Characterization of silicone gel properties for high power IGBT modules and MEMS

Silicone gels provide the dielectric insulation in insulated gate bipolar transistor (IGBT) power modules to prevent partial discharge, inhibit moisture ingress and keep out contaminants from the internal circuitry. The junction temperatures of these power modules are located between 150^oC and 175^oC and these temperatures will increase to 200^oC in the near future. In addition, power modules are expected to operate for 15 to 20 years. The development time of these power modules is getting shorter to meet the market expectations. Similar demanding conditions are expected for micro-electromechanical systems (MEMS) applications. Hence, there is a need to use characterization tools to short-list silicone gels for further analysis or building of qualification units. Amongst the three silicone gels analysed here, sample C shows the most promise because of its lack of thermal events during the DSC analysis. Sample C also maintains the softness and inertness during the thermal ageing at 150^oC for up to 1000 hours. These studies show that judicious use of DSC-TGA, FTIR and gel penetrometer can provide valuable information for the said purpose.