COPPER PLATING DEPOSITS are used for both functional and decorative applications. They are used widely as underplates in multiplate systems, as barrier coatings, as stopoffs in heat treatment, and for heat transfer (e.g., as heat sinks). They also find use in electroforming, in electromagnetic shielding, and in plating of electronic circuitry. The smoothness and brightness of copper deposits can be improved through buffing techniques because copper is a relatively soft metal. Copper deposits also act as thermal expansion barriers, especially in multiplate systems, due to their ability to absorb the stress produced when metals with different thermal expansion properties undergo temperature changes or if the deposit is thermally shocked. Similarly, corrosion failures from cracking caused by physical deformation of a part can be reduced by incorporation of a soft metal such as copper in the composite plate. Copper plating is also used as a final finish in some decorative applications and is sometimes used alone in applications where a durable and attractive surface is required. However, copper tarnishes and stains rapidly when exposed to the atmosphere and must be protected against this by an overcoating of clear lacquer or another suitable type of corrosion-resistant finish.

Copper can be deposited from both electrolytic and autocatalytic (electroless) electrolytes that are alkaline or acid.

Cyanide and noncyanide, pyrophosphate alkalines plus sulfate and fluoborate acid baths are the electrolytes used in the electrolytic deposition of copper deposits. For additional information, see the article "Electroless Copper Plating" in this Volume.

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