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|Identification of thermo-mechanical fatigue fracture location by transient thermal analysis for high-temperature operating SiC power module assembled with ZnAl eutectic solder|
|Keywords: 250 °C operating SiC power module, Zn-Al eutectic solder, transient thermal analysis|
|Silicon carbide (SiC) power devices can operate at a higher power density than conventional silicon (Si) power devices, attracting attention as a candidate for future power devices. In order to derive the maximum potential of SiC power devices, power modules for high-temperature operation are developed. A power module which is composed of SiC-MOSFETs, silicon nitride active metal brazed copper (SiN-AMC) substrates and a baseplate is fabricated. The baseplate is made of copper-tungsten (CuW), in order to match the coefficient thermal expansion (CTE) to SiN-AMC substrate. The SiN-AMC substrate and the baseplate are bonded with Zn- Al eutectic solder (melting point: 382 °C), as well as die bond, to improve heat dissipation performance. It is easily expected that thermo- mechanical fatigue fracture of a large area solder portion, such as the substrate bonding, occurs due to thermal deformation during thermal cycling. Conventional solder defects are inspected by X-ray computed tomography (CT). There is an issue that the solder defects cannot be detected, since the baseplate is made with heavy metals such as tungsten on the other hand the ZnAl solder is light metal. If the solder of the heat dissipation path deteriorates, the thermal resistance increases. In order to nondestructively evaluate solder defects, thermal resistance evaluation using transient thermal analysis method attracts attention. The transient thermal analysis method is able to evaluate the thermal resistance of each portion between the device and the baseplate using a curve called|
|Fumiki Kato, Senior Researcher
National Institute of Advanced Industrial Science and Technology