

Time (minutes)





Time on Adhesion after Time on Adhesion after ElectrolessElectroless

CopperCopper

•Highest adhesion grading occurred with the sample sonicated

for 30 minutes •The control sample failed the tape test resulting in an adhesion

grade of 1

Swell and Etch -

1.0


IsolaIsola

370HR 370HR SEM Analysis SEM Analysis --

Magnification x 500Magnification x 500

As Recieved30 minutes Sonication

Exposed glass

No debris

Swell and Etch

Exposed glass

Debris




370HR370HR CONCLUSIONSCONCLUSIONS

1.

Surface modification of this high Tg

Epoxy can be achieved by the application of ultrasound through DI water at 40ºC

2.

Optimal sonication

time for adhesion is 30 minutes3.

30 minutes sonication

time also corresponds to highest

roughness and lowest gloss. SEM analysis shows glass exposure but no debris.

4.

2 and 3 suggest a rough, debris free surface is important for optimal adhesion

5.

Swell and Etch samples gave high weight loss, but roughness and gloss data suggest a smooth surface.

6.

SEM analysis indicates a lot of debris -

probably the reason for poor adhesion

7.

Swell and Etch samples may be over-etched


Sonochemical Surface ModificationSonochemical Surface Modification Other materials testedOther materials tested

Cycolac

S705 –

ABS/PC

Noryl

HM4025 –

Polyphenylene

ester / polystyreneCourtesy of Moulded Circuits

Ceramic Material

Other materials under investigation:

Glass –

optical circuits

Coated ‘paper’

–

printed/plastic electronics


NorylNoryl

HM4025HM4025 DI Water, 40DI Water, 40°°CC

, 60 minutes, 60 minutes


As received 20 kHz Ultrasonic Probe


CycolacCycolac

S705 ABS/PC S705 ABS/PC DI Water, 40DI Water, 40°°CC



As Received 20 kHz Ultrasonic Probe


Ceramic Material Ceramic Material DI Water, 40DI Water, 40°°CC



AS received 20 kHz Ultrasonic Horn


Sonochemical Surface ModificationSonochemical Surface ModificationA route to Lean, Green and Clean

Manufacturing ?

LEANOne stage process

GREENLower temperatures, reduced energy costs, less rinsing, lower

waste treatment costs.

CLEANNon-hazardous chemistry


The Sonochemistry Centre at Coventry UniversityFaculty of Health and Life Sciences

Coventry UniversityCoventry, CV1 5FB, UK

www.coventry.ac.uk/sonochemistry

CONTACT DETAILSCONTACT DETAILS

[email protected] - +44 (0) 24 76 888 624

Mobile – 07706 955 901Fax +44 (0) 24 76 888173


Sonochemical Surface ModificationSonochemical Surface ModificationProject funded by

Industrial Partners

MOULDED CIRCUITS LTD

Laminate supplied by………


Thank youThank you

Any Questions ?

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An Evaluation of Sonochemical Surface Modification for ... · PDF fileAn Evaluation of Sonochemical Surface Modification for Electronic Manufacture. ... Epoxy. 5. Other materials