Note: Descriptions are shown in the official language in which they were submitted.
~7Z~93
The present invention relates to the electxodeposition
of metal and, in particular to the elec~rodeposition o~ metal
from metal-bearing electrolyte by electrore~ining or electro-
winning. More particularly, the invention relates to the
design and construction of an integrated cathode unit and a
method for using same in the simultaneous electrodeposition of
a multiplicity of separated metal deposits of similar size and
shape.
In production-scale electrometallurgical practice,
refined metal is recovered in large tonnages from solution by
batch electrodeposition onto numerous cathode "starting sheets".
Periodically, the cathodes, with accumulated metal, are removed
from the tank and sheared into pieces which are sized for
convenient handling in the secondary industries for which they
are destined. This practice is labour intensive and methods
have been described whereby individual deposits are produced by
plating onto a modified cathode having conductive islands
regularly spaced in an insulating background. The deposits are
subsequently removed by mechanical stripping and the cathode
is reused.
This basic concept has been described in U.S. Patent
3,860,509 where it has been used to generate fine, powder-like
metal continuously on microscopic islands, but the technique
; disclosed therein is unsuitable for batch commercial applica-
tions where much larger deposits are involved.
For iarge deposits, the industry has found it necessary
to compromise and, instead use batch plating on conventionally-
sized rectangular cathodes having relatively large conductive
islands. The metal is recovered by mechanical stripping and
the cathode is reused. The prior art relating to this field, as
far as is known, is disclosed only in Canadian Patent 955,195
and U.S. Patent 3,577,330 and 3,668,081, and their equivalents
in other countries.
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It is obvious that the success o~ this new field of
art is very much dependent on the ability o~ the reusable
cathode to withstan~ repeated cycling through the plating and
stripping operations. The conductive islands, typically at
least 5/8" in diameter, are sufficiently large that the metal
deposits, which correspond substantially in size to the
conductive areas, form a firm bond with the island. Indeed, a
fragile bond must be avoided to prevent the loss of product into
the electrolytic tank.
Consequently, the stripping operation, which tears the
metal product from the island, subjects the cathode to consider~
able mechanical wear over and above the vigorous handling it
routinely encounters during transfer to and from the electro-
lytic tanks. It follows that cathodes for this application
must be rugged, self-supporting structures capable of resisting
the relatively rough treatment inherent in this industrial
application.
A prior art cathode, of the type referred to in the
three patents described above, consists of a conductive metal
sheet partially covered with a thin coating of non-conductive
material in such a pattern that selected isolated areas of the
metal sheet remain exposed as conductive metal islands. The
most serious drawback of these so-called "permanent cathode
mandrels" is their short service life, which is generally only
ten plating cycles or less. In any masking design, the conduc-
tive islands are inherently depressed in relation to the
masking layer and, during electrodeposition, metal is deposited
into the resulting cavity. The bond at the interface between
the masking material and the underlying metal substrate is
critical to the usefulness of the cathode in the metal stripping
operation since, when deposits are remo~ed, the mask is
subjected to considerable abuse, particularly at the ridge where
the mask surrounds the depressed islands. Where the masking
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7Z9L~93
material is torn away, the island is undesirably enlarged with
the result that abnormal deposits form during subsequent
electrodeposition which, on removal, destroy the coating even
further. The deterioration is both rapid and cumulative and
results in the cathode being withdrawn from service for re-
masking within about ten electrodeposition cycles. The search
for a suitable masking technique has ranged in an increasingly
complex sequence from electroplating paints, inks and tape in
the early patents, to epoxies, applied to a chromium plate
stainless steel sheet, in a later patent, and latterly to vit-
reous enamel layers. Each improvement identifies the vulnerable
feature of the cathodes to be their inability to withstand
repeated electrodeposition because of the deterioration of the
mask.
It has now been found that by the use of a design and
construction novel to this field of art, a reusable integrated
cathode unit with conductive islands is provided that is rugged,
durable, and more reliable than previous cathodes. At the same
time, it has been found that the advantages of the integrated
cathode unit of the present invention are not restricted solely
to its physical attributes, but are also to be found in the
simplicity it imparts to the electroplating method associated
with its use and the improved properties of the electrodepo~its
so produced.
