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Title:
COPPER WIRE AND A PROCESS FOR MAKING SAME
Document Type and Number:
WIPO Patent Application WO/2000/048758
Kind Code:
A1
Abstract:
This invention relates to copper wire (30) and process for making copper wire comprising: (A) electrodepositing copper foil, characterized by a twinning or stacking fault population in its crystal structure, having a thickness of about 0.0002 to about 0.02 inches from an electrolyte solution (18) containing a copper ion concentration of about 30 to about 120 grams per liter, a free sulfuric acid concentration of about 40 to about 120 grams per liter, a chloride ion concentration of less than about 1 ppm, an organic additive concentration of no more than about 1 ppm, and a metallic impurity level of less than about 2000 ppm, using a current density of about 40 to about 480 amps per square foot; and (B) cutting and shaping the electrodeposited copper foil to form a strand of copper wire, characterized by an occluded oxygen content of less than about 200 ppm, while maintaining the temperature of the copper below its melting point.

Inventors:
Schatzberg, Susan E. (38042 Second Street #201 Willoughby, OH, 44094, US)
Clouser, Sidney J. (11960 Aquilla Road Chardon, OH, 44024, US)
Hasegawa, Craig J. (36530 Stevens Boulevard Willoughby, OH, 44094, US)
Wright, Roger N. (12 Maria Court Rexford, NY, 12148, US)
Application Number:
PCT/US1999/031068
Publication Date:
August 24, 2000
Filing Date:
December 29, 1999
Export Citation:
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Assignee:
ELECTROCOPPER PRODUCTS LIMITED (Suite 288 1255 West Baseline Road Mesa, AZ, 85202, US)
International Classes:
B21C37/04; C25D1/04; C25D3/38; (IPC1-7): B21C37/00; C25D1/04; C25D3/38
Foreign References:
US5679232A1997-10-21
Attorney, Agent or Firm:
Duchez, Neil A. (Renner, Otto Boisselle & Skla, P.L.L. 19th floor 1621 Euclid Avenue Cleveland OH, 44115, US)
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Claims:
Claims
1. A copper wire made from electrodeposited copper foil, said copper wire having an occluded oxygen content of less than about 200 ppm and being reducible in tensile testing to greater than 98% RIA, said copper foil being characterized by a twinning or stacking fault population in its crystal structure.
2. The wire of claim wherein said wire has a combined metallic impurity level of less than about 65 ppm.
3. The wire of claim 1 wherein said wire is reducible in tensile testing to 100% RIA.
4. The wire of claim 1 wherein said wire has a gage smaller than AWG 52.
5. The wire of claim 1 wherein said wire has a gage of about AWG 55 or smaller.
6. The wire of claim 1 wherein said wire has a gage of about AWG 62 or smaller.
7. A process for making copper wire that is reducible in tensile testing to greater than 98% RIA, said process comprising: (A) electrodepositing copper foil having a thickness in the range of about 0.0002 inch to about 0.02 inch from an electrolyte solution having a copper ion concentration in the range of about 30 to about 120 grams per liter, a free suifuric acid concentration in the range of about 40 to about 120 grams per liter, a chloride ion concentration of less than about 1 ppm, an organic additive concentration of no more than about 1 ppm, and a metallic impurity level of less than about 2000 ppm, using a current density in the range of about 40 to about 480 amps per square foot, said copper foil being characterized by a twinning or stacking fault population in its crystal structure; and (B) cutting and shaping said electrodeposited copper foil to form a strand of copper wire while maintaining the temperature of said copper below its melting point, said copper wire being characterized by an occluded oxygen content of less than about 200 ppm.
8. The process of claim 7 wherein said foil has a thickness in the range of about 0.001 to about 0.015 inch.
9. The process of claim 7 wherein said copper ion concentration is in the range of about 40 to about 60 grams per liter.
10. The process of claim 7 wherein said copper ion concentration is in the range of about 95 to about 115 grams per liter.
11. The process of claim 7 wherein said chloride ion concentration is less than about 0.2 ppm.
12. The process of claim 7 wherein no organic additives are added to said electrolyte solution.
13. The process of claim 7 wherein said current density is in the range of about 80 to about 120 amps per square foot.
14. The process of claim 7 wherein said current density is in range of about 400 to about 480 amps per square foot.
15. The process of claim 7 wherein said wire has a gage of AWG 55 or smaller. AMENDED CLAIMS [received by the International Bureau on 17 May 2000 (17,05.00) new claim 16 added ; remaining claims unchanged (2 pages) 0] form a strand of copper wire while maintaining the temperature of said copper below its melting point, said copper wire being characterized by an occluded oxygen content of less than about 200 ppm.
16. 8 The process of claim 7 wherein said foil has a thickness in the range of about 0.001 to about 0.015 inch.
17. The process of claim 7 wherein said copper ion concentration is in the range of about 40 to about 60 grams per liter.
18. The process of claim 7 wherein said copper ion concentration is in the range of about 95 to about 115 grams per liter.
19. The process of claim 7 wherein said chloride ion concentration is less than about 0.2 ppm.
20. The process of claim 7 wherein no organic additives are added to said electrolyte solution.
21. The process of claim 7 wherein said current density is in the range of about 80 to about 120 amps per square foot.
22. The process of claim 7 wherein said current density is in range of about 400 to about 480 amps per square foot.
23. The process of claim 7 wherein said wire has a gage of AWG 55 or smaller.
24. A process for making copper wire comprising the steps of ; (A) electrodepositing copper foil having a twinning or stacking fault population in its crystal structure; and (B) cutting and shaping the electrodeposited copper foil to form a strand of copper wire while maintaining the temperature of said copper below its melting point; wherein said electrodepositing step and said cutting and shaping steps are performed in such a manner that the copper foil has a thickness in the range of about 0.0002 inch to about 0.02 inch and the copper wire has an occulded oxygen content of less than about 200 ppm and is reducible in tensile testing to greater than 98% RIA; wherein said electrodepositing step comprises electrodepositing the copper foil from an electrolyte solution having a copper ion concentration in the range of about 30 to about 120 grams per liter, a free sulfuric acid concentrations in the range of about 40 to about 120 grans per liter, a chloride ion concentration of less than about 1 ppm, an organic additive concentration of no more than about 1 ppm, and a metallic impurity level of less than about 2000 ppm and using a current density in the range of about 40 to about 480 amps per square foot.
Description:
TITLE: COPPER WIRE AND A PROCESS FOR MAKING SAME Technical Field This invention relates to copper wire and to a process for making such copper wire.

