LED Lightfare 08 (1)

8/6/2019 LED Lightfare 08 (1)

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LED Technologyfor Lighting Folks

May 26, 14.00 to 17.00

Kevan Shaw BSc IALD PLDA MSLL

1Tuesday, 27 May 2008


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Learning Objectives

Understand the Manufacturing process of LEDs and theconsequences for specific availability of LEDs in the market

Develop the ability to work out real life performance of LEDsand LED products from marketing information

Critically asses suitability for lighting tasks and create meaningfulspecifications



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What is Solid State Lighting?

Conventional Methods of converting electrical energy to light:

Heating up bits of wire

Passing Electricity through gas at near vacuumPassing Electricity through gas above atmospheric pressure



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How About LEDs

Passing Electricity through small amounts of crystalline solids

Solid State device

Works well with other semiconductors

Initially used for panel indicatorsDiscovered in 1962 by Nick Holonyak

In 1963 he predicted white LEDS with 10X efficiency ofIncandescent



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Early LED colour

Initially red mass produced from 1969GaAsP Gallium Arsenide Technology

produced red, amber and yellow

early green produced by IR and phosphor

GaAIA Gallium Aluminum Arsenide Highbrightness red LEDs from 1984

Shuji Nakamura of Nichia 1993InGaN Indium Gallium Nitride Technology

produced blue and green

Allowed development of White LED



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Current Technology

Based on InGaN and AlAnGaP

Many colours possible

Colour varies with growth temperature of active layer

Efficiency drops in GreenDifferent compositions behave differentlyReds and ambers have shorter life and greater colour shifts

Blues more stable, UV most stable



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Construction of LEDs

Standard 5mm LED

Epoxy body sometimescolored

Leads identified for polarity

Reflector maximises lightoutput

Die, semiconductor thatemits light



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Construction of LEDs

High output LEDs

Large die with reflector

Mounted to Slug heat sink

Leads exit to side clear of light path

Moulded lens gathers and directs light

Various distribution patterns

Many different packages



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Heat Issues

Large heat sink necessary

Limit to efficiency of energy transfer

Contained energy becomes heat

Effective efficiency between 10% and 25%Largest surface area to volume most efficient

Shape important due to light trapped by total internal reflection

Smallest dies are most efficient but create least lumens



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LED Colour

Each type of LED emits light in a narrow band width

Good for saturated colour

Limited for RGB mixed white



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White LEDs

Fluorescence; uses blue die with phosphor

Combination of Blue from die and Yellow from phosphor givesvisual white

Colour not even across LED

Warmer colours less efficient



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Phosphor technology

Best is Itrium Aluminium Garnate Cerium

Produces broad spectrum yellow

90% efficient converting blue to yellow

Deficient in Red

Strontium Sulphide EuropiumProduces increased red

Much less efficient

Can create pink tinge in 2700K range

Importance of even thicknessConsistent colour

Match binning of phosphor with LED

Recent development of phosphor wafers or better control ofthickness



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Spectral Distribution of White

Cool White, 5000K

Warm White, 3500K



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Ranges of White



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White Light LEDs

Research goal to create white light directly from dieZnSe (Zinc Selenide) is a candidate technology not high output

Development as Zinc Oxide nanostructure semiconductor RGB



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LED Manufacturing Stages

Reasons for product variation

The Wafer

The Die

The Package



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The Wafer

Disk of the crystalline material that forms semiconductor

Grown on mineral substrate: EpitaxySaphire, Silicone Carbide 2 or 6 diameter

Aim to use 12 Silicone for economy

Tightly controlled conditions to achieve uniform resultFirst layer grown at 1000C

Second at 700C

Final at 1000 C

Risk of changes to middle layer

Substrates flexVaries thickness of layers

Process takes 5 to 6 hours



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Inspection and Measurement

Initial assessment of manufacturing success

Visual Inspection



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The Wafer

Wafer Maps



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The Die

Wafer literally diced like carrots!

Dies binned

For colour (chromaticy)

For forward voltageFor output



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Packaging

Connections made to die

Die inserted in package

Many dies in same package

Device tested for:forward voltage

colour (chromacity)

lumen output

LEDs then Binned



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Binning

Much discussed aspect of LEDs

At end of production line measurements madefraction of a second

device at room temperature 25C

fully automated processFirst stage of quality control

possibly the most important

Aspects tested:

ColorLumen Output

Forward Voltage



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Heat Issues

Temperature in diedetermines LED survival

determines operating life

determines light output

determines efficiencyHigher the temperature

lower the life

lower light output

lower the efficiency

Critical temperature much lower than conventional lampsTH lamp pinch 350C

LED internal temperatures 100C to 150C absolute maximum depends onchip



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Who Does What?

All stages protected by patents that affect final product

Multistage process undertaken by different companies

When specified, LED usually already in fitting

Quality and performance depends on integration in fitting

Fitting Manufacturer dependent on electronic componentsuppliers stock availability

Stock availability depends on manufacture results

Forward selling to favored customers



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Standards

Manufacturers have failed the specifier and end user

Manufacturers create own standardsmeasurement

binning

specification criteriaWe have to learn to interpret information presented in different

formatsdo your own research!



