China SSL 2012

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Technical discussion of the mechanisms, rates, and causes of color shift and light depreciation in LED Lamps

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China SSL 2012

  1. 1. Designing and Delivering Quality in SSL mark_mcclear@cree.com November 5, 2012
  2. 2. SSL Quality Begins with the LED Lamp • LED lamp types, construction • Sources of light degradation • Applications impact • Right LED lamp for the application Copyright © 2012 Cree, Inc. pg. 3
  3. 3. An LED Lamp is a Complex SystemLED Chip: – Determines raw brightness and efficacyPhosphor system: – Determines color point, color quality and color point stabilityPackage: – Protects the chip and phosphor – Helps with light and heat extraction – Primary in determining LED lifetime Copyright © 2012 Cree, Inc. pg. 4
  4. 4. Different LED Lamp Architectures Ceramic Substrate, Silicone Dome Large COB array, Al, Ag Substrate Molded Plastic Package, Silver Lead Frame “High Bright” LEDs designed for consumer applications Copyright © 2012 Cree, Inc. pg. 5
  5. 5. Different Sources of Light Degradation2. Phosphor Degradation 3. Silicone Encapsulant Degradation 1. Chip Degradation 3 Sources4. Al, Ag Substrate Degradation 3. Silicone Encapsulant Degradation 2. Phosphor Degradation 1. Chip Degradation 5 Sources 5. Plastic Degradation 2. Phosphor 3. Silicone Encapsulant Degradation Degradation 4 Sources 1. Chip Degradation 4. Plastic Degradation Copyright © 2012 Cree, Inc. pg. 6
  6. 6. LED Chip Degradation (Generic, all types) 100% 90%% LF 80% 70% Time (hours) 50,000 • LED chips actually get brighter over the first 10- 20k hours of operation • Real LED chip degradation is very, very slow… Copyright © 2012 Cree, Inc. pg. 7
  7. 7. Phosphor Degradation (Generic, all types) 100% 90%% LF 80% 70% Time (hours) 50,000 • Phosphors are chemically very stable over time also Copyright © 2012 Cree, Inc. pg. 8
  8. 8. Possible Sources of Phosphor Degradation Illuminated Object Phosphor LED Chip Phosphor coating is put on chip, generally does not degrade Phosphor can peel at the edges, let less blue light through to be converted – color shift, loss of light Micro-delaminations can occur over time, thermal stress – further loss of light, potential for color shift Copyright © 2012 Cree, Inc. pg. 9
  9. 9. Encapsulant Degradation (Generic, all types) 100% 90%% LF 80% 70% Time (hours) 50,000 • Rapid initial degradation (first 5k hrs), stable long term Copyright © 2012 Cree, Inc. pg. 10
  10. 10. Encapsulant Degradation Source• Silicone encapsulants theoretically cross-link like this: R R R R Siloxane Si O Si O Si O Si O (R2SiO)n R R R R• Silicone encapsulants actually cross-link like this: R O R R R R O R R O Si O CO Si O Si O Si O Si O Si Si O O CH3 O Si Si O Si Si O SiO O CH3 Si O Si O Si O Si O R CH3 Si R R R CO2 R R CO R CO2 Si R R R R Si R R• …and a lot of *stuff* comes off them…• Weight loss can slightly reduce RI, long stranded polymer chains can turn brown/absorb light… Copyright © 2012 Cree, Inc. pg. 11
  11. 11. Plastic & Metal Substrate Degradation 100% 90%% LF 80% 70% Metal (Al, Ag) Plastic Time (hours) 50,000 • Similar degradation profiles, plastic degradation is typically a bit more pronounced Copyright © 2012 Cree, Inc. pg. 12