Background of the Invention In conventional wire drawing, wire is pulled through drawing dies that reduce the cross-sectional area of the wire as it is drawn. Typically, this process is completed with the wire subjected to compressive stresses on the surface and tensile stresses along the center drawing line as the wire is drawn. Properly aligned capstans pull the drawn wire along the process in tension as well. A wire breaks out of the machine when the stress is greater than the material strength. The presence of an inclusion, oxide particle, void, etc. reduces the localized strength of the wire resulting in wire breakage.

It is known that even in high purity copper wire, there are microvoids and small oxide inclusions in the material that orient themselves along the drawing line (the tensile axis) during metalworking. As these voids come together or coalesce, they eventually reach a sufficient size such that failure occurs. This phenomenon limits the size to which the wire may be reduced or drawn. This often occurs when the wire diameter is about 0.0008" or 52 AWG. Drawing to finer gages is very difficult and expensive due to breakouts and often not possible.

The term"high reduction copper wire"refers to copper wire which when subjected to tensile testing undergoes a high reduction in its cross sectional area prior to fracturing. The reduction is measured as a percentage reduction in cross sectional area (% RIA) from the original cross sectional area to the cross sectional area of the tip of the fracture surface. A copper wire that is 98% reducible undergoes a reduction in its cross sectional area of 98% prior to fracturing. A copper wire that is 100% reducible is a copper wire that exhibits a pure ductile rupture when subjected to tensile testing; this wire ultimately breaks during the tensile testing but the fracture surface resembles a pin point.

Standard electrolytic tough pitch (ETP) copper wire with 100-600 ppm oxygen typically shows about 80-90% RIA. Oxygen-free electronic (OFE) wire with less than 10 ppm oxygen typically shows from 90-97% RIA. Ultra-pure copper typically shows 95-98% RIA. Until now the general consensus in the industry has been that greater than 98% RIA, and especially 100% RIA, was impossible to achieve in commercial practice. This invention provides a copper wire capable of achieving an RIA greater than 98%, and in one embodiment an RIA of 100%, and a process for making such wire.

US Patent 5,679,232 discloses a process for making metal wire, comprising: (A) forming metal foil; (B) cutting said foil to form at least one strand of metal wire; and (C) shaping said strand of wire to provide said strand with desired cross-sectional shape and size. This process is suitable for making copper wire having a very thin diameter (e. g., about 0.0002 to about 0.02 inch).

Summary of the Invention This invention relates to copper wire made from electrodeposited copper foil, said copper wire having an occluded oxygen content of less than about 200 ppm and being reducible in tensile testing to greater than 98% RIA, said copper foil being characterized by a twinning or stacking fault population in its crystal structure. This invention also relates to a process for making the foregoing copper wire, the process comprising: (A) electrodepositing copper foil having a thickness in the range of about 0.0002 inch to about 0.02 inch from an electrolyte solution having a copper ion concentration in the range of about 30 to about 120 grams per liter, a free sulfuric acid concentration in the range of about 40 to about 120 grams per liter, a chloride ion concentration of less than about 1 ppm, an organic additive concentration of no more than about 1 ppm, and a metallic impurity level of less than about 2000 ppm, using a current density in the range of about 40 to about 480 amps per square foot (ASF), said copper foil being characterized by a twinning or stacking fault population in its crystal structure; and (B) cutting and shaping said electrodeposited copper foil to form at least one strand of copper wire while maintaining the temperature of

said copper below its melting point, said copper wire being characterized by an occluded oxygen content of less than about 200 ppm.

Brief Description of the Drawings In the annexed drawings, like parts and features are designated by like reference numerals.

Fig. 1 is a flow sheet illustrating one embodiment of the electrodeposition step of the inventive process wherein copper foil is electrodeposited on to a vertically oriented cathode, the cathode is subsequently removed from the electrolyte solution and the foil is score cut to form a strand of copper wire which is then separated from the cathode.

Fig. 2 is a flow sheet illustrating another embodiment of the electrodeposition step of the inventive process wherein copper foil is electrodeposited on to a horizontally oriented cathode, the foil is then separated from the cathode.

Fig. 3 is a schematic illustration of a slitting step used with the inventive process wherein a strip of copper foil is slit to form a plurality of thin strands of copper wire.

Fig. 4 is an exploded schematic illustration of the cutting blades used to slit a strip of copper foil during a slitting step of the inventive process.

Fig. 5 is a schematic illustration of a fragmented strip of copper foil which has been partially slit pursuant to a slitting step of the inventive process.

Fig. 6 is a flow sheet illustrating the step of converting a strand of copper wire having a square or rectangular cross section to a strand of copper wire having a round cross section.

Fig. 7 is a schematic illustration of a process for drawing copper wire pursuant to the inventive process.

Fig. 8 is a photograph of the fracture surface of the 100% RIA sample of Example 1 taken at a magnification of 300X.

Fig. 9 is a photograph of the fracture surface of the 100% RIA sample of Example 2 taken at a magnification of 300X.

Fig. 10 is an optical micrograph of a foil sample from Example 2 taken at a magnification of 400X showing a large twinning or stacking fault population in the crystal structure of the foil sample.

Fig. 11 shows an overview of the microstructure of a foil sample from Example 2 taken at a magnification of 2500X using SEM, the microstructure having a large twinning or stacking fault population.

Fig. 12 shows an overview of the microstructure of a foil sample from Example 2 taken at a magnification of 2500X using SEM, the microstructure having a large twinning or stacking fault population.

Fig. 13 shows an overview of the microstructure of the foil sample from Example 2 taken at a magnification of 20, OOOX using TEM, the microstructure having a large twinning or stacking fault population.

Fig. 14 shows an overview of the microstructure of the foil sample from Example 2 taken at a magnification of 50, OOOX using TEM, the microstructure having a large twinning or stacking fault population.

