Metal matrix composite power modules: improvements in reliability and package integration

This paper compares metal matrix composite (MMC) baseplate power modules to standard copper baseplate power modules with respect to high current applications. The comparison is made both from a reliability and a package integration perspective. Reliability continues to be a key concern in applications where motor drives are subjected to thermal cycling. Modules with copper baseplates exhibit poor mechanical reliability since the thermal mismatches are high between the baseplate and the other materials in the package. Package integration of the power stage with the rest of the package is difficult with copper based modules since the only geometry that can be economically produced is stamped two dimensional baseplates. MMC materials are combinations of metals and ceramics with variable properties. A silicon carbide/aluminum composite (a moldable material with controlled thermal expansion coefficient) offers elegant solutions to the reliability and package integration concerns of standard modules. This study, conducted at Motorola's Hybrid Power Module Operation, examines the benefits that can be realized in both of these areas by using MMC baseplates in high current power modules. Measurement and finite element methods are used to study reliability. Additionally, design concepts for integrated packaging and integrated power systems are also explored.