Accelerated life test of high power white light emitting diodes based on package failure mechanisms

Accelerated life tests of high-power white light emitting diodes (LEDs) were conducted under an unbiased highly accelerated temperature and humidity test (HAST) and a normal aging test. The conditions in the unbiased HAST were 110 °C-85% RH, 130 °C-85% RH without bias. During the aging, the degradation mechanisms of optical power reduction and degradation of 455 mm blue wavelengths that were better than phosphors related yellow emission bands were observed. The microscopy analysis showed that this effect could be ascribed to the bubbling and discoloration of the silicone encapsulating material of the package. It is thought that these features are also responsible for the optical power reduction and thermal resistance increase.