Study on current and junction temperature stress aging effect for accelerated aging test of Light emitting diodes

In recent years, Light emitting diodes (LEDs) has become more and more popular because of their low power consumption, low-pollution and long-life. Currently, the common lumen maintenance test of LED follows IES LM80-08 standard, which costs at least 6000 hours for measurement and prolongs the time-to-market schedule. In our previous researches, a modified accelerated aging test algorithm using different high temperature stress without input current was successfully proposed. And through the experiment, it shows that the modified accelerated aging test algorithm, which derived from Arrhenius equation, cannot fit the lifetime of LEDs aging in temperature and current stress. It recommends that the life prediction model has to make consideration of both heat and current. First of all, we need to measure the lumen maintenance in same junction temperature with different current. In this research we will use a validated finite element model and use thermal resistance of LED to predict the junction temperature of chip under different current input. And use the forward voltage method to measure the junction temperature to validate the simulation result and calculation result. During the experiment we found out the heating type and the size of oven will influence junction temperature of LED seriously. We need to consider about the oven when conducting aging test of LED in the future to make sure whether the measured result is correct. In summary, we found out the corresponding relation between current and ambient temperature for same junction temperature and oven's effect for junction temperature measurement. It would provide some considerations to the accelerated aging test with developed degradation prediction model in the future.