Warping model of SiC Power Module after Reflow Soldering

The mismatch in coefficients of thermal expansion (CTE) among materials in silicon carbide (SiC) power modules during reflow soldering leads to significant warpage of the Direct Bonded Copper (DBC) substrate and then increases residual stresse between the DBC and the SiC device, adversely affecting device and module stability and reliability. However, quantitative analyses of warpage behavior of the SiC module and effective mitigation strategies remain limited. In this paper, a thermo-mechanical coupled finite element model of a 62 mm, 1200 V/300 A SiC half-bridge power module is established to simulate the warpage phenomenon under realistic reflow soldering conditions. Simulation results indicate a typical warpage profile with a raised center and lowered edges, matching experimental measurements within a maximum error of 4.7%. The maximum stress value of the solder layer reached 564 MPa. To mitigate warpage and solder-layer stresses, a mechanical pre-warping method is proposed and evaluated. Simulation and experimental analyses show that applying pre-warping between 250 μm and 500 μm can significantly reduce the warpage of DBC substrate up to 27.3% and the stress of solder-layer up to 44%. However, further increases in pre-warp magnitude yield diminishing improvements and introduce substantial initial stresses. This paper quantitatively clarifies the impact of pre-warping magnitude on the suppression of DBC substrate warpage and the stress reduction of solder-layer, providing practical guidance for optimal SiC power module packaging design and improved reliability.