Compatibility evaluation between dielectric breakdown strength and thermal conduction in epoxy/boron-nitride composite

The power module for the electrical vehicle needs electrical insulation material with high thermal conductivity. In this paper, we investigated the compatibility between dielectric breakdown strength and thermal conduction in epoxy/boron-nitride composite, in comparison with epoxy/alumina composite. The breakdown test was carried out under the application of dc lamp voltage and impulse voltage at high temperature. The prepared epoxy/boron-nitride composite was found to have lower dc-breakdown strength than that of the prepared epoxy/alumina composite. On the other hand, the epoxy/boron-nitride composite was higher thermal conductivity, e.g. 11 W/mK, than that of the epoxy/alumina composite, e.g. 4 W/mK In order to compare the breakdown voltage under the condition of the same heat-transfer quantity, we focused the specimens with different thickness whose heat-transfer quantity, e.g. 11 W/K, was the same. Finally, we clarified that the epoxy/boron-nitride composite could have higher breakdown voltage at 140°C than the epoxy/alumina composite with thin thickness under the same heat-transfer quantity in this material condition.