The investigation of the electrical contact resistance through thin oxide layer on a nanometer scale

Electrical connectors plated with tin are widely used in automobiles. Therefore, it is important to understand electrical conduction mechanism and contact structure of tin plating which is coated with thin oxide layer in order to realize small electrical connectors which are able to operate under low load force condition. Then we constructed nano-manipulator to be able to observe the mechanical contact, measure the load force and electrical resistance simultaneously in a scanning electron microscope. As a result, we found that the electrical resistance drastically reduces as the load force increases, and could observe that the tin penetrates into cracks in oxide layer and finally reaches on the surface. These results are the same as those of tin oxide layer fabricated by sputtering. Therefore, it is confirmed that the tin appearance on the contact surface is very important for electrical conduction even in the case of tin with natural oxide. For size miniaturization and load force reduction of tin plating connectors in near future, it is necessary to focus on the oxide layer fracturing and control the tin appearance on the contact interface.