Gold plating

Gold plating is a method of depositing a thin layer of gold onto the surface of another metal, most often copper or silver (to make silver-gilt), by chemical or electrochemical plating. This article covers plating methods used in the modern electronics industry; for more traditional methods, often used for much larger objects, see gilding.

There are several types of gold plating used in the electronics industry:

Pre-Columbian smiths working in northern Peru gilded and silvered copper objects by electrochemical replacement techniques.

During the excavations in 1987–1990 at Sipan, a spectacular treasure of gold and silver ornamental and ceremonial artifacts was recovered, dating to AD 50–300. These objects demonstrate the outstanding craftsmanship of the Moche metalsmiths. Alloys of copper with gold and some silver were employed, known as tumbaga.

There are five recognized classes of gold plating chemistry:

Gold plating of silver is used in the manufacture of jewelry. Like copper, silver atoms diffuse into the gold layer, causing slow gradual fading of its color and eventually causing tarnishing of the surface. This process may take months and even years, depending on the thickness of the gold layer. A barrier metal layer is used to counter this effect. Copper, which also migrates into gold, does so more slowly than silver. The copper is usually further plated with nickel. A gold-plated silver article is usually a silver substrate with layers of copper, nickel, and gold deposited on top of it.

Gold, applied by either evaporated methods or Electroplating has been specified by NASA to thermally control spacecraft instruments thanks to its 99% reflectivity in Infrared Wavelengths.

Gold plating is often used in electronics, to provide a corrosion-resistant electrically conductive layer on copper, typically in electrical connectors and printed circuit boards.

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