Thermal design of a high current circuit board for automotive applications

The demand of cost reduction and limited installation space for automotive applications requires new and innovative approaches. One approach is to substitute DCB substrates with high current circuit boards. These circuit boards with fully embedded actives like IGBTs and Diodes allows to avoid the use of bonding wires at all and benefit from the less expensive standard circuit board technologies. Moreover it should be possible to use double sided cooling for such devices. In this paper we investigate the influence of several geometry and material parameter, like layer thicknesses, thermal conductivity and cooling power on the thermal performance of a fully embedded 650V class half bridge test board. As input for the simulations the thermal conductivity of prepreg materials were measured. It could be shown that layer thicknesses have a significant impact of the necessary cooling power. The embedding of chips directly into laminated substrates seems reliable regarding thermal loading. Further results will be obtained by thermal measurements.