It is an object of the present invention to provide an
integrated cathode unit for the simultaneous production of a
multiplicity of metal electrodeposits thereon.
It is another object of the present invention to provide
an integrated cathode unit that is highly resistant to physical
damage during repeated electrodeposition and stripping cycles
and is characteriæed by long life and low frequency of repairO
It is a further object of the present invention to pro-
vide a method which makes use of the integrated cathode unit
-- 3 --
~ 7Z~33
in the production of me-tal electro~eposits o~ improved shape.
Other objects and advantages will become apparent from
the following description taken in conjunction with the accompanying
drawings in which:
Figure 1 is an isometric projection of a broken-away portion of one
embodiment of the metal assembly that makes up one com-
ponent of the cathode unit.
Figure 2(a) is an isometric projection of a broken-away portion of
a second embodiment of the metal assembly of the present
invention showing the surrounding non-conductive material.
~igure 2(b) shows an end view of Figure 2(a).
Figure 3 is a broken-away portion of an isometric projection of the
metal assembly according to a third embodiment of the
invention~
Figure 4(a) shows a section of a portion of the cathode unit pro-
duced from the assembly of Figure 3.
Figure 4(b) illustrates a modification of the embodiment depicted
in Figure 4(a)~.
Figure 4(c) is a sectional view of a modification of the embodiment
described in Figure 4(a).
Figure 5 illustrates the integrated cathode unit generally con-
templated by the present invention.
Figure 6(a) and (b) are reproductions of electrodeposits produced
according to the method of -the present invention.
Figure 6(c)and (d) are mid-point shape reproductions of sections
of the electrodeposits shown in Figures 6(a) and 6(b)o
Broadly speaking, the apparatus of the present invention
is a rectangular reusable cathode unit having two working faces
for the simultaneous batch electrodeposition thereon of a multi-
plicity of discrete metal deposits, the cathode unit comprising
an integrated whole of two interlocking parts, a substantially
rigid slab of non~conductive material with a conductive metal
assembly embedded therein, said assembly having -
. j, . . .
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projections at spaced locations that penetrate the surface of the
~lab thereby forming an array of solid, conduc~ive metal islands,
each metal island having a surface area of less than about 0.2
square inches and more than ~bout 0.02 square inches and being
flush with or raised above the surface of the slab and separated
from each other sufficiently ~or the electrodeposition of discrete
metal deposits thereon, each of which has a basal area several
times larger than that of the island on which it is deposited.
The invention also relates to a method for electrodepositing
a multiplicity of discrete metal electrodeposits from an electrolyte
said method characterized by:
i)employing in said electrolyte a reusable integrated
cathode unit having two working faces and comprising two
interlocking parts consisting of a substantially rigid
slab of non-conductive material with a conductive metal
assembly embedded therein, said assembly having projections
at spaced locations that penetrate the surface of the slab
thereby forming an array of solid, conductive metal
islands, each metal island having a surface area of less
than about 0.2 square inches and more than about 0.02
square inches and being flush with or raised above the
surface of the slab and separated from the nearest
island sufficiently for the electrodeposition of metal
deposits thereon so that each of said deposits wil~ have
a'basal area several times larger than that of the island
on which it is deposited,
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ii~ passing elec~ric current throuyh the electrolyte,
iii) electrodepositing metal on said cathode unit
thereby producing individual metal deposits weighing
at least 0.18 oz but not more than 1.8 oz,
; iv) removing the deposits from the cathode unit,
v) reusing the cathode unit in the electrolyte for
further metal electrodeposition.
Finally, the invention relates to a cathodically
deposited metal product of substantially hemi-spherical or semi-
ellipsoidal shape having a flat base of area A and a maximumheight, h, measured perpendicularly from the flat base, the
product weighing between 5 g (0.18 oz~ and 5~ g (1.8 oz),
having a total surface area at least three times that of its
flat base and a ratio h/A of at least 0.3 in l.
