The thermal impedance of new power semiconductor modules using AlN substrates

Increasing operating voltages of IGBT modules result in higher dissipation heat as well as additional requirements on the insulation and partial discharge. The most important part affected here is the substrate. AlN ceramic with a thermal conductivity of typically /spl lambda/=180 W/mK is clearly superior to the conventional Al/sub 2/O/sub 3/ ceramic at /spl lambda/=27 W/mK. The thermal and thermomechanical properties of AlN substrates have been investigated in view of IGBT modules. Measurements of the thermal resistance R/sub th/ of the AlN substrates assembled with IGBTs gave values less than that of Al/sub 2/O/sub 3/ substrates by a factor greater than three. In complete IGBT power modules a factor of two is achieved. Temperature cycling test of AlN substrates and modules show a reliability similar to those of Al/sub 2/O/sub 3/ i.e. the reliability requirements are fulfilled.