Hybrid Electrodeposition and Characteristics of Ag-Graphene Composite Films on Cu Sheets Toward High-Performance Electric Connectors

Abstract

Recently, silver (Ag) plating for automotive connector has been attracted extensively attention due to the fast progress of HEV/EV system and as a promising candidate material to substitute the costive gold (Au) plating. The Ag plating film possesses the highest conductivity among the metals and excellent corrosion resistance next to Au plating. However, Ag plating suffers a low wear resistance problem because of the soft nature of Ag metal (~80 Hv). Because an oxidation film is difficult to form on silver surface, the corrosion resistance is good. More serious problem of Ag plating is that an adhesion phenomenon often occurs during sliding wear actions as terminal mating materials, because an oxidation film is difficult to form on Ag surface owing to the good corrosion resistance as a noble metal. To solve those problems, many studies focused on fabricate hard Ag plating by adding some alloy elements like Co, Sb, and Se or adding graphite powder into Ag plating films, which improved wear resistance but sacrificed electric conductivity. Here, we propose a new Ag-graphene electro-plating film, with the graphene functioning as solid lubricant and electric component, which may reinforce the wear resistance while without lowering its electric conductivity. The Ag-graphene composite films were fabricated on Cu sheets by a hybrid electrodeposition method, i.e., combining electrodeposition of Ag and electrophoric deposition of graphene nano-flakes, in a non-cyanate plating bath. The graphene nano-flakes were prepared by an electrochemical peeling method from a graphite material. The microstructures, chemical composition, and crystalline structure of the anodized specimens before and after annealed were investigated FE-SEM (EDS), XRD, GD-OES, FT-IR, and Raman spectroscopy. Moreover, the electric resistance meter and wear resistance were also investigated, compared to commercial Ag plating as reference.Figs. 1a and 1b show the surface FE-SEM images of as-electrodeposited pure Ag and Ag-graphene films respectively. It can be seen that, except for the featured Ag nano-particles, some blurry films can be observed on the Ag film in Fig. 1b. The EDS analysis result in Fig.1c demonstrates a strong C peak, indicating the co-deposition of carbon clearly. Moreover, the inclusion of graphene in Ag films were also confirmed by Raman spectra and XRD measurements. The electric resistance of Ag-graphene composite films was equivalent to the commercial Ag films, and the detail results will be reported on the meeting. Figure 1