Process for making wire

This invention relates to 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 particularly suitable for making copper wire, especially copper wire having a very thin diameter (e.g., about 0.0002 to about 0.02 inch).

TECHNICAL FIELD 
This invention relates to a process for making wire. More particularly, 
this invention relates to a process for making wire by the steps of 
forming metallic foil, then cutting the foil to form one or more strands 
of wire, and shaping the strands to provide the wire with a desired cross 
sectional shape and size. This invention is particularly suitable for 
making copper wire. 
BACKGROUND OF THE INVENTION 
The conventional method for making copper wire involves the following 
steps. Electrolytic copper (whether electrorefined, electrowon, or both) 
is melted, cast into bar shape, and hot rolled into a rod shape. The rod 
is then cold-worked as it is passed through drawing dies that 
systematically reduce the diameter while elongating the wire. In a typical 
operation, a rod manufacturer casts the molten electrolytic copper into a 
bar having a cross section that is substantially trapazoidal in shape with 
rounded edges and a cross sectional area of about 7 square inches; this 
bar is passed through a preparation stage to trim the comers, and then 
through 12 rolling stands from which it exits in the form of a 0.3125" 
diameter copper rod. The copper rod is then reduced to a desired wire size 
through standard round drawing dies. Typically, these reductions occur in 
a series of machines with a final annealing step and in some instances 
intermediate annealing steps to soften the worked wire. 
The conventional method of copper wire production consumes significant 
amounts of energy and requires extensive labor and capital costs. The 
melting, casting and hot rolling operations subject the product to 
oxidation and potential contamination from foreign materials such as 
refractory and roll materials which can subsequently cause problems to 
wire drawers generally in the form of wire breaks during drawing. 
By virtue of the inventive process, metal wire is produced in a simplified 
and less costly manner when compared to the prior art. In one embodiment, 
the inventive process utilizes a copper source such as copper shot, copper 
oxide or recycled copper; this process does not require use of the prior 
art steps of first making copper cathodes then melting, casting and hot 
rolling the cathodes to provide a copper rod feedstock. 
SUMMARY OF THE INVENTION 
This invention relates to a process for making metal wire, comprising: (A) 
forming metal foil; (B) cutting said foil to form at least one strand of 
wire; and (C) shaping said strand of wire to provide said strand with 
desired cross-sectional shape and size. This invention is particularly 
suitable for making copper wire, especially copper wire with a very thin 
or ultra thin diameter, for example, diameters in the range of about 
0.0002 to about 0.02 inch.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The wire that is made in accordance with the inventive process can be made 
of any metal or metal alloy that can be initially formed into a metallic 
foil. Examples of such metals include copper, gold, silver, tin, chromium, 
zinc, nickel, platinum, palladium, iron, aluminum, steel, lead, brass, 
bronze, and alloys of the foregoing metals. Examples of such alloys 
include copper/zinc, copper/silver, copper/tin/zinc, copper/phosphorus, 
chromium/molybdenum, nickel/chromium, nickel/phosphorous, and the like. 
Copper and copper-based alloys are especially preferred. 
The metallic foils are made using one of two techniques. Wrought or rolled 
metallic foil is produced by mechanically reducing the thickness of a 
strip or ingot of the metal by a process such as rolling. Electrodeposited 
foil is produced by electrolytically depositing the metal on a cathode 
drum and then peeling the deposited strip from the cathode. 
The metal foils typically have nominal thicknesses ranging from about 
0.0002 inch to about 0.02 inch, and in one embodiment about 0.004 to about 
0.014 inch. Copper foil thickness is sometimes expressed in terms weight 
and typically the foils of the present invention have weights or 
thicknesses ranging from about 1/8 to about 14 oz/ft.sup.2. Useful copper 
foils are those having weights of about 3 to about 10 oz/ft.sup.2. 
Electrodeposited copper foils are especially preferred. 
In one embodiment, 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, electrodeposited copper foil is formed on a horizontally 
mounted rotating cylindrical cathode and then is peeled off as a thin web 
as the cathode rotates. This thin web of copper foil is cut to form one or 
more strands of copper wire, and then the strands of copper wire are 
shaped to provide a desired cross-sectional shape and size. 
