Heat-resistant and electrical properties of bismaleimide modified epoxy resin

The ever-increasing development of power modules requires epoxy (EP) encapsulants to have excellent heat-resistance capability. Many studies have been conducted on improving the heat-resistance of epoxy encapsulants and have made important achievements in recent years. However, the electrical insulation of the EP-based high heat-resistance materials has not been paid enough attention and less studied. In this paper, BMI/EP systems have been prepared, and the electrical characteristics and heat-resistance of the modified BMI/EP have been investigated. Dynamic thermomechanical analysis shows the introduction of BMI greatly improves the heat-resistance of the epoxy systems. The electrical conductivity and breakdown characteristics of BMI/EP samples were measured at 30, 50, and 70 °C, respectively. The analysis of space charge indicates the trap distribution in the 10%BMI can significantly suppress carrier migration, resulting in the highest electric breakdown strength and the lowest current density. The excellent insulation properties with improved heat-resistance demonstrate that BMI/EP has great potential to be used in power modules.