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