Electroless copper coating process for chromium metal powders

Abstract

Disclosed herein are methods for electrolessly coating copper onto a chromium metal powder, the method comprising adding a nickel-coated chromium powder to an aqueous electroless copper plating bath comprising a source of copper cations, a copper-cation complexing agent, a copper-cation reducing agent, and a first base, thereby forming a copper-coated chromium metal powder. Also disclosed are copper-coated chromium metal powders prepared by a disclosed method.

What is claimed is: 
     
         1 . A method for electrolessly coating copper onto a chromium metal powder, the method comprising adding a nickel-coated chromium powder to an aqueous electroless copper plating bath comprising a source of copper cations, a copper-cation complexing agent, a copper-cation reducing agent, and a first base, thereby forming a copper-coated chromium metal powder;
 wherein the nickel-coated chromium powder is prepared by adding chromium powder to an aqueous electroless nickel plating bath comprising a source of nickel cations, a nickel-cation complexing agent, a nickel-cation reducing agent, and a second base, thereby coating the chromium powder with nickel.   
     
     
         2 . The method of  claim 1 , wherein the chromium powder has not been subjected to a roughening treatment prior to coating the chromium powder with nickel. 
     
     
         3 . The method of  claim 1 , wherein the nickel-coated chromium powder has not been subjected to a roughening treatment prior to coating the nickel-coated chromium powder with copper. 
     
     
         4 . The method of  claim 1 , wherein the source of copper cations is a cupric (Cu(II)) salt. 
     
     
         5 . The method of  claim 4 , wherein the cupric (Cu(II)) salt is copper sulfate (CuSO 4 ), copper chloride (CuCl 2 ), copper nitrate (Cu(NO 3 ) 2 ), copper acetate (Cu(OAc) 2 ), copper flouride (CuF 2 ), copper bromide (CuBr 2 ), copper carbonate (CuCO 3 ), copper chlorate (Cu(ClO 3 ) 2 ), copper phosphate (Cu 3 (PO 4 ) 2 ), copper perchlorate (Cu(ClO 4 ) 2 ), copper sulfide (CuS), copper tetrafluroborate (Cu(BF 4 ) 2 ), or a combination thereof. 
     
     
         6 . The method of  claim 1 , wherein the copper-cation complexing agent is a tartrate salt, an alkanol amine, a glycolic acid, ethylenediaminetetraacetic acid (EDTA), or a combination thereof. 
     
     
         7 . The method of  claim 6 , wherein the alkanol amine, when present, is a C 1 -C 14  alkanol amine. 
     
     
         8 . The method of  claim 7 , wherein the alkanol amine, when present, is ethanolamine, diethanolamine, triethanolamine, N,N,N′,N′-tetrakis(2-hydroxypropyl)ethylenediamine), or a combination thereof. 
     
     
         9 . The method of  claim 1 , wherein the first base is sodium hydroxide, lithium hydroxide, potassium hydroxide, tetraethylammonium hydroxide, lime, or a combination thereof. 
     
     
         10 . The method of  claim 1 , wherein the copper-cation reducing agent is glyoxylic acid, formaldehyde, dimethylamine borane, borohydride, hypophosphite, hydrazine, sucrose, glucose, dithionite, or a combination thereof. 
     
     
         11 . The method of  claim 1 , wherein the source of nickel cations is a nickel(II) salt. 
     
     
         12 . The method of  claim 11 , wherein the nickel(II) salt is nickel sulfate (NiSO 4 ), nickel chloride (NiCl 2 ), nickel flouride (NiF 2 ), nickel iodide (NiI 2 ), nickel bromide (NiBr 2 ), nickel formate (Ni(CHO 2 ) 2 ), nickel acetate (Ni(CH 3 CO 2 ) 2 ), nickel ammonium sulfate (Ni(NH 4 ) 2 (SO 4 ) 2 , nickel sulfamate (Ni(SO 3 NH 2 ) 2 , nickel fluoborate (Ni(BF 4 ) 2 ), nickel borate (Ni 3 (BO 3 ) 2 ), or a hydrate or combination thereof. 
     
     
         13 . The method of  claim 1 , wherein the nickel-cation complexing agent is sodium pyrophosphate. 
     
     
         14 . The method of  claim 1 , wherein the second base is ammonium hydroxide. 
     
     
         15 . The method of  claim 1 , wherein the nickel-cation reducing agent is sodium hypophosphite. 
     
     
         16 . The method of  claim 1 , wherein the chromium powder has an average particle size ranging from 10-150 microns. 
     
     
         17 . The method of  claim 1 , consisting essentially of the steps recited. 
     
     
         18 . The method of  claim 1 , consisting of the steps recited. 
     
     
         19 . A copper-coated chromium metal powder prepared by the process of  claim 1 . 
     
     
         20 . The metal powder of  claim 19 , comprising from 1% to 50% by weight of copper and 0.2% to 10% by weight of nickel.