Chemistry: electrical and wave energy – Apparatus – Electrolytic
Reexamination Certificate
1999-06-22
2001-02-06
Bell, Bruce F. (Department: 1741)
Chemistry: electrical and wave energy
Apparatus
Electrolytic
C204S206000, C204S211000, C204S212000, C204S213000, C204S216000, C204S242000, C204S280000, C204S281000
Reexamination Certificate
active
06183607
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to processes for electrodepositing metal, and more particularly, to an anode for use in such processes. The present invention is particularly applicable in forming high quality, porous-free, thin copper foil and will be described with particular reference thereto; it being understood, however, that the present invention may also find advantageous application in electroforming other metal foils, or in forming copper foils of greater thicknesses.
BACKGROUND OF THE INVENTION
The basic technique in forming electrodeposited foil has not changed greatly over the years. In this respect, electrodeposited copper foil is generally formed by immersing a rotating drum cathode in an electrolytic solution containing copper ions. An anode formed from one or more arcuate sections of electrically conductive material is immersed in the electrolytic solution and positioned adjacent the drum cathode. The anode is formed to have a surface generally conforming to the curvature of the drum cathode so as to define a uniform inner electrode gap therebetween. Copper foil is formed on the rotating drum by applying a current, having a current density lower than the limiting current density of the electrolytic solution, to the anode and cathode. The electrodeposited foil is continually removed from the drum cathode as it emerges from the electrolytic solution so as to permit continuous foil production.
The actual production of copper foil begins through the nucleation of copper atoms on the surface of the drum cathode as the cathode initially enters the electrolytic solution. Copper continuously builds up onto these copper atoms as the drum continues to rotate past the energized anode through the electrolytic solution.
The current distribution at the entry point of the drum cathode surface has a significant effect on the quality of the copper nucleation. In this respect, copper nucleation is a rapid process, and it has been found that a uniform, sharp rise in current density at the point where the surface of the drum cathode enters the electrolytic solution can remarkably increase the density of copper formed on the drum, which in turn, reduces the porosity of the resulting foil. In other words, a quick current rise at the surface of the drum as it enters the electrolytic solution is critical for good copper nucleation. As the demand for thinner foils becomes greater, the initial copper nucleation on the drum surface becomes more important to insure porous-free copper foil.
Conventional electrolytic cells known heretofore have typically included anodes that were totally immersed in the electrolytic solution. Such arrangements produce slow current “ramping-up” as the drum cathode enters the electrolytic solution, which in turn, causes insufficient copper nucleation on the surface of the drum cathode. This slow current ramp-up occurs because the desired current density on the surface of the drum cathode does not occur until the surface of the drum is radially opposite the immersed anode. To improve the current ramping-up time, it has been known to place an insulator shield on the top (i.e., along the upper edge) of the immersed anode. While such an arrangement improves the current ramp up compared to an immersed anode alone, it does not completely eliminate the problem. To further improve the copper nucleation, it has also been known to use a strike anode (second anode) disposed near the surface of the electrolytic solution at the entry point of the surface of the drum cathode. The strike anode is energized at a higher current density than the main anode. A problem with this arrangement is that it requires a second rectifier to control the second anode, i.e., the strike anode. Moreover, though copper nucleation is improved using a strike anode, such a method does not totally eliminate the slow current ramping-up problem.
U.S. Pat. No. 5,833,819 to O'Hara et al. proposes the use of a partially immersed “net-type strike anode” instead of a solid strike anode to reduce ramping-up time. While this net-type strike anode significantly reduces current ramping-up time, and improves the copper nucleation, it still requires a second rectifier for operation. Moreover, both the aforementioned “strike anode” and the net-type strike anode disclosed in U.S. Pat. No. 5,833,819 disclose applying a higher current density to the surface of the drum cathode as it enters the electrolytic solution, and both require some type of insulator plate between the strike anode and the main anode.
The present invention overcomes these and other problems and provides an anode that eliminates slow current ramping-up problems, and does not require an insulator plate or a second rectifier for supplying a higher current density to the surface of the drum cathode.
SUMMARY OF THE INVENTION
In accordance with a preferred embodiment of the present invention, there is provided an apparatus for producing metal foil, comprising a drum cathode having an outer plating surface and an anode section. The drum cathode is partially immersed to a set level in an electrolytic solution and is rotatable about a generally horizontal axis. The anode section is comprised of a main anode portion immersed in the electrolytic solution. The main anode portion has a semi-cylindrical curved anode surface facing the drum cathode. The main anode portion is dimensioned to be spaced from the plating surface of the drum cathode so as to define a generally uniform gap therebetween. An anode extension portion is disposed at the upper end of the main anode. The anode extension portion has a first zone having at least one opening formed therein. The first zone is spaced a predetermined distance from the plating surface of the cathode and is immersed in the electrolytic solution wherein a portion of the first zone projects above the set level of the electrolytic solution. One energy source is connected to the anode assembly for energizing the main anode portion and the anode extension portion at the same electrical potential.
In accordance with an aspect of the present invention, there is provided an electrodeposition cell for electrodepositing metal onto a surface of a rotating drum that is partially immersed in an electrolytic solution. The cell includes an anode comprised of a main anode body portion and an anode extension portion. The main anode body portion has an arcuate main anode body surface having a radius of curvature slightly larger than the radius of curvature of the drum. The main anode body portion is totally immersed in the electrolytic solution adjacent the drum wherein a generally uniform gap is formed therebetween. The anode extension portion has an open, lattice-like structure and an anode extension surface facing the drum. The anode extension portion is disposed within the electrolytic solution wherein a portion thereof extends above the electrolytic solution such that the electrolytic solution can flow through the open lattice-like structure. A power source is connected to the main anode body portion and the anode extension portion to produce a like potential on the anode body surface and the anode extension surface, wherein the main anode body portion produces a first current density on the drum in a zone where the drum and the main anode body portion are adjacent and the anode extension portion produces a second current density on the drum in a zone where the drum and the anode extension portion are adjacent. The second current density is less than the first current density.
It is an object of the present invention to provide an anode assembly for use in electrodepositing metal onto a cathodic surface.
Another object of the present invention is to provide an anode assembly for use with a rotating drum cathode for producing high quality, porous-free metallic foil.
Another object of the present invention is to provide an anode assembly as described above having a portion thereof to facilitate good copper nucleation on the surface of a drum cathode.
Another object of the present invention is
Briggs John C.
Clouser Sidney J.
Stevens Michael L.
Wang Jiangtao
Bell Bruce F.
Centanni Michael A.
GA-TEK Inc.
Kusner Mark
LandOfFree
Anode structure for manufacture of metallic foil does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Anode structure for manufacture of metallic foil, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Anode structure for manufacture of metallic foil will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2587358