A Method And Composition For Selectively Stripping Nickel From A Substrate

Abstract

A method of stripping nickel from a stainless steel substrate comprises providing a stainless steel substrate 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 from a stainless steel substrate. 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 stainless steel substrate comprises providing a stainless steel substrate and contacting the stainless steel substrate with phosphate ions, and an oxidizer.

What is claimed is:  
     
         1 . A method of stripping nickel from a stainless steel substrate, comprising: 
 providing a stainless steel substrate comprising a nickel deposit on a stainless steel surface; and    contacting the nickel deposit with 
 phosphate ions, and  
 an oxidizer;  
   under conditions effective to remove at least a portion of the nickel deposit from the surface.    
     
     
         2 . The method of  claim 1  wherein the stainless steel substrate is equipment used during the manufacture of printed wiring boards.  
     
     
         3 . The method of  claim 1  wherein said surface is bright after said contacting step.  
     
     
         4 . The method of  claim 1  wherein said surface is uniform after said contacting step.  
     
     
         5 . The method of  claim 1  wherein said nickel deposit comprises electroless nickel.  
     
     
         6 . The method of  claim 1  wherein said surface is not significantly etched after said contacting step.  
     
     
         7 . The method of  claim 1  further comprising contacting said nickel deposit with ammonium ions.  
     
     
         8 . The method of  claim 1  wherein said phosphate ions are provided in an aqueous solution at a concentration of at least about 10 g/L.  
     
     
         9 . The method of  claim 1  wherein said oxidizer is provided in an aqueous solution at a concentration of about 15 to about 100 g/L.  
     
     
         10 . The method of  claim 1  wherein said contacting step occurs at a pH between about 2 and about 12.  
     
     
         11 . The method of  claim 1  wherein said contacting step occurs at a pH higher than about 3.  
     
     
         12 . The method of  claim 1  wherein said contacting step occurs at a temperature between about 0 and about 100° C.  
     
     
         13 . The method of  claim 1  wherein the duration of said contacting step is from about 5 to about 600 minutes.  
     
     
         14 . The method of  claim 1  wherein said phosphate ions, and oxidizer are provided in the form of a single solution.  
     
     
         15 . The method of  claim 1  wherein said contacting step is carried out by forming a bath of phosphate ions and peroxide in aqueous solution and immersing said nickel deposit in said bath.  
     
     
         16 . The method of  claim 1  wherein said conditions are effective to remove substantially all of said nickel deposit from at least a portion of said stainless steel surface.  
     
     
         17 . The method of  claim 1  wherein said oxidizer is selected from the group consisting of peroxides, persulfates and nitric acid.  
     
     
         18 . An aqueous solution comprising: 
 phosphate ions,    ammonium ions, and    an oxidizing agent    present in amounts effective to strip nickel from a stainless steel substrate.    
     
     
         19 . An aqueous solution for stripping nickel from a stainless steel substrate comprising from about 1% to about 10% by weight hydrogen peroxide and from about 5% to about 30% by weight of an ammonium phosphate.