U.S. patent number 3,848,319 [Application Number 05/339,306] was granted by the patent office on 1974-11-19 for procedure for fabricating ultra-small gold wire.
This patent grant is currently assigned to Albert A. Ciardi, Jr.. Invention is credited to Paul E. Hendrickson.
United States Patent |
3,848,319 |
Hendrickson |
November 19, 1974 |
PROCEDURE FOR FABRICATING ULTRA-SMALL GOLD WIRE
Abstract
The procedure for fabricating ultra-small precious metal or
metal alloy wire comprising the steps of fabricating and annealing
a copper sleeve with an axially aligned opening formed therein,
forming and annealing a precious metal core and inserting the core
into the opening, the sleeve and the core having outer dimensions
preferably formed in the ratio of ten to one, mechanically binding
the core to the sleeve to produce a bi-metallic wire combination,
reducing the size of the wire combination on suitable wire drawing
dies and then chemically removing the sleeve from the precious
metal wire.
Inventors: |
Hendrickson; Paul E. (Wayne,
PA) |
Assignee: |
Ciardi, Jr.; Albert A.
(Philadelphia, PA)
|
Family
ID: |
23328417 |
Appl.
No.: |
05/339,306 |
Filed: |
March 8, 1973 |
Current U.S.
Class: |
29/419.1;
29/423 |
Current CPC
Class: |
B21C
37/047 (20130101); Y10T 29/4981 (20150115); Y10T
29/49801 (20150115) |
Current International
Class: |
B21C
37/00 (20060101); B21C 37/04 (20060101); B23p
017/00 () |
Field of
Search: |
;29/423,424,419,DIG.11 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Lanham; C. W.
Assistant Examiner: Di Palma; Victor A.
Attorney, Agent or Firm: Spivak, Esq.; Karl L.
Claims
I claim:
1. The method of fabricating ultra-small precious metal or metal
alloy wire comprising the steps of
A. forming a copper sleeve having a first cross-sectional size and
annealing the sleeve,
1. said copper sleeve being formed with an axially aligned opening
having a second cross-sectional size;
B. forming a core of precious metal or metal alloy having a third
cross sectional size and annealing the core, said annealing being
carried out separately from annealing the sleeve,
1. the ratio of the first cross-sectional size to the third
cross-sectional size being at least five to one,
2. the second cross sectional size being formed slightly larger
than the third cross-sectional size;
C. inserting the previously annealed core into the opening and then
reducing the second cross-sectional size to equal the third
cross-sectional size to mechanically bond the core to the
sleeve;
D. reducing the cross-sectional size of the sleeve and the cross
sectional size of the core in the same ratio as the initial sizes
by successive size reductions until the core is reduced to the
ultra-small wire size range, and
E. removing the sleeve chemically from the core to produce an
ultra-small precious metal wire.
2. The method of claim 1 wherein the ratio of sleeve to core is ten
to one.
3. The method of claim 1 wherein the copper sleeve, the opening and
the core are all initially formed to square cross-sectional
configurations.
4. The method of claim 3 wherein the sleeve and core combination is
introduced to successively smaller sized carbide wire drawing dies
to achieve smaller wire sizes.
5. The method of claim 4 wherein the sleeve and core combination is
drawn to 36 A.W.G. without employing diamond wire drawing dies.
6. The method of claim 5 and the additional step of cleaning the
sleeve and core combination at least as often as every fourth
reduction on the wire drawing dies.
7. The method of claim 1 wherein the reduction of the second cross
sectional size is carried out simultaneously throughout the length
of the copper sleeve to provide overall bonding.
Description
BACKGROUND OF THE INVENTION
This invention relates in general to the field of manufacturing
fine wire, and more particularly, is directed to a procedure for
fabricating ultra-small gold wire.
In the production of ultra fine wire, prior workers in the art have
previously achieved the desired small wire diameter by drawing
processes whereby the metal or metal alloy is drawn through a hole
in a plate or a block of harder material which is known as a die.
This operation converts the configuration of the starting material,
for example a rod, to an elongated wire of reduced cross section.