Three embodiments of the cathode unit are hereinafter
referred to as the stud-wire, stud-plate and corrugated-wire `
embodiments.
The manufacture of an integrated cathode unit
according to the stud-wire embodiment of the invention
comprises, in part, the construction of an electrically conduc-
tive metal assembly such as that shown in Figure 1. The
assembly consists of a conductive frame 4 housing a series of
conductive metal wires 5 to which are attached numerous solid
cylindrical studs 6 each of which normally has a diameter up to
about 1/2". It is preferred that the studs be regularly
spaced and project in a direction normal to the plane in which
the wires lie, but it will be appreciated that other arrange-
ments and orientations of the studs are within the scope o~ ~he
invention. The wires may receive nominal support from conduc-
tive cross-bars 7 until a later stage in the manufacturing
process. Electrical contacts 3 are welded to this assembly as
shown. The material chosen for the transport of current in the
~0'~'~9L93
cathode can be any conductive me~al -that is inert to the
electrolytic solution with which it is in contact. Nickel-
chromium steels such as ~ISI type 304 stainless have been
found particularly satisfactory in this regard. The metal
wires should be thick enough to carry the current and diameters
between 1/8" and 3/8" have been found most adequate. The number
of studs on the metal assembly is selected to maximize the
number of sites for metal deposition on the cathode unit while
at the same time minimizing the space between product metal
electrodeposits.
The metal assembly is embedded in a slab of non-
conductive material such as a plastic. The term "plastic 1I will
be used hereinafter in describing various embodiments of the
invention since, as a group, plastics have been found to be the
most convenient materials. It should be understood, however,
that any substance is satisfactory that has the properties of
being inert to the electrolyte, strong enough to withstand the
normal wear and tear encountered in repeated service, and has
a coefficient of expansion sufficiently compatible with the
embedded metal to prevent serious separation of the two as a
result of the changes of temperature encountered during manu- ;
facture or service. Numerous plastics have such suitable
combination of properties including epoxies, polyurethanes,
polypropylene, polyethylene and acrylics. Inert fillers such
as glass or chemically active modifiers can also be used as
required, to adjust the properties of the plastic material.
Embedding can be achieved by heating the plastic and
causing it to flow around the assembly inside a rigid mould
using the technique known as injection moulding. Alternatively,
liquid resins can be poured into a mould cavity, or, two sheets
of the plastic material with the metal assembly between them
can be hot-pressed together. Whichever technique is used, the
aim is to intimately merge the plastic with the metal assembly
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1~D7;2~3
thereby formin~ the integra-ted cathode slab depicted in
Figure 5.
The end result is a rig.id inteyrated slab cathode
unit composed of two intimately merged complementary parts.
With ~his design, the metal assembly and the non-conductive
slab are mutually interlocked and inseparable. It will be
appreciated, therefore, that the novel integrated design of
the present cathode unit provides a ready solution to the prior
art problem of bonding metal to non-conductive material.
A second embodiment of the invention (plate~stud) is
characterized by the conductive metal assembly illustrated in
isometric section in Figure 2(a) and in end projection in
Figure 2~b). A conductive metal plate 8, with electrical
connection, 3, is provided with a series of solid cylindrical
projections or studs, 9, which, in the embodiment shown in
Figure 2, are aligned with their axes normal to the plane of
the plate. The plate is between 1/16" and 3/16" thick and is
typically, but not necessarily, stainless steel. The metal
studs, which, advantageously, ar~ also made from stainless
steel, are less than 1/2" in diameter and up to about 1/2" long~
The means to affix these studs are varied and include welding,
riveting, or other techniques. The resulting metal assembly
then is embedded in non-conductive material, e.g. plastic 2
(shown in broken outline only in Figure 2(a)~ by any of the
previously described methods to create the integrated cathode
unit shown in Figure 2 and having the external appearance
depicted in Figure 5, of flat conductive metal islands flush
with the surface of the non-conductive slab 2. The studs pro-
vide adequate gripping sites for the plastic 2 but to promote
superior interlocking of the metal assembly and the plastic, it
is advantageous to provide for a continuum of the plastic
through the metal assembly, for example, by perforating the
steel plate at a multiplicity of locations between the
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107Z493
projections, one such perforation 16 being shown i~ Fiyure 2.
