Research on microstructure and shear strength of Al alloy jointed by sputtered Cu thin film deposited through HiPIMS and DCMS techniques

Abstract

Transient liquid phase bonding (TLP bonding) in jointing technology is a promising method for achieving precision joining of aluminum alloys and creating low-cost products for use in the electric vehicles (EVs) industry, which can contribute to a low-carbon economy. This research is primarily focused on the jointing technology of aluminum alloys and is divided into two parts. The first part involves vacuum soldering between A6063 aluminum alloy with copper layers of 1, 3 and 5 μm thickness, and tin solder under thermal treatment. The second part is Cu-Al eutectic bonding. In this study, we used Ar ions to bombard the surface of A6063 aluminum alloy to remove the oxide layer and deposited a copper layer using direct-current magnetron sputtering (DCMS) and high-power impulse magnetron sputtering (HiPIMS). We then analyzed the joint interface of the samples using Scanning Electron Microscope (SEM), Energy-Dispersive X-ray Spectroscopy (EDS), and Scanning Acoustic Tomography (SAT) to calculate the joint ratio of the entire joint surface. Finally, we measured the shear strength to evaluate the bonding effect. The results indicate that the eutectic bonding method exhibits better bonding performance for aluminum alloys compared to the soldering method. Furthermore, the shear strength increased with increasing thickness of the sputtered copper layer. When comparing two sputtering technologies, the copper films sputtered by HiPIMS system exhibit better quality those produced by the DCMS system. As a result, aluminum alloy bonding completed with HiPIMS has higher bonding strength, demonstrating that HiPIMS is a powerful coating tool.