Thermal Shock Test Lifetime Improvement with Optimized Adhesion Strength between Epoxy Resin and Copper

Abstract:
In this paper, we examined and verified an improvement of thermal shock test lifetime in epoxy resin encapsulated power semiconductor modules by improving the adhesion reliability between the epoxy resin and the copper plates of the insulating substrate. When power modules encapsulated with epoxy resin are subjected to thermal shock test (TST), significant thermal stress is generated due to the difference in the thermal expansion coefficient of each component inside the power module. As a result, the epoxy resin delaminates from copper plates of a insulation substrate. Delamination of the epoxy resin from the copper gradually increases with the number of TST cycles, which adversely affects the reliability of the power module. This work confirmed that the adhesion strength with the epoxy resin can be doubled by forming an appropriate oxide film on the copper plates. Power modules with oxidized copper showed that the epoxy resin delamination occurred area after the TST target cycle was about 70% less than that of the module without the oxide film. Finally, the TST lifetime of the power module was enhanced to more than TST 1,000 cycles.