Evaluation of Leak Current and Charge Accumulation in Epoxy Resin at High Temperature Under High DC Stress

In this paper, the leakage current and charge accumulation characteristics of epoxy resin at high temperature under high electric stress were investigated. Generally, ceramic materials are used for the insulating substrate of power modules, but they are being replaced by epoxy resin-based substrates to reduce cost and to improve a heat cycle resistance. In polymeric insulating materials such as epoxy resin, dielectric breakdown occurs due to increased leakage current and distortion of the internal electric field caused by the space charge accumulation when high DC voltage is applied for a long time at high temperature. Therefore, it is important to understand the leakage current characteristics and the space charge accumulation characteristics of insulating materials at high temperature under high electric field. In this study, the leakage current and the charge accumulation of two types of epoxy resins made with different curing agents were evaluated using a direct current integrated charge method (DCIC-Q(t)) at high temperature under high electric field. The results show epoxy resin with acid anhydride curing agents (EP-NH) has a better insulating performance than that with amine-based curing agents (EP-A).