Gold plating

Gold Plating Chemistry

• Alkaline gold cyanide for gold and gold alloy plating
• Neutral gold cyanide for high-purity plating
• Acid gold plating for bright hard gold and gold alloy plating
• Non-cyanide, generally sulphite or chloride-based for gold and gold alloy plating
• Miscellaneous

Jewelry

• Gold flashed / Gold washed - gold layer thickness less than 0.5 micron
• Gold plated - gold layer thickness greater than or equal to 0.5 micron
• Heavy gold plated / Vermeil - gold layer thickness greater than or equal to 2.5 micron
• Gold plated silver jewelry can still tarnish as the silver atoms diffuse into the gold layer, causing slow gradual fading of its color and eventually causing tarnishing of the surface
• A barrier metal layer is used to counter this effect - these can be nickel or rhodium

Space Applications

• Gold, applied by evaporated methods or electroplating, has been specified by NASA to thermally control spacecraft instruments, due to its 99% reflectivity in infrared wavelengths

Electronics

• 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
• Direct gold-on-copper plating can cause tarnishing and formation of an oxide and/or sulphide layer
• A layer of nickel is often deposited on the copper substrate before the gold plating to improve wear resistance and reduce the impact of pores
• Both the nickel and gold layers can be plated by electrolytic or electroless processes
• Selective plating is used to deposit the nickel and gold layers only on areas where it is required

Other Types and Significance

• Soft, pure gold plating is used in the semiconductor industry and is easily soldered and wire bonded
• Bright hard gold on contacts has a higher hardness and purity, but contains a small amount of nickel and/or cobalt that interferes with die bonding
• Bright hard gold on printed circuit board tabs is deposited using lower concentration of gold in the baths and usually contains nickel and/or cobalt
• Soldering gold-plated parts can be problematic as gold is soluble in solder and can form brittle intermetallics
• Daniel Davis Jr. - inventor of gold plating as a business
• Gold filled jewelry
• Nickel-gold plating copper PCB traces
• References on gold plating
• Historical significance of gold plating

Gold plating Mentions

Gold plating Data Sources