Takukazu Otsuka

High-temperature silicon carbide and silicon on insulator based integrated power modules

This paper presents the challenges and results of fabricating a high temperature silicon carbide based integrated power module. The gate driver for the module was integrated into the power package and is rated for an ambient temperature of 250 °C. The power module was tested up to 300 V bus voltage, 160 A peak current, and 250 °C junction temperature.

Large current SiC power devices for automobile applications

The high current SiC MOSFETs and high-temperature operation IPM with SiC MOSFETs were fabricated. 300A switching in inductive load circuits was performed using a single chip SiC trench MOSFET. And 250 °C (the junction temperature of SiC DMOSFETs) operation of SiC IPMs with a new high-temperature bonding method and high-temperature materials (case, encapsulation) was successfully performed.

High-performance SiC power devices and modules with high temperature operation

The expectation for SiC devices in advanced power electronics applications for saving energy has been still larger. The 4H-SiC planer MOSFETs with high blocking voltage (1300V) and large current (40A) were fabricated. In addition, we have succeeded in fabricating the larger current (300A) 4H-SiC trench MOSFET with low-on resistance (2.6mΩcm2). And, regarding high-temperature operation, SiC IPMs can be successfully fabricated by using a new bonding soldering method which can withstand even 400°C.

Stacked resin structure for reducing warpage of transfer-molded modules

The transfer-molded package with ceramic substrate is widely developed for power modules in the industrial and automobile applications. However, the difference in coefficient of thermal expansion (Δ CTE) between the ceramics and the molding resin is a significant problem, which is the fundamental cause of “warpage”. This research provides a new concept where the stacked resin structure is composed of two kinds of molding resins and as a result, the advantage of reduced warpage can be confirmed. Generally, the warpage is designed to be reduced by adjusting the properties of the molding resins to minimize the ACTE from the substrate. Meanwhile, our FEA simulation revealed that using two molding resins with the large and small ACTE from the substrate reduce more effectively the warpage than the one with the small ACTE. This mechanism is due to warping stress contribution from the stacked resins in the opposite of the original warpage direction. We fabricated the transfer-molded package with the stacked-resin structure and confirmed that the warpage can be reduced compared to the conventional structure. Also, the experimental results of the warpage showed good agreement with the simulation results.