A Fourier Series-Based Steady-State Thermal Resistance Model for Power Module

The finite-element method (FEM) is conventionally employed to evaluate the thermal performance of power modules (TPPM), but it demands substantial computational resources and time. This study introduces a novel approach for TPPM assessment through a Fourier series-based steady-state thermal resistance model (FSS-TRM), which offers enhanced computational efficiency and accuracy. The FSS-TRM integrates conduction and spreading resistance via a mathematical-physical method, explicitly focusing on redefining conduction resistance to optimize computational efficiency. The accuracy of the FSS-TRM is ensured by solving the heat conduction differential equation to obtain spreading resistance. To assess the reliability of the FSS-TRM, the model is tested across varying direct bonded copper (DBC) configurations and chip sizes. Experimental results reveal that the maximum error of the FSS-TRM compared with the conventional COMSOL approach is below 4%. In addition, the FSS-TRM's capability to predict TPPM is verified through testing a representative power module in a 34-mm package, demonstrating an error of only 0.9% compared with both COMSOL and experimental results. Notably, the computational efficiency of the FSS-TRM is significantly improved, exceling COMSOL by five orders of magnitude. Therefore, the proposed FSS-TRM provides an accurate and efficient alternative to FEM for TPPM estimation.