Internal Stress Relief and Efficiency Improvement Method of PSiP Power Module Based on Surface Grinding and Post-curing Approach

High-Power-Density Power Modules utilizing Double-Side-Molding Power-System-in-Package (DSM-PSiP) can be enhanced with high thermal-conductivity epoxy molding compound (EMC) to dissipate heat. However, the curing process, as well as coefficient of thermal expansion (CTE) mismatch between EMC and ferrite core generate significant compressive stresses on the ferrite core, which leads to efficiency degradation and localized overheating. To address the shortcomings of the existing solutions, in this paper, an internal stress relief method based on surface grinding and post-curing approach is proposed. Experimental verification on a high-power-density double-clamp zero-voltage-switching (DCZVS) flyback prototype shows a 0.65% improvement in full-load efficiency and a 58% reduction in additional core losses due to the molding process after performing the proposed internal stress relief method. The experiments demonstrate the feasibility of the internal stress relief method for High-Power-Density Power Modules applications, and the method improves the converter efficiency without compromising structural integrity and package density.