Regeneration method for a plating solution

Abstract

The invention relates to a method of depositing a layer of metal and to a method of regenerating a solution containing metal ions in a high oxidation state. To regenerate tin ions consumed from a tin plating solution by metal deposition, it has been known in the art to carry the plating solution over metallic tin to cause tin (II) ions to form. However, the amount of tin contained in thus regenerated baths slowly and continuously increases. The solution to this problem is to utilize an electrolytic regeneration cell that is provided with at least one auxiliary cathode and with at least one auxiliary anode. Tin serving for regeneration is electrolytically deposited from the solution onto the at least one auxiliary cathode in the electrolytic regeneration cell. The solution is carried over the tin serving for regeneration in order to reduce formed tin (IV) ions to tin (II) ions.

1 . A method of depositing a metal layer, comprising the following method steps: 
 a. Preparing a metal plating bath containing metal ions in a low oxidation state;    b. Depositing a metal layer from the metal plating bath onto a work piece;    c. Bringing the metal plating bath in contact with the metal serving for regeneration in order to reduce metal ion in a high oxidation state contained in the metal plating bath to metal ions in a low oxidation state,    wherein an electrolytic regeneration cell comprised of at least one auxiliary cathode and of at lease one auxiliary anode is provided and wherein the metal serving for regeneration is electrolytically deposited from the metal plating bath onto the at least one auxiliary cathode.    
     
     
         2 . The method of  claim 1 , wherein the method serves for depositing tin containing layers, wherein the metal ions in the low oxidation state are Sn(II) ions and the metal ions in the high oxidation state are Sn(IV) ions and wherein the metal is metallic tin.  
     
     
         3 . The method of  claim 1 , wherein the at least one auxiliary cathode is made of copper or of a copper alloy.  
     
     
         4 . The method of  claim 1 , wherein the at least one auxiliary cathode is made of an inert material.  
     
     
         5 . The method of  claim 4 , wherein the at least one auxiliary cathode is made of platinized titanium.  
     
     
         6 . The method of  claim 1 , wherein the metal is deposited in scales onto the at lease one auxiliary cathode by adjusting the cathodic current density.  
     
     
         7 . The method of  claim 1 , wherein metal deposited onto the at least one auxiliary cathode is mechanically removed and wherein, after removal, the metal is contacted with the metal plating bath in order to reduce metal ions in a high oxidation state contained in the metal plating bath to metal ions in a low oxidation state.  
     
     
         8 . The method of  claim 1 , wherein the at lease one auxiliary anode is separated from the space surrounding the at least one auxiliary cathode by a membrane.  
     
     
         9 . The method of  claim 8 , wherein the membrane is configured such that the metal ions may not permeate said membrane.  
     
     
         10 . The method of  claim 8 , wherein said membrane is an anion exchange membrane or a monoselective ion exchange membrane.  
     
     
         11 . The method of  claim 8 , wherein an acid is provided to the space surrounding the at least one auxiliary anode.  
     
     
         12 . The method of  claim 1 , wherein at least one electrode containing the metal to be deposited is contacted with the metal plating bath and wherein the at least one electrode is polarized anodically relative to at least one further electrode so that the at least one electrode containing the metal to be deposited dissolves at least partially.  
     
     
         13 . The method of  claim 1 , wherein the workpiece is conveyed in horizontal direction through a coating chamber for deposition of the metal layer.  
     
     
         14 . A method of regenerating a solution containing metal ions in a high oxidation state, in which method the solution is brought into contact with a metal serving for regeneration in order to reduce the metal ions in a high oxidation state metal ions in a low oxidation state,  
       wherein an electrolytic regeneration cell comprised of at least one auxiliary cathode and of at least one auxiliary anode is provide and wherein the metal serving for regeneration is electrolytically deposited from the solution onto the at least one auxiliary cathode.  
     
     
         15 . The method of  claim 14 , wherein the method serves for regenerating a tin containing solution, wherein the metal ions in the low oxidation state are Sn(II) ions and the metal ions in the high oxidation state are Sn(IV) ions and wherein the metal is metallic tin.  
     
     
         16 . The method of  claim 9 , wherein an acid is provided to the space surrounding the at least one auxiliary anode.  
     
     
         17 . The method of  claim 10 , wherein an acid is provided to the space surrounding the at least one auxiliary anode.  
     
     
         18 . A method of depositing a metal layer, comprising the following method steps: 
 a. Preparing a metal plating bath containing metal ions in a low oxidation state;    b. Depositing a metal layer from the metal plating bath onto a work piece;    c. Bringing the metal plating bath in contact with the metal serving for regeneration in order to reduce metal ion in a high oxidation state contained in the metal plating bath to metal ions in a low oxidation state;    wherein an electrolytic regeneration cell comprised of at least one auxiliary cathode and of at least one auxiliary anode is provided and wherein the metal serving for regeneration is electrolytically deposited from the metal plating bath onto the at least one auxiliary cathode;    wherein the method serves for depositing tin containing layers, wherein the metal ions in the low oxidation state are Sn(II) ions and the metal ions in the high oxidation state are Sn(IV) ions and wherein the metal is metallic tin;    wherein the metal is deposited in scales onto the at least one auxiliary cathode by adjusting the cathodic current density;    wherein the at least one auxiliary anode is separated from the space surrounding the at least one auxiliary cathode by a membrane; and    wherein the membrane is configured such that the metal ions may not permeate said membrane.    
     
     
         19 . The method of  claim 18 , wherein said membrane is an anion exchange membrane or a monoselective ion exchange membrane; and 
 wherein an acid is provided to the space surrounding the at least one auxiliary anode.    
     
     
         20 . The method of  claim 19 , wherein at least one electrode containing the metal to be deposited is contacted with the metal plating bath and wherein the at least one electrode is polarized anodically relative to at least one further electrode so that the at least one electrode containing the metal to be deposited dissolves at least partially.