Description of the Preferred Embodiments The electrodeposited copper foil used to make the inventive copper wire is produced by electrolytically depositing the copper on a cathode. The copper foil typically has a nominal thickness ranging from about 0.0002 inch to about 0.02 inch, and in one embodiment about 0.001 to about 0.015 inch and in one embodiment about 0.004 to about 0.01 inch. Copper foil thickness is sometimes expressed in terms weight and typically the foils of the present invention have a weight ranging from about 1/8 to about 14 oz/ft2. Useful copper foils are those having weights of about 1/2 to about 10 oz/ft2, and in one embodiment about 6 to about 10 oz/ft2, and in one embodiment about 7 to about 9 oz/ft2.

It is a critical feature of this invention that the copper foil used to make the inventive copper wire is electrodeposited copper foil and that this electrodeposited copper foil is characterized by the presence of a twinning or stacking fault population in its crystal structure. While not wishing to be bound by theory, it is believed that this crystal defect structure is directly related to the

high reduction (i. e., greater than 98% RIA) characteristics of the inventive copper wire. The twinning or stacking fault population can be observed using microscopic analysis, transmission electron microscopy (TEM) analysis, or scanning electron microscopy (SEM) analysis. These are shown in Figs. 10-14 which are micrographs taken at magnifications ranging from 400X to 50, OOOX of the foil sample from Example 2. In each case a large twinning or stacking fault population is shown in the crystal structure of the foil.

It is also critical that during the inventive process for making the copper wire that the electrodeposited foil or the wire not be subjected to melting.

Again while not wishing to be bound by theory, it is believed that such melting tends to destroy the twinning or stacking fault population in the crystal structure. The destruction of this crystal defect structure destroys the high reduction properties (i. e., RIA greater than 98%) of the inventive copper wire.

Thus, it is critical that the cutting and shaping steps of the inventive process be conducted at a temperature below the melting point of the copper being treated.

The electrodeposited copper foil is produced in an electroforming cell equipped with a cathode and an anode. The cathode can be vertically or horizontally mounted and is in the form of a cylindrical mandrel. The anode is adjacent to the cathode and has a curved shape conforming to the curved shape of the cathode to provide a uniform gap between the anode and the cathode.

The gap between the cathode and the anode generally measures from about 0.3 to about 2 centimeters. In one embodiment, the anode is insoluble and made of lead, lead alloy, or titanium coated with a platinum family metal (i. e., Pt, Pd, Ir, Ru) or oxide thereof. The cathode has a smooth surface for receiving the electrodeposited copper and the surface is, in one embodiment, made of stainless steel, chrome plated stainless steel or titanium.

In one embodiment, the copper foil is electrodeposited on a horizontally mounted rotating cylindrical cathode and then peeled off as a thin web as the cathode rotates. This thin web of copper foil is cut to form a plurality of strands of copper wire, and then the strands of copper wire are shaped and drawn to provide a desired cross-sectional shape and size.

In one embodiment, the copper foil is electrodeposited on a vertically mounted cathode to form a thin cylindrical sheath of copper foil around the cathode. The cylindrical sheath of copper foil typically has a thickness of about 0.0002 to about 0.02 inch, and in one embodiment about 0.001 to about 0.01 5 inch, and in one embodiment about 0.004 to about 0.01 inch. This cylindrical sheath of copper is score cut to form a thin strand of copper wire which is peeled off the cathode and then shaped and drawn to provide a desired cross- sectional shape and size.

The chemistry of the electrolyte solution and the electrodeposition conditions are critical to achieving the high reduction copper wire of the invention. The electrolyte solution flows in the gap between an anode and a cathode, and an electric current is used to apply an effective amount of voltage across the anode and the cathode to deposit copper on the cathode. The electric current can be a direct current or an alternating current with a direct current bias. The electrolyte solution has a free sulfuric acid concentration generally in the range of about 40 to about 120 grams per liter, and in one embodiment about 70 to about 90 grams per liter. The temperature of the electrolyte solution in the electroforming cell is generally in the range of about 20°C to about 90°C, and in one embodiment about 20°C to about 35°C, and in one embodiment about 50°C to about 70°C. The copper ion concentration is generally in the range of about 30 to about 120 grams per liter, and in one embodiment about 40 to about 60 grams per liter, and in one embodiment about 95 to 115 grams per liter. The free chloride ion concentration is less than about 1 ppm, and in one embodiment less than about 0.9 ppm, and in one embodiment less than about 0.7 ppm, and in one embodiment less than about 0.5 ppm, and in one embodiment, less than about 0.3 ppm, and in one embodiment less than about 0.2 ppm, and in one embodiment less than about 0.15 ppm, and in one embodiment less than about 0.1. The metallic impurity level of the electrolyte solution is less than about 2000 ppm, and in one embodiment less than about 1000 ppm, and in one embodiment less than about 500 ppm. The current density is in the range of about 40 to about 480 ASF,

and in one embodiment about 80 to about 120 ASF, and in one embodiment about 400 to about 480 ASF.

In one embodiment, copper is electrodeposited using a horizontally mounted cathode, and the velocity of the flow of the electrolyte solution through the gap between the anode and the athode is in the range of about 0.2 to about 5 meters per second, and in one embodiment about 1 to about 3 meters per second.

In one embodiment, copper is electrodeposited using a vertically mounted cathode rotating at a tangential velocity of up to about 400 meters per second, and in one embodiment about 10 to about 175 meters per second, and in one embodiment about 50 to about 75 meters per second, and in one embodiment about 60 to about 70 meters per second. In one embodiment, the electrolyte solution flows upwardly between the vertically mounted cathode and anode at a velocity in the range of about 0.1 to about 10 meters per second, and in one embodiment about 1 to about 4 meters per second, and in one embodiment about 2 to about 3 meters per second.

During the electrodeposition of copper, the electrolyte solution may contain one or more organic additives. However, it is critical that the combined concentration of such organic additive (s) be no more than about 1 ppm, and in one embodiment no more than about 0.5 ppm and in one embodiment, no more than about 0.2 ppm, and in one embodiment no more than about 0.1 ppm. In one embodiment, no organic additives are added and thus the concentration of such organic additives is zero.

