Lifetime evaluation of solder layer in an IGBT module under different temperature levels

Solder layers are highly important parts of the IGBT module which establish the internal electrical connections, mechanical support and cooling channel of module. The function of the IGBT module is deeply dependent on the reliability of solder layers. A Finite Element (FE) model based on actual Insulated Gate Bipolar Transistor (IGBT) module is established to analyze how temperature levels of power cycling load influence the fatigue life of solder layer. 42 power cycling loads were designed with different temperature profiles, simulation results found that with the increase of junction temperature variation, the life parameter which has a negative correlation with solder life grows at an exponential rate. As the same time, with the increase of minimum junction temperature, the life parameter will have a near linear growth. Accordingly, life of solder layer get shorter when junction temperature variation and minimum junction temperature become higher. Finally, a life evaluation function of the solder layer has been established which made temperature profiles as the input variables and life parameter as the output variable.