Design of Packaging Structure in High Voltage Power Modules to Avoid Surface Breakdown

In high voltage power modules, the triple point lies between metallization, ceramic and silicone gel. Electric stress is much higher at triple point than average electric field. The situation gets worse when the triple point lies in the electrode spacing. Short distance between electrodes can enhance the electric stress and increase the damage from repeated PDs. This paper proves that interface between ceramic and silicone gel is a weak insulation area. Repeated partial discharges (PD) can induce surface breakdown along the interface area. Consequently, triple point combines high electric stress and weak insulation together. In order to separate the interface area from the edge of metallization, this paper proposes a new geometry of the ceramic substrate.