AlSiC composite materials in IGBT power modules

The reliability of IGBT modules is limited by thermal fatigue of soft solder layers due to different coefficients of thermal expansion. A thermally matching conducting material can be produced from Al matrix composites containing high volume fractions of SiC particulates. Variously processed prototypes of AlSiC baseplates were investigated with a view to their suitability for IGBT power modules. The volume fraction of SiC particulates as well as their thermal conductivity, heat capacity, thermal expansion and mechanical properties were determined. The thermal conductivity of AlSiC increases with the SiC content to reach more than 200 W/mK, which exceeds that of the matrix alloy of about 180 W/mK. The remarkable plastic elongation of the material during initial heating indicates that it originally contained internal stresses which relax during heating by the plastification of the matrix. The mechanical and physical properties of the tested AlSiC materials are appropriate for applications in high-power IGBT modules. Annealing treatment is recommended for AlSiC to reduce the internal stresses