Reducing EMC Problems Caused by Power Semiconductors Using an Electrically Non-Conducting Heat Sink

In power electronics, wide band gap materials enable faster transients and higher switching frequencies. Therefore, more efficient power electronic systems can be realized, but also greater EMC problems in magnitude and frequency arise. Heat sinks, which are often necessary for cooling power semiconductors, are a source of EMC issues. In this paper, on the one hand investigations about currents through grounded aluminum heat sinks for power semiconductors are reported. The aim is to show how much common mode current can be inhibited by using ceramic aluminum nitride heat sinks which does not need to be grounded. Furthermore, the ground current reduction potential by careful selection of isolation is shown when using an aluminum heat sink. Often the isolation between semiconductor and heat sink is chosen only considering electric strength and “as thin as possible” for heat transfer. On the other hand, results regarding the influence of a ceramic aluminum nitride heat sink on radiated interferences are reported to enable a discussion on the influence of a AIN ceramic heat sink for power electronics regarding conducted and radiated interferences.