Hard encapsulation of automotive power modules by epoxy potting – encapsulant selection assisted by thermo-mechanical simulation

Encapsulation with soft silicone gel by potting is the standard technology in packaging of automotive power modules with sixpack topology and highest power densities. Large-area potting of liquid hard encapsulant material is another option for realization of a hard encapsulation. Large substrate, heatsink and module size in general, multi-material stack-up, heavy cyclic thermal loads during operation, high temperature and high voltage operation possess challenges to the material choice for hard encapsulation. Within this study different power module packages have been hard encapsulated, delamination and brittle fracture of the encapsulant as well as damage of the encapsulated structure through the encapsulant are thereby observed. Corresponding thermo-mechanical simulations were set up and used to detect and investigate the failure reasons. It was found that mechanical properties of encapsulants are well adapted to the encapsulated power module packaging structures. Special attention has therefore to be put on geometrical specialties such as etching trenches and bus bar connections.