高压大功率IGBT用液晶环氧性能研究（二）：电气绝缘特性

doi:10.19595/j.cnki.1000-6753.tces.232018

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Abstract Encapsulating materials with high thermal conductivity excellent heat resistance and electrical insulation have great application prospects in the field of high-voltage and large-power insulated gate bipolar transistors (IGBT). All organic liquid crystalline epoxy is a good candidate because of its theoretically high thermal conductivity, high glass-transition temperature, and outstanding electrical insulation performance. It can be attributed its unique liquid crystalline self-assembly ordered domains and a mass of rigid molecular structures. More importantly, the two new epoxy monomers have low viscosity under high temperature conditions, which is very suitable for potting process of epoxy for the encapsulation of IGBT. Therefore, it has great advantages in the future application of encapsulation of high-voltage and large-power devices. In this work, a novel liquid crystalline epoxy (named TMB-5+) with dual mesogenic units was constructed. Benefits by ordered liquid crystalline domains and a large number of rigid structures, the new liquid crystalline epoxy exhibits excellent heat resistance and thermal conductivity. The related research was presented in the first paper of this work. This paper is the second in a series of papers, which investigates the electrical insulation performance of liquid crystalline epoxy.
Firstly, the dielectric breakdown strength of the new liquid crystalline epoxy film was studied. The study showed that the TMB-5+ sample containing double mesogenic units exhibited a higher breakdown strength, reaching 126.72kV/mm, which was 46.9% higher than traditional epoxy. The higher phenyl content and denser liquid crystalline domains in the TMB-5+ sample were considered to be beneficial for improving the breakdown strength. Base on simulation of the free volume and mean square displacement of the new epoxy, we found that the liquid crystalline epoxy has lower free volume parameters and weaker movement ability of molecular chain under the electric field. These factors also showed positive impacts on improving the breakdown strength. Secondly, the partial discharge capacity of liquid crystalline epoxy was studied, and it was found that liquid crystalline epoxy has lower partial discharge capacity under the same voltage of 8 kV. The results of the measuring thermal stimulation depolarization current showed that the liquid crystalline crosslinking material with dual mesogenic units had an increased trap energy level and enhanced the ability to capture electrons. Both lower partial discharge capacity and higher trap energy levels contribute to reducing the breakdown risk of epoxy materials. In addition, the dielectric constant and dielectric loss were analyzed, and it was found that liquid crystalline domains can effectively suppress the reversal of dipoles, thereby reducing the dielectric constant of the material. And the liquid crystalline epoxy exhibits excellent thermal and electrical insulation properties, as well as good mechanical properties. This study emphatically characterized electrical insulation and thermal performance of liquid crystalline epoxy resin, and can provide certain practical reference for the application of new epoxy resin in the insulation packaging materials of high-voltage and large-power IGBT.

Key words： Insulating potting material biphenyl liquid crystalline epoxy biphenyl liquid crystalline curing agent electrical insultaing performance molecular dynamic simulation

Received: 04 December 2023

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TM211

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	Wang Zhengdong
	Cao Xiaolong
	Yang Ganqiu
	Luo Meng
	Zhou Yuanhang

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Wang Zhengdong,Cao Xiaolong,Yang Ganqiu等. Research on Properties of Liquid Crystalline Epoxy for High-Voltage and Large-Power IGBT (Part 2): Electrical Insulation Performance[J]. Transactions of China Electrotechnical Society, 2025, 40(3): 878-889.

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https://dgjsxb.ces-transaction.com/EN/10.19595/j.cnki.1000-6753.tces.232018 OR https://dgjsxb.ces-transaction.com/EN/Y2025/V40/I3/878

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