Olin Corporation

Christopher P Laurello

Julius C Fister

Szuchain F Chen

Derek E Tyler

Arvind Parthasarathi

Dennis R Brauer

The present invention is directed to a coated substrate, comprising: an antitarnish layer deposited on a substrate in an amount effective to prevent tarnishing of said coated substrate; and an outer layer deposited onto said antitarnish layer, said outer layer comprising tin or tin alloys having at least 50% by weight tin. The present invention is also directed to coated substrates having a concentration gradient of antitarnish agent diffused into the coating, as well as methods of forming such coated substrates.

Tarnish deterring tin coating

A tin coated electrical or electronic component has enhanced resistance to oxidation and tarnishing as well a smaller increase in contact resistance when exposed to elevated temperatures. These benefits are achieved by depositing a relatively thin, on the order of 5-50 angstroms thick, layer of zinc on the tin coating prior to heating. A subsequent step of heating the sample to a temperature and time effective to convert all free tin to an intermetallic imparts the additional advantage of reducing the coefficient of friction.

Tin coatings incorporating selected elemental additions to reduce discoloration

A method of introducing an anti-tarnish agent into the matrix of a tin coating to reduce oxidation and/or yellowing of the tin coating. The agent is preferably zinc, indium or phosphorous and can be deposited in a molten form to alloy with the existing tin coating. Alternatively, the existing tin coating may be exposed to a chemical bath including the agent and later heated to reflow the tin coating and agent thereby incorporating the agent into the matrix of the tin coating.

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Milford, CT, United States of America

Christopher P Laurello