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Technology changes

New chips available last year show 2X efficiency gain

This is after 2-3 years of slow change

New technology, flip-chip

Substrate removed from die almost doubles light emitting area

Emitting Surface now at top of chip

Good package and reflector design allows this light to beemitted usefully

Further major increases will require this kind of technicaladvance.

Internal Quantum efficiency now 80% Blue 20% Green 50% Red



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OLEDs

Use organic compounds rather than crystalline

Potentially simpler to manufacture

Printing technique allows for complex patterns or arrays

Flexible substrate:Incorporate in cloth

Roll up light fixtures!

Technology development:Focused on flat panel displays & TVs

Lighting work funded by Govt.



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OLED issues

Limited life of organic material, 14,000 hours for blue

Sensitive to moisture and oxygen, sealing limits life

Current efficiencies 10Lm/W to 20LmW same as incandescent!

As power goes up colour goes green!

CRI currently in 70s at best



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OLED State of the Art

At Frankfurt Light and BuildOsram prototype product

Ingo Maurer fixture



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OLED Opportunities

Flexible and not size limited

Possibility for complex arrays, colour/ pattern changing

Simple printing techniques, potentially cheap production

Transparent substrates, at last the disappearing light-source

Possibility for combining light and photo-voltaic



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Continuous Improvement

Another problem dressed up as an advantage

Time scale of architectural projects longer than time forchanges in LEDs

Specified products frequently improved with new devices or

same device with improved outputCan create design problems with balance of light levels



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State of the Art

Best bins of best LEDs achieve efficiency of approx. 60LmW

Highest output stock available LEDs produce:Warm White Cree 73 Lm X 0.85 temp correction X 2.1 current = 130 Lm @1A

Cool White Cree 107 Lm X 0.85 temp correction X 2.1 current = 191 Lm @1A

Warm White Luxeon 130Lm X .87 temp correction = 113Lm @1.5ACool White Luxeon 100Lm X .87 temp correction = 87 Lm@ 1A

Stock of best LEDs expensive and limitedFavoured markets, automotive etc

Forward purchasing, big companies

Stock Holdings:Luxeon Rebel

Luxeon K2TFFC



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Questions?



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LED Performance Data

Mostly measured at junction temperature of 25CData samples taken on a pulse of power too short to heat chip

Results in overstatement of performance

Similar to tests for binning

Bins match published criteriaBins DO NOT match at operating conditions

Fitting manufacturers must re-bin at operating temperaturesOut of tolerance LEDs a problem

Products made in batches that match, but each batch differs

Difficulty in replacing faulty fittings to match originals



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Bases of Measurement

Light Output : LumensBased on Human visual response V() Curve

Colours in narrow wavelengths dont fit well

Apparent output greater than indicated by measurement

Black PhotopicGreen Scotopic


C


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Colour Rendering Index

Originated in 1930s by CIEComparison between Black Body Radiator and Test Source

8 medium saturated colour samples 3 saturated, skin and leaf green

Range of colours selected for general illumination,

works very well for fluorescent sourcesDoesnt work well for LEDS

National Institute of Standards and Testing, Yoshi OhnoProposal for new measure Color Quality Scale (CQS)

Based on Saturated samples matched with source at same Color

Temperature

Test patch colours used for CRI


H D R l L f


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How to Determine Real LifePerformance

Manufacturers data not in common format

Simple fitting, 3W LED emergency light- 60lm (min!) @ 25 driven at 700ma

- Temperature de-rating :

- with small heat sink at 48C assuming 16C/W Thermalresistance of package gives Tj 90C = 78% = 47Lm


H D i R l Lif


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How to Determine Real LifePerformance

Manufacturers data not in common format

Simple fitting, 3W LED emergency light- 60lm (min!) @ 25 driven at 700ma

- Temperature de-rating :

- with small heat sink at 48C assuming 16C/W Thermalresistance of package gives Tj 90C = 78% = 47Lm

Fitting submitted to test housemeasured output 39.4 lm driven at 700ma

LED only operating at 13lm/W



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LED lif


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LED life

Early promises of 100,000 hours were wildly optimisticSome effort to standardize through ASSIST (Alliance for Solid

State Illuminations and Technologies)

For illumination life is to 70% of initial Lumens

For display life is to 50% of initial Lumens


O ti


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Optics

LEDs have built in basic optics.Lambertian distribution

Useful light distribution provided by separate optical elementsTypical distributions, spot, medium, wide and oval

Each type of LED requires unique opticsEach LED in fixture requires its own optic

Mounted at manufacture, not interchangeable


O tics


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Optics

Multiple optic units simplify manufactureTertiary optic to vary distribution

Specialized optics for particular applications


Environmental Issues


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Price per lumen of LED exceeds all other lightsource

$25 per KLm now, target for widespread adoption $5 per KLm

Incan less than $1 KLm, Fluro $8 KLm Retail Prices

revenues consumed by continuous development

Additional cost must be argued on basis of

low maintenancelow energy in use

System has finite lifenot always determined before installation

whole system will require replacement at end of life

- Issues with WEEE for disposal and re-cycling


Energy Efficiency


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Energy Efficiency

Much emphasis on energy in use to exclusion of other aspectsExample showed real world energy efficiency of 3 LmW!

