Electroless tin and tin-lead alloy plating baths
AssigneeAMP Incorporated
InventorThomas F. Davis
Life of this patent
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Abstract
Salt compositions and baths thereof useful in, and methods for, immersion plating of tin and tin-lead alloys which give greatly increased deposition rates and thicker coatings of better quality accomplished by incorporating into immersion plating tin bath compositions soluble plumbous salts in the amount of from 0.5 grams per liter calculated on the basis of elemental lead to the maximum amount soluble in the bath and a sulphur-containing complexing agent for the tin and lead such as thiourea or a thiourea-type derivative. Preferably the salt elements are stannous chloride, lead chloride, sodium hypophosphite (as a solubility enhancer) and with hydrochloric acid used as a agent for adjusting the pH in the resulting bath from 0.5 to 1.0.
Claims9
A salt composition, when diluted with 1 liter of water and sufficient hydrochloric acid to provide a solution having a pH of 0.5 to 1, is suitable for immersion plating [tin-lead alloys] essentially tin at increased rates, the salt composition [comprising] consisting essentially of the proportions of:
- ______________________________________ a. hydrous stannous chloride from about 10 to about 150 g, (SnCl.sub.2 . 2H.sub.2 O) b. lead chloride from about 1 to about 12 g, (PbCl.sub.2) c. sodium hypophosphite from about 10 to about 100 g, (NaH.sub.2 PO.sub.2 . H.sub.2 O) and d. thiourea from about [15] 40 about 100 g, (NH.sub.2 . CS . NH.sub.2) ______________________________________
A salt composition for immersion plating a tin-lead alloy, when diluted with 1 liter of water and sufficient hydrochloric acid to provide a solution having a pH of 0.5 to 1, said salt composition [comprising] consisting essentially of the proportions of:
- ______________________________________ a. hydrous stannous chloride from about 5 to about 100 g. (SnCl.sub.2 . 2H.sub.2 O) b. lead chloride from about 2 to 25 g. (PbCl.sub.2) c. sodium hypophosphite from about 60 to 100 g. (NaH.sub.2 PO.sub.2 . H.sub.2 O) and d. thiourea from about 100 about 150 g. (NH.sub.2 . CS . NH.sub.2) ______________________________________
Dependencies are inferred from the claim text.