Electro-thermal-mechanical analyses on stress in silver sintered power modules with different copper interconnection technologies

Increasing demands for higher energy efficiency and operating at harsh environments lead to the development of new compact power electronics, which is complemented by new interconnection technologies. Investigations were made on a planar copper interconnection technology. The characteristic difference to other technologies can be seen in the replacement of bonding wires by planar copper interconnects and the high voltage applicability of the resulting modules. A high voltage and temperature resistant polymeric foil provides the insulation. Electrical connection is made by structured electrodeposited copper structures, which allow for additional heat spreading from top of the dies. Investigations on the thermo-mechanical behavior of prototype inverter modules, which use silver sintering and copper wire bonding technology or, alternatively, planar copper interconnection technology are reported. Fully coupled electrical-thermal-mechanical finite element (FE-) simulations were used to get realistic transient temperature loadings as well as mechanical stresses, also including wire heating or heating of the planar metallization, respectively. Improved thermal performance of the planar technology could be shown. A parametric FE-study was made to minimize delamination failure risks of planar structures based on cohesive zone modeling. Studies on processing dependent properties of the key materials sintered silver, electroplated copper, and dielectric foils are reported, which are indispensable for simulation input.