Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
use U~10,973/il,076/11,118
CY~NIDE-FREE COPPER PLYING PROCESS Ply I
';~.
Background of the Invention
The use of cyanide salts in copper plating electrolytes
has become environmentally disfavored because of ecological
considerations. Accordingly a variety of non-cyanide electrolytes
for various metals have heretofore teen proposed for use as
replacements for the well-known and conventional commercially
employed cyanide counterparts. For example, U.S. Patent No.
3,475,293 discloses the use of certain diphosphonates for
electroplating diva lent metal ions; U.S. Patents Nos. 3,706,634 and
3,706,635 disclose the use of combinations of ethylene Dunn
twitter (ethylene phosphoric acid), 1-hydroxyethylidene-1,
l-diphosphonic acid, and aminotri ethylene phosphoric acid) as
suitable completing agents for the metal ions in the bath; Us So
Patent No. 3,833,486 discloses the use of water soluble pnosphonate
chelating agents for metal ions in which the bath further contains
at least one strong oxidizing agent; while U.S. Patent No.
3,928,147 discloses the use of an organophosphorus chelating agent
for pretreatment of zinc die castings prior to electroplating with
electrolytes of the types disclosed in U.S. Patents 3,475,293,
3,706,634 and 3,706,635.
While the electrolytes and processes disclosed in the
aforementioned United States patents have provided satisfactory
electrode posits under carefully controlled conditions, such
electrolytes and processes have not received widespread commercial
I
acceptance in view of one or more problems associated with their
practice. A primary problem associated with sun prior art
electrolytes has been inadequate adhesion of the copper deposit Jo
zinc and zinc alloy substrates. Another such problem relates to
the sensitivity of such electrolytes to the presence of
contaminants such as cleaners, salts of nickel plating solutions,
chromium plating solutions and zinc metal ions introduced into the
electrolyte during conventional commercial practice Still another
problem is the hazardous nature of strong oxidizing agents employed
in certain of such prior art electrolytes.
The present invention overcomes many of the problems and
disadvantages associated with prior art cyanide-free copper plating
solutions by providing a process employing an electrolyte which is
cyanide-free providing an environmentally manageable system, which
will function to produce an adherent copper deposit on conductive
substrates including steel, brass and zinc base metals such as zinc
die casts and the like; which will efficiently produce ductile,
fine-grained copper deposits at thicknesses usually ranging from
about 0.015 to about 5 miss (0.000015 to about 0.005 inch), which
is more tolerant of the presence of reasonable concentrations of
contaminants such as cleaning compounds, salts of nickel and
chromium plating solutions and zinc metal ions as normally
introduced into a plating bath in a commercial practice, and which
is of efficient and economical operation. The invention further
encc~lpasses a novel insoluble alloy anode employed in the practice
of the process.
Summary of the Invention
The benefits and advantages of the present invention are
achieved in accordance with the process aspects thereof by
employing a cyanide-free aqueous electrolyte containing controlled,
effective amounts of cupric ions, an organ6-phosphonate chelating
agent, a buffering agent, hydroxyl and/or hydrogen ions to provide
a pi from mildly acid to moderately alkaline, and optionally but
preferably, a wetting agent. The copper ions may be introduced by
a bath soluble and compatible copper salt, to provide a cupric ion
concentration in an amount sufficient to electrode posit copper, and
generally ranging from as low as about 3 to as high as about 50
grams per liter (g/l) under selected conditions. me
organo-phosphonate chelating agent is a compound selected from the
group consisting of 1-hydroxy-ethylidene-1, l-diphosphonic
acid (HEMP) by itself present in an amount of about 50 to about 500
g/l, a mixture of HEMP and aminotri - (ethylene phosphoric acid)
(ATOP) in which HEMP is present in an amount of at least about 50
percent by weight of the mixture, and a mixture of HEMP and
ethylenediamine twitter tmethylene phosphoric acid) (EDqMP) in which
HEMP is present in an amount of at least about 30 percent by weight
of the Metro, as well as the bath soluble and compatible salts
and partial salts thereof. When mixtures of HEMP and ATOP or HEMP
and En are employed as the chelating agent instead of HEMP by
itself, a reduction in the concentration of the chelating agent can
be used due to the increased chelating capacity of the Arm and
ELOPE compounds in comparison to that of HEMP. The concentration
of the organo-phosphonate chelating agent will range in
a proportional relationship to the specific amount of
copper ions present in the bath and is usually controlled
to provide an excess of the chelating agent relative to
the copper ions present.
