The present study deals with the experimental and simulation procedures for establishing the interfacial fracture toughness of Epoxy Molding Compounds-Copper leadframe interfaces at dry and pressure cooker conditions, temperature larger than 100 掳C and 100% RH. It is shown that steam significantly decreases the interfacial toughness at temperatures above the Tg of the Epoxy Molding Compounds. The effects of temperature and mode mixity on critical interface properties are also investigated.