High-Heat-Resistance Polymers for SiC Power Modules

Power semiconductor devices are critical to CO₂-reduction technology. In this study, we focus on a silicon carbide (SiC) device with a wide bandgap (WBG), which operates with low loss and high efficiency at temperatures up to 300°C. Conventional isolation/sealing technologies are unable to cope with such high operating temperatures; therefore, new advanced materials are necessary. In this report, we introduce SiC power module platforms to evaluate an alternative technology involving various encapsulating materials, bonding materials, and techniques for assembly. We attempted to produce four types of platforms, PT-1 through PT-4. Fig. 1 presents the cross section and a photograph of the platform PT-3, which was assembled from a Si insulated-gate bipolar transistor (IGBT) and a SiC diode. A simulation analysis was performed to evaluate the optimum properties of the platforms from the viewpoint of their reliabilities. The purpose of this project is to accelerate the development of high-heat-resistance materials and bonding technologies through the abovementioned evaluation platforms. We identify this project as “KAMOME-PJ (Kanagawa Advanced Module for Material Evaluation).” As a pertinent example, we report a novel polymer alloy having both high heat resistance and low thermal expansion (CTE). This alloy was prepared by melt mixing of two compounds,bismaleimide diphenyl methane (BMI) and 3,3’-(methylen-1,4-diphenylen) -bis(3,4-dihydro-2H-1,3-benzoxazine) (P-d). The resin comprising BMI 1.0 vs. P-d 0.3 exhibited superior thermal properties and processability. When cured at only 200°C for 4 h, the glass transition temperature of the resulting product was above 300°C. An encapsulation material was prepared using this polymer alloy, whose properties are described in Table 1 and are compared to those of conventional epoxy materials.