Time-Resolved Non-Linear Electric Field Simulation on Liquid Embedded Substrate

Transient electric field evolution near triple point region of a power module has been simulated taking into account the non-linear material properties (conductivity, permittivity) versus temperature and electric field. An insulating liquid (Jarytherm® DBT, dibenzyltoluene) is used for encapsulation of an alumina substrate, instead of Silicone gel. A typical voltage of 10kV is considered for the simulation, relevant of future wide band gap power modules able to operate at high voltage and temperature. The simulation shows that electric field enhancement in the encapsulant is highly dependent on time, as well as on temperature. For short duration of the applied voltage, a very high electrostatic field appears at first, which decreases rapidly after a few µs due to field re-arrangement by conduction. This high field duration is reduced with increasing temperature. A large field enhancement within the substrate also occurs.