Electrolysis bath for electrodepositing silver-tin alloys

Abstract

The invention relates to an electrolysis bath for electrodepositing silver-tin alloys that, in addition to water serving as a solvent with a pH value of less than 1.5, contains a water-soluble silver compound, a water-soluble tin compound and an organic complexing agent. In order to obtain a stable electrolysis bath that enables the homogenous deposition of a compact tin-silver alloy with any type of composition, an aliphatic complexing agent having a sulfide group and an amino group is used as a complexing agent, whereby the functional groups are bound to different carbon atoms.

1 . An electrolytic bath for electrodepositing silver-tin alloys, which in addition to water as a solvent with a pH of less than 1.5 comprises a water-soluble silver compound, a water-soluble tin compound and an organic complexant, wherein the complexant is an aliphatic complexant and has a sulfide group and an amino group which are linked to different carbon atoms.  
     
     
         2 . The electrolytic bath as claimed in  claim 1 , wherein the sulfide group and the amino group are linked to adjacent carbon atoms.  
     
     
         3 . The electrolytic bath as claimed in  claim 1 , wherein the complexant has fewer than seven carbon atoms.  
     
     
         4 . The electrolytic bath as claimed in  claim 1 , wherein the complexant has a disulfide bridge.  
     
     
         5 . The electrolytic bath as claimed in  claim 1 , wherein the complexant is a compound from the group consisting of cysteamine, cysteine, cystamine or cystine.  
     
     
         6 . The electrolytic bath as claimed in  claim 1 , wherein the concentration of the silver ions is 0.1-20 g/l, based on silver.  
     
     
         7 . The electrolytic bath as claimed in  claim 1 , wherein the concentration of the tin ions is 1-50 g/l, based on tin.  
     
     
         8 . The electrolytic bath as claimed in  claim 1 , wherein the particle concentration of the complexant is greater than the particle concentration of the silver.  
     
     
         9 . The electrolytic bath as claimed in  claim 1 , wherein the tin compound is selected from the group of Sn(II) halides, Sn(IV) halides, alkali metal stanates, tin alkanesulfonates or is ammonium stanate, Sn(II) sulfate or SnO, tin citrate or tin oxalate.  
     
     
         10 . The electrolytic bath as claimed in  claim 1 , wherein the silver compound is silver nitrate, silver sulfate, Ag 2 O, a silver halide, a silver alkanesulfonate or a silver diamine complex.  
     
     
         11 . The electrolytic bath as claimed in  claim 1 , wherein the acid used to adjust the pH is an alkanesulfonic acid.  
     
     
         12 . An electrolytic bath as claimed in  claim 1 , which comprises brighteners, cross-linking agents and conducting salts in the form of customary additives.  
     
     
         13 . The use of an electrolytic bath as claimed in  claim 1  to produce a tin-silver alloy.