Surface melting of a substrate prior to plating
AssigneesWestern Electric Company, Inc., Bell Telephone Laboratories, Incorporated
InventorsClifton W. Draper, Satya P. Sharma
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Abstract
Substrates for use in electrical contacts are prepared prior to plating by rapid surface melting by means of a laser beam or an electron beam. Improved microscopic surface characteristics are obtained. In a preferred embodiment, improved macroscopic surface roughness characteristics are also obtained by shorter-duration melting, typically by means of a pulsed YAG laser. Gold which has been electroplated onto copper alloys prepared by this technique has shown improved resistance to sulfur and chlorine corrosive atmospheres. This allows, for example, a thinner layer of a protective metal to be used to obtain a given degree of protection.
Claims15
A method of making an electrical contact including the step of depositing a protective layer on at least a first portion of a metal substrate characterized by melting at least a second portion of the surface of said substrate with said first portion at least partially overlapping said second portion to a depth of less than 0.1 millimeters by means of an electron beam or laser beam prior to said deposition, wherein the duration of said melting at a given location on said substrate is less than 10 milliseconds, wherein said protective layer comprises at least one metal selected from the group consisting of gold, silver, platinum, ruthenium, rhodium, iridium, and palladium, and wherein said melting substantially reduces the average metallic grain diameter of said surface of said substrate.
The method of claim 8 further characterized in that said gold or gold alloy is deposited upon said substrate by electroplating.
Dependencies are inferred from the claim text.