High Reliability Wire-Less Power Module Structure

Power electronic modules, based on a range of semiconductor technologies are widely used to control and convert electrical power system, such as industrial, railway, and even electric vehicle applications. The most common technology of a die-level interconnect is wire bonding. Maturity, flexibility and low cost are main factors, which explain the use of the wire bonding technology. However, it has electrical limitation (such as parasitic inductance) and thermomechanical limitations such as thermal stress due to coefficient of thermal expansion (CTE) difference leading to the fatigue and eventually a failure. IGBTs with dual solderable metals on top and bottom of the die offer a wire-less assembly option with enhanced reliability and lower manufacturing cost [1], [2]. In this paper, a wire-less Cu-clip package were used to investigate the power module performance. By replacing the Al wires with copper spacer and copper clip significant lower on-state voltage drop of the IGBT about 5% and large increase in heat exchange area, thus resulting in 22%~25% thermal resistance reduction and 27% junction temperature reduction. Additionally, the junction temperature distribution can be more uniform. The simulation results show that the package stray inductance can also be reduced about 24% with wire-less structure. Wire-less structure could improve not only electric, thermal performance, but also reliability of power modules.