The organic additive, when used, can be active sulfur-containing materials. The term"active-sulfur containing material"refers to materials characterized generally as containing a bivalent sulfur atom both bonds of which are directly connected to a carbon atom together with one or more nitrogen atoms also directly connected to the carbon atom. In this group of compounds, the double bond may in some cases exist or alternate between the sulfur or nitrogen atom and the carbon atom. Thiourea is a useful active sulfur-containing material. The thioureas having the nucleus

and the iso-thiocyanates having the grouping S = C = N-are useful. Thiosinamine (allyl thiourea) and thiosemicarbazide are also useful. The active sulfur-contain- ing material should be soluble in the electrolyte solution and be compatible with the other constituents.

The organic additive can be a gelatin. The gelatins that are useful herein are heterogeneous mixtures of water-soluble proteins derived from collagen.

Animal glue is a useful gelatin.

The organic additive can be one or more additives selected from saccharin, caffeine, molasses, guar gum, gum arabic, the polyalkylene glycols (e. g., polyethylene glycol, polypropylene glycol, polyisopropylene glycol, etc.), dithiothreitol, amino acids (e. g., proline, hydroxyproline, cysteine, etc.), acrylamide, sulfopropyl disulfide, tetraethylthiuram disulfide, benzyl chloride, epichlorohydrin, chlorohydroxylpropyl sulfonate, alkylene oxides (e. g., ethylene oxide, propylene oxide, etc.), the sulfonium alkane sulfonates, thiocarbamoyidisulfide, selenic acid, or a mixture of two or more thereof.

In one embodiment, a horizontally mounted rotating cathode is used and copper foil is peeled off the cathode as it rotates. The foil is slit using one or several slitting steps to form a plurality of strips of copper having widths of about 0.1 to about 1 inch, and in one embodiment about 0.1 to about 0.5 inch, about 0.2 to about 0.3 inch, and in one embodiment about 0.25 inch. These strips of copper are then cut to widths that are about 1 to about 3 times the thickness of the foil, and in one embodiment the width to thickness ratio is about 1.5: 1 to about 2: 1. In one embodiment a 6 oz/ft2 foil is cut into a strand having a width of 0.250 inch, then cut into a plurality of strands each having widths of 0.012 inch. The strands are then rolled and drawn to provide copper wire with a desired cross sectional shape and size.

In one embodiment, the copper is electrodeposited on a rotating cathode, which is in the form of a cylindrical mandrel, until the thickness of the copper on the cathode is from about 0.005 to about 0.050 inch, or about 0.010 to about 0.030 inch, or about 0.020 inch. Electrodeposition is then discontinued and the surface of the copper is washed and dried. A score cutter is used to cut the copper into a thin strand of copper which is then peeled off the cathode.

The score cutter travels along the length of the cathode as the cathode rotates.

The score cutter preferably cuts the copper to within about 0.001 inch of the cathode surface. The width of the strand of copper that is cut is, in one embodiment, from about 0.005 to about 0.050 inch, or from about 0.010 to about 0.030 inch, or about 0.020 inch. In one embodiment, the copper strand has a square or substantially square cross-section that is from about 0.005 x 0.005 inch to about 0.050 x 0.050 inch, or about 0.010 x 0.010 inch to about 0.030 x 0.030 inch, or about 0.020 x 0.020 inch. The strand of copper is then rolled and drawn to provide copper wire with a desired cross-sectional shape and size.

In one embodiment, the copper strands are rolled using one or a series of Turks heads shaping mills wherein in each shaping mill the strands are pulled through two pairs of opposed rigidly-mounted forming rolls. These rolls are grooved to produce shapes (e. g., rectangles, squares, etc.) with rounded edges.

Powered Turks head mills wherein the rolls are driven can be used. The Turks head mill speed can be about 100 to about 5000 feet per minute, and in one embodiment about 300 to about 1500 feet per minute, and in one embodiment about 600 feet per minute.

In one embodiment, the copper strands are subjected to sequential passes through three Turks head mills to convert a wire strand with a rectangular cross section to a wire strand with a square cross section. In the first pass, the strands are rolled from a cross-section of 0.005 x 0.010 inch to a cross-section of 0.0052 x 0.0088 inch. In the second, the strands are rolled from a cross- section of 0.0052 x 0.0088 inch to a cross-section of 0.0054 x 0.0070 inch.

In the third pass, the strands are rolled from a cross-section of 0.0054 x 0.0070 inch to a cross-section of 0.0056 x 0.0056 inch.

In one embodiment, the strands of wire are subjected to sequential passes through two Turks head mills. In the first pass, the strands of wire are rolled from a cross-section of 0.008 x 0.010 inch to a cross-section of 0.0087 x 0.0093 inch. In the second pass, the strands are rolled from a cross-section of 0.0087 x 0.0093 inch to a cross-section of 0.0090 x 0.0090 inch.

The strands of copper wire can be cleaned using known chemical, mechanical or electropolishing techniques. In one embodiment, strands of copper wire, which are slit from copper foil or are score cut and peeled off the cathode, are cleaned using such chemical, electropolishing or mechanical techniques before being advanced to Turks head mills for additional shaping.

Chemical cleaning can be effected by passing the wire through an etching or pickling bath of nitric acid or hot (e. g., about 25°C to 70°C) sulfuric acid.

Electropolishing can be effected using an electric current and sulfuric acid.

Mechanical cleaning can be effected using brushes and the like for removing burrs and similar roughened portions from the surface of the wire. In one embodiment, the wire is degreased using a caustic soda solution, washed, rinsed, pickeled using hot (e. g., about 35°C) sulfuric acid, electropolished using sulfuric acid, rinsed and dried.

In one embodiment, the strands of copper wire that are made in accordance with the invention have relatively short lengths (e. g., about 500 to about 5000 ft, and in one embodiment about 1000 to about 3000 ft, and in one embodiment about 2000 ft), and these strands of wire are welded to other similarly produced strands of wire using known techniques (e. g., butt welding) to produce strands of wire having relatively long lengths (e. g., lengths in excess of about 100,000 ft, or in excess of about 200,000 ft, up to about 1,000,000 ft or more).