In one embodiment, copper foil is electrodeposited on a vertically mounted 
cathode to form a thin cylindrical sheath of copper around the cathode. 
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 to provide a 
desired cross-sectional shape and size. 
In one embodiment, a copper 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 velocity of the flow 
of the electrolyte solution through the gap between the anode and the 
cathode is generally 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. The 
electrolyte solution has a free sulfuric acid concentration generally in 
the range of about 70 to about 170 grams per liter, and in one embodiment 
about 80 to about 120 grams per liter. The temperature of the electrolyte 
solution in the electroforming cell is generally in the range of about 
25.degree. C. to about 100.degree. C., and in one embodiment about 
40.degree. C. to about 70.degree. C. The copper ion concentration is 
generally in the range of about 40 to about 150 grams per liter, and in 
one embodiment about 70 to about 130 grams per liter, and in one 
embodiment about 90 to about 110 grams per liter. The free chloride ion 
concentration is generally up to about 300 ppm, and in one embodiment up 
to about 150 ppm, and in one embodiment up to about 100 ppm. In one 
embodiment, the free chloride ion concentration is up to about 20 ppm, and 
in one embodiment up to about 10 ppm, and in one embodiment up to about 5 
ppm, and in one embodiment up to about 2 ppm, and in one embodiment up to 
about 1 ppm. In one embodiment, the free chloride ion concentration is 
less than about 0.5 ppm, or less than about 0.2 ppm, or less than about 
0.1 ppm, and in one embodiment it is zero or substantially zero. The 
impurity level is generally at a level of no more than about 20 grams per 
liter, and typically no more than about 10 grams per liter. The current 
density is generally in the range of about 50 to about 3000 amps per 
square foot, and in one embodiment about 400 to about 1800 amps per square 
foot. 
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 can 
optionally contain one or more 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 
##STR1## 
and the iso-thiocyanates having the grouping S.dbd.C.dbd.N-- are useful. 
Thiosinamine (allyl thiourea) and thiosemicarbazide are also useful. The 
active sulfur-containing material should be soluble in the electrolyte 
solution and be compatible with the other constituents. The concentration 
of active sulfur-containing material in the electrolyte solution during 
electrodeposition is in one embodiment preferably up to about 20 ppm, and 
in the range of about 0.1 to about 15 ppm. 
The copper electrolyte solution can also optionally contain one or more 
gelatins. The gelatins that are useful herein are heterogeneous mixtures 
of water-soluble proteins derived from collagen. Animal glue is a 
preferred gelatin because it is relatively inexpensive, commercially 
available and convenient to handle. The concentration of gelatin in the 
electrolyte solution is generally up to about 20 ppm, and in one 
embodiment up to about 10 ppm, and in one embodiment in the range of about 
0.2 to about 10 ppm. 
The copper electrolyte solution can also optionally contain other additives 
known in the art for controlling the properties of the electrodeposited 
foil. Examples include 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, 
thiocarbamoyldisulfide, selenic acid, or a mixture of two or more thereof. 
In one embodiment, these additives are used in concentrations of up to 
about 20 ppm, and in one embodiment up to about 10 ppm. 
In one embodiment, the copper electrolyte solution is free of any organic 
additives. 
During the electrodeposition of copper, it is preferred to maintain the 
ratio of applied current density (I) to diffusion limited current density 
(I.sub.L) at a level of up to about 0.4, and in one embodiment up to about 
0.3. That is, I/I.sub.L is preferably about 0.4 or less, and in one 
embodiment about 0.3 or less. The applied current density (I) is the 
number of amperes applied per unit area of electrode surface. The 
diffusion limited current density (I.sub.L) is the maximum rate at which 
copper can be deposited. The maximum deposition rate is limited by how 
fast copper ions can diffuse to the surface of the cathode to replace 
those depleted by previous deposition. It can be calculated by the 
equation 
##EQU1## 
The terms used in the foregoing equation and their units are defined below: 
______________________________________ 
Symbol 
Description Units 
______________________________________ 
I Current Density Amperes/cm.sup.2 
I.sub.L 
Diffusion Limited 
Amperes/cm.sup.2 
Current Density 
n Equivalent Charge 
Equivalents/mole 
F Faraday's Constant 
96487 (Amp)(second)/equivalent 
C.degree. 
