Study on thermal degradation of high power LEDs during high temperature and electrical aging

As a new kind of semiconductor photoelectric device, Light-emitting diodes (LEDs) have begun to play an important role in many illumination applications due to their excellent performance in terms of high brightness, energy-saving and environment friendly. However, thermal management is one of the major issues to be improved for implementing LEDs into illumination applications because heat affects the light performance and reliabilities. When it comes to talk about the thermal management of an LED, thermal resistance is an important device performance parameter, indicating the obstruction of the heat flow from the p-n junction to the ambient during operation. So most of manufacturers try to use high thermal conductivity material to lower the thermal resistance from the p-n junction to the LED board, and then the junction will be at a lower temperature during operation. In this paper, accelerated aging tests with high temperatures and currents were carried out on the LEDs. T3Ster was used to analyze the heat conduction path which influenced the luminous efficiency, the die-attached interfaces thermal resistance significantly increased after aging test, the more of the accelerated stress, the great die-attached interfaces thermal resistance increase. Voids in the die-attached may not only lead to increase of the junction temperature, but also result in the addition of the temperature difference. Accordingly, the results were helpful in enhancing the performance and reliability of high-power LEDs.