Comparison of blue and white packaged LED degradation

Phosphor incorporation into blue LEDs package is one of the most commonly used methods to produce white light currently. Phosphor converts the incoming blue light from GaN chip into yellow light, which is then combined with the blue to produce light that is perceived as white light. However, apart from light conversion, phosphor also generates heat and over prolonged operation time under ambient or electrical stress, the light conversion efficiency of phosphor can degrade and hence produce more heat. This chapter aims specifically at the understanding of the blue and white light degradation trends under different conditions, namely LEDs with and without phosphor. Statistical, physical, and modeling techniques are employed to understand the degradation mechanisms under MET test conditions. Gap introduced at the molding part and encapsulant interface is found to be the main degradation mechanism, which allows large amount of moisture to penetrate inside the white LEDs as compared to the blue LEDs.