Method of electroplating tin films with indium using an alkanesulfonic acid based electrolyte

Abstract

A method comprising incorporating indium into an entire Sn film for preventing the growth of whiskers from the Sn film, wherein the Sn film is applied to a metallic substrate.

What is claimed is: 
     
         1 . An electrolyte composition comprising:
 (a) a divalent tin salt;   (b) a trivalent indium salt; and   (c) an alkanesulfonic acid.   
     
     
         2 . The composition of  claim 1 , further comprising a chelating agent. 
     
     
         3 . The composition of  claim 2 , wherein the chelating agent is an organic carboxylic acid or a salt thereof. 
     
     
         4 . The composition of  claim 2 , wherein the chelating agent is gluconic acid, malic acid, tartaric acid, ethylenediaminetetraacetic acid, nitrilotriacetic acid, diethylenetriaminepentaacetic acid, a salt of gluconic acid, a salt of malic acid, a salt of tartaric acid, a salt of ethylenediaminetetraacetic acid, a salt of nitrilotriacetic acid, or a salt of diethylenetriaminepentaacetic acid. 
     
     
         5 . The composition of  claim 1 , further comprising a hydrogen suppressor. 
     
     
         6 . The composition of  claim 6 , wherein the hydrogen suppressor comprises an oligomer or a polymer of ethylene oxide, or an epihalohydrin copolymer. 
     
     
         7 . The composition of  claim 1 , further comprising a pH adjustor to adjust the pH range of the composition to 0.1 to 5. 
     
     
         8 . The composition of  claim 7 , wherein the pH adjustor is a caustic alkali agent. 
     
     
         9 . The composition of  claim 1 , further comprising a chelating agent, a hydrogen suppressor, and a pH adjustor. 
     
     
         10 . The composition of  claim 9 , wherein the chelating agent is an organic carboxylic acid or a salt thereof, the hydrogen suppressor is an oligomer or a polymer of ethylene oxide, or an epihalohydrin copolymer, and the pH adjustor is a caustic alkali agent. 
     
     
         11 . The composition of  claim 1 , wherein the alkanesulfonic acid is methanesulfonic acid. 
     
     
         12 . The composition of  claim 10 , wherein the alkanesulfonic acid is methanesulfonic acid. 
     
     
         13 . The composition of  claim 1 , wherein the composition has a pH of 0.1 to 5. 
     
     
         14 . The composition of  claim 9 , wherein the chelating agent is gluconic acid, malic acid, tartaric acid, ethylenediaminetetraacetic acid, nitrilotriacetic acid, diethylenetriaminepentaacetic acid, a salt of gluconic acid, a salt of malic acid, a salt of tartaric acid, a salt of ethylenediaminetetraacetic acid, a salt of nitrilotriacetic acid, or a salt of diethylenetriaminepentaacetic acid. 
     
     
         15 . A method comprising:
 providing an electrolyte bath comprising (a) a divalent tin salt, (b) a trivalent indium salt, and (c) an alkanesulfonic acid; and   co-electroplating tin and indium from the electrolyte bath onto a metallic substrate.   
     
     
         16 . The method of  claim 15 , wherein 0.2 to 50 atomic percent indium is co-electroplated, based on the total amount of tin and indium. 
     
     
         17 . The method of  claim 15 , wherein the electrolyte bath further comprises a chelating agent. 
     
     
         18 . The method of  claim 15 , wherein the electrolyte bath further comprises a chelating agent, a hydrogen suppressor, and a pH adjustor. 
     
     
         19 . A method comprising:
 co-electrodepositing indium, tin, and at least one additional metal other than indium and tin onto a metallic substrate thereby preventing growth of whiskers from the resulting film, wherein the film is an alloy containing greater than 90 wt % Sn.   
     
     
         20 . A method comprising:
 co-electrodepositing tin, indium and at least one additional metal selected from Cu, Ag, Zn, Pb, Bi, Cd, or Au onto a metallic substrate thereby preventing growth of whiskers from the resulting film.   
     
     
         21 . A method comprising:
 co-electrodepositing tin and indium onto a copper lead frame thereby preventing growth of whiskers from the resulting film.