Thermal-electrical-force Properties of Liquid Crystalline Epoxy for High-voltage High-power IGBT Potting Application

As the insulated gate bipolar transistor (IGBT) continues to evolve toward high-power and high-voltage operation, the device is faced with the risk of temperature overheating, breakdown failures, material ruptures, and other failures inside the device. In order to meet the increasingly harsh operating environment of the IGBT, there is an urgent need to develop a high-performance liquid crystalline epoxy potting material. In this paper, a biphenyl-type liquid crystal epoxy 4,4-biphenyldiglycidyl ether (BP) is prepared, and the effect laws of curing temperature and co-mingled bisphenol A epoxy system (EB-BP%) on the electrical insulating properties and thermo-mechanical properties of BP are explored. The results show that BP with sulfonamide (SAA) exhibits a distinct spherical liquid crystalline domain morphology at a curing temperature of 170℃ (BS-170), and the thermal conductivity (λ) and breakdown field strength (E_b) of BS-170 are 0.397 W·m^-1·K^-1and 47.403 kV·mm^-1, respectively, which are 67.5% and 6% higher than those of bisphenol A epoxy. The λ of EB-30 in the blended system of BP and bisphenol A epoxy reaches 0.301 W·m^-1·K^-1, which is 28.6% higher than that of bisphenol A epoxy. In addition, EB-30 exhibits excellent tensile strength and elongation at break. Therefore, BP/EB shows better overall performance when used as an IGBT encapsulation material. This study can provide effective ideas and theoretical basis for the development of new high-performance insulating materials for IGBT encapsulation.