Cyanide-free electroplating baths for white bronze based on copper (i) ions

Abstract

Copper alloy electroplating baths include one or more sources of copper (I) ions and one or more sources of tin ions to electroplate copper/tin alloys of mirror bright white bronze. The copper alloys may also include one or more sources of silver ions to electroplate ternary alloys of bright white bronze containing copper/tin/silver. The copper alloy electroplating baths are cyanide-free.

What is claimed is: 
     
         1 . An electroplating bath comprising one or more sources of copper (I) ions, one or more sources of alloying tin ions, optionally one or more sources of alloying silver ions, one or more compounds having a formula:
   X—S—Y  (I)
   wherein X and Y may be the same or different and may be substituted or unsubstituted phenol groups, HO—R— or —R′S—R″—OH wherein R, R′ and R″ may be the same or different and are linear or branched alkylene radicals having 1 to 20 carbon atoms; and one or more tetrazoles wherein a mole ratio of the one or more tetrazoles to the copper (I) ions in the electroplating bath is ≧1 and a mole ratio of the one or more tetrazoles to the one or more compounds of formula (I) is 0.05 to 4, the electroplating bath is cyanide-free.   
     
     
         2 . The electroplating bath of  claim 1 , wherein X and Y are different and are HO—R— or —R′—S—R″—OH, and R, R′ and R″ may be the same or different. 
     
     
         3 . The electroplating bath of  claim 1 , wherein the one or more tetrazoles have a formula: 
       
         
           
           
               
               
           
         
         wherein M is hydrogen, NH 4 , sodium or potassium and R 1  is substituted or unsubstituted, linear or branched (C 2 -C 20 )alky, or substituted or unsubstituted (C 6 -C 10 )aryl. 
       
     
     
         4 . A method of electroplating comprising:
 a) contacting a substrate with an electroplating bath comprising one or more sources of copper (I) ions, one or more sources of alloying tin ions, optionally one or more sources of alloying silver ions, one or more compounds having a formula:
   X—S—Y  (I)
 
   wherein X and Y may be the same or different and may be substituted or unsubstituted phenol group, HO—R— or —R′S—R″—OH wherein R, R′ and R″ may be the same or different and may be linear or branched alkylene radicals having 1 to 20 carbon atoms; and one or more tetrazoles, wherein a mole ratio of the one or more tetrazoles to the copper (I) ions in the electroplating bath is ≧1 and a mole ratio of the one or more tetrazoles to the one or more compounds of formula (I) is 0.05 to 4, the electroplating bath is cyanide-free; and   b) electroplating a copper/tin alloy or optionally a copper/tin/silver alloy on the substrate.   
     
     
         5 . The method of  claim 4 , wherein X and Y are different and are HO—R— or —R′—S—R″—OH, and R, R′ and R″ may be the same or different. 
     
     
         6 . The method of  claim 4 , wherein the one or more tetrazoles have a formula: 
       
         
           
           
               
               
           
         
         wherein M is hydrogen, NH 4 , sodium or potassium and R 1  is substituted or unsubstituted, linear or branched (C 2 -C 20 )alky, or substituted or unsubstituted (C 6 -C 10 )aryl. 
       
     
     
         7 . The method of  claim 4 , further comprising electroplating a finishing layer of silver, gold, palladium or chromium on the copper/tin alloy or the copper/tin/silver alloy.