Thermal management of power electronic devices is essential for reliable performance especially at high power levels. One of the most important activities in the thermal management and reliability improvement is acquiring the temperature information in critical points of the power module. However accurate temperature estimation either vertically or horizontally inside the power devices is still hard to identify. This paper investigates the thermal behavior of high power module in various operating conditions by means of Finite Element Method (FEM). A novel 3D thermal impedance network considering the multi-layer thermal coupling among chips is proposed.
The impacts to the thermal impedance by various cooling and heating conditions are also studied. It is concluded that the heating and cooling conditions will have influence on the junction to case thermal impedances and need to be carefully considered in the thermal modelling. The proposed 3D thermal impedance network and the extraction procedure are verified in a circuit simulator and shows to be much faster with the same accuracy compared to FEM simulation. This network can be used for life-time estimation of IGBT module considering the whole converter system and more realistic loading conditions of the device.