Low temperature soldering of Al alloy modified with sputtered and ion implanted Cu coatings

A novel technique was developed to solder the Al alloy at a low temperature. In the newly-developed technique, the surfaces of the 2024 Al alloy were modified with the Cu coatings synthesized by magnetron sputtering and ion implantation. The impacts of the deposition conditions, including the substrate bias, deposition rate, gas flow rate, and etc, on the interfacial adhesion of the Cu coating and soldering quality were evaluated. The Cu coatings were characterized with X-ray diffraction, scanning electron microscopy, and atomic force microscopy. The results show that the Cu-coating significantly improves the soldering conditions of the Al alloy, and that the bias strongly affects the (111) preferentially-oriented, Cu coating. As the bias increased, the Cu deposition rate decreased, and the surface roughness changed in a decrease-increase mode. For instance, grown at -300 V, the maximum shear strength at the soldered joints were found to be 24.47 MPa, with locally elongated ripples along the shear force direction at the fracture.