Internship - Estimation of the effect of the combination of thermal and humidity stresses on the lifetime of IGBT modules

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General context

Power modules (IGBTs and MOSFETs) are the heart of power electronic converters. The reliability of these power modules is mainly estimated through empirical lifetime models made from large databases from accelerated cycling tests. These tests consist of the amplification of the stress compared to the normal operating conditions of the module in order to accelerate the mechanisms of degradation followed by an extrapolation towards the low stresses to estimate the lifespan of the module. The constraints usually taken into account are the thermal constraints due to the environment (passive cycling) or from the self-heating of the active chips during the switching phases (active cycling). However, the module in its application environment (fields of transport, renewable energies, etc.) is also subject to electrochemical stress caused by the humidity of the environment. High humidity, high temperature (H3TRB) reverse bias testing is performed independently of thermal cycling testing. Nevertheless, an interaction of the two types of stress is possible and can cause a reduction in the lifespan of the modules. An in-depth analysis of the effect of humidity on the aging indicators usually considered in accelerated aging tests (VCE, RDS, leakage current, etc.) must be carried out first. In a second step, the effect of the combination of humidity and thermal cycling constraints is essential to get as close as possible to the real constraints that the power modules undergo and thus to develop more precise lifetime models.