In one embodiment, the strands of copper wire that are made in accordance with the invention are drawn through one or more dies to provide the strands with round cross-sections. The die can be a shaped (e. g., square,

oval, rectangle, etc.)-to-round die or a round-to-round die wherein the incoming strand of wire contacts the die in the drawing cone along a planar locus, and exits the die along a planar locus. The included die angle, in one embodiment, is about 8°, 12°, 16° or 24°, or others known in the art. In one embodiment, prior to being drawn, these strands of wire are cleaned and we ! ded (as discussed above). In one embodiment, a strand of wire having a square cross- section of 0.0056 x 0.0056 inch is drawn through a die in a single pass to provide a wire with a round cross-section and a cross-sectional diameter of 0.0056 inch (AWG 35). The wire is then be further drawn through additional dies to further reduce the diameter.

In one embodiment, the drawn copper wire produced in accordance with the invention is drawn through a series of dies with the diameter being reduced to a gage of AWG 36 or smaller, and in one embodiment AWG 40 or smaller, and in one embodiment AWG 42 or smaller, and in one embodiment AWG 44 or smaller, and in one embodiment AWG 46 or smaller, and in one embodiment AWG 48 or smaller, and in one embodiment AWG 50 or smaller, and in one embodiment AWG 52 or smaller, and in one embodiment AWG 55 or smaller.

In one embodiment, the gage is reduced to AWG 60 or smaller, and in one embodiment it is AWG 62 or smaller. These copper wires are sometimes referred as ultra thin copper wires.

It is critical that the inventive copper wire has an occluded oxygen content of less than about 200 ppm, and in one embodiment less than about 150 ppm, and in one embodiment less than about 120 ppm, and in one embodiment less than about 100 ppm, and in one embodiment less than about 80 ppm, and in one embodiment less than about 60 ppm, and in one embodiment less than about 50 ppm.

In one embodiment, it is critical that the combined metallic impurity level of the inventive copper wire be no more than about 65 ppm, and in one embodiment no more than about 50 ppm, and in one embodiment no more than about 40 ppm, and in one embodiment no more than about 35 ppm.

It is also critical that the inventive copper wire is reducible in tensile testing to greater than 98% RIA, and in one embodiment about 98.5% RIA or greater, and in one embodiment about 99% RIA or greater, and in one embodiment about 99.5% RIA or greater. In one embodiment, the inventive copper wire is reducible to 100% RIA.

In one embodiment, the wire made by the inventive process has a copper content of about 99% to about 99.999% by weight, and in one embodiment about 99.9% to about 99.99% by weight.

In one embodiment, the wire made by the inventive process has an ultimate tensile strength (UTS) at 23°C in the range of about 35,000 psi to about 95,000 psi, and in one embodiment about 50,000 psi to about 95,000 psi, and in one embodiment about 60,000 psi to about 95,000 psi, and in one embodiment about 65,000 psi to about 75,000 psi. In one embodiment, the elongation for this wire at 23°C is about 0% to about 24%, and in one embodiment about 8% to about 18%, and in one embodiment about 9% to about 16%.

In one embodiment, the wire made by the inventive process is cold worked to a reduction of about 60% and as such has a UTS at 23°C in the range of about 65,000 psi to about 90,000 psi, and in one embodiment about 70,000 psi to about 75,000 psi; and an elongation at 23°C of about 0% to about 4%, and in one embodiment about 0% to about 2%.

In one embodiment, the wire made by the inventive process is cold worked to a reduction of about 60% and then annealed at a temperature of 200°C for two hours and as such has a UTS at 23°C in the range of about 25,000 psi to about 40,000 psi, and in one embodiment about 27,000 psi to about 30,000 psi; and an elongation at 23°C in the range of about 30% to about 50%, and in one embodiment about 35% to about 45%.

In one embodiment, the copper wire made by the inventive process has a conductivity of at least about 100% IACS (International Annealed Copper Standard), and in one embodiment about 100% to about 102. 7% IACS.

Referring to the illustrated embodiments, and initially to Fig. 1, a process for making a strand of the inventive copper wire is disclosed wherein copper is electrodeposited on a cathode to form a thin cylindrical sheath of copper foil around the cathode; this cylindrical sheath of copper foil is then score cut to form a thin strand of copper wire which is peeled off the cathode. This thin strand of copper wire is subsequently shaped and drawn to provide the inventive wire. The apparatus used with this process includes an electroforming cell 10 that includes vessel 12, vertically mounted cylindrical anode 14, and vertically mounted cylindrical cathode 16. Vessel 12 contains electrolyte solution 18.

Also included are score cutter 20, guides 22 and 24, and reel 26. Cathode 16 is shown in phantom submerged in electrolyte solution 18 in vessel 12; it is also shown removed from vessel 12 adjacent score cutter 20. When cathode 16 is in vessel 12, anode 14 and cathode 16 are coaxially mounted with cathode 16 being positioned within anode 14. Cathode 16 rotates at a tangential velocity of up to about 400 meters per second, and in one embodiment about 10 to about 175 meters per second, and in one embodiment about 50 to about 75 meters per second, and in one embodiment about 60 to about 70 meters per second. The electrolyte solution 18 flows upwardly between the cathode 16 and anode 14 at a velocity in the range of about 0.1 to about 10 meters per second, and in one embodiment about 1 to about 4 meters per second, and in one embodiment about 2 to about 3 meters per second.

A voltage is applied between anode 14 and cathode 16 to effect electrodeposition of the copper foil on to the cathode. In one embodiment, the current that is used is a direct current, and in one embodiment it is an alternating current with a direct current bias. Copper ions in electrolyte 18 gain electrons at the peripheral surface 17 of cathode 16 whereby metallic copper plates out in the form of a cylindrical sheath of copper foil 28 on the surface 17 of cathode 16. Electrodeposition of copper on cathode 16 is continued until the thickness of the copper foil 28 is at a desired level, e. g., about 0.005 to about 0.050 inch. Electrodeposition is then discontinued. The cathode 16 is removed from the vessel 12. Copper foil 28 is washed and dried. Score cutter 20 is

then activated to cut copper foil 28 into a thin continuous strand 30. Score cutter 20 travels along screw 32 as cathode 16 is rotated about its center axis by support and drive member 34. Rotary blade 35 cuts copper foil 28 to within about 0.001 inch of the surface 17 of cathode 16. Wire strand 30, which has a square or rectangular cross-section, is peeled off cathode 16, advanced through guides 22 and 24 to reel 26 where it is wound.

