Method and Composition for Selectively Stripping Nickel from a Substrate

Abstract

A method of stripping nickel from a printed wiring board comprises providing a printed wiring board with a nickel deposit on a surface and contacting the nickel deposit with phosphate ions and an oxidizer. An aqueous solution comprises ammonium ions, phosphate ions and an oxidizing agent present in amounts effective to strip nickel. An aqueous solution comprises about 1% to about 10% by weight hydrogen peroxide and about 5% to about 30% by weight of an ammonium phosphate. A method of pre-treating a copper substrate comprises providing a printed wiring board having a copper substrate and contacting the copper substrate with phosphate ions, and an oxidizer. A method of neutralizing permanganate on a printed wiring board comprises providing a printed wiring board with a permanganate residue on the printed wiring board and contacting the permanganate residue with phosphate ions, and an oxidizer.

1 - 25 . (canceled) 
   
   
       26 . An aqueous solution comprising:
 phosphate ions,   ammonium ions, and   an oxidizing agent   
     wherein said aqueous solution has a pH between about 2.3 and about 5. 
   
   
       27 . The aqueous solution of  claim 26 , wherein said phosphate ions, ammonium ions and oxidixer are present in amounts such that said solution is effective to remove substantially all of a nickel deposit from at least a portion of a surface. 
   
   
       28 . The aqueous solution of  claim 27 , wherein said surface is a copper surface. 
   
   
       29 . The aqueous solution of  claim 27 , wherein said surface is a printed wiring board and said phosphate ions, ammonium ions and oxidixer are present in amounts such that said solution is effective to strip nickel without damaging a soldermask. 
   
   
       30 . The aqueous solution of  claim 27  wherein said nickel deposit is electroless nickel. 
   
   
       31 . The aqueous solution of  claim 26 , wherein said phosphate ions, ammonium ions and oxidixer are present in amounts such that said solution is effective to brighten a copper substrate. 
   
   
       32 . The aqueous solution of  claim 26 , wherein said phosphate ions, ammonium ions and oxidixer are present in amounts such that said solution is effective to neutralize a permanganate residue. 
   
   
       33 . The aqueous solution of  claim 26 , wherein said phosphate ions are provided in an aqueous solution at a concentration of at least about 10 g/L. 
   
   
       34 . The aqueous solution of  claim 26 , wherein said oxidizer is provided in an aqueous solution at a concentration of about 15 to about 100 g/L. 
   
   
       35 . The aqueous solution of  claim 26 , wherein said ammonium ions are provided in an aqueous solution at a concentration of about 1 to about 100 g/L. 
   
   
       36 . The aqueous solution of  claim 26 , wherein said oxidizer is selected from the group consisting of peroxides, persulfates and nitric acid. 
   
   
       37 . The aqueous solution of  claim 26 , wherein a source of said phosphate ions is selected from the group consisting of ammonium phosphate monobasic, sodium phosphate monobasic, ammonium phosphate dibasic, ammonium phosphate tribasic, potassium phosphate monobasic, potassium phosphate dibasic, potassium phosphate tribasic, phosphoric acid and soluble phosphate salts. 
   
   
       38 . The aqueous solution of  claim 26 , wherein a source of said ammonium ions is selected from the group consisting of ammonium phosphate monobasic, ammonium phosphate dibasic, ammonium phosphate tribasic, ammonium hydroxide, ammonium chloride, ammonium carbonate, ammonium sulfate and soluble ammonium salts. 
   
   
       39 . An aqueous solution comprising from about 1% to about 10% by weight hydrogen peroxide and from about 5% to about 30% by weight of an ammonium phosphate. 
   
   
       40 . The aqueous solution of  claim 39 , wherein said solution is effective to remove substantially all of a nickel deposit from at least a portion of a surface. 
   
   
       41 . The aqueous solution of  claim 40  wherein said surface is a copper surface. 
   
   
       42 . The aqueous solution of  claim 40 , wherein said surface is a printed wiring board and said solution is effective to strip nickel without damaging a soldermask. 
   
   
       43 . The aqueous solution of  claim 39 , wherein said solution is effective to brighten a copper substrate. 
   
   
       44 . The aqueous solution of  claim 39 , wherein said solution is effective to neutralize a permanganate residue. 
   
   
       45 . The aqueous solution of  claim 39 , wherein said aqueous solution has a pH between about 2.3 and about 5