Electrical and tribological properties of hot-dipped tin separable contacts with fluorinated lubricant layers

Abstract

Degradation phenomena occurring during the lifetime of tinned separable electrical contacts remain a factor of loss of reliability to be minimized. In this paper, friction, wear and electrical properties of hot-dipped tin coatings on bronze substrates are analysed with various techniques, in order to show the improvement due to a well-suited fluorinated lubricant layer. Contacts are of the sphere on plane type. Coupons are cut from strips of tinned CuSn/sub 4/. The sphere contacts are obtained by forming the coupons. Macroscopic friction cycles simulating insertion and withdrawal of separable contacts are performed, as well as fretting cycles. Wear is characterized by topographic examination of the tracks and by surface analyses. We first describe macroscopic friction of dry contacts. Then the anti-friction and anti-wear behaviour of two perfluorinated ethers is evaluated for both conditions. Large differences are observed with the two chosen lubricants. Fretting tests are then performed on connector terminals in order to validate the results in closer-to-use conditions. Outstanding friction and wear reduction are recorded which can be linked to the particular behaviour of the fluorinated layers on tin.