Friction Force Reduction for Electrical Terminals using Solution-Processed Reduced Graphene Oxide Coating

Electrical connectors and terminals are widely used in the automotive industry. It is desirable to mate the electrical connections using materials or coatings with low friction force to improve the ergonomics of the assembly process while maintaining good electrical conduction over the lifetime of the vehicle. We have previously shown that plasma-enhanced chemical vapor deposition (PECVD) of graphene on gold (Au) and silver (Ag) terminals can significantly reduce the insertion force (friction force during the terminal insertion process). However, the cost of this deposition method is rather high, and its high temperature process (> 400 ^oC) makes it impractical for materials with low melting temperatures. For example, tin (Sn) coating with a melting temperature of 232 ^oC is commonly used in electrical connectors, which cannot sustain the high temperature process. In this study, reduced graphene oxide was prepared using a low-cost solution process and applied onto metallic terminals. The reduced graphene oxide (rGO) suspended in polyalphaolefin (PAO) base oil was coated on Sn terminals via a dip-coating method. Insertion force tests with and without the rGO coating were performed on Sn terminals. The reduction of friction between two sliding metal surfaces while preserving the same level of electrical conduction has been successfully demonstrated. Comprehensive characterizations with four-probe resistance measurements and Raman spectroscopy were performed. In addition, we carried out a systematic study of the lubrication effect from both PAO and rGO for comparison. Given the advantages of low-cost and simple synthesis processes, rGO in PAO solution can be employed to lubricate electrical terminals to significantly reduce insertion force while maintaining good electrical conduction.