Enhancing dielectric strength of thermally conductive epoxy composites by preventing interfacial charge accumulation using micron-sized diamond

Epoxy-resin-based dielectric materials play a crucial role in the fabrication of advanced power electronic devices. However, because of a high voltage stress and high heat generation density caused by device miniaturization and high-power density, epoxy composites must possess a high dielectric strength and thermal conductivity. In this study, a general strategy is developed to improve the dielectric strength of thermally conductive epoxy composites using a micron-sized diamond, by preventing an interfacial charge accumulation at the inorganic fillers–epoxy matrix interface that would reduce the interfacial electric field strength. Therefore, the dielectric strength and thermal conductivity of the epoxy composites were significantly and simultaneously improved without any additional physicochemical modification of the micron-sized diamond surface. The reported percentage increase in the dielectric strength among the highly thermal conductive epoxy composites is the highest in the last decade. In addition, the diamond/epoxy composites exhibited lower relative permittivity and excellent mechanical, thermal, and processing properties. These results suggest that the diamond/epoxy composites can be widely used for the fabrication of power electronic devices with a high voltage stress and high heat generation density.