The drawing process is repeated as often as necessary by using dies
with successively smaller holes until the desired reduction in
cross sectional area is obtained. When working in the ultra fine
wire area, for example wires having a diameter of one
one-thousandths of an inch, it has been the common practice to
employ diamond dies. Such dies are relatively expensive in
manufacture and in use, thus resulting in a greater cost for the
ultra fine wire thereby produced. When the desired final wire size
is greater than four one-thousandths of an inch, it is possible to
employ carbide dies and not diamond dies to thereby reduce
equipment costs. The carbide dies can be economically and
practically used in wire drawing down to four one-thousandths of an
inch. With smaller wire diameters, it is the usual practice always
to utilize diamond dies.
In the case of drawing ultra fine gold wire, it has been found that
the physical strength of the gold element was such that the wire
drawing procedure could only be utilized to draw gold wire down to
two one-thousandths of an inch by utilizing conventional wire
drawing equipment due to the weakness of the material itself.
Accordingly, at the present time, there is no inexpensive method or
apparatus capable of drawing gold wire as fine as one
one-thousandths of an inch.
SUMMARY OF THE INVENTION
The present invention relates generally to the field of forming
fine wires, and more particularly, is directed to a procedure for
fabricating ultra-small, pure gold wire of one one-thousandths of
an inch diameter or less in size.
The present invention features a method which starts with a copper
sheath of square cross sectional configuration which has a square
axial bore provided therein. A square gold or other precious metal
bar of suitable cross sectional dimensions to easily slide within
the axial bore is formed and placed in position within the axial
bore. The geometry of the initial components is such that the ratio
of measurements of the copper sheath to the gold bar is initially a
ratio of at least 5 to 1, and preferably is precisely at the ratio
of 10 to 1.
The assembled copper clad gold bar is entered into suitable square
shaped wire reduction rolls and is reduced sufficiently to
mechanically bond the gold bar to the copper sleeve, thereby
creating a composite wire having a ratio of ten to one, copper to
gold. Continued reduction of the assembled product is achieved by
employing conventional wire reducing rolls. Steps are taken to
change the configuration from square to round in well known
manner.
By continued reduction, any desired gauge, for example 30 A.W.G.,
can be reached so that the copper sheath will measure 0.010 inches
outside diameter. Wires of this diameter can be conveniently drawn
by employing carbide dies. The gold core diameter will remain in
the same ratio of 10 to 1, thereby resulting in a gold wire
diameter of 0.001 inches. At 31 A.W.G., the sheath diameter will be
0.0089 inches and a gold core of 0.00089 inches will result. At 32
gauge, the sheath will measure 0.008 inches and a gold core of
0.0008 inches will result. At 33 gauge, the sheath diameter will be
0.0071 inches and the gold core will be reduced to 0.00071 inches.
At 34 gauge, the sheath will measure 0.0063 inches and a gold core
of 0.00063 inches will result. At 35 gauge, the sheath will measure
0.0056 inches and the gold core of 0.00056 inches will result. At
36 gauge, the sheath diameter will be 0.005 inches and a gold core
of 0.0005 inches will result.
When the desired gold wire is achieved, the composite material can
be cut into lengths and the lengths can be placed in a glass
container for etching or removing the copper sheath from the finish
gold core wire by employing a suitable acid, for example, nitric or
sulphuric acid. The ultra-small pure gold wire thus produced will
meet known gold wire standards, for example ASTM Designation:
F72-69 entitled "Gold Wire For Semi-conductor Head-Bonding" as
published by the American Society For Testing and Materials.
It is therefore an object of the present invention to provide an
improved procedure for fabricating ultra-small pure gold wire of
the type set forth.
It is another object of the present invention to provide an
improved method for fabricating ultra-small pure gold wire by
employing a copper sheath and a gold core in an initial ratio of 10
to 1.
It is another object of the present invention to provide a novel
method for fabricating ultra-small pure gold wire wherein a gold
bar is placed within a copper sheath having an initial ratio of ten
to one, copper to gold, and wherein the components are
simultaneously reduced by wire drawing in the same ten to one ratio
until the ultra fine wire size is achieved.
It is another object of the present invention to provide a novel
method for fabricating ultra-small pure gold wire wherein a gold
bar is inserted into a copper sheath and the assembly is reduced by
drawing to the ultra fine range, wherein the strength of the copper
sheath is employed to permit gold to be drawn to diameters of 0.001
inches or less.
