Thermal stress analysis of colored LEDs

Abstract

This paper illustrates the development and the experimental validation of a life model for LEDs subjected to thermal stress. The basis is the Arrhenius model for electrical insulation. The parameters of the life model are derived from accelerated life tests carried out on five samples of LEDs emitting light of different colours, namely red, green and blue. Each sample was subjected to a given value of constant temperature until the failure of all specimens. The diagnostic property for denoting failure is the residual light emitted by the LEDs under rated forward current, monitored continuously by a diagnostic system controlled via LabView. This study is the first step of an investigation whose ultimate goal is characterizing the endurance of LEDs having different colours to the stresses they face on duty, among which temperature is often one of the most challenging.