Gold-plated contacts: Effect of thermal aging on contact resistance

A study was made of the effect of thermal aging on the contact resistances of pure gold platings, as well as of cobalt- and nickel-hardened gold plati ngs (Hard Golds), on copper. Samples were aged at several temperatures, and contact resistance was determined by probing according to ASTM B-667. It w as found that, although nickel underplate retards the rate of increase of c ontact resistance of pure gold, it may accelerate the rate for Hard Golds. This effect becomes more pronounced with increasing hardener content and Ha rd Gold thickness. Nickel-golds are more stable than cobalt-golds.