Optical degradation mechanisms of mid-power white-light LEDs in LM-80-08 tests

•Different degradation mechanisms at different case temperatures•Both deteriorations of blue chip and silver-coating lead frames dominated at 55 °C•Only blue chip deterioration dominated at 85 °C and 105 °C•Degradation separation by using spectrum analysis method

In this paper, the optical degradation mechanisms of mid-power white-light LEDs, were studied by using high temperature operation life tests, according to the IES standard LM-80-08. As a consequence, it is found that, (1) the degradation mechanisms are different for LED packages aged at different case temperatures; (2) the optical degradation is a result of combination of chip-related degradation mechanisms and package-related degradation mechanisms. In details, for LEDs aged at 55 °C, the optical degradation was induced by both the deterioration of blue chip and silver-coating lead frames, while for LEDs aged at 85 °C and 105 °C, only blue chip deterioration was considered as the main degradation mechanism.