For meeting the high strength and light weight demands in the structural components of modern engineering applications,heterogeneous integrations of dissimilar materials are used extensively.In these heterogeneous structures,higher thermal and mechanical stresses would develop because of discontinuities in material properties across the interface.Furthermore,the lack of metallic or covalent bonds between the dissimilar materials would make the interface very susceptible to debonding.As a result,interface delamination is considered as one of the dominant failure modes.A preferred methodology for assessing the reliability associated to interfacial delamination is the fracture mechanics approach,which consists of analyzing the delamination driving forces and comparing them to the interfacial fracture resistance.While the subject of analyzing fracture driving forces for interfaces in interconnect structures was investigated by many researchers,the fracture responses of materials interfaces in many state-of-the-art engineering structures are unavailable.To close this gap,it is essential to characterize the subcritical growth rates of the interface defects quantitatively,in particularly under realistic mixed-mode fatigue loading conditions.