Method and apparatus for making very low roughness copper foil

1. A method for smoothing a copper foil, comprising:

applying a positive current to the copper foil,

applying a negative current to a first cathode plate in a first electrolytic polishing solution and a second cathode plate in a second electrolytic polishing solution,

dipping the copper foil in the first electrolytic polishing solution, wherein a side of the copper foil faces the first cathode plate,

removing the copper foil from the first electrolytic polishing solution, and

dipping the copper foil in the second electrolytic polishing solution, wherein a side of the copper foil faces the second cathode plate;

wherein

the first electrolytic polishing solution is of a different temperature, acidity and/or corrosion inhibitor concentration from the second electrolytic polishing solution, and

the second electrolytic polishing solution has a lower electrolytic polishing rate than the first electrolytic polishing solution.

2. A method for manufacturing a copper foil having very low roughness, the method comprising the steps of;

pickling a copper foil ( 40 ) manufactured by electrodepositon or mechanical rolling within an acid pickling bath ( 100 ) containing an acid solution ( 100 a ) (S 1000 );

electrolytic polishing the copper foil through electrolysis by applying a positive current to the copper foil ( 40 ) and by applying a negative current to the cathode plate ( 210 ) with dipping the copper foil ( 40 ) to face a cathode plate ( 210 ) within at least one electrolytic polishing bath ( 200 ) installed with the cathode plate and containing an electrolytic polishing solution ( 200 a ) (S 2000 ); and

washing the polished copper foil ( 40 ) within a water washing bath ( 300 ) containing water (S 3000 );

wherein the electrolytic polishing step is performed at a gradually decreasing electrolytic polishing rate using a plurality of electrolytic polishing baths ( 200 ) containing the electrolytic polishing solutions ( 200 a ) of different electrolytic polishing rates, which electrolytic polishing solutions have different acidity(pH), temperature, and concentration of corrosion inhibitor.

3. The method according to claim 2 , wherein the electrolytic polishing solution ( 200 a ) is selected one or at least two from the group consisting of phosphoric acid, sulfuric acid, hydrochloric acid, nitric acid and boric acid.

4. The method according to claim 3 , wherein the electrolytic polishing solution ( 200 a ) further comprises a corrosion inhibitor formed of one or at least two combinations selected from the group consisting of chromic acid, urea, mercaptan, and sulfur compounds.

5. The method according to claim 2 , wherein the electrolytic polishing solution ( 200 a ) has an acidity within a pH range of 2.0 to 3.5.

6. The method according to claim 2 , wherein the electrolytic polishing step is performed in the electrolytic polishing solution having a temperature of 20 to 90° C.

7. The method according to claim 2 , wherein the electrolytic polishing step is performed at a current density of 10 to 70 A/dm 2 .

8. The method according to claim 2 , wherein the electrolytic polishing step is performed during 20 to 120 seconds per one electrolytic polishing bath ( 200 ).

9. The method according to claim 2 , wherein the electrolytic polishing step is performed with the electrolytic polishing solution ( 200 a ) having a laminar flow on the surface of the copper foil ( 40 ).

10. The method according to claim 2 , wherein the electrolytic polishing step is performed by installing the cathode plate ( 210 ) to face a matt side of the copper foil having a relatively high roughness.

11. The method according to claim 2 , wherein the electrolytic polishing step is performed by arranging alternately the electrolytic polishing bath ( 200 ) having the cathode plate ( 210 ) installed to face only the matt side of the copper foil and the electrolytic polishing bath ( 200 ) having the cathode plate ( 210 ) installed to face only the shiny side of the copper foil.

12. The method according to claim 2 , wherein the electrolytic polishing step polishes the copper foil precisely as the temperature of the electrolytic polishing solution ( 200 a ) within a plurality of baths ( 200 ) is set to be lower according to the direction of the arrangement of the baths, which is the same as the proceeding direction of the copper foil.

13. The method according to claim 2 , wherein the electrolytic polishing step polishes the copper foil precisely as the acidity (pH) of the electrolytic polishing solution ( 200 a ) within a plurality of baths ( 200 ) is set to be higher according to the direction of the arrangement of the baths, which is the same as the proceeding direction of the copper foil.

14. The method according to claim 2 , wherein the electrolytic polishing step polishes the copper foil precisely as the concentration of the corrosion inhibitor added to the electrolytic polishing solution ( 200 a ) within a plurality of baths ( 200 ) is set to higher according to the direction of the arrangement of the baths, which is the same as the proceeding direction of the copper foil.

15. The method according to claim 14 , wherein the corrosion inhibitor includes one or at lest two chemical compounds selected from the group consisting of chromic acid, urea, mercaptan, and sulfur compounds.

16. The method according to claim 2 , wherein the acid solution ( 100 a ) includes one selected from the group consisting of sulfuric acid of pH 5.0 or less, hydrochloric acid of pH 5.0 or less, and a mixed solution of sulfuric acid of pH 5.0 or less and hydrochloric acid of pH 5.0 or less.