Analysis of Surface Mount Heat Sinks for SiC MOSFETs Concerning Heat Dissipation and EMC Behaviour

In this paper, the benefits and drawbacks of the usage of surface mount heat sinks for SMT package semiconductors are analysed and discussed. These heat sinks are utilized in addition to conventional heat dissipation through the printed circuit board using thermal vias in a three-phase SiC-MOSFET inverter, building a hybrid cooling approach. Advantages concerning the heat dissipation in comparison to the cooling only through thermal vias are examined regarding the heating temperatures of the semiconductor devices. A decreased heating caused by the heat sinks leads to a lower junction temperature, lower thermal stress and better operating conditions. A reduction of the temperature-dependent on-resistance of the MOSFETs could additionally contribute to lower conduction losses. Furthermore, it will be investigated which impacts on the EMC behaviour of the circuit occur using the heat sinks within fast switching topologies. Being directly soldered to the modified drain pads of the MOSFETs, the copper-based heat sinks are consequently connected to the fast changing drain potentials. This could lead to differences concerning the conducted and radiated EMC behaviour of the circuit.