The impact of mold compound on power cycling capability of SiC MOSFETs in double sided cooled modules

The impact of the mold compound on the power cycling capability of semiconductor devices is a decisive factor for their lifetime. Previous studies on discrete devices showed up to five times higher lifetime with mold compound [1]. In this work, the influence of the mold compound was experimentally investigated on double sided cooled modules (DSC). Half-bridge modules with SiC MOSFETs were tested under similar conditions with and without mold compound. As there are no source bond wires in the analysed DSC modules, particular attention was paid to the resulting failure modes. The DSC modules with mold compound showed only slight traces of ageing after the test. In the DSC modules without mold compound, previously defined end of life (EoL) criteria were reached and the failure analysis showed clear signs of degradation mainly in solder layer S2 due to the power cycling test (PCT) at the front-side interconnection between spacer and chip. A positive impact of the mold compound on the DSC module was concluded.