Research on the improvement and regulation mechanism of silicone gel encapsulation insulation performance for high-voltage power devices

Packaging insulation is a key factor restricting the reliability of power electronic devices under high power density and extreme conditions. In this study, hexagonal boron nitride (h-BN) was used as a filler to prepare silicone gel based composite insulators via physical modification. The effect of BN doping on insulation performance and its mechanism were explored, combining microstructural analysis and molecular dynamics simulations. The results indicate that the doping of BN enhances the crosslinking density of the material and results in a more compact material structure, thereby improving the breakdown voltage of the composite material. However, the insulation defects introduced by filler agglomeration cause the breakdown voltage to decrease at high doping ratios. The breakdown voltage is highest when the BN content is 2 %, with more pronounced improvement under 100 V/ns. Charge migration at the interface between the matrix and filler dominates the changes in dielectric properties, leading to a significant increase in interfacial polarization in the low-frequency region and conductive polarization in the high-frequency region. Both the real and imaginary parts of the relative permittivity increase with the addition of BN. Based on the key performance indicators of various engineering projects, when the BN doping concentration is 2 %, the breakdown voltage under high voltage rise rate (d u /d t ) can be improved by 39.99 % while achieving a synergistic improvement in insulation performance, thermal stability, and thermal conductivity. This approach holds promise for widespread application in the packaging of next-generation wide-bandgap power devices.