||This paper tries to explore the phosphor optical characteristics through reliability tests using white light emitting diodes (WLEDs) with a high color rendering index|
(CRI ,Ra＞90). Based on light mixing principles and considering the high CRI, three color-coded powders were mixed separately with silicone into a phosphor, and then
bottomed with blue chips into WLEDs. The three powders were oxide nitride (red), YAG (yellow), and silicate (green).
Two kinds of samples were fabricated – phosphor and emitters similar to commercial products. Both cool-white (CCT=5650~7000K, lumen efficiency＞60 lum/w.) and
warm-white (CCT=2850~3250K, lumen efficiency＞50 lum/w.) samples passed the Bin Code distribution process and brightness measurement. The results indicate better
lumen efficiency than previously published research.
After the three kinds of mono-colored phosphors were created, .we implemented the reliability test in which three CREE standards were chosen. These standards were (1)
high temperature with high humidity test (60℃ , 90% humidity) in operating and non-operating condition; (2) thermal shock test (-40℃ ~125℃ ); (3) life time test.
The thermal shock test showed the decaying power of intensity for red, yellow, and green phosphors were 11.7%, 17.5%, and 19.3% respectively. These results demonstrate that the red phosphor has the best thermal resistance. However, after the high temperature with high humidity tests, the decaying power of intensity for red,yellow, and green phosphor were 15.7%, 10.1% and 6.4% correspondingly. These results show that the green phosphor has best aqua resistance. In the life time test of
emitters, the decaying power of intensity for the cool-white emitter was 3.2%, while the warm-white emitter showed 4.2%. As such, cool-white emitters were concluded to
have better reliability than warm-white emitters.