The third embodiment of the invention (corrugated-
wire) uses the conductive metal assembly illustrated in Figure
3. In this embodiment, the metal assembly is composed of a
series of corrugated metal wires 10 attached to an end frame 11
in such a way that the wires are substantially parallel and
the peaks of the corrugations are staggered. Cross-members 12
may provide temporary support and spacing means before -the
assembly is embedded in a non-conductive material. Electrical
contacts 3 are attached to the end-frame. The corrugates wires
are of similar composition to the studs described hereinabove
and have diameters between 1/8" and 3/8". The metal assembly
is embedded in a slab of non-conductive material using a mod-
ification of the moulding techniques described earlier. The
sides of the mould, or steel backing sheets, in this case are
pre-lined with rubber, or other soft material that allows the
peaks of the wire corrugation to be depressed therein. This
technique provides an integrated cathode unit having raised
islands as shown, in section, in Figure 4(a). The peaks of
the currugations protrude through the plastic thereky creating
elliptical islands 13 raised above the non-conductive slab 2.
Figure 4(b) illustrates a modification of the embod-
iment in which the raised islands of Figure 4(a) are truncated,
by grinding for example, to form flat elliptical islands 14
on the non-conductive slab 2.
All the embodiments of the cathode described herein-
; above can be modified by the application of a soft deformable
plastic or rubber-like material to the metal assembly prior to
its being embedded in the slab. The deformable material provides
a zone between the conductive metal assembly and the plastic
in which it is embedded. A suitable material is provided by,
for example, a vinyl resin dispersed in a non-volatile plastic-
izer, known in the art as a plastisol, although it should be
_ g _
~07'~ 3
understood that any substance having similar properties is
poten-tially usable. The resulting cathode unit, shown in Figure
4(c) for the raised corrugated-wire embodiment has an elastic
zone, 15, between the metal island 3 and the non-conductive slab
material 2 around it.
The preceeding description makes it clear that all the
embodiments and modifications of the integrated cathode unit of
the present invention share a common distinguishing feature.
The part of the conductive metal island that interfaces with
the plastic is either flush or raised above the surface of the
plastic. The interface zone is crucial to the cathode unit
because it is the site that is subject to the most wear during
the removal of electrodeposits. Thus, the metal islands may
have any configuration provided their surface is flush wi$h or
slightly above the surface of the plastic.
Figure 5 is a general external representation of the
cathode unit contemplated by the present invention sho~ing
conductive metal island 1 integrated with a slab of non-conduct-
ive material 2. Electrical connections 3 provide current to
the islands for electrodeposition of metal thereon.
It will be appreciated by skilled practitioners in
this field that the use of the flat island modifications of any
of the embodiments of the integrated cathode unit herein
particularly described is particularly advantageous because of
the simplicity with which a fresh working surface can be created
when repair is indicated. A simple sanding, grinding, buffing
or similar technique removes worn or damaged material and
generates a fresh cathode surface. This simple restoration
feature of the present invention takes on added significance
when, as described hereinafter, evidence is available which shows
that the cathode unit of the present invention readily out-
performs the prior art cathodes in service life between repairs.
In using the cathode unit in a preferred electrolytic
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1~7;~33
method to produce metal, it has been discovered, quite
surprisingly, ~hat a unique, crown-shaped product results when
the island areas are less than about 0.2 square inches. The
crown-shaped deposits resulting from electrodeposition on
circular and elliptical islands are shown ln Figures 6(a) and
(b) respectively, with mid-point sections of the deposits being
illustrated in Figures 6(c) and (d).
The crown-shaped product has a large component of
growth in the direction normal to the cathode surface. It is
convenient, therefore, to quantitatlvely describe the shape of
the electrodeposit by assigning a shape parameter, S, defined
as the height of the deposit, h, divided by its basal area, A.
