Epoxy Mold Compound Encapsulation Concept for Large-Area Power Devices

A new concept for encapsulation of discrete bipolar high-power devices using epoxy mold compound (EMC) is demonstrated on silicon 4.5-kV press-pack fast recovery diodes (FRDs) with wafer diameter up to 130 mm and molybdenum pressure-release buffer up to 140 mm in diameter. The silicon wafers can be bonded to molybdenum disks using the low-temperature bonding (LTB) process or they can be fixed mechanically by the EMC without direct bonding (free floating). The encapsulated devices can be applied as housing-less or they can be inserted into hermetic ceramic housings with pole piece of 143 mm. The design aspects relevant for reliable operation are presented using multiphysics simulation in COMSOL. The summary of passed reliability tests, including electrical testing in true application conditions, demonstrates readiness of the concept for demanding applications in the temperature range up to 140 °C.