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 (Δ 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 Δ 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.