Parametric Study of Joint Height for a Medium-Voltage Planar Package

Due to the thin structure used in planar packaging, the electric field intensity within the encapsulation is high, leading to degradation of the dielectric performance. To resolve this issue, a metal posts interconnected parallel plate structure (MPIPPS) is used to reduce the high electric field concentration in the power module. However, the high bonding joint in MPIPPS causes large thermo-mechanical stress within the solder layers. This paper proposes a methodology to optimize the joint height based on a trade-off between the thermo-mechanical performance and dielectric performance of the power module. The impact of the joint height on thermo-mechanical stress and dielectric performance of the module is investigated quantitatively using ANSYS and Maxwell simulations. The results show that using a 0.4mm joint height and Nusil R-2188 encapsulation, the power module can achieve 3 kV breakdown voltage. Experimental results agree with the simulation results.