High Elongation Electroless Copper Process

Abstract

An electroless copper deposition composition, comprising: (a) a source of copper ions; (b) a chelator; (c) a source of alkalinity; (d) a reducing agent; (e) nickel ions; (f) a bipyridine; (g) optionally, an additional stabilizer; and (h) optionally, a water soluble polymer. The electroless copper deposition composition can be used to deposit a ductile copper deposit on a substrate that exhibits high % elongation and high tensile strength.

What is claimed is: 
     
         1 . An electroless copper deposition composition, comprising:
 a) a source of copper ions;   b) a chelator;   c) a source of alkalinity;   d) a reducing agent;   e) 0.02 to 0.04 g/L nickel ions;   f) 0.001-0.05 g/L of a bipyridine;   g) 0.00001 to 0.0001 g/L of an additional stabilizer, wherein the additional stabilizer is selected from the group consisting of dithiobiuret, diethyldithiocarbamate, ammonium, sodium or potassium pyrrolidinethiocarbamate, thiomalic acid, and combinations of one or more of the foregoing; and   h) 0.01 to 1 g/L of a water-soluble polymer;
 wherein the composition is at least substantially free of ethylenediaminetetraacetic acid, cyanide, ferrocyanide, or cyanide derivatives; and 
 wherein the composition is free of any additional components that would have a detrimental effect on ductility. 
   
     
     
         2 . The electroless copper deposition composition according to  claim 14 , wherein the source of copper ions is selected from the group consisting of copper chloride, copper sulfate, copper nitrate, copper oxide, and combinations of one or more of the foregoing. 
     
     
         3 . The electroless copper deposition composition according to  claim 14 , wherein the chelator is selected from the group consisting of tartaric acid and salts thereof, citric acid and salts thereof, malic acid and salts thereof, acetic acids and salts thereof, and combinations of one or more of the foregoing. 
     
     
         4 . The electroless copper deposition composition according to  claim 3 , wherein the chelator comprises potassium sodium tartrate. 
     
     
         5 . The electroless copper deposition composition according to  claim 14 , wherein the reducing agent comprises formaldehyde. 
     
     
         6 . The electroless copper deposition composition according to  claim 14 , wherein the bipyridine comprises 2,2′-dipyridyl. 
     
     
         7 . (canceled) 
     
     
         8 . The electroless copper deposition composition according to  claim 14 , wherein the additional stabilizer comprises dithiobiuret or thiomalic acid. 
     
     
         9 . The electroless copper deposition composition according to  claim 14 , wherein the concentration of the bipyridine in the electroless copper deposition composition is in the range of about 0.001 to about 0.05 g/L. 
     
     
         10 . The electroless copper deposition composition according to  claim 14 , wherein the water soluble polymer comprises a methoxypolyethylene glycol. 
     
     
         11 . (canceled) 
     
     
         12 . The electroless copper deposition composition according to  claim 14 , wherein the composition contains no measurable concentration of ethylenediaminetetraacetic acid, cyanide, ferrocyanide or cyanide derivatives. 
     
     
         13 . The electroless copper deposition composition according to  claim 14 , wherein the molar ratio of chelator to copper ions is in the range of about 1:1 to about 10:1. 
     
     
         14 . An electroless copper plating bath consisting essentially of:
 a) a source of copper ions;   b) a chelator;   c) a source of alkalinity;   d) a reducing agent;   e) 0.02 to 0.04 g/L nickel ions;   f) a bipyridine;   g) 0.00001 to 0.0001 g/L of an additional stabilizer, wherein the additional stabilizer is an organic compound containing divalent sulfur; and   h) 0.01 to 1 g/L of a water-soluble polymer, wherein the water-soluble polymer is methoxypolyethylene glycol,
 wherein the electroless copper plating bath is at least substantially free of ethylenediaminetetraacetic acid, cyanide, ferrocyanide or cyanide derivatives. 
   
     
     
         15 . A method of electroless copper deposition on a substrate, the method comprising the steps of:
 contacting the substrate with an electroless copper plating solution for a period of time to deposit copper on the substrate, the electroless copper plating solution comprising:   
       a) a source of copper ions; 
       b) a chelator; 
       c) a source of alkalinity; 
       d) a reducing agent; 
       e) 0.02 to 0.04 g/L nickel ions; 
       f) a bipyridine; 
       g) 0.00001 to 0.0001 g/L of an additional stabilizer, wherein the additional stabilizer is an organic compound containing divalent sulfur; and 
       h) 0.01 to 1 g/L of a water-soluble polymer, wherein the water-soluble polymer is methoxypolyethylene glycol; and
 wherein the composition is free of any additional components that would have a detrimental effect on ductility. 
 
     
     
         16 . The method according to  claim 15 , wherein the substrate comprises acrylonitrile butadiene styrene. 
     
     
         17 . The method according to  claim 16 , wherein the substrate is doped with a copper chromite catalyst and laser ablated, wherein the electroless copper deposits on the laser ablated substrate. 
     
     
         18 . The method according to  claim 15 , wherein the concentration of the bipyridine in the electroless copper plating solution is in the range of about 0.001 to about 0.05 g/L. 
     
     
         19 . The method according to  claim 15 , wherein the copper deposit exhibits a % elongation of at least 10% as measured according to ASTM E-345. 
     
     
         20 . The method according to  claim 15 , wherein the copper deposit exhibits a % elongation of at least 12% as measured according to ASTM E-345. 
     
     
         21 . The method according to  claim 15 , wherein the copper deposit exhibits a % elongation of at least 14% as measured according to ASTM E-345. 
     
     
         22 . The method according to  claim 15 , wherein the electroless copper plating solution is at least substantially free of ethylenediaminetetraacetic acid, cyanide, ferrocyanide, or cyanide derivatives. 
     
     
         23 . The method according to  claim 15 , wherein the additional stabilizer is present in the electroless copper plating solution at a concentration of 0.00001 to 0.0001 g/L, wherein the additional stabilizer is selected from the group consisting of dithiobiuret, diethyldithiocarbamate, ammonium, sodium or potassium pyrrolidinethiocarbamate, thiomalic acid, and combinations of one or more of the foregoing.