Single Solution for Electro-Electroless Deposition of Metals

Abstract

A hybrid electro-electroless deposition process whereby multiple metal films layers are deposited from a single plating solution which includes both electroless and electroplating components. The article to be plated is immersed in the solution, and electric current is selectively applied at determined voltages for predetermined times, at selected intervals to effect electroplating in conjunction with electroless deposition. Electroplated metal layers are interspersed with electroless deposited metal layers.

1 . A process for deposition of a multi-layer metal coating on a metal substrate to be plated, the process comprising,
 at least partially immersing said substrate into a plating bath, the plating bath comprising a reducing agent, and a source of metal plating ions, the plating ions comprising one or more from the grouping consisting of copper ions, gold ions, nickel ions, zinc ions, silver ions, boron ions, cobalt ions and phosphorous ions,   providing a sacrificial metal anode and cathode in said plating bath, and electrically connecting said anode and cathode,   selectively supplying power to said anode, wherein said power is supplied in a pulsed time-wise manner to alternately effect anode oxidation and the formation of an electro-deposition plating layer of metal ions from the anode on the substrate, and the formation of an electroless deposition plating layer of the plating ions from the bath solution.   
     
     
         2 . The process of  claim 1 , wherein said substrate is provided as said cathode. 
     
     
         3 . The process of  claim 1 , wherein the plating ions comprise gold and/or copper ions. 
     
     
         4 . The process of  claim 1 , further comprising maintaining the plating bath at a temperature of between about 40° C. to less than about 99° C., and preferably from about 95° C. to about 98° C. 
     
     
         5 . The process of  claim 1 , wherein said plating ions are gold ions, and said anode comprises a metal selected from the group consisting of nickel, a nickel alloy and cobalt. 
     
     
         6 . (canceled) 
     
     
         7 . The process as claimed in  claim 1 , wherein said substrate comprises magnesium or a magnesium alloy, said anode comprises zinc, and said plating ions comprise nickel, zinc and phosphorous ions in relative amounts selected to form an electroless Ni—Zn—P plating layer. 
     
     
         8 . The process as claimed in  claim 1 , wherein power is supplied to said anode from a power source as alternating current. 
     
     
         9 . The process as claimed in  claim 8 , wherein said power is supplied to said anode at 5 to 45 minute intervals, for a period of time selected at between about 30 and 600 seconds. 
     
     
         10 . The process as claimed in  claim 9 , wherein power is supplied to said anode at a voltage between about 8 and 80 volts, and preferably at about 9 and 50 volts. 
     
     
         11 . The process as claimed in  claim 1 , wherein said reducing agent comprises sodium hypophosphite, and the source of metal plating ions is selected from the group consisting of sodium tetrachloroaurate, nickel sulfate heptahydrate, zinc sulfate heptahydrate, boric acid, cobalt chloride heptahydrate, and nickel chloride hexahydrate. 
     
     
         12 . A process for forming multiple metal coatings on a substrate, the process comprising:
 providing a portion of the substrate to be plated in a plating bath, the plating bath comprising a reducing agent and sodium tetrachloroaurate as a source of gold ions,   introducing a nickel or nickel alloy anode into said plating bath,   electrically connecting said anode to said substrate as a cathode,   selectively supplying power to said anode in a pulsed time-wise manner to alternately form on the portion of the substrate to be plated, layer of the an electro-deposited nickel and electroless deposited layers of gold.   
     
     
         13 . The process as claimed in  claim 12 , wherein the substrate comprises a metal selected from the group consisting of Mg, Pd, Rh, Au, Ag, Cu, Ni, Co, Fe, and their alloys. 
     
     
         14 . The process as claimed in  claim 13 , wherein said power is supplied to said anode at 5 to 45 minute intervals, for a period of time selected at between about 30 and 600 seconds, and preferably between about 120 and 300 seconds. 
     