Bulk Cupric Ion Mole/cm.sup.3 
Concentration 
D Diffusion Coefficient 
cm.sup.2 /second 
.delta. 
Concentration Boundary 
cm 
Layer Thickness 
t Copper transfer number 
dimensionless 
______________________________________ 
The boundary layer thickness .delta. is a function of viscosity, diffusion 
coefficient, and flow velocity. In one embodiment, the following parameter 
values are useful in electrodepositing copper foil: 
______________________________________ 
Parameter Value 
______________________________________ 
I (A/cm.sup.2) 1.0 
n (eq/mole) 2 
D (cm.sup.2 /s) 3.5 .times. 10.sup.-5 
C.degree. (mole/cm.sup.3,Cu.sup.+2 (as CuSO.sub.4)) 
1.49 .times. 10.sup.-3 
Temperature (.degree.C.) 
60 
Free sulfuric acid (g/l) 
90 
Kinematic Viscosity (cm.sup.2 /s) 
0.0159 
Flow rate (cm/s) 200 
______________________________________ 
In one embodiment, a rotating cathode is used and copper foil is peeled off 
the cathode as it rotates. The foil is cut using one or several cutting 
steps to form a plurality of strands or ribbons of copper having 
cross-sections that are approximately rectangular in shape. In one 
embodiment, two sequential cutting steps are used. In one embodiment, the 
foil has a thickness in the range of about 0.001 to about 0.050 inch, or 
about 0.004 to about 0.010 inch. The foil is cut into strands having 
widths of about 0.25 to about 1 inch, or about 0.3 to about 0.7 inch, or 
about 0.5 inch. These strands 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-ounce foil is cut into a strand having a cross-section of about 
0.008.times.0.250 inch, then cut to a cross-section of about 
0.008.times.0.012 inch. The strand is then rolled or drawn to provide the 
strand 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.times.0.005 inch to about 
0.050.times.0.050 inch, or about 0.010.times.0.010 inch to about 
0.030.times.0.030 inch, or about 0.020.times.0.020 inch. The strand of 
copper is then rolled or drawn to provide it with a desired 
cross-sectional shape and size. 
Generally, the metal wire made in accordance with the invention can have 
any cross-sectional shape that is conventionally available. These include 
the cross sectional shapes illustrated in FIGS. 3-20. Included are round 
cross sections (FIG. 3), squares (FIGS. 5 and 7), rectangles (FIG. 4), 
flats (FIG. 8), ribbed flats (FIG. 18), race tracks (FIG. 6), polygons 
(FIGS. 13-16), crosses (FIGS. 9, 11, 12 and 19), stars (FIG. 10), 
semi-circles (FIG. 17), ovals (FIG. 20), etc. The edges on these shapes 
can be sharp (e.g., FIGS. 4, 5, 13-16) or rounded (e.g., FIGS. 6-9, 11 and 
12). These wires can be made using one or a series of Turks heads mills to 
provide the desired shape and size. They can have cross sectional 
diameters or major dimensions in the range of about 0.0002 to about 0.02 
inch, and in one embodiment about 0.001 to about 0.01 inch, and in one 
embodiment about 0.001 to about 0.005 inch. 
In one embodiment, the strands of metal wire 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. In one embodiment, 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 wire strands are subjected to sequential passes 
through three Turks head mills to convert a wire with a rectangular cross 
section to a wire with a square cross section. In the first, the strands 
are rolled from a cross-section of 0.005.times.0.010 inch to a 
cross-section of 0.0052.times.0.0088 inch. In the second, the strands are 
rolled from a cross-section of 0.0052.times.0.0088 inch to a cross-section 
of 0.0054.times.0.0070 inch. In the third, the strands are rolled from a 
cross-section of 0.0054.times.0.0070 inch to a cross-section of 
0.0056.times.0.0056 inch. 
In one embodiment, the strands are subjected to sequential passes through 
two Turks head mills. In the first, the strands are rolled from a 
cross-section of 0.008.times.0.010 inch to a cross-section of 
0.0087.times.0.0093 inch. In the second, the strands are rolled from a 
cross-section of 0.0087.times.0.0093 inch to a cross-section of 
0.0090.times.0.0090 inch. 
