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Interfacial adhesion is of important concern for multilayered structures such as
microelectronic packages. Environmental effects, i.e., high temperatures and
moisture diffusion, change the mechanical properties of polymeric materials and,
more importantly, degrade the adhesion between the polymeric adhesives and
substrates. Delamination between the Epoxy Molding Compound (EMC) and the
copper-based leadframe during the solder reflow process is a common failure
mechanism in plastic encapsulated IC devices.
This work shows the influence of aging in dry and humid conditions on the
adhesion between EMC and copper. Bi-layer Copper / EMC beams were exposed
to moist environments to reach the saturation condition. Standard fracture tests
were performed for the determination of the critical force at the moment of crack
onset. The effects of thermal residual stresses, hygroscopic swelling and
viscoelasticity on the measured interfacial fracture toughness for a specific mode
angle were investigated by Finite Element Analysis (FEA).