     
         15 . The process as claimed in  claim 12 , wherein
 said power is supplied in a pulsed time-wise manner at a voltage selected at between about 1 and 120 volts, and further comprising maintaining said plating bath at a temperature between about 90° C. and 99° C.   
     
     
         16 . (canceled) 
     
     
         17 . A process for alternatively depositing metal coatings on a substrate, the process comprising,
 immersing a portion of the substrates to be plated in a plating bath, the plating bath including a least one source of plating ions selected from the group consisting of sodium tetrachloroaurate, nickel sulfate heptahydrate, zinc sulfate heptahydrate, boric acid, cobalt chloride heptahydrate, nickel chloride hexahydrate,   providing a metal anode and a cathode in said plating bath, said anode being in electrical communication with said cathode,   
       selectively supplying power to said anode in a pulsed time-wise manner to form on the portion of the substrate to be plated, alternating electro-deposited metal layers and electroless deposited metal layers, said power being supplied to said anode from a power source as alternating current. 
     
     
         18 . The process as claimed in  claim 17 , wherein said substrate is provided as said cathode, said substrate being selected from the group consisting of Mg, Pd, Rh, Au, Ag, Cu, Ni, Co, Fe, and their alloys. 
     
     
         19 . The process as claimed in  claim 18 , wherein the plating bath further includes sodium hypophosphite as a reducing agent. 
     
     
         20 . (canceled) 
     
     
         21 . The process as claimed in  claim 17 , wherein said power is supplied to said anode at 5 to 45 minute intervals, for a period of time selected at between about 30 and 600 seconds, and preferably between about 120 and 300 seconds, and wherein power is supplied to said anode at a voltage of between about 40 and 120 volts, and preferably at about 60 and 70 volts. 
     
     
         22 . (canceled) 
     
     
         23 . A process for the deposition of multiple layers of thin metal films on a substrate comprising:
 preparing a plating bath comprising an electroless plating metal component and electroplating metal component; and   immersing the substrate in a plating bath to effect electroless plating of the electroless plating metal component;   with said substrate remaining immersed in said bath, selectively apply a selected voltage over a predetermined interval or series of intervals to effect electroplating of the electroplating metal component thereon; and   wherein the plating bath solution is a two part solution comprising,   a first part comprising:
 1 to 4 grams, and preferably about 2 grams per litre sodium tetrachloroaurate as said electroless plating metal component: 
 5 to 15 grams, and preferably about 10 grams per litre boric acid; and 
 up to 2 grams, and preferably about 1 gram per litre sodium hydroxide, 
   a second part comprising:
 7 to 12 grams, and preferably about 9.5 grams per litre sodium thiosulfate; 
 2 to 5 grams, and preferably about 3.75 grams per liter sodium sulfite, and 
 7.5 to 15 grams, and preferably about 10 grams per liter of boric acid. 
   
     
     
         24 . (canceled) 
     
     
         25 . The process as claimed in  claim 23 , wherein the plating bath further comprises a dopant solution comprising:
 25 to 50 grams per litre cobalt chloride heptahydrate; and   25 to 50 grams per litre nickel chloride hexahydrate.   
     
     
         26 . The process as claimed in  claim 23 , wherein the plating bath solution has a pH of at least 8. 
     
     
         27 . The process as claimed in  claim 23 , wherein plating bath solution further includes up to 25 grams per litre sodium hypophosphite, and optionally up to 100 grams per litre sodium citrate tribasic. 
     
     
         28 . The process as claimed in  claim 23 , wherein both electroless and electroplating are effected at a temperature of up to 99° C. and preferably between about 50° C. and 80° C. 
     
     
         29 . The process as claimed in  claim 23 , wherein the substrate comprises a nickel substrate or a copper substrate. 
     
     
         30 . The process as claimed in  claim 23 , wherein the electroless plating metal component comprises gold, and the electroplating metal component is selected from the group consisting of nickel, cobalt and nickel/cobalt alloys.