Multi-physics simulation and reliability analysis for LED luminaires under step stress accelerated degradation test

In this paper, the 3D model of a LED luminaire is built using the software Pro/Engineer and then the model is transferred to ANSYS Workbench platform where the LED luminaire under the temperature and humidity conditions during step stress accelerated degradation test (SSADT) is simulated. The simulation results of temperature distribution, humidity distribution and stress distribution of the model at three levels of temperature (45°C, 65°C, 85°C) and 60% RH (Relative Humidity) are acquired using multi-physics approach. In the post-processing of temperature data, combining Yamaoshi?s optical power empirial formula of LED degradation with the junction temperature in simulation, the optical decay curves at each stage of the test are obtained. Then, the long-term life test (LTLT) at room temperature (25°C) and SSADT at three levels of temperature are performed to illustrate the validity of simulation. The lumen maintenance of 3 LED luminaires by LTLT and 5 samples by SSADT are analyzed to evaluate the luminous flux, optical decay rate and reliability under different working and ambient conditions. Finally, a comparison is made between the results of experiment and simulation. It is shown that the simulation results agree well with optical decay curves from the test, which indicates that the method can be used to predict the optical decay of LED luminaires.