Thus, referring to Figure 6(c).
S = h = 4h
~ n
For crown-shaped electrodeposits, the shape parameter,
S, is at least 0.3 in 1 and commonly about 0.45 in 1, In -~
contrast, electrodeposits grown on islands greater than about
0.20 square inches in area are button-shaped and typically
have a value of S of only about 0.2 in 1 or lower.
It will be appreciated from Figure 6 that the crown-
shaped product of the present invention is characterized by a
size which is several times larger than the islands on which
they were grown. In contrast, it is known that the button-
shaped products is recovered in sizes corresponding substantial--
ly to the size of the conductive islands. The weight of the
crown deposit is kept between about 5 g and 50 g by controlling
the length of the plating period. E'or deposits below about
S g in weight the cathodes require cycling about every two days
and the original labour-saving advantage of the cathode tends
to be lost. Above the 50 g, the deposits are so thick there is
danger of contact with the corresponding anode.
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The shape of the product and its size relative to the
conductive island is of significant practical importance Thus
the crown-shaped deposits of the present invention show a large
component of growth in a direction normal to the plating
surface as distinct from basal growth, which is defined as
growth parallel to the plating surface. The plating of metal
on cathodes having conductive islands is normally limited by
touching of adjacent deposits as a result of basal growth
between the conductive islands. For a given basal diameter,
therefore, by virtue of its increased height, a crown-shaped
product can be significantly heavier than a disc-shaped product.
Accordingly, the plating cycles can be much longer, for e~ample
2 weeks instead of the more conventional one week, and the
frequency with which the cathodes must be stripped of their
deposits is correspondingly decreased. The longer plating
cycle is of great practical advantage because it reduces
operating costs in the method while, at the same -time, it
increases the service life of the cathode unit.
A further advantage of the crown shape of the electro-
deposits of the present invention is its relatively large
surface area. This characteristic is beneficial to dissol-
ution rates in plating or melting operations. The substantially
hemispherical shape of the deposits has a theoretical surface
area of 3nr , where r is the basal radius. This is a 50~ larger
area than obtained with a button-shaped deposit of equal radius.
The actual increase is probably far greater than 50% because
of the convoluted texture of the crown shapes as shown in
Figure 6.
Whereas the preferred method of the present invention
makes use of island areas less than 0.20 square inches and more
than about 0.02 square inches, this does not have to be the case.
It will be appreciated that all the benefits and advantages of
the rugged cathode unit described herein apply equally to
electrodeposition methods which employ island areas greater
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l~Z4~3
than 0.20 square inches.further advantage to be gained from the integrated
cathode unit and method of the present invention lies in its
potential for automation. This potential exists primarily
because the integrated cathode units of the present invention
are exceptionally rugged, required no pre-treatment before
plating, such as roughening the surface, and are capable of
very long service life. Thus it is conceived that the product
stripping process could be conducted within the electrolytic
tanks from which the crown product would be subsequently
recovered without need for removal of the cathode units.
The cathode unit and method of the present invention
can be applied to the production of any base metal but
advantageously to the electrodeposition of nickel, cobalt and
copper or alloy composition thereof.
The following examples indicate the nature and
advantages of the invention.
Example 1
Two corrugated-wire cathode units, one prepared
according to the corrugated-wire modification in which the
surface is ground to expose flat islands (cathode A), and the
other according to the modification of raised islands (cathode
B), both measuringapproximately 41" x 25" x 1/2" thick (excluding
electrical contacts~ and having about 1,650 304 stainlesssteel
elliptical conductive islands each approximately 3/8" on its
ma~or dimensions and 3/16" on its minor dimensions and surrounded
by non-conductive epoxy resin, were installed between insoluble
anodes in the production tank of a nickel electrowinning operation.
The electrolyte composi.tion was as follows:
Ni 68.9 g/L
So22 49.6 g/L
Cl 89.7 g/L
Na 27.0 g/L
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.:
~0~24~3
El3BO3 14.6 g/L
and it had a p~ o~ 2.5 at the operating temperature of 60C.
