May 12, 2015
Silver – A Superior Finish for High Current Applications
Connector designers have available a wide selection of finishes to consider for high current applications, both noble as well as non-noble metals. The choice would consider performance as well as cost aspects. Failures of high current contacts are somewhat distinct from those of signal contacts, which in that case are primarily associated with loss of information. In contrast, the failure of a high current contact could involve something as catastrophic as the initiation of a fire, with its associated risks.
In this short discourse, we will focus on silver and discuss a number of attributes that characterize it as a finish for high current applications. Silver has the highest value of electrical conductivity of any material – this is clearly a significant factor when considering the ability of a contact to carry current. Silver is “semi-noble”, in that although oxide formation is mitigated, it is susceptible to the formation of tarnish films. As with noble metals, silver will not degrade as a consequence of fretting corrosion. For electrical contacts, by utilizing the recommended normal forces and plating thicknesses, successful performance (in spite of tarnish formation) can be expected.