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

• Published in: Advanced engineering materials Vol. 18; no. 6; pp. 1066 - 1074
• Main Authors: Hoppe, Christian, Ebbert, Christoph, Voigt, Markus, Schmidt, Hans Christian, Rodman, Dmytro, Homberg, Werner, Maier, Hans Jürgen, Grundmeier, Guido
• Format: Journal Article
• Language: English
• Published: Blackwell Publishing Ltd 01.06.2016
• Subjects: Aluminum; Annealing; ANNEALING PROCESSES; Chemical bonds; Copper; Covalence; Crosslinking; DEFORMATION; ENGINES; INTERFACES; JOINING; Plastic deformation; PLASTIC STRAIN
• ISSN: 1438-1656; 1527-2648
• DOI: 10.1002/adem.201500501

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. Molecular interface modification is shown to improve the copper and aluminum joining by plastic deformation. The pilger process in combination with a moderate thermal annealing step leads to the formation of a covalent link according to Cu–S–(CH2)–SiOx–Al2O3/Al which results in a high mechanical strength of the joint.