Research on failure mechanism of the phosphors and sealants for white light emitting diode package

As known to all, photometric and colorimetric quality of LED illumination mainly depends on LED chip, phosphor and sealant. The investigation on failure mechanism of the three parts carries critical meanings for improving reliability of LED production. This paper mainly focus on reliability and failure mechanism of the three kinds of phosphor and three kinds of sealant which are wildly used in high power white light emitting diode package. In this work, high temperature-humidity aging experiment and other material science related detecting methods were involved. We prepared phosphor samples by stamping phosphor powder into pieces before aging experiment. After high temperature-humidity aging experiment, we found that aluminate based phosphors show excellent stability compared with silicate based phosphor. The silicate based phosphor will turn to amorphization in high temperature-humidity environment. Its composition and morphology will be changed greatly. We fabricated blue LED modules which were filled by three kinds of different sealants. After 300 hours high temperature aging experiment, silicone based sealants (methyl silicone and phenyl silicone) have shown much better thermal stability than epoxy resin based sealant. Two kinds of silicone based sealants only appeared slightly yellowing, but epoxy resin occurred serious carbonization.