LED EVENEMENT 2013

www.osram-os.com LED EVENEMENT 2013

AGENDA 1. Identify the Nature of the Potential Faillure 2. Why do we need to bin LEDs? 3. Colour binning @ OSRAM Opto Semiconductors 4. Mixing of LEDs the Brilliant Mix concept 5. Mixing of LEDs the Mix-To-Match concept 6. Experiment and conclusion 2

Producing LEDs is like baking a cake...... with a quite complicated recipe... 3

Producing LEDs is like baking a cake...... with a quite complicated recipe... USING LEDs: need to follow essential recipes to get best results 4

Producing LEDs is like baking a cake...... with a quite complicated recipe... Faillure Modes: USING LEDs: Irreversible need to follow essential recipes to get best results current max min product specification device capability Reversible AVOID Undesired Behaviour min temperature max 5

Producing LEDs is like baking a cake...... with a quite complicated recipe... Faillure Modes: USING LEDs: need to follow essential recipes to get best results AVOID Undesired Behaviour current max min min product specification temperature device capability max Irreversible: - Aging - Out of SOA Corrosion EOS I > Imax Accelerated Aging Reversible: - In SOA Vf, Colour shift Colour / Brightness appearance out of spec Samples => full production 6

Degradation Mechanisms of LEDs During the lifetime of an LED we can observe different phases of aging relative luminous intensity [%] 100 50 initial degradation (positive or negative, chip related) package aging Time when package aging is finished depends on the LED driving conditions. overstress accelerates package degradation stable phase Example aging curve Depends on the LED Design (e.g. reflector) long-term chip-degradation time [h] (linear) 7

Degradation Mechanisms of LEDs The different phases are influenced by different factors: Degradation Influencing Factors Chip Degradation (Initial and long term) Converter degradation Package degradation Temperature Current Temperature Current Humidity Temperature Short wavelength 8

The production of LEDs is similar to cooking... The challenge is to generate only a very small variation in the production. Exemplary production distribution CIEy 0.43 0.42 0.41 0.4 0.39 0.38 0.37 9R 9S 9T 9Q 9P 8R 8S 8T 9O 8Q 8P 7R 7S 7T 8O 7Q 7P 7O 6Q 6R 6S 6T 6P 6O 5Q 5R 5S 5T 5P 5O 4Q 4R 4S 4T 4P 4O 0.4 0.42 0.44 0.46 CIEx Colour Distribution Customer s target 0 80 90 100 110 120 130 Flux Distribution CIEy 0.43 0.42 0.41 0.4 0.39 0.38 0.37 9R 9S 9T 9Q 9P 8R 8S 8T 9O 8Q 8P 7R 7S 7T 8O 7Q 7P 7O 6Q 6R 6S 6T 6P 6O 5Q 5R 5S 5T 5P 5O 4Q 4R 4S 4T 4P 4O 0.4 0.42 0.44 0.46 CIEx Colour Distribution 0 80 90 100 110 120 130 Flux Distribution 9

Why do we need a colour binning and a tight selection of colour coordinates for LEDs? Lamp-to-lamp variation Applications are very sensitive to small differences in color especially if: low (reflected) luminance is involved (like wallwashing) large plain surfaces are visible (signage / backlighting) 10

Background for SSL colour binning: The well known experiment from MacAdam MacAdam asked the test person at different colour coordinates to vary the colour a little bit until a colour shift is visible. Based on the results he generated a plot of the resulting ellipse parameters g11 g12 g22 and a formula where: C = 1: standard deviation of colour matching (SDCM) C = 2: the chromaticity is just noticible different 11

What are the existing solutions in the LED industry to meet tight colour requirements? LED technology has developed several approaches for a solution of the problem: In-line testing and correction Additional production steps can reduce color spread Binning and selection Logistics at LED maker to deliver different bins to different customers Huge stock / No stock / delivery risk / innovation risk Multi-color systems and color steering RGB or Brilliant Mix steering involves complex electronics and sensors Mixing of LEDs in multi-led systems 12

Option 1: Fine binning Selection is adaptable to customer requirements The OSRAM OS fine binning system is using the ANSI colour bins and divides it into smaller bin of a size around 2-3 SDCM. 13

Option 2: MacAdam binning One colour coordinate for all! The OSRAM OS Ellipse binning is using the MacAdam ellipses as boundary for the bins. 14

Option 3: Meeting the colour coordinate requirements by mixing 3 coloured LEDs Brilliant Mix: The combination of a greenish white LED, a blue or bluish white LED and a red LED 15

