Preparation of New Epoxy Composites and a Study on Their Thermal and Electrical Insulation Properties

With the ongoing development of insulated gate bipolar transistors (IGBTs) toward higher voltage, greater power density, and miniaturization, there is an increasing demand for enhanced thermal conductivity in packaging materials. Conventional epoxy resins, widely used for encapsulating power modules, exhibit relatively low thermal conductivity after curing, making them inadequate to meet the growing heat dissipation requirements of IGBT devices. To address this challenge, this study aims to develop a novel epoxy composite material with high thermal conductivity. A biphenyl-based aliphatic liquid crystalline epoxy monomer was synthesized through molecular structure design and incorporated as a filler into a curing system composed of a bisphenol A epoxy resin (E-51), 4,4′-diaminodiphenylmethane (DDM) curing agent, and butyl glycidyl ether (BGE) diluent. A series of epoxy composite films was subsequently prepared. Experimental results indicate that the optimized composite film (LE-20) achieved a maximum thermal conductivity of 0.266 W·m–1·K–1, which is 37.8% higher than that of the plain epoxy film (LE-0). Its glass transition temperature reached 189 °C (LE-20), representing a 43% improvement. In terms of electrical properties, the breakdown field strength of LE-20 was 316.96 kV/mm, slightly lower than that of LE-0. However, through further compositional optimization, the breakdown strength was significantly enhanced, reaching a value of 474.87 kV/mm (LE-15+).