Corrosion Resistant Barrier Formed by Vapor Phase Tin Reflow

Abstract

A copper substrate for use as a contact having tin plating, nickel plating and gold plating overlying the substrate. A combination of tin plating is applied over a copper substrate; nickel plating is applied over the tin plating; and gold plating is applied over the nickel plating to form a stack. The stack is then processed by a vapor phase tin reflow step that results in the formation of intermetallics and eliminates stannous oxide layers that may otherwise form on the tin layer. The intermetallic layers provide excellent corrosion resistance, and serve as diffusion barriers to prevent the further migration of either nickel atoms or copper atoms into the tin, and tin atoms outwardly into either the nickel or the copper. Regardless of the thickness, the interfaces are substantially free of oxides, in particular tin oxide, and not prone to delamination.

Dependencies are inferred from the claim text.