The process depletes the electrolyte solution 18 of copper ions and organic additives (if any organic additives are used). These ingredients are continuously replenished. Electrolyte solution 18 is withdrawn from vessel 12 through line 40 and recirculated through filter 42, digester 44 and filter 46, and then is reintroduced into vessel 12 through line 48. Sulfuric acid from vesse ! 50 is advanced to digester 44 through line 52. Copper from a source 54 is introduced into digester 44 along path 56. In one embodiment, the copper that is introduced into digester 44 is in the form of copper shot, scrap copper wire, copper oxide or recycled copper. In digester 44, the copper is dissolved by the sulfuric acid and air to form a solution containing copper ions.

Organic additives, when used, are added to the recirculating solution in line 40 from a vessel 58 through line 60. In one embodiment, active sulfur- containing organic additives are added to the recirculating solution in line 48 through line 62 from a vessel 64. In one embodiment, no organic additives are added.

The illustrated embodiment disclosed in Fig. 2 is identical to the embodiment disclosed in Fig. 1 except that electroforming cell 10 in Fig. 1 is replaced by electroforming cell 110 in Fig. 2; vessel 12 is replaced by vessel 112; cylindrical anode 14 is replaced by curved anode 114; vertically mounted cylindrical cathode 16 is replaced by horizontally mounted cylindrical cathode 116; score cutter 20, guides 22 and 24, screw 32 and support and drive member 34 are replaced by roll 118; and reel 26 is replaced by take-up roll 1 26.

In the electroforming cell 110, a voltage is applied between anode 114 and cathode 116 to effect electrodeposition of copper foil on the cathode. In one embodiment, the current that is used is a direct current, and in one

embodiment it is an alternating current with a direct current bias. Copper ions in electrolyte solution 18 gain electrons at the peripheral surface 117 of cathode 1 16 whereby metallic copper plates out in the form of a copper foil layer on surface 117. Cathode 116 rotates about its axis and the copper foil layer is peeled from cathode surface 117 as continuous web of foil 122. The foil 122 passes over roll 118 and is wound on take-up roll 126. The electrolyte is circulated and replenished in the same manner as described above for the embodiment disclosed in Fig. 1.

The slitting step of the inventive process is best illustrated with reference to Figs. 3-5. Prior to this step of the process, the copper foil 122 produced in the embodiment of the process illustrated in Fig. 2 is cut or slit using one or more conventional slitting steps to provide a strip of copper foil having a relatively narrow width (e. g., about 0.1 to about 1 inch, and in one embodiment about 0.25 inch). This strip of copper foil, identified as strip 200 in Figs. 3 and 5, is then further slit using the slitting apparatus 202 illustrated in Fig. 3. In this step of the process, the copper strip 200 is slit to form a plurality of strands of wire having square or rectangular cross sections. In the illustrated embodiment depicted in Figs. 3-5, the copper strip 200 is slit using slitter 203 to form product wire strands 204,206,208,210 and 212. Scrap wire strands 21 6 and 218 are also formed. The sequence of this process step involves unwinding the copper strip 200 from reel 220, advancing it through accumulator 222 to tension sheave 224, and then around tension sheave 224 to slitter 203.

Accumulator 222 includes fixed sheave 226 and dancer sheave 228 which are provided for maintaining tension in copper strip 200 as it is advanced to slitter 203. In slitter 203, the copper strip 200 is slit to form wire strands 204,206, 208,210 and 212, and these wire strands are advanced from slitter 203 to product spools 234,236,238,240 and 242, respectively. Scrap wire strands 216 and 218 are also formed in slitter 203, and these strands are advanced to spools 246 and 248, respectively. The scrap wire strands 216 and 218 may be recycled to digestor 44. The product wire strands 204,206,208,210 and 212 have square or rectangular cross sections, each of the strands having, in

one embodiment, widths of about 0.008 to about 0.02 inch, and in one embodiment about 0.008 to about 0.012 inch; and thicknesses (or heights) of about 0.0002 to about 0.02 inch, and in one embodiment about 0.001 to about 0.015 inch, and in one embodiment about 0.004 to about 0.01 inch. In one embodiment, each of the product wire strands has a rectangular cross section, the width being about 0.012 inch and the thickness (or height) being about 0.008 inch. In one embodiment, each of the product wire strands has square or substantially square cross-sections that is from about 0.005 x 0.005 inch to about inch, or about 0. 010 x 0.010 inch to about 0. 030 x 0.030 inch, or about 0.020 x 0.020 inch.

In slitter 203, the copper strip 200 is slit using a cutting blade assembly which is schematically illustrated in Fig. 4 and identified generally by the reference numeral 250. The cutting blade assembly 250 includes edge spacers 252,254,256 and 258, cutting blades 260,262,264,266 and 268, and spacers 270,272,274,276 and 278. The cutting blades and spacers can be constructed of any tool steel suitable for cutting copper foil. An example of such a tool steel is M2. The thicknesses (or widths) of the cutting blades 260, 262,264,266 and 268 are typically in the range of about 0.002 to about 0.2 inch, and in one embodiment about 0.008 to about 0.014 inch, and in one embodiment about 0.0105 inch. The thicknesses (or widths) of the spacers 270,272,274,276 and 278 are typically in the range of about 0.002 to about 0.2 inch, and in one embodiment about 0.008 to about 0.014 inch, and in one embodiment about 0.011 inch. The thickness (or width) of the edge spacers 252,254,256 and 258 can range from about 0.1 to about 0.5 inch, and in one embodiment about 0.2 to about 0.4 inch, and in one embodiment each of their thicknesses are about 0.3745 inch. The diameters of the edge spacers and the cutting blades can range from about 2 to about 6 inches, and in one embodiment about 3 to about 5 inches. The diameters of the spacers 270, 272,274,276 and 278 can range from about 2 to about 6 inches, and in one embodiment about 3 to about 5 inches. The cutting blade assembly 250 may

include additional cutting blades and spacers which are not shown in the drawings but would be readily apparent to those skilled in the art.

