Environmentally friendly gold electroplating compositions and methods

Abstract

Gold electroplating compositions are substantially free of many environmental toxins to provide an environmentally friendly pure gold electroplating composition. The substantially pure gold electroplating compositions may electroplate gold over a broad current density range to deposit bright to matte gold layers on various types of electronic components and decorative articles.

What is claimed is: 
     
         1 . A gold electroplating composition comprising one or more sources of gold ions from gold-cyanide salts, one or more sources of phosphate ions, one or more sources of phosphonic acids or salts thereof, sodium potassium tartrate and one or more sources of antimony (III) ions, the gold electroplating composition is free of free-cyanide. 
     
     
         2 . The gold electroplating composition of  claim 1 , wherein the gold-cyanide salts are chosen from potassium gold cyanide, sodium gold cyanide, and ammonium gold cyanide. 
     
     
         3 . The gold electroplating composition of  claim 1 , wherein the one or more sources of phosphate ions are chosen from phosphoric acid, sodium dihydrogenate phosphate and potassium dihydrogenate phosphate. 
     
     
         4 . The gold electroplating composition of  claim 1 , wherein the one or more phosphonic acids have a formula: 
       
         
           
           
               
               
           
         
         wherein n is an integer from 2 to 3, M 1  and M 2  may be the same or different and are chosen from hydrogen, ammonium, lower alkyl amine or an alkali metal cation and Z is a radical equal in valence to n and is a linear or branched, substituted or unsubstituted (C 1 -C 12 )alkyl or an N-substituted (C 2 -C 3 )alkyl wherein the Z radical has a carbon atom linked to a phosphorus atom of formula (I). 
       
     
     
         5 . The gold electroplating composition of  claim 1 , wherein the one or more sources of antimony (III) ions are chosen from potassium antimony tartrate, sodium antimony tartrate, antimony sulfate and antimony chloride. 
     
     
         6 . The gold electroplating composition of  claim 1 , wherein the gold electroplating composition is substantially free lead, arsenic, thallium, hydrazine and sulfites. 
     
     
         7 . A method of electroplating gold comprising:
 a. providing a gold electroplating composition comprising one or more sources of gold ions from gold-cyanide salts, one or more sources of phosphate ions, one or more sources of phosphonic acids or salts thereof, sodium potassium tartrate and one or more sources of antimony (III) ions, the gold electroplating composition is substantially free of free-cyanide;   b. contacting a substrate with the gold electroplating composition; and   c. electroplating gold on the substrate using direct current or pulse current at a current density of 0.03 ASD or greater.   
     
     
         8 . The method of electroplating gold of  claim 7 , wherein the current density is from 1 ASD to 50 ASD. 
     
     
         9 . The method of electroplating gold of  claim 7 , wherein the gold-cyanide salts are chosen from potassium gold cyanide, sodium gold cyanide, and ammonium gold cyanide. 
     
     
         10 . The method of electroplating gold of  claim 7 , wherein the one or more sources of phosphate ions are chosen from phosphoric acid, sodium dehydrogenate phosphate and potassium dehydrogenate phosphate. 
     
     
         11 . The method of electroplating gold of  claim 7 , wherein the one or more phosphonic acids have a formula: 
       
         
           
           
               
               
           
         
         wherein n is an integer from 2 to 3, M 1  and M 2  may be the same or different and are chosen from hydrogen, ammonium, lower alkyl amine or an alkali metal cation and Z is a radical equal in valence to n and is a linear or branched, substituted or unsubstituted (C 1 -C 12 )alkyl or an N-substituted (C 2 -C 3 )alkyl wherein the Z radical has a carbon atom linked to a phosphorus atom of formula (I). 
       
     
     
         12 . The method of electroplating gold of  claim 7 , wherein the one or more sources of antimony (III) ions are chosen from potassium antimony tartrate, sodium antimony tartrate, antimony sulfate and antimony chloride. 
     
     
         13 . The method of electroplating gold of  claim 7 , wherein the gold electroplating composition is substantially free of free-cyanide, lead, arsenic, thallium, hydrazine and sulfites. 
     
     
         14 . The method of electroplating gold of  claim 7 , wherein the substrate is a printed circuit board, a contact for a connector, switch or decorative article.