Study on the lifetime characteristics of power modules under power cycling conditions

This study presents a study on non-linear accumulative modelling for power module lifetime estimation in non-accelerated operation. The model focuses on solder fatigue based on monitoring the internal thermal resistance of the module. Initially, the relatively small junction temperature variation (T-j) cycles contribute little to the lifetime consumption, but with an initial damage the effect becomes noticeable. The original Coffin-Manson accumulation approach is extended for complex mission profiles. The proposed non-linear accumulation model has three aspects: a Coffin-Manson relationship is first established; the thermal resistance degradation is then used to quantify damage accumulation; the effects of the average junction temperature (T-jmean) and T-j on the rate of degradation are finally included through the parameters of the non-linear accumulation model which also depends on the effect of the present condition of the module. Experiments demonstrate the phenomena and verify the proposed model.