Thermal improvement of press-pack packages: Pressure dependent thermal contact resistance with a thin silver interlayer between molybdenum substrate and silicon carbide chip

In typical press-pack, free-floating packages the thermal contact resistance between chip and substrate is a major limiting factor for the cooling ability of the power module. We report an introduction of a new, thin Silver interlayer between Molybdenum substrate and chip, and how it improves the thermal contact. The thermal contact resistances were measured with and without a Silver interlayer at different pressures. The surface roughness of the SiC chip and the Molybdenum substrate were characterized. The thermal contact resistances were measured at three different heating power levels. The results show a significant reduction of the thermal contact resistance with only a few micrometer Silver interlayer. The improved cooling effect of a Silver interlayer was also demonstrated with a fluid dynamics type of 3 D simulation comparing temperature distributions with and without a Silver interlayer. These results project a possible thermal improvement in press-pack packages.