The strands of wire can be cleaned using known chemical, mechanical or 
electropolishing techniques. In one embodiment, strands of copper wire, 
which are cut 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.degree. C. 
to 70.degree. 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.degree. C.) sulfuric acid, electropolished using 
sulfuric acid, rinsed and dried. 
In one embodiment, the strands of metal 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 wire that are made in accordance with the 
invention are drawn through a die to provide the strands with round 
cross-sections. The die can be a shaped (e.g., square, oval, rectangle, 
etc.)-to-round pass 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.degree., 12.degree., 16.degree., 24.degree. or others known in the art. 
In one embodiment, prior to being drawn, these strands of wire are cleaned 
and welded (as discussed above). In one embodiment, a strand of wire 
having a square cross-section of 0.0056.times.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 can then be 
further drawn through additional dies to reduce the diameter. 
The drawn metal wire, especially copper wire, produced in accordance with 
the inventive process has, in one embodiment, a round cross section and a 
diameter in the range of about 0.0002 to about 0.02 inch, and in one 
embodiment about 0.001 to about 0.01 inch, and in one embodiment about 
0.001 to about 0.005 inch. 
In one embodiment, the metal wire is coated with one or more of the 
following coatings: 
______________________________________ 
(1) Lead, or lead alloy (80 Pb--20Sn) 
ASTM B189 
(2) Nickel ASTM B355 
(3) Silver ASTM B298 
(4) Tin ASTM B33 
______________________________________ 
These coatings are applied to (a) retain solderability for hookup-wire 
applications, (b) provide a barrier between the metal and insulation 
materials such as rubber, that would react with the metal and adhere to it 
(thus making it difficult to strip insulation from the wire to make an 
electrical connection) or (c) prevent oxidation of the metal during 
high-temperature service. 
Tin-lead alloy coatings and pure tin coatings are the most common; nickel 
and silver are used for specialty and high-temperature applications. 
The metal wire can be coated by hot dipping in a molten metal bath, 
electroplating or cladding. In one embodiment, a continuous process is 
used; this permits "on line" coating following the wire-drawing operation. 
Stranded wire can be produced by twisting or braiding several wires 
together to provide a flexible cable. Different degrees of flexibility for 
a given current-carrying capacity can be achieved by varying the number, 
size and arrangement of individual wires. Solid wire, concentric strand, 
rope strand and bunched strand provide increasing degrees of flexibility; 
within the last three categories, a larger number of finer wires can 
provide greater flexibility. 
Stranded wire and cable can be made on machines known as "bunchers" or 
"stranders." Conventional bunchers are used for stranding small-diameter 
wires (34 AWG up to 10 AWG). Individual wires are payed off reels located 
alongside the equipment and are fed over flyer arms that rotate about the 
take-up reel to twist the wires. The rotational speed of the arm relative 
to the take-up speed controls the length of lay in the bunch. For small, 
portable, flexible cables, individual wires are usually 30 to 44 AWG, and 
there may be as many as 30,000 wires in each cable. 
A tubular buncher, which has up to 18 wire-payoff reels mounted inside the 
unit, can be used. Wire is taken off each reel while it remains in a 
horizontal plane, is threaded along a tubular barrel and is twisted 
together with other wires by a rotating action of the barrel. At the 
take-up end, the strand passes through a closing die to form the final 
bunch configuration. The finished strand is wound onto a reel that also 
remains within the machine. 
In one embodiment, the wire is coated or covered with an insulation or 
jacketing. Three types of insulation or jacketing materials can be used. 
These are polymeric, enamel, and paper-and-oil. 
In one embodiment, the polymers that are used are polyvinyl chloride (PVC), 
polyethylene, ethylene propylene rubber (EPR), silicone rubber, 
polytetrafluoroethylene (PTFE) and fluorinated ethylene propylene (FEP). 
Polyamide coatings are used where fire-resistance is of prime importance, 
such as in wiring harnesses for manned space vehicles. Natural rubber can 
be used. Synthetic rubbers can be used wherever good flexibility must be 
maintained, such as in welding or mining cable. 
Many varieties of PVC are useful. These include several that are 
flame-resistant. PVC has good dielectric strength and flexibility, and is 
particularly useful because it is one of the least expensive conventional 
insulating and jacketing materials. It is used mainly for communication 
wire, control cable, building wire and low-voltage power cables. PVC 
insulation is normally selected for applications requiring continuous 
operation at low temperatures up to about 75.degree. C. 
