Charaterization of A Nonlinear Conductivity Encapsulant for Electric Field Reduction in High-Voltage Power Module Packaging

Electrical insulation, particularly the partial discharge at triple points, remains a challenge in high-voltage SiC power module packaging. To address this issue, a field-dependent conductivity (FDC) insulation material was employed as a coating at the triple points of the direct-bond-copper (DBC) substrate prior to the encapsulation with silicon gel. The FDC material was developed by incorporating 0.1 wt.% -1.0 wt.% metal nanoparticle fillers into a silicon gel matrix. Experimental results have validated that the FDC material exhibits nonlinear conductivity characteristics, specifically an exponential increase with electric field. Notably, the FDC material with filler content as low as 0.5 wt.% has a low viscosity of 500 mPa·s. This ensures uniform potting during the module packaging process and contributes to excellent electric field homogenization effects. The results of 2D and 3D model simulation reveal that, when subjected to a high voltage of 15 kV, the electric field is reduced by 47.6%, i.e., dropping from 50.2 kV/mm to 26.3 kV/mm in comparison to the sample encapsulated solely with silicon gel. These findings suggest that the proposed FDC material presents a viable solution for enhancing the insulation performance in the packaging of high-voltage power modules.