Analytical solution of thermal spreading resistance in power electronics

A good understanding of thermal spreading resistance is crucial for thermal management in power electronics. In this paper, an analytical solution is developed for the determination of thermal spreading resistance with a heat source placed on a three-layer substrate, wherein the same footprint is assumed for different layers. An approximate approach is then proposed based on the analytical model when the substrate has unequal layer dimensions. Both the analytical model and the approximate approach are validated by comparing results with numerical simulations, and quite good agreement is observed. Moreover, to further improve the thermal performance of a power module, a new material with high thermal conductivity is used as an additional heat spreader. Parametrical study of the effect of such a heat spreader is carried out. Results show that the material holds promise for application in power electronics.