Life tests of Nichia AlGaN/InGaN/GaN blue-light-emitting diodes

摘要

We report on results of life testing Nichia NLPB500 blue LEDs in a temperature controlled chamber, with computer automation of equipment operation and data collection. The tests began with 18 newer (Nichia batch 4B0001) and two older (Nichia batch S403024, acquired a year earlier) LEDs, operated at 20 mA continuous wave (CW) and 23(degree)C. Light from each LED was coupled to an optical fiber and fed directly to individual photodetectors. General trend for the 18 newer LEDs was for the output intensity to increase at a faster rate within the first 50 h and then at a slower rate of the remainder of the first test. The output intensity of the two older LEDs increase within the first 50 h then decreased during the remainder of the first 1000 h. All 20 of the LEDs in the first 1000-h test were subjected to a second 1650-h test at 23(degree)C and at currents 20-70 mA CW. Only one LED, an older device, suffered a soft failure during this second test. The remaining LEDs underwent a third test at 30(degree)C and a fourth test at 35(degree)C, all at various currents. We will perform failure analysis.