Temperature dependence of space charge behavior in hydrocarbon-based thermosetting resins under high DC electric stress

Recently, some next-generation semiconductors such as SiC and GaN, which can be operated at high temperature under high electric field, have been developed, and power devices using these semiconductors have been reduced in size with higher power output. However, while the semiconductors themselves are available at high temperature under high electric stress, there is no suitable material which show a good performance as the insulating layer for the semiconductors under such a severe condition. Therefore, to realize the usage with the inherent ability of the next-generation semiconductors, it is required to develop the insulating material that shows an excellent characteristic even under such severe condition. In this study, we focused on insulating properties of Dicyclopentadiene (DCP) resin and Tricyclopentadiene (TCP) resin which are hydrocarbon-based thermosetting resin. These resins exhibit stable dielectric properties at high temperatures. Furthermore, these resins are characterized by high formability because of their low viscosity. However, polymer insulation material has a possibility of dielectric breakdown by accumulating a space charge under a high DC stress. Since, there are few investigations of space charges formed in epoxy resins and hydrocarbon-based thermosetting resins under high DC stress at high temperature, especially near the glass transition temperature of them. the space charge distributions in DCP and TCP under high DC stress at high temperature were measured using the pulsed electro-acoustic (PEA) method. As a result, it was observed that a significant amount of space charges accumulated in all resins at high temperature under high DC stress. At temperature of 100 °C or higher, it was found that the space charge accumulation property in hydrocarbon-based thermosetting resins was different from that observed at lower temperature below 80 °C, while the space charge behaviors in hydrocarbon based thermosetting resins at higher temperature than 100 °C were not much different from those observed in epoxy and thermosetting resins. It suggested that the insulating performance in the epoxy resin may be changed at such high temperature, while the DCP and TCP may show their good performance as insulating material.