1. XLamp XR-E Lighting-Class LED Lumen Maintenance July 2009

5. LED Lumen Maintenance History <1990 LEDs were used as indicators. Lifetime did not matter too much. 2008 IES LM-80-2008 is published. 2009 Cree publishes reliability white paper (T AIR ). 2001 Lumileds (Philips) introduces first High Power LED. Lifetime testing gets more serious. 2004 LRC/ASSIST publishes first work on the topic. Basic science understood. 2006 LRC/ASSIST publishes ASSIST recommends test procedure for lifetime testing of High Power LEDs, which becomes the basis for IESNA LM-80-2008 standard. 2007 Philips Lumileds publishes white paper, extending the knowledge of the industry on the topic (I F ). 1990’s LEDs used for traffic signals and exit signs. First basic studies on LED lifetime performed.

6. LED Lumen Maintenance Critical Parameters 4. I F Forward Current / Drive Current 1. T AIR Ambient Air Temperature 2. T J Junction Temperature 3. T SP / T C / T S Solder-Point Temperature / Case Temperature

7. T J & T SP Linked by Thermal Resistance 1. T AIR Ambient Air Temperature 2. T J Junction Temperature 3. T SP / T C / T S Solder-Point Temperature / Case Temperature 4. I F Forward Current / Drive Current T J = T SP + ( [R th j-sp ] x [V F ] x [ I F ] ) Thermal Resistance Forward Voltage

13. L 70 Lifetime Prediction – T AIR = 35ºC

14. L 70 Lifetime Prediction – T AIR = 45ºC

15. L 70 Lifetime Prediction – T AIR = 55ºC

16. L 70 Lifetime Prediction – T AIR = 65ºC

17. L 70 Lifetime Prediction – T AIR = 75ºC

18. L 70 Lifetime Prediction – T AIR = 85ºC

19. L 70 Lifetime Prediction – I F = 350 mA

20. L 70 Lifetime Prediction – I F = 700 mA

21. L 70 Lifetime Prediction – I F = 1000 mA