Accelerated Ageing Test and Lifetime Prediction of MOSFETs

An active power cycling test-bed for a power MOSFET is presented in this publication. This setup is used to create temperature dependent load cycles of 24 parallel devices. After a passive calibration step the drain-to-source voltage is used to estimate the junction temperature. The devices are then heated until a predefined value is reached. The setup is power cycled until at least 20 channels failed and then analysed using metallographic cross-sections. Furthermore, this setup records the thermal impedance of each channel over time. With these data it is possible to detect and predict a solder fatigue (crack, void) during operation. Finally after all load cycles the results were evaluated by Weibull plots and a lifetime estimation for other temperatures is given in the way of a stress-life curve. The results suggest a comparable lifetime compared to ceramic-based components, if the substrate does not have an influence as a source of faults.