Process for whisker-free aqueous electroless tin plating

Abstract

A process of preserving solderability and inhibiting tin whisker growth of exposed copper or copper alloy surfaces on a substrate comprises the steps of preparing an immersion tin plating solution substantially free of other immersion-platable metals; applying the immersion tin plating solution to the substrate to form a tin coating on the surfaces; preparing an immersion alloy plating solution containing at least two immersion-platable metals; applying the immersion alloy plating solution to the substrate by immersing the substrate in the immersion alloy plating solution to form an alloy cap layer on the tin coating. The immersion platable metals in the immersion alloy plating solution may be at least two metals selected from tin, silver, bismuth, copper, nickel, lead, zinc, indium, palladium, platinum, gold, cadmium, ruthenium and cobalt. The immersion platable metals may be added to the solution in the form of metal salts

Dependencies are inferred from the claim text.