Time evolution of packaged LED lamp degradation in outdoor applications

摘要

Degradation of Silicone used in high power white LEDs as molding material has significant impact on the LED's lifetime and efficacy. This work provides a detail study on the impact of moisture, temperature and thermal aging on the packaging materials by tracing its progression of degradation under high temperature and humidity conditions. Silicone degradation via discoloration and cracks formation is identified and its cracks depth is found to decrease as the time progressesdue to diffusion mechanism and this led to highly distorted surface. It is found that Silicone undergo hydrolysis, condensation, thermal oxidation and thermal aging over its lifespan, and discoloration is mainly due to hydrolysis while cracks formation is mainly due to thermal oxidation. The decrease in the crack depth is due to thermal aging where diffusion of silicon oligomer occurs.