  12. 12. Plastic & Metal Degradation Mechanism • This LED lamp architecture depends on metal substrate and plastic sidewall reflectivity • Plastic can degrade under photon bombardment and thermal stress • Metal can tarnish due to application environmental conditions (moisture, sulfur, etc.) • Both can reduce LED lamp light output… Copyright © 2012 Cree, Inc. pg. 13
  13. 13. Plastic Degradation in Low Cost Packaging 100% 90%% LF 80% 70% Plastic Time (hours) 50,000 • Plastic degrades quickly and blocks light in this package architecture • No metal to reflect the light Copyright © 2012 Cree, Inc. pg. 14
  14. 14. Combined: Ceramic/Silicone Dome 100% 90%% LF 80% LED Chip Phosphor 70% Encapsulant Combined 3 Sources Time (hours) 50,000 • Typical LM-80 performance at 85°C, med-high current density (chip size dependent) Copyright © 2012 Cree, Inc. pg. 15
  15. 15. Combined: Plastic/Metal LF, Substrate 100% 90%% LF 80% LED Chip Phosphor 70% Encapsulant Metal (Al, Ag) Plastic Combined 5 Sources Time (hours) 50,000 • Typical LM-80 performance at 85°C, med-high current density (chip size dependent) Copyright © 2012 Cree, Inc. pg. 16
  16. 16. Combined: “High Bright” LEDs 100% 90% LED Chip Phosphor% LF 80% Encapsulant Plastic Combined 70% 4 Sources Time (hours) 50,000 • Typical LM-80 performance at 85°C, med-high current density (chip size dependent) Copyright © 2012 Cree, Inc. pg. 17
  17. 17. Typical LM-80 Performance by Lamp Type 100% Ceramic/Silicone Dome 90%% LF 80% Plastic, Leadframe / COB 70% “High Brightness” LEDs 5mm LEDs Time (hours) 50,000 • Ceramic/Si Dome LED lamp architecture generally have superior Lumen Maintenance vs. Plastic/Metal architectures • Both can be Lighting-class, always demand the LM-80 report • HB LED Lamps – demand the LM-80 report • 5mm lamps – LM-80 is NOT defined Copyright © 2012 Cree, Inc. pg. 18
  18. 18. Light Degradation at the Application Level Time zero 1000 hours Brightness Color Copyright © 2012 Cree, Inc. pg. 19
  19. 19. This may be OK for some consumer applications☼ BrightnessCopyright © 2012 Cree, Inc. pg. 20
  20. 20. ☼ BrightnessCopyright © 2012 Cree, Inc. pg. 21
  21. 21. ☼ BrightnessCopyright © 2012 Cree, Inc. pg. 22
  22. 22. We don’t typically have this kind ofcontrol on our lights…☼ BrightnessCopyright © 2012 Cree, Inc. pg. 23
  23. 23. ☼ HueCopyright © 2012 Cree, Inc. pg. 24
  24. 24. ☼ HueCopyright © 2012 Cree, Inc. pg. 25
  25. 25. ☼ HueCopyright © 2012 Cree, Inc. pg. 26
  26. 26. No remote control for this either… ☼ HueCopyright © 2012 Cree, Inc. pg. 27
  27. 27. Is it OK for this Application?? Probably for some markets, probably NOT for others Copyright © 2012 Cree, Inc. pg. 28
  28. 28. Very Application Dependent As Installed 3 Months Later You don’t want to be that guy… Copyright © 2012 Cree, Inc. pg. 29
  29. 29. Select the Right LED For Right SSL Application • LED lamps are complex systems with different parts XLamp XP-G2 XLamp XP-G XLamp XP-E XLamp XP-C that degrade at different rates XLamp XLamp XLamp XLamp XLamp XLamp XB-D XPE-HEW XT-E XTE-HV XM-L XML-HV • Quality and reliability in SSL applications can be very dependent on the XLamp MP-L XLamp MT-G2 XLamp MT-G XLamp MC-E LED lamp architecture • High Bright and 5mm XLamp MX-6 LEDs should not be XLamp ML-E/C/B XLamp CXA2011 XLamp XLamp used for most CXA1507/12 CXA2520/30 Lighting Applications Copyright © 2012 Cree, Inc. pg. 30

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