Immersion plating and plated structures
AssigneeInternational Business Machines Corporation
InventorsEmanuel I. Cooper, Charles C. Goldsmith, Stephen Kilpatrick, Carmen M. Mojica, Henry A. Nye, III
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Abstract
A first metal is plated onto a substrate comprising a second metal by immersing the substrate into a bath comprising a compound of the first metal and an organic diluent. The second metal is more electropositive than the first metal. The organic diluent has a boiling point higher than a eutectic point in a phase diagram of the first and second metals. The bath is operated above the eutectic point but below the melting point of the second metal. For example, bismuth is immersion plated onto lead-free tin-based solder balls, and subsequently redistributed by fluxless reflow. Plated structures are also provided.
Claims41
A process for plating a first metal onto a substrate which comprises a second and different metal that is more electropositive than the first metal, which comprises immersing said substrate into a bath comprising a compound of said first metal and an organic diluent having a boiling point higher than an eutectic point in a phase diagram of the first and second metals;
- and
- wherein the bath is at a temperature above said eutectic point but below the melting point of said second metal.
A process for plating bismuth onto a substrate which comprises immersing the substrate to be coated into a bath comprising a bismuth compound, an organic diluent having a boiling point greater than 150° C. and an acid, and wherein the bath is above the eutectic temperature of an alloy to be formed from reaction of the bismuth with the substrate.
A composition consisting essentially of a bismuth compound, an organic diluent having a boiling point about 150° C., and having an acid pH.
Dependencies are inferred from the claim text.