Coating processes – Immersion or partial immersion – Metal base
Patent
1993-12-03
1995-02-21
Beck, Shrive
Coating processes
Immersion or partial immersion
Metal base
4274431, B05D 118
Patent
active
053914023
ABSTRACT:
An electroless immersion plating process for depositing a tin-bismuth plate onto a surface formed of copper or the like comprises immersing the surface into an acidic aqueous solution comprising a tin alkane sulfonate compound, preferably tin methane sulfonate, and a bismuth alkane sulfonate compound, preferably bismuth methane sulfonate. The solution also contains thiourea in an amount effective to reduce tin at the surface. The bismuth compound is added in an amount to produce a bismuth concentration that is less than about 1.0 gram per liter. Furthermore, the ratio of tin to bismuth in the solution is at least 30 to 1, and preferably at least 50 to 1. The process deposits a dense, adherent plate composed of a tin-bismuth alloy containing at least 50 weight percent tin and preferably containing greater than 70 weight percent tin, which plate is well suited for use in microelectronic soldering operations.
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Fuerhaupter Harry
Growney Alicia
Melton Cynthia M.
Beck Shrive
Fekete Douglas D.
Motorola
Utech Benjamin L.
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