It is a further object of the present invention to provide a novel
method of fabricating ultra-small gold wire of 0.001 inches
diameter or less wherein the need for diamond dies can be
completely eliminated.
It is another object of the present invention to provide a novel
method for fabricating ultra-small pure gold wire of 0.001 diameter
or less in size wherein gold wire is copper clad and the copper
cladding has a tendency to increase the working characteristics of
the composite structure through increased strength.
As used in this specification, the term "ultra-small" may be
considered as those wires having a diameter of 0.001 inches or
less.
It is a further object of the present invention to provide a novel
method for fabricating ultra-small pure gold wire that is simple in
procedure, inexpensive in equipment costs and trouble free in
operation.
Other objects and a fuller understanding of the invention will be
had by referring to the following description and claims of a
preferred embodiment thereof, taken in conjunction with the
accompanying drawings, wherein like reference characters refer to
similar parts throughout the several views and in which:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a partial, perspective view of the end of an initial
square copper sheath in accordance with the present invention.
FIG. 2 is a view similar to FIG. 1 showing a gold bar in the
process of being inserted into the central opening of the
sheath.
FIG. 3 is a cross sectional view taken along Line 3--3 of FIG. 2,
looking in the direction of the arrows.
FIG. 4 is an enlarged schematic, elevational view showing a
reduction in wire gauge size of the composite material.
FIG. 5 is a schematic, elevational view showing one method of
removing the copper sheath from the gold wire.
FIG. 6 is a perspective view of a spool upon which the ultra-small
pure gold wire produced in accordance with the present method is
being wound.
DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION
Although specific terms are used in the following description for
the sake of clarity, these terms are intended to refer only to the
particular structure of my invention selected for illustration in
the drawings and are not intended to define or limit the scope of
the invention.
The invention will be described with the sheath to core dimensional
relationship of 10 to 1. It will be appreciated however, that other
relationships such as 5 to 1 or over can be similarly utilized. In
order to practice the present invention, a gold or other precious
metal or metal alloy ingot should be prepared by melting pure gold
in a clay-graphite crucible in an oxidizing atmosphere. The melting
precious metal or alloy is then poured into a graphite split mold
at preferably approximately 50.degree. F. above the melting point
of gold, or approximately at a temperature in the 1,950.degree. to
2,000.degree. F range. The mold should preferably be preheated and
an oxidizing atmosphere should be employed during the melting and
pouring operations. Slow pouring is advisable to reduce the dangers
of cold shuts and surface imperfections. The gold is then
conventionally rolled to reduce the size, but great precautions
should be taken to guarantee the cleanliness of the rolls from any
metallic objects. Cleaning must be done every fourth reduction on
the wire reducing rolls. At no time should the wire be permitted to
rub on the metallic plate, either when entering or exiting the
rolls. This cleaning process is necessary to remove very small
micro particles which may be carried over from the rolling process.
In the preferred embodiment, the rolling and cleaning processes
should be continued until the gold wire bar 14 has been reduced to
approximately 0.320 inches square. The gold wire is then cleaned
and annealed at 970.degree. F. for 15 minutes.
Separately, a copper sleeve 10 is prepared by either casting or
machining to a square configuration having outside dimensions of
precisely 31/4 inches with a longitudinally extending, central,
square opening 12 machined or otherwise provided therein. The
square opening 12 is formed to a configuration whereby each of the
sides measures precisely 0.375 inches. The copper sleeve 10 is then
annealed in a reducing atmosphere such as nitrogen at 1,000.degree.
F. for 15 minutes. It is noteworthy that at no time is the
composite gold-copper assembly ever annealed together. In this
manner, by separately annealing the gold and copper components, it
is possible to avoid any diffusion whatsoever of gold into copper
or copper into gold when the gold bar 14 and copper sheath 10 are
brought into contact. Thus, the copper can be readily removed by
acid treatment as hereinafter more fully set forth when the
composite article is finished to the desired final size diameter.
The annealed gold bar 14 is then inserted into the square opening
12 of the separately annealed sheath 10. It will be noted that the
side dimensions of the gold bar 14 are precisely 0.320 inches and
the dimensions of the opening 12 are 0.375 inches, thereby
permitting an easy, sliding fit without the need for employing any
tools or other mechanical devices.