To control the initial growth o~ the deposits, the current to
; the cathode units was increased in steps for the first three days
and thereafter maintained substantially constant for the remain-
ing four days of deposition as seen in Table 1.
TABLE I: Current Levels During Plating Cycle
Current (Amps/Cathode)
Day Cathode Unit A Cathode Unit B
. . . _
10 1 80 90
2 140 150
3 260 270
4 260 270
5 260 270
6 265 270
7 270 185
The starting current density for cathode unit A was about 126
A/ft2 and for cathode unit B 142 A/ft2. The voltage at 200
amps was 2.65 V.
~fter seven days of electrodeposition the two cathode
units were removed from the production tank and the nickel
deposits were readily separated from the surface by use of a
scraper. The shape of the deposits was uniform and approxi-
mately semi-ellipsoidal. The average weight was 22 grams and
the semi-ellipsoid dimensions averaged 1-1/8" diameter at the
base with an overall height of 1/2" measured normally from the
slab sur~ace. The base of each deposit, therefore, had an area
about seven times larger than that of the original conductive
island. The cathode units were inspected after the deposits had
been removed and it was found that none of the epoxy encapsulat-
ing material had dislodged during removal of the deposits.
Example 2
Cathode units manufactu~edaccording to the present
.., , 1~
~07'~4~3
invention were reused repeate~ly according to the method
described above and -their long service life without need for
repair is demonstrated below.
The following laboratory-scale tests were run using
cathode units representing the various flat island modi~ications
of the corrugated and stud-wire embodiments described herein.
The electrolyte was similar to that of Example 1, each cathode
unit measured about 13 1/2" x 6 1/2" x 1/2" thick and the con-
ducting medium in all cases was 304 stainless steel. The
corrugated-wire cathode units had 108 elliptical conductive
islands with an average area of about 0.07 in2 and the stud-wire
cathode units had 154 circular islands each 1/4" in diameter and
having an area of 0.049 in2. The overall island area was,
therefore, approxi~ately constant for all cathodes at about
7.5 in . The starting current was 7.5 amps which corresponded
to a starting current density of about 144 A/ft2. This current
density decreased as platingoccurred due to the three-dimensional
growth of the deposit, and was estimated to be about 20 A/ft
at the end of the plating cycle. Three plating cycles were
completed each week and thus each cycle had a total feed of 22.5
amp-days.
After each plating cycle, the cathode units, with
attached deposits, were removed from the electrolytic tank, water
rinsed, and lightly scraped to detach the deposits. The cathode
units were then returned to the electrodeposition operation
for the next cycle. The service life of the cathode unit was
defined by the number of plating cycles achieved by a given
cathode unit before the surface required repair.
TABLE~ Service LiEe of Various Cathode Units
Cathode Type Plating
Test Metal Assembly Slab Cycles
C Uncoated Corruga-ted-Wire Polyethylene 34
D Uncoated Corrugated-Wire Polypropylene 35
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~V7~h4~3
Plastisol Coated Araldite and 60
Corruga-ted-Wire Hycar CTBN*
FUncoated Stud-~ire Polypropylene 90
GPlaskisol Coated Stud-Wire Araldite and 120
Hycar CTBN
* Araldite is the trade mark identifying an epoxy resin and
Hycar CTBN is a trade mark identifying a rubberizer additive.
It is seen from Table II that the cathodes of the
present invention are all characterized by a much longer plating
life than those of the prior art.
Example 3
A series of deposition tests were run on two cathodes
having islands of two respectively different sizes. Each
cathode was used to plate 14 g deposits under two different
starting current densities. The electrolyte was similar to that
of Example 1. The results are shown in Table 111.
TAsLE III: Effect of starting Current Density and
Island Size of Product Shape
Island Diameter Starting Current Density Shape Factor
(in) (A/ft2) S, (in 1)
.
5/8" 50 .24
5/8" 200 .22
5/16"l 50 .46
5~16" 200 .43
The electrodeposits from the 5/8" diameter islands were disc-
shaped, virtually identical in overall shape and differed only
in the surface texture. The electrodeposits formed on the
smaller islands were both crown-shaped and qualitatively dis-
tinct from the disc-shaped deposits.