Benefit of brilliant mix: high efficacy & colour rendering index over a large CCT range 16

Applications for white tune ability with Brilliant Mix and arctic white Circadian Rhythm, Simulate Skylight Offices Schools Nursing Shift Workers Residential, etc 4500 K 2700 K 3000 K Situative Illumination with the right CCT Retail Museum Theater, etc 4000 K Planckian Curve 3500 K Challenges: Colour Mixing Colour Control 17

Option 4: The Mix to Match concept mixing different white M i x t o M a t c h Smart Mixing of Single LEDs Match the customer s requirements 18

The Mix to Match concept mixing different white LEDs to meet the colour target Luminaire with OSLON SSL LCW CRDP: => Mixing of different bins / e.g. 3000K 9 8 7 6 4 5 Possible combination: KS6S-KS8R-KR6T-KR5T LED4 LED3 R S T Fixture Colour Specification KR KS LED1 LED2 Delivery of right combination within a shipping box to eliminate stock risk 19

Experiment: Setup of linear luminance and colour homogeneity measurement Colour luminance camera Measurement points Variable distance to diffuser = r e.g. 8-40mm Evaluation of 10 LEDs Pitch LED to same LED = 30mm (LED sequence pitch) Pitch LED to next LED = 10mm (LED pitch) 20

Experiment: Visualization of brightness and colour homogeneity In the beginning, the differences in colour and brightness are clearly visible. With increasing distance between LED and diffuser, homogeneity improves significantly. r=8mm r=10mm r=12mm r=16mm r=20mm r=25mm r=30mm r=40mm 21

Experiment: Setup of linear luminance and colour homogeneity measurement r=16mm r=30mm Luminance Variation Luminance Variation Average Luminance Luminance Average Luminance Luminance 120000 60000 100000 50000 Luminance in cd/m² 80000 60000 40000 Luminance in cd/m² 40000 30000 20000 20000 10000 0 0 LED1 LED2 LED3 LED4 LED5 LED6 LED7 LED8 LED9 LED10 LED1 LED2 LED3 LED4 LED5 LED6 LED7 LED8 LED9 LED10 LED Position LED Position MacAdam Ellipses in CxCy 5 Step MacAdam CxCy 4 Step MacAdam CxCy 3 Step MacAdam CxCy 2 Step MacAdam CxCy MacAdam Ellipses in CxCy 5 Step MacAdam CxCy 4 Step MacAdam CxCy 3 Step MacAdam CxCy 2 Step MacAdam CxCy Cy 0,390 0,385 0,380 0,375 0,370 0,365 0,360 0,355 0,350 0,345 0,340 0,350 0,355 0,360 0,365 0,370 0,375 0,380 0,385 0,390 Cx Cy 0,390 0,385 0,380 0,375 0,370 0,365 0,360 0,355 0,350 0,345 0,340 0,350 0,355 0,360 0,365 0,370 0,375 0,380 0,385 0,390 Cx 22

Experiment: Setup of linear luminance and colour homogeneity measurement 1,000 Homogeneity Ratio in Lv_min/Lv_max Homogeneity Ratio Lv_min/Lv_max 0,900 0,800 0,700 0,600 0,500 0,400 0,300 0,200 At a distance of approximately 1,5x LED pitch, the luminance or illuminance homogeneity of the system may be sufficient for most applications. The bigger the distance, the better the homogeneity. 0,100 0,000 0,010 0,009 r = 0 r = 8 r = 10 Max r = du'v' 12 and r = SDCM 16 r vs = 20 distance r = 25 r = 30 r = 40 10 9 du'v' 0,008 0,007 0,006 0,005 0,004 0,003 0,002 0,001 8 7 6 5 4 3 2 1 SDCM At a distance of approximately 1x LED Sequence pitch, the white colour homogeneity of the system may be sufficient for most applications. The bigger the distance, the better the homogeneity. 0,000 r = 0 r = 8 r = 10 r = 12 r = 16 r = 20 r = 25 r = 30 r = 40 0 23

SUMMARY Understand the key influencing factors and nature of potential Faillures Identify and avoid reversible Faillures Minimise influencing factors for irreversible Faillures Tight colour requirements are typical for the SSL market More and more applications become very sensitive to different colours The tight colour requirements can be fulfilled by: OSRAM OS Fine Binning OSRAM OS MacAdam Binning Brilliant Mix Mixture of 3 coloured LEDs Mix-to-Match Mixture of white LEDs In order to achieve a homogeneous appearance in luminance and colour, a distance to the diffuser of 1-1.5 times the LED pitch is necessary. 24

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