Direct liquid cooling module with high reliability solder joining technology for automotive applications

We developed the direct-liquid-cooling IGBT module which enabled downsizing of a power control unit for HEV system and high reliability simultaneously. This module eliminates thermal grease by unifying a ceramic substrate and a heat sink. It contributes this module realized the reduction of thermal resistance 30 % compared to the conventional indirect liquid cooling type. High thermal conductive Si₃N₄ ceramics for the substrate and lightweight aluminum heat sink that are suitable for automotive use demand are applied. The technological challenge of this module is to overcome the decrease of the reliability of the joint by large CTE mismatch between substrate and heat sink. We developed the Sn-Sb based solder material which can attain high reliability for automotive use with large CTE mismatch components. And IGBT module with this new solder is applied to HEV.