Polyethylene, because of its low and stable dielectric constant, is useful 
when better electrical properties are required. It resists abrasion and 
solvents. It is used chiefly for hookup wire, communication wire and 
high-voltage cable. Crosslinked polyethylene (XLPE), which is made by 
adding organic peroxides to polyethylene and then vulcanizing the mixture, 
yields better heat-resistance, better mechanical properties, better aging 
characteristics, and freedom from environmental stress cracking. Special 
compounding can provide flame-resistance in cross-linked polyethylene. The 
usual maximum sustained operating temperature is about 90.degree. C. 
PTFE and FEP are used to insulate jet aircraft wire, electronic equipment 
wire and specialty control cables, where heat resistance, solvent 
resistance and high reliability are important. These electrical cables can 
operate at temperatures up to about 250.degree. C. 
These polymeric compounds can be applied over the wire using extrusion. The 
extruders are machines that convert pellets or powders of thermoplastic 
polymers into continuous covers. The insulating compound is loaded into a 
hopper that feeds it into a long, heated chamber. A continuously revolving 
screw moves the pellets into the hot zone, where the polymer softens and 
becomes fluid. At the end of the chamber, molten compound is forced out 
through a small die over the moving wire, which also passes through the 
die opening. As the insulated wire leaves the extruder it is water-cooled 
and taken up on reels. Wire jacketed with EPR and XLPE preferably go 
through a vulcanizing chamber prior to cooling to complete the 
cross-linking process. 
Film-coated wire, usually fine magnet wire, generally comprises a copper 
wire coated with a thin, flexible enamel film. These insulated copper 
wires are used for electromagnetic coils in electrical devices, and must 
be capable of withstanding high breakdown voltages. Temperature ratings 
range from about 105.degree. C. to about 220.degree. C., depending on 
enamel composition. Useful enamels are based on polyvinyl acetals, 
polyesters and epoxy resins. 
The equipment for enamel coating the wire is designed to insulate large 
numbers of wires simultaneously. In one embodiment, wires are passed 
through an enamel applicator that deposits a controlled thickness of 
liquid enamel onto the wire. Then the wire travels through a series of 
ovens to cure the coating, and finished wire is collected on spools. In 
order to build up a heavy coating of enamel, it may be necessary to pass 
wires through the system several times. Powder-coating methods are also 
useful. These avoid evolution of solvents, which is characteristic of 
curing conventional enamels, and thus make it easier for the manufacturer 
to meet OSHA and EPA standards. Electrostatic sprayers, fluidized beds and 
the like can be used to apply such powdered coatings. 
Referring now to the illustrated embodiments, and initially to FIG. 1, a 
process for making copper wire is disclosed wherein copper is 
electrodeposited on a cathode to form a thin cylindrical sheath of copper 
around the cathode; this cylindrical sheath of copper is then score cut to 
form a thin strand of copper wire which is peeled off the cathode and then 
shaped to provide the wire with a desired cross sectional shape and size 
(e.g., round cross section with a cross sectional diameter of about 0.0002 
to about 0.02 inch). 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, Turks head shaping mill 22, die 24 and reel 26. Cathode 16 is shown in 
phantom submerged in electrolyte 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 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 
28 around on the surface 17 of cathode 16. Electro-deposition of copper on 
cathode 16 is continued until the thickness of the copper sheath 28 is at 
a desired level, e.g., about 0.005 to about 0.050 inch. Electro-deposition 
is then discontinued. The cathode 16 is removed from the vessel 12. Copper 
sheath 28 is washed and dried. Score cutter 20 is then activated to cut 
copper sheath 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 sheath 28 to within 
about 0.001 inch of the surface 17 of cathode 16. Wire strand 36, which 
has a rectangular cross-section, is peeled off cathode 16, advanced 
through Turks head mill 22 wherein it is rolled to convert the cross 
sectional shape of the wire strand to a square shape. The wire is then 
drawn through die 24 wherein the cross sectional shape is converted to a 
round cross-section. The wire is then wound on reel 26. 
