In the next article in the “Connector Basics” series, Ed Bock of APEX Electrical Interconnection Consultants looks at the attributes of silver and explains why it’s a superior finish for high-current applications.
Connector designers have a wide selection of finishes to consider for high-current applications, both noble as well as non-noble metals. It is important to evaluate 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 result in something as catastrophic as a fire.
Silver has the highest value of electrical conductivity of any material; clearly, this is 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.