The assembled copper clad gold bar is then entered into
conventional, square shaped wire reduction rolls (not shown) and is
reduced from the original outside measurement of 3.250 inches
square to 3.200 inches square. In this manner, the dimensions of
the opening 12 will be reduced to 0.320 inches to mechanically bond
the copper sleeve 10 to the gold bar 14 at a ratio of 10 to 1,
copper to gold. The outside dimensions of the copper sleeve 10 will
then be 3.200 inches on each side and the dimensions of the hole 12
and the gold bar 14 will be precisely 0.320 inches on each side,
causing a tight mechanical bond.
With the composite material thus bonded, continued reduction on
carbide wire reducing rolls 18 can conventionally proceed by
standard reductions in a manner well known to those skilled in the
art, until the size of 0.325 inches outside measurement is
obtained. One end of the assembled, reduced unit can then be forged
or otherwise pointed and rounded for a length of approximately 4
inches to a size slightly less than a conventional carbide wire
drawing die 18, for example 0.290 inches diameter so as to permit
the mechanical pull of the elongated wire combination 16 through
the die 18 for its entire length. This operation will change the
shape of the wire 16 from square cross-sectional configuration to a
partially round cross-sectional configuration 20.
The assembled, partially round unit 20 is then again forged or
pointed for a length of approximately 4 inches to a size slightly
less than the next round shaped carbide wire drawing die, namely a
die of 0.257 inches diameter. At this stage, the shape of the wire
will be changed from its original square shaped cross-sectional
configuration to a perfectly round shaped copper clad gold wire 22
after having been mechanically, conventionally pulled through the
die 18.
The composite round wire 22 is then reduced from the 0.257 inches
(No. 2 A.W.G.) by A.W.G. reductions on a conventional wire machine
(not shown). When 30 A.W.G. is reached by the carbide wire drawing
dies (not shown), the copper sheath will measure 0.010 inches
outside diameter and a gold core diameter of 0.001 inches will
result. At 31 A.W.G., the outside diameter of the copper sleeve
will measure 0.0089 inches and the gold core diameter of 0.0089
inches will result. At 32 gage, the outside diameter will measure
0.008 inches and the gold core will measure 0.0008 inches, as shown
in the following table:
SIZE DIAMETER DIAMETER A.W.G. COPPER SLEEVE GOLD CORE
______________________________________ 30 0.0100 0.0010 31 0.0089
0.00089 32 0.0080 0.0008 33 0.0071 0.0007 34 0.0063 0.00063 35
0.0056 0.00056 36 0.0050 0.0005
______________________________________
When the desired final diameter of gold core is reached, the gold
wire 24 will be finished with the copper sheath 26 still intact.
The spooled end is then fed at a rate of approximately 10 feet or
more per minute to a conventional, miniature wire straightening
machine (not shown) that runs in a rotary motion to straighten the
wire. If desired, the composite copper clad gold wire 22 of reduced
diameter can be cut into lengths as required and then placed into a
glass or other suitable container 28 for etching or otherwise
removing the copper sheath 26 from the gold core wire 24 by
employing a bath 30 such as nitric acid. The cut lengths remain in
the nitric acid bath 30, a sufficient length of time until all of
the copper sheath 26 has been removed. Optionally, the composite
copper clad wire 22 may be continuously fed into the bath 30 by
employing suitable rolls 32, 34, 36 in a manner to automatically
and continuously remove the copper sheath 26 from the gold wire 24.
If necessary, the pure gold, ultra-fine wire 24 can be thoroughly
rinsed in conventional manner to remove any etchents and then dried
by air prior to use. If desired, the gold wire 24 may be
conventionally wound upon a finished wire spool 38 for storage
purposes prior to use.
Although I have described the present invention with reference to
particular embodiments therein set forth, it is understood that the
present disclosure has been made only by way of example and that
numerous changes in the details of construction may be resorted to
without departing from the spirit and scope of the invention. Thus,
the scope of the invention should not be limited by the foregoing
specification, but rather by the scope of the claims appended
hereto.
* * * * *