The process depletes the electrolyte solution 18 of copper ions and organic 
additives. 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 vessel 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 are added to the recirculating solution in line 40 from a 
vessel 58 through line 60. In one embodiment, active sulfur-containing 
material is added to the recirculating solution in line 48 through line 62 
from a vessel 64. The addition rate for these organic additives is, in one 
embodiment, in the range of up to about 14 mg/min/kA, and in one 
embodiment about 0.2 to about 6 mg/min/kA, and in one embodiment about 1.5 
to about 2.5 mg/min/kA. 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; and score cutter 20, screw 32 and support 
and drive member 34 are replaced by roller 118 and slitter 120. 
In the electroforming cell 110, a voltage is applied between anode 114 and 
cathode 116 to effect electrodeposition of copper 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 116 whereby metallic copper plates out in the form of a 
copper foil layer on surface 117. Cathode 116 rotates about its axis and 
the foil layer is withdrawn from cathode surface 117 as continuous web 
122. The electrolyte is circulated and replenished in the same manner as 
described above for the embodiment disclosed in FIG. 1. 
Copper foil 122 is peeled off cathode 116 and passes over roller 118 into 
and through slitter 120 wherein it is slit into a plurality of continuous 
strands 124 of copper wire having cross-sections that are rectangular or 
substantially rectangular in shape. In one embodiment, the copper foil 122 
is advanced to slitter 120 in a continuous process. In one embodiment, the 
copper foil is peeled off cathode 116, stored in roll form, and then later 
advanced through the slitter. The rectangular strands 124 are advanced 
from slitter 120 through Turks head mill 22 wherein they are rolled to 
provide strands 126 having square cross-sections. Strands 126 are then 
drawn through die 24 wherein they are drawn to form copper wire 128 with 
round cross-sections. Copper wire 128 is wound on reel 26. 
The following examples are provided for purposes of illustrating the 
invention. 
EXAMPLE 1 
Electrodeposited copper foil having a weight of 6 oz/ft.sup.2 is made in an 
electroforming cell using an electrolyte solution having a copper ion 
concentration of 50 grams per liter, and a sulfuric acid concentration of 
80 grams per liter. The free chloride ion concentration is zero and no 
organic additives are added to the electrolyte. The foil is cut, then 
advanced through a Turks head mill and then drawn through a die to form 
copper wire. 
EXAMPLE 2 
Electrodeposited copper foil having a width of 84" inches, a thickness of 
0.008" inch and a length of 600 feet is collected on a roll. The foil is 
reduced using a series of slitters from the original width of 84" to 0.25" 
wide ribbons. The first slitter reduces the width from 84" inches to 24", 
the second from 24" to 2", and the third from 2" to 0.25" inch. The 0.25" 
ribbons are slit to 0.012" wide ribbons. These ribbons, or slit-sheared 
copper wires, have a cross section of 0.008.times.0.012". This copper wire 
is prepared for metal shaping and forming operations. This consists of 
degreasing, washing, rinsing, pickling, electropolishing, rinsing, and 
drying. Single strands of wire are welded together and spooled for pay-off 
into further processing. The strands of wire are clean and burr-free. They 
are shaped to a round cross section using a combination of rolls and 
drawing dies. The first pass uses a miniaturized powered Turks head 
shaping mill to reduce the 0.012" dimension sides to approximately 
0.010-0.011". The next pass is through a second Turks head mill wherein 
this dimension is further compressed to approximately 0.008-0.010", with 
the overall cross section being squared. Both passes are compressive, 
relative to the dimensions cited above, with an increase in the transverse 
dimension (the dimension in the cross section direction perpendicular to 
the direction of compression) and an increase in wire length. The edges 
are rounded with each pass. The wire is then passed through a drawing die 
wherein it is rounded and elongated having a diameter of 0.00795", AWG 32. 
An advantage of this invention is that when the metallic foil, especially 
copper foil, is produced using electrodeposition, the properties of the 
wire made from such foil can be controlled to a great extent by the 
composition of the electrolyte solution. Thus, for example, electrolyte 
solutions containing no organic additives and having a free chloride ion 
concentration of below 1 ppm, and in one embodiment zero or substantially 
zero, are particularly suitable for producing ultra thin copper wire 
(e.g., AWG 25 to about AWG 60, and in one embodiment AWG 55). 
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.