Molecular Engineering of Aluminum–Copper Interfaces for Joining by Plastic Deformation

Interface modification based on ultra‐thin mercapto‐propyl(trimethoxy)silane (MPTMS) films is shown to promote joining of copper and aluminum by plastic deformation followed by a heat treatment. The surface morphology and the surface chemistry of the metal substrates were analyzed by means of FE‐SEM, XPS, and FT‐IRRAS. The spectroscopic data show that the MPTMS film is crosslinked via Si–O–Si bonds and that stable Cu–S and Si–O–Al interfacial bonds are formed. The shear‐force tests of the joints led to force displacement curves that are characteristic for a covalently bonded interface. Complementary cross sectional SEM and EDS analysis of the joint proved that a defect‐free interface was formed without any measureable interdiffusion of metals across the interface or cracking of an oxide films.