In one embodiment, a metal working lubricant is applied to the surface of copper strip 200 as it is advanced through the slitter 203. The lubricant may be any known metal working lubricant that is used for cutting or slitting copper.

An example is Die Magic, which is a product of Diversified Technology Incorporated.

As indicated above, the copper strip 200 is slit in slitter 203 to form product wire strands 204,206,208,210 and 212 as well as scrap wire strands 216 and 218. All of these wire strands are advanced from slitter 203 over wire guides (or rollers) 300 and 302 to guide 304, and then under guide 304 to guide 306. Wire strand 204 is advanced over guide 306, around guide 308 to product spool 234. Guide 304 is equipped with a load sensor which senses the tension in the wire strands in contact with it and this information is used to control the rotation of spool 234 and thereby control the tension in wire strand 204. The remaining wire strands are advanced to guide 310, and then under guide 310 to guide 312. Wire strand 206 is advanced from guide 312 to spool 236. Guide 310 is equipped with a load sensor which senses the tension in the wire strands in contact with it and provides a signal for controlling the rotation of spool 236 and the tension in wire strand 206. The remaining wire strands are advanced from guide 312 to guide 314, and then under guide 314 to guide 316. Wire strand 208 is advanced from guide 316 around guide 318 to spool 238. Guide 314 is equipped with a load sensor which senses the tension in the wire strands in contact with it and provides a signal to control the rotation of spool 238 and thereby control the tension in wire strand 208. The remaining wire strands are advanced from guide 316 to guide 320, and then under guide 320 to guide 322. Wire strand 210 is advanced from guide 322 to spool 240.

Guide 320 is equipped with a load sensor which provides a signal to control the rotation of spool 240 and thereby control the tension in wire strand 210. The remaining wire strands are advanced from guide 322 to guide 324, and then under guide 324 to guide 326. Wire strand 212 is advanced from guide 326

around guide 328 to spool 242. Guide 324 is equipped with a load sensor which senses the tension in the wire strands in contact with it and provides a signal to control the rotation of spool 242 and thereby control the tension in wire strand 212. The remaining wire strands are advanced from guide 326 to guide 330, and then under guide 330 to guide 332. Wire strand 216 is advanced from guide 332 to guide 334, and then around guide 334 to spool 246. Guide 330 is equipped with a load sensor that provides a signal to control the rotation of spool 246 and thereby control the tension in wire strand 216.

Wire strand 218 is advanced from guide 332 to guide 336, under guide 336 to guide 338, over guide 338 to guide 340, and under guide 340 to spool 248.

Guide 336 is equipped with a load sensor that senses the tension in wire strand 218 and provides a signal to control the rotation of spool 248 and thereby control the tension in wire strand 218.

It will be apparent to those skilled in the art that although the slitter assembly disclosed in Figs. 3 and 4 provides for the production of five product wire strands and two scrap wire strands, additional product wire strands can be produced by providing additional cutting blades in the cutting blade assembly 250. Similarly, the width of the product wire strands that are produced can be varied by varying the size of the spacers used in the cutting blade assembly 250. Also, the lengths of the product wire strands produced by this assembly can be varied by varying the length of the copper strip 200 that is used with this slitting step. The product wire strands that are produced can be welded to other similarly produced wire strands using known techniques (e. g., butt welding) to produce wire strands having longer lengths.

It will also be apparent to those skilled in that the slitter assembly disclosed in Figs. 3 and 4 can also be used to slit the foil 1 22 (Fig. 2) to make the copper strip 200. The only difference relative to the slitter assembly discussed above would be that the slitter 203 would be equipped to handle a wider roll of foil (e. g., foil roll with a width about 3 to about 60 inches, and in one embodiment about 6 to about 48 inches, and in one embodiment about 12 to about 30 inches), and the cutting blade assembly would be adapted to cut

copper strips with wider widths (e. g., widths of about 0.1 to 1 inch, and in one embodiment about 0.25 inch).

In one embodiment, the square or rectangular cross-sectioned wire strands produced by the slitting step of the inventive process illustrated in Figs.

3-5 are initially subjected to treatment in a shaping line where the cross sections are converted from such squares or rectangles to wire strands with round or oval cross sections. The wire strands with oval or round cross sections are then drawn through round dies to provide wire strands with round cross sections of desired size. Referring to Fig. 6, wire strand 204 is unwound from spool 234 and advanced to accumulator 400. (Alternatively, any of wire strands 206, 208,210 or 212 may be unwound from spools 236,237,240 or 242, respectively, and advanced to accumulator 400.) Wire strand 204 is then advanced from accumulator 400 to shaping unit 410. Accumulator 400 includes fixed sheave 402 and dancer sheave 404 which are provided for maintaining the tension in wire strand 204 as it is advanced to shaping unit 410.

Wire strand 204 entering shaping unit 410 typically has a square or rectangular cross section with a width of about 0.006 to about 0.02 inch, and in one embodiment about 0.010 to about 0.014 inch; and a height (or thickness) of about 0.002 to about 0.02 inch, and in one embodiment about 0.006 to about 0.01 inch. In one embodiment, the wire strand 204 entering shaping unit 410 has a rectangular cross section with the dimensions of about 0.008 x 0.012 inch. The shaping unit 410 is comprised of a power driven Turks head mill, a pull-through Turks head mill in combination with a capstan unit, or a die box in combination with a capstan unit. In shaping unit 410, the cross section of the wire strand 204 is transformed from a rectangular or square shape to an oval shape. In one embodiment, the major diameter of the oval is about 0.008 to about 0.014 inch, and in one embodiment about 0.008 to about 0.010 inch; and the minor diameter is about 0.004 to about 0.01 inch, and in one embodiment about 0.006 to about 0.009 inch. In one embodiment, the wire strand that is shaped in shaping unit 410 has an oval cross section with a major diameter of about 0.010 inch and a minor diameter of about 0.008 inch. Wire

strand 204 is advanced from shaping unit 410 over dead weight dancer sheave 420 to shaping unit 430. Shaping unit 430 is comprised of a die box in combination with a capstan unit. In shaping unit 430 the oval shape of the cross section of the wire is rounded to form a round cross section or a nearly rounded cross section. In one embodiment, the wire strand that is shaped in shaping unit 430 is round or nearly round and has a major diameter of about 0.008 to about 0.012 inch, and in one embodiment about 0.009 to about 0.010 inch. In one embodiment, the wire strand that is formed in shaping unit 430 is substantially round with a major diameter of 0.009 inch and a minor diameter of 0.008 inch. The wire strand is advanced from shaping unit 430 through accumulator 440 to spool 450 where it is wound. Accumulator 440 includes fixed sheave 442 and dancer sheave 444 which are provided for maintaining tension in the copper wire strand as it is advanced from shaping unit 430 to spool 450.

