Three-Dimensional Structural Transition of Tin Plated Fretting Contacts

In recent years, there has been increasing demand to miniaturize wiring harness connectors in automobiles due to the increasing volume of electronic equipment and the reduction of the installation space allocated for the electronic equipment in automobiles for the comfort of the passengers. With this demand, contact failure caused by the fretting corrosion seems to become a serious problem in the future. In a previous study by the authors, three-dimensional SEM observations of tin plated fretting contacts using FIB (Focused Ion Beam)-SEM method have been conducted at the 1^st peak contact resistance points of tin plating thickness 1 and 5 μm. In this report, three-dimensional SEM observations have been made for tin plated fretting contacts before and during the contact resistance increase with tin plating thickness 1 and 5 μm. With these observations, the three dimensional structural transition from tin to tin oxide have been confirmed quantitatively. Based on these observation results, the conductive mechanism of a degraded tin plated contact interface in terms of percolation conduction has been considered.