LEDs mostly Low Output for Low Energy

Announcements of LEDs achieving 130 LmW in lab tests

No data provided to protect intellectual propertyconclusion that only very small or highly cooled LEDs can be this

efficient

Order codes exist for 100 LmW chip at Tj25C

at Tj 90C = 80lm from data sheetavailable chips not to special order are 74 Lm/W at Tj 25C

at Tj 90C = 58lm therfore 58lm/W which is reasonable


Manufacturing Issues


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Manufacturing Issues

Form factor of LEDs vary by manufacturer and by technologylimited interchangeability

fitting manufactures constantly need to redesign fittings and circuitboards

Life of fitting determined by life of LED or Driverlife variable over wide range

LEDs not individually replaceable

technology shorter life than fittings

LED availability variable

Preferred supply, automotive and aeronauticsProduction variable


LED Fixtures


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LED Fixtures

Manufacturers do different things as well!Board production

Pick and place machines

Manual Assembly


Fixtures and Power Supplies


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Fixtures and Power Supplies

High degree of manual assemblyTesting also manual and basic


Quality Control


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Quality Control

Vital part of the processLED binning for colour

LED binning for output

Optical Alignment


Determining Responsibility


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Determining Responsibility

Impossible to determine bin of LED installed on boardLED manufacturer cannot control thermal design of fittings

Light output, colour and life depend on thermal and electronicdesign

Quality and warranty claims difficult to resolveRectification frequently only possible by total replacement of

fitting


The State of the Art


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The State of the Art

Acceptable efficiencies for General Lighting applicationsWide range of output and efficiencies for each device

No way of determining Bin Specification for installed device

Cost versus Output for different bins of same LED

Information still requires working out to determineperformance

Poor fitting output data for most manufacturers


Lamp Replacement Products


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Lamp Replacement Products

Is this a good idea?MR16 replacement 8W 240Lm

Down-light retrofit 18 X 1W LEDs

LED fluorescent replacement

None match full luminouscharacteristics of lamp!



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How to Specify


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How to Specify

Start with Lightsource - what do you want to achieve?White Light - Single source

Colour temperature?

Colour quality, acceptable Bin Range

Acceptable variability, Direct view ? Mixed output?White Light - Multi colour

Colour appearance

Colour rendition

3 source RGB or 4 source RGBA

Colour MixingSaturated colours RGB

Pastel colours or accurate matching RGBA or RGBW

Single colour

Bin specification.53Tuesday, 27 May 2008


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System Design


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y g

Performance specification:Operating conditions

climate, particularly for outdoor fittings

Installation, insulated voids? Airflow around fitting?

Visible outputFixtures lighting same surface?

Fixtures directly viewed?

Control systemStandard protocol? DMX

Compatible control gear

Describe operation in detail

MaintenanceFuture availability of fittings and LEDs?

Are fittings repairable55Tuesday, 27 May 2008

Controllability


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y

LEDs easy to control - they arean electronic component!

Facades of light easy to do

Imagery allows architecture to

change day and nightReactive and interactive

surfaces, walls and ceilings

LEDs deliver colour easily andefficiently compared withother light sources


The Future


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Field of light products much more likely to be successfuloptimizes use of LED and existing backlight technology

opens possibilities for fittings not to be rectangular or circular

no longer are fitting sizes restricted by set dimensions of lamps

First product recall,High efficiency LEDs recalled from fittings manufacturersProduction halted for 4 months

Line voltage LEDsSeol semiconductor Acriche

2W & 4W 120V and 230V warm and cool white30LmW to 40 LmW headline efficacy

No transformer losses

Simplified Wiring


The Future


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Multi colour chips on same wafer - White by color mixingComplex circuits on chip - Acriche?

Zinc Oxide Nanotechnology Semiconductor

LED materials can also produce energy from light

LED detectors / emittersDevelopment of Photovoltaics using InGaN junctions


Conclusion


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LEDs increasingly common in lighting applicationsThey remain the most complex light-source to design and

specify

Manufacturers are guardians of knowledge

Big players potential to monopolize design to installation

Professional Lighting Design community must learn more

Personal research and demanding information from suppliers

Professionals must determine the suitable light-source for everyapplication

LEDs will never be the universal light-source for all applications



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Thank you

and have fun with light!


Index


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About SSLLED Manufacture

Who Does What

Continuous improvement

StandardsReal Life Performance

LED Life

Technology Changes

The Future


White Light LEDs

Conclusion


Documents

LED Lightfare 08 (1)