Referring now to Fig. 7, the round or substantially round wire strand 204 produced in shaping unit 430 (Fig. 6) is drawn through a series of dies in die box 460 to produce a wire strand with a round cross section and desired diameter which is collected on spool 470. Die box 460 contains an array of round dies 462 selected to reduce the wire strand to the desired diameter or wire gage.

In Fig. 7, there are 14 dies depicted, but those skilled in the art will recognize that any desired number of dies can be used. Wire strand 204 is advanced from spool 450, over sheave 480, through the first die in die box 460, around sheave 490, under die box 460, around sheave 480 and to and through the second die in die box 460. This sequence is continued until the wire strand goes through the last die in die box 460 and is then advanced to sheave 490, and from sheave 490 to spool 470 where it is collecte. The reduction required for each die can be determined by those skilled in the art. In one embodiment, a full reduction is achieved in each die (e. g., 34 AWG to 35 AWG). In one embodiment, a 1/3 reduction is achieved with each die (e. g., 34 AWG to 34 1/3 AWG). During the reduction in die box 460, conventional metal working lubricants are employed for the purpose of lubricating the dies. Any metal

working lubricant suitable for drawing copper wire can be used. Examples include HSDL No. 2 and HSDL No. 20, both of which are products of G.

Whitfield Richards Co. During this wire drawing step, the wire strands can be reduced from about AWG 32 to about AWG 48, and in one embodiment from about AWG 32 to about AWG 54. In one embodiment, copper wire strands having gages of about AWG 32 to about AWG 62 or smaller can be made. In a particularly advantageous embodiment, wire strands having gages of about AWG 20 to about AWG 62 or smaller, and in one embodiment about AWG 30 to about AWG 62, and in one embodiment about AWG 40 to about AWG 62, and in one embodiment about AWG 45 to about AWG 62, and in one embodiment about AWG 50 to about AWG 62, and in one embodiment about AWG 55 to about AWG 62 can be made.

An advantage of the present invention is that ultra fine wire having gages of about AWG 50 to about AWG 62 or smaller, and in one embodiment about AWG 55 to about AWG 62, and in one embodiment AWG 55 to about AWG 60 can be made.

The following examples are provided for purposes of further illustrating the invention.

Example 1 Electrodeposited copper foil having a weight of 6 oz/ft2 is made in an electroforming cell of the type illustrated in Fig. 2 using an electrolyte solution having a copper ion concentration of 48.5 grams per liter, and a sulfuric acid concentration of 84.9 grams per liter. The free chloride ion concentration is less than 0.1 ppm and no organic additives are added to the electrolyte. The current density is 95.2 ASF. A sample of the foil is slit to provide a wire strand with a rectangular cross section of 0.010 x 0.012 inch. This wire strand is tested for UTS and elongation at 23°C, and for % RIA. The UTS is 39,400 pounds per square inch. The elongation is 22.1 %. The RIA is 100%. The RIA test sample fracture surface, magnified at 300X, is shown in Fig. 8. This test sample has an area reduction of 100% with no dimples. A sample of the wire strand is advanced through a Turks head mill and then drawn through a series of dies to

provide a copper wire having a round cross section and a gage of AWG 52. A sample of this wire is further reduced through a series of dies to provide a wire sample with a gage of AWG 55.

Example 2 Electrodeposited copper foil having a weight of 6 oz/ft2 is made in an electroforming cell of the type illustrated in Fig. 2 using an electrolyte solution having a copper ion concentration of 107 grams per liter, and a sulfuric acid concentration of 75 grams per liter. The free chloride ion concentration is 0.1 ppm. Animal glue is added to the electrolyte at a concentration of 0.8 ppm.

The current density is 440 ASF. The foil is characterized by the presence of a large twinning or stacking fault population in its crystal structure. This is shown in Figs. 10-14. Fig. 10 is an optical micrograph of a sample of this foil taken at a magnification of 400X. Figs. 11 and 12 show twinning using an SEM at a magnification of 2500X. Fig. 13 shows twinning at a magnification of 20, OOOX using a TEM. Fig. 14 shows twinning at a magnification of 50, OOOX using a TEM. A sample of the foil is slit to provide a wire strand with a rectangular cross section of 0.010 x 0.012 inch. This wire strand is tested for UTS and elongation at 23°C, and for % RIA. The UTS is 51,200 pounds per square inch. The elongation is 1.9%. The RIA is 100%. The RIA test sample fracture surface, magnified at 300X, is shown in Fig. 9. This figure indicates an area reduction of 100% although two dimple-like features appear on the shoulder of the fracture cone. The foil contains the following impurities (all numerical values being in ppm): Se <0.2 Bi 0.3 Sb <1 Pb 0.1 As <1 S 2 Sn <1 Ni 1 Fe 2 Ag 7 02 36

A sample of the wire strand is advanced through a Turks head mill and then drawn through a series of dies to provide a copper wire with a round cross section and a gage of AWG 52. A sample of this wire is further reduced through a series of dies to provide wire with a gage of AWG 58.

While the invention has been explained in relation to its preferred embodiments, it is to be understood that various modifications thereof will become apparent to those skilled in the art upon reading the specification.

Therefore, it is to be understood that the invention disclosed herein is intended to cover such modifications as fall within the scope of the appended claims.