Electrolysis: processes – compositions used therein – and methods – Electrolytic coating – Depositing predominantly single metal coating
Reexamination Certificate
2000-06-22
2003-03-04
Nguyen, Nam (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electrolytic coating
Depositing predominantly single metal coating
C205S296000, C205S297000, C205S138000, C205S077000, C204S290100
Reexamination Certificate
active
06527939
ABSTRACT:
BACKGROUND OF THE INVENTION
I. Field of the Invention
The invention is directed to copper foil electrodeposition cells containing organic substituent in the electrolyte. The cells may have an electrode having a first active coating layer and an additional layer that is of no significant activity. The metal can be deposited in cell operation that does not exhibit an adverse effect on electrode potential.
II. Description of the Related Art
It is well known to use coatings for electrodes having a significant quantity of platinum group metal or oxides in them that provide the electrochemical activity of a coating. However, these components are often subject to attack by substances in the electrolyte, especially substituents used in metal electrodeposition electroplating systems. Prior art devices can lose, through interaction with organic substituents in electrolytes, the coating components, as well as loss due to slow attrition of the platinum group metal from standard coatings. The slow attrition loss can be due at least in part to chemical/electrochemical dissolution.
It has, however, been found difficult to provide electrodes of extended service life, especially in electrolyte environments such as used in copper foil electrodeposition and which contain organic substituents detrimental to the stability of the components of an active coating as would contain a platinum group metal or oxide. It would, therefore, be desirable to provide an electrode capable of exhibiting extended lifetimes in such an environment. It would also be desirable to provide an electrode allowing extended electrode lifetimes while having decreased loading of the platinum group metal coating.
SUMMARY OF THE INVENTION
The present invention relates generally to an improved method for copper foil electrodeposition. The method is operational in electrolyte environments containing organic substituent, and overcomes the difficulties associated with electrode operation in such an environment, while providing more advantageous overall results.
The method uses an electrode having a topcoat layer of a valve metal oxide, which can be more stable in the electrolyte, and can minimize significant exposure of any platinum group metal or oxide in a base coating to the electrolyte, thus extending the lifetime of the electrode. This can be achieved without an adverse effect on the cell electrode potential, which was unexpected.
In one aspect, the invention is directed to a method for electrodepositing copper metal foil from an electrolyte solution having organic substituent that is contained in an electrolytic cell comprising at least one oxygen evolving anode, which method provides extended anode activity while maintaining cell electrode potential during said copper electrodeposition, which method comprises:
providing an unseparated electrolytic cell;
establishing in the cell an electrolyte containing organic substituent, and containing the copper metal in solution;
providing an anode in the cell in contact with the electrolyte which anode has multiple coating layers on an electrode base of a valve metal, the electrode base having at least one coating layer of an electrochemically active coating and at least one topcoating layer of a valve metal oxide coating or a tin oxide coating layer, whereby the active coating layer contains a first composition and the topcoating layer contains a second composition;
impressing an electric current on the anode; and
conducting the electrodeposition of the copper foil.
Still other benefits and advantages of the invention will become apparent to those skilled in the art upon a reading and understanding of the following detailed specification.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The electrolytic process of the present invention is particularly useful in the electrodeposition of copper foil, and particularly such deposition from a sulfate electrolyte. The electrode described herein when used in such an electrodeposition process will virtually always find service as an anode. Thus, the word “anode” is often used herein when referring to the electrode, but this is simply for convenience and should not be construed as limiting the invention.
A cell using the present invention can be an electrolytic cell where a gap is maintained between electrodes, and the cell electrolyte is contained within the gap. The electrolyte as a sulfate-containing electrolyte might contain sulfuric acid or copper sulfate. The electrolyte will typically be an aqueous electrolyte, i.e., a water-based electrolyte. The copper might be dissolved in the medium of the electrolyte, such as copper sulfate dissolved in an aqueous medium.
The electrolyte will contain organic substituents. A representative constituent used in the electrodeposition of copper foil is gelatin. Such substituent might also include one or more of thiourea, amines, and animal glue. Some organic additives, as might be present, are disclosed in U.S. Pat. No. 4,469,564 to Okinaka, et al, which patent is incorporated herein by reference. As will be understood, the electrolyte ingredient for plating is copper. The one or more organic substituents are additives to the electrolyte which are generally added to the bath to improve aspects of the plating process such as deposition uniformity.
In addition to providing an unseparated cell and establishing an electrolyte containing organic substituent, plus copper metal in solution, there will be provided in the copper deposition process an anode having multiple coating layers on an electrode base of a valve metal. The layers can be represented by an active layer and at least one topcoating layer that can be a valve metal oxide coating. The active coating layer, or underlayer, contains a first composition and the topcoating layer contains a second composition. These layers will be more particularly described hereinbelow. A coating of the valve metal oxide alone generally only sustain low current densitites in cell operation. It was unexpected that in the copper foil deposition process as described herein, that such operation can sustain an elevated current density for an extended time. As representative of such operation is copper foil deposition at a current density of at least 5 kiloamps per square meter (kA/m
2
), and often at a density of at least 10 kA/m
2
, for a cell operating time of over 1,000 hours.
For the electrode having multiple coating layers, the base of a valve metal can be such metal including titanium, tantalum, zirconium, niobium, and tungsten. Of particular interest for its ruggedness, corrosion resistance and availability is titanium. As well as the normally available elemental metals themselves, the suitable metals of the electrode base can include metal alloys and intermetallic mixtures, as well as ceramics and cermets such as contain one or more valve metals. For example, titanium may be alloyed with nickel, cobalt, iron, manganese or copper. More specifically, grade 5 titanium may include up to 6.75 weight percent aluminum and 4.5 weight percent vanadium, grade 6 up to 6 percent aluminum and 3 percent tin, grade 7 up to 0.25 weight percent palladium, grade 10, from 10 to 13 weight percent plus 4.5 to 7.5 weight percent zirconium and so on.
By use of elemental metals, it is most particularly meant the metals in their normally available condition, i.e., having minor amounts of impurities. Thus, for the metal of particular interest, i.e., titanium, various grades of the metal are available including those in which other constituents may be alloys or alloys plus impurities. Grades of titanium have been more specifically set forth in the standard specifications for titanium detailed in ASTM B 265-79.
The electrode base may take various forms, i.e., any of those forms that may be used for the deposition of copper foil, and including mesh, sheet, blades, tubes or wire form. It is contemplated, that for the electrodeposition process the anode base member may be a multi-layer member, e.g., a multi-layer mesh member, such as is disclosed in U.S. Pat. No. 5,783,050, or a multi-layer member havi
Eltech Systems Corporation
Hudak, Shunk & Farine Co. LPA
Nicolas Wesley A.
Tyrpak Michele M.
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