Process for producing copper foil by electrolytic deposition of copper

Abstract

The invention relates to a process for producing copper foil by electrolytic deposition of copper metal on a rotating drum cathode and, in particular, to the means for dissolving the copper to be deposited in the process. In the process, copper is electrolytically deposited on a rotating drum cathode, which is partially immersed in an electrolyte solution contained in a plating tank; the deposited copper layer is peeled off the part of the drum cathode that is not immersed in the electrolyte solution to obtain the copper foil; an insoluble anode is used as counter-electrode to the drum cathode; the electrolyte solution contains copper ions, organic additives and an Fe2+/Fe3+ redox system; the concentration of copper ions in the electrolyte solution is maintained constant by passing the electrolyte solution through a copper dissolution unit; in the copper dissolution unit, the electrolyte solution is in contact with an auxiliary anode and an auxiliary cathode; copper metal and an oxygen-containing gas are introduced into the copper dissolution unit; the auxiliary anode is in contact with the copper metal; the oxygen-containing gas contacts the surface of the copper metal; the copper metal continuously dissolves into the electrolyte solution by being oxidized by the Fe3+ component of the Fe2+/Fe3+ redox system.

1 . A continuous process for producing copper foil, wherein
 copper is electrolytically deposited on a rotating drum cathode ( 3 ), which is partially immersed in an electrolyte solution ( 4 ) contained in a plating tank;   the copper layer deposited on the drum cathode ( 3 ) is peeled off the part of the drum cathode ( 3 ) that is not immersed in the electrolyte solution ( 4 ) to obtain the copper foil;   an insoluble anode is used as counter-electrode to the drum cathode ( 3 );   the electrolyte solution ( 4 ) contains copper ions, organic additives and an Fe 2+ /Fe 3+  redox system;   the concentration of copper ions in the electrolyte solution ( 4 ) is maintained constant by passing the electrolyte solution ( 4 ) through a copper dissolution unit ( 5 );   in the copper dissolution unit ( 5 ), the electrolyte solution ( 4 ) is in contact with an auxiliary anode ( 7 ) and an auxiliary cathode ( 6 );   copper metal and an oxygen-containing gas are introduced into the copper dissolution unit ( 5 );   the auxiliary anode ( 7 ) is in contact with the copper metal;   the oxygen-containing gas is introduced such that bubbles ( 11 ) thereof contact the surface of the copper metal;   the copper metal continuously dissolves into the electrolyte solution ( 4 ) by being oxidized by the Fe 3+  component of the Fe 2+ /Fe 3+  redox system and optionally the oxygen contained in the oxygen-containing gas.   
     
     
         2 . The process according to  claim 1  wherein the organic additives contained in the electrolyte solution comprise at last one organic sulfur-containing compound as brightener, at least one nitrogen-containing compound as levelling agent, and at least one oxygen-containing compound as carrier. 
     
     
         3 . The process according to  any one of the preceding claims  wherein the electrolyte solution contains 20-250 g/l of copper sulfate pentahydrate, 50-350 g/l of sulfuric acid, 15-200 g/l of iron (II) sulfate heptahydrate, 0.01-0.18 g/l of chloride ions. 
     
     
         4 . The process according to  any one of the preceding claims  wherein the electrolyte solution contains methanesulfonic acid and the iron and/or copper salts thereof. 
     
     
         5 . The process according to any one of  claim 1, 2 or 4 , wherein the electrolyte solution is substantially free of sulfuric acid and/or sulfate salts. 
     
     
         6 . The process according to  claim 2  wherein the total concentration of brightener compound present in the electrolyte solution is from 0.01 mg/l to 100 mg/l. 
     
     
         7 . The process according to  claim 2  wherein the total concentration of levelling agent compound present in the electrolyte solution is from 0.5 mg/l to 400 mg/l. 
     
     
         8 . The process according to  claim 2  wherein the total concentration of carrier compound present in the electrolyte solution is from 0.005 g/l to 20 g/l. 
     
     
         9 . The process according to  any one of the preceding claims  wherein the current density at the drum cathode is from 20 to 100 A/dm 2 . 
     
     
         10 . The process according to  any one of the preceding claims  wherein the amount of copper deposited on the drum cathode is from 10 to 50 kg/min. 
     
     
         11 . The process according to  any one of the preceding claims  wherein copper is deposited on the rotating drum cathode at a temperature of from 15 to 70° C. 
     
     
         12 . The process according to  any one of the preceding claims  wherein the concentration of copper ions in the electrolyte solution present in the plating tank is from 80 to 90 g/l. 
     
     
         13 . The process according to  any one of the preceding claims  wherein the part of the electrolyte solution withdrawn from the plating tank is introduced into the copper dissolution unit ( 5 ) at a location that is closer to the auxiliary cathode ( 6 ) than to the auxiliary anode ( 7 ) so that the withdrawn part comes into contact with the auxiliary cathode ( 6 ) first. 
     
     
         14 . The process according to  any one of the preceding claims  wherein the part of the electrolyte solution withdrawn from the plating tank is introduced into the copper dissolution unit ( 5 ) having a concentration of the Fe 3+  ions which is higher than the concentration of the Fe 3+  ions which leaves the copper dissolution unit ( 5 ) back into the plating tank. 
     
     
         15 . The process according to  any one of the preceding claims  wherein the voltage applied between the auxiliary anode ( 7 ) and the auxiliary cathode ( 6 ) is 1 to 9 V.