Partial discharge behaviour of power electronic packaging insulation

The partial discharge behaviour of the insulation between power electronic devices, e.g. IGBT's (Insulated Gate Bipolar Transistors), and its heat sink has been investigated. In conventional IGBT packages this insulation consists of a ceramic layer which is metallized on both sides embedded in silicon gel. Voids at the interface between ceramic and copper due to delamination as well as gas filled bubbles in silicon gel located at the border of metallisation were revealed as major sources of partial discharges. Especially discharges starting at the border of metallisation will deteriorate the insulation. Furthermore a significant decrease of the PD inception voltage with an increase of temperature could be observed.