Impact of Thermal Interface Materials on the Device Thermal Coupling in Semiconductor Power Modules

This article studies on the influence of different thermal interface materials (TIMs) on the thermal coupling among devices inside the semiconductor power modules. In particular, an insulated-gate bipolar transistor (IGBT) power module equipped with free-wheeling fast recovery diodes (FRDs) is investigated with two types of TIMs, namely the thermal grease and graphite sheet. The theoretical analysis of thermal coupling among the chips inside the power module is carried out, which is followed by the numerical simulation and experimental test results. The agreement among the results verifies that lower thermal conductivity of the TIMs leads to stronger thermal coupling among chips. As both the self-heating and coupling thermal impedances are dependent on the TIM thermal conductivity, the variation of their contribution ratio to the total thermal resistance is quantified. The influence of TIMs on the mutual coupling between the IGBT and FRD chips is also characterized.