Using high-speed switching, SiC power devices can reduce on-resistance in the on-state to realize low power converter losses. In addition, SiC power devices can be operated in high temperatures; thus, their cooling systems can be reduced in size or removed altogether, thereby increasing the power density of the power converter. The authors have studied a power module and power converter using properties of SiC power devices, and have previously proposed a power converter having high power density with a power module that is capable of high temperature operation , a gate driving technique for SiC power devices to prevent false turn-on with high-speed switching, and development of a noise filter for high-speed switching or high-frequency switching. In this study, we designed and fabricated a SiC power module with a built-in snubber circuit. This power module is operable in high temperatures over 200 °C.

Baseplate material properties for realizing high temperature resistant power modules are investigated. Power modules should have a tolerance for heavy thermal cycle load and retain their original performance. Therefore, it is important to improve the reliability of the heat dissipation path, which is the soldered joint between the baseplate and ceramic substrate. This study aimed to improve reliability by appropriately selecting the baseplate material and relaxing the thermal stress in the soldered joint. We conducted a series of verification tests using four types of baseplate material. Our results clarified that a smaller mismatch of coefficient of thermal expansion (CTE) between the baseplate and ceramic substrate contributes to an improvement in reliability, especially in case of W–Cu as the baseplate material. Conversely, the results also clarified that baseplate plastic deformation contributes to an improvement in reliability even if the CTE mismatch is large, in the case of Al.

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A high temperature sandwich structured power module for high temperature SiC power semiconductor devices has been accomplished. Problems were found in the high temperature building-up process of the module caused by excess warpage of the ceramic substrate. Also the high temperature operation of the power module brings an excess warpage of the structure caused by parts having different coefficients of thermal expansion (CTEs) from each other. In this paper, some countermeasures to overcome the problems are demonstrated.

This article reports on a flip-chip bonding technology using an Al bump at high temperatures, such as for SiC semiconductors. In recent years, double-sided mounting structures have been proposed for purposes of miniaturization and low inductance. The surface-mounting method requires durability against high temperatures. We propose a new technique for the flip-chip bonding of an Al bump made from bonding wire. The recrystallization temperature of Al is under 250°C. As a result, there is an expectation of mitigating mechanical stress between the chip and the bonded substrate. We conducted a high-temperature aging test at 250°C for 3,000 h and a thermal shock test between −40°C and 250°C for 3,000 cycles. Results indicate that the shear strength of the Al bump meets the requirements specified in the IEC60749-19 guideline up to 2,000 cycles at room temperature.