This example shows clearly that the crown-shape of the
product, and its associated advantages, is not due to operating
at the higher current density that attends the use of a smaller
island, but results intrinsically from the absolute size of the
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island itself.
Example 4
Additional tests were run, similar to those of Example3, but using a constant island size of 7/16" and a constant
current density of 200 A/ft2. Deposition times, however, were
varied thereby giving rise to deposits of different weights.
This test thus studied the effect of deposit weight on deposit
shape. The results are shown in Table IV.
TAsLE IV: Relationship setween Electrodeposit Weight
and Shape
...... :
Deposit Weight Shape Factor S
g (in~l)
.35
.34
.31
This example shows that the deposits retain a roughly
constant shape factor as they grow. It is evident, therefore,
that these results, taken in con~unction with those of Example
3, show that the absolute island size is the most important
variable in determining product shape. The two examples also
serve to deflne the limits of the invention. Example 3 showed
that button-shapes resulted from deposition on 5/g" diameter
islands and the present Example, in contrast, shows that a
7/16" diameter isiand yields a crown deposit. A practicable
cut-off limit for island sizes for deposition of crowns accord-
ing to the present invention appears, therefore, to be a diameter
of about 1/2", or equivalently, an area of about 0.20 in2.
Example 5
. . .
A cathode was manufactured according to the modifica-
tion of the plastisol-coated corrugated wire embodiment using
raised islands rathex than the flat islands described in Example 2.
The matrix material was a mixture of Araldit with Hycar CTBN.
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~v~z~g3
All electrodeposition parameters, including current density,were similar to those of Examples 1 and 2. ~he cathode lasted
; 56 cycles and yielded deposits that were even more readily
removed than those ~rom cathodes having the flat island mod-
ification. The product deposits, apart from a depression in
the base corresponding to the raised islands, were in all
respects similar to earlier deposits.
Example 6
A laboratory-sized cathode was constructed in which a
stud-wire assembly with a plastisol coating, was embedded in a
plastic slab of Araldite with Hycar CTsN. The cathode had 154
islands on its surface, each 5/16" in diameter.
The cathode was immersed in a cell containing an
electrolyte similar to that of Example 1. A current of 16.5
amps was fed to the cell which corresponded to a starting
current density of 210 A/ft2. Electrodeposition of nickel was
continued for a 14 day period after which the cathode and
deposits were removed from the tank and the deposits removed
by a light scraping action.
None of the deposits had bridged and they were all
crown-shaped with excellent surface uniformity. Their average
weight was about 34 grams and typical measurements were about
7/8" diameter at the base and 7/16" in height.
Example 7
A cathode with 5/16" diameter islands was constructed
from a 304 stainless steel plate-stud metal assembly embedded
in polyurethane. The cathode was immersed in a cell containing
an electrolyte similar to that of Example 1 under a current of
16.5 amps which corresponded to a starting current density of
210 A/ft . Three electrodeposition cycles were conducted each
week with each cycle being terminated by stripping of the nickel
electrodeposits in the manner previously described. The cathode
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had lasted 40 cycles at time of writing and showed no evidenceof deterioration.
Example 8
A deposition test was run on a cathode having 5/16"
diameter islands. The cathode was placed in a cell containing
a copper-bearing sulphate electrolyte and copper was plated on
the islands up to a weight of about 30 grams using a starting
current density of 140 A/ft?. The test was repeated using
5/8" diameter islands. The deposits grown from the 5/16" islands
were crown-shaped and had an S factor of 0.4 in 1 whereas the
5/8" islands deposits were disc~like and had an S ~actor of
0.22 in 1.
Example 9
A deposition test was run, similar to that of Example
8, but employing a cobalt chloride electrolyte. The resulting
cobalt deposits were very similar in shape to the copper de-
posits of Example 8 and to nickel deposits plated under the
same conditions. The conclusion is therefore drawn that the
method of the present invention can be applied to the electro-
deposition of copper and cobalt.
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