Friction Force Reduction in Electrical Terminals with 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 a lower insertion force in order 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. However, the cost of this deposition method is rather high, and the high temperature process (>400oC) makes it impractical for metallic coating with a lower melting temperature such as tin (Sn), which melts at 230oC. In this study, reduced graphene oxide was prepared by using a low-cost solution process and applied onto metallic terminals. The reduced graphene oxide (r-GO) suspended in a polyalphaolefin (PAO) base oil was coated on Sn terminals via a dip-coating method. An insertion force test with and without the r-GO coating was performed on Sn terminals. The reduction of friction between two sliding metal surfaces while maintaining the same level of electrical conduction has been successfully demonstrated. In addition, a systematic study of the lubrication effect from both PAO and r-GO will be presented. Comprehensive characterizations, including scanning electron microscopy (SEM), four-probe resistance characterization, and Raman spectroscopy, were performed. Given the advantages of low-cost and simple synthesis processes, r-GO in PAO solution can be employed to lubricate electrical terminals to provide significant insertion force reduction while maintaining good electrical conduction.