In addition to the foregoing, the bath contains
a suitable compound such as alkali metal carbonates,
acetates and/or borate as a stabilizing agent as well as
a buffering agent which is present in an amount usually of
at least about 5 up to about 100 g/l with amounts of at
least about 20 g/l being required in most instances. The
bath further contains hydroxyl and/or hydrogen ions to
provide an electrolyte from mildly acidic (pi 6) to
moderately alkaline (pi 10.5) with a pi of about 9 to
about 10 being usually preferred. The bath may optionally
and preferably further contain a bath soluble and
compatible wetting agent present in an amount up to about
0.25 g/l.
` In accordance with the process aspects of the
present invention, the cyanide-free electrolyte as
hereinabove described is employed for electrode positing a
fine-grained ductile, adherent copper strike on conductive
substrates including ferrous-base substrates such as
steel, copper-base substrates such as copper, bronze and
brass; and zinc-base substrates including zinc die
castings. The substrate to be plated is immersed in the
electrolyte as a cathode and 2 soluble copper anode in
combination with an insoluble ferrite anode is employed to
provide a copper anode to ferrite anode surface area ratio
of about 1:2 to about 1: 6 . The electrolyte is
electrolyzed by passage of current between the cathode and
anode for a period of time of about 1 minute to as long as
several hours and even days in order to deposit the
desired thickness of copper on the cathodic substrate.
The bath can be operated at a temperature of from about
100 to about 160F with temperatures of about 110 to
about 140F being preferred. The particular temperature
employed will vary depending on the specific bath
composition in order to optimize plate characteristics.
The bath can be operated at a current density of about 1
to about 80 amperes per square toot (AS), depending on
bath composition, employing a cathode to anode ratio
usually of about 1:2 to about 1:6~ It has been
surprisingly discovered that, uniform, adherent and
fine-grained deposits are obtained by electrifying the
substrates prior to immersion in the electrolyte. In the
case of zinc-base substrates, electrification of the part
at a voltage of at least about 3 volts has been found
necessary to attain satisfactory adhesion of the copper
deposit The specific operating parameters and
composition of the electrolyte will vary depending upon
the type of basis metal being plated, the desired
thickness of the copper plate to be deposited, and time
availability in consideration of the other integrated
plating and rinsing operations.
In accordance with a further process aspect of
the present invention, the cyanide-free electrolyte as
hereinabove described is employed for electrode positing a
fine-grained ductile, adherent copper strike on conductive
substrates including ferrous-base substrates such as
steel, copper-base substrates such as copper, bronze and
brass; and zinc-base substrates including zinc die
castings. The substrate to be plated is immersed in the
electrolyte as a cathode and a soluble copper anode in
combination with an insoluble nickel-iron anode is
employed to provide a copper anode to nickel-iron alloy
anode surface area ratio of about 1:2 to about I The
electrolyte is electrolyzed by passage of current between
the cathode and anode for a period of time of about 1 minute to US
long as several hours and even days in order to deposit the desired
thickness of copper on the cathodic substrate. The bath can be
operated at a temperature of from about 100 to about 160F with
temperatures of about 110 to about 140F being preferred. The
particular temperature employed will vary depending on the specific
bath composition in order to optimize plate characteristics. The
bath can be operated at a current density of about 1 to about 80
amperes per square foot (AS), depending on bath composition,
employing a cathode to anode ratio usually of about 1:1 to about
1:6. It has been surprisingly discovered, that uniform, adherent
and fine-grained deposits are obtained by electrifying the
substrates prior to immersion in the electrolyte. In the case of
zinc-base substrates, electrification of the part at a voltage of
at least about 3 volts has been found necessary to attain
satisfactory adhesion of the copper deposit. The specific
operating parameters and composition of the electrolyte will vary
depending upon the type of basis petal being plated, the desired
thickness of the copper plate to be deposited, and time
availability in consideration of the other integrated plating and
rinsing operations.
The present invention further contemplates a novel
nickel-iron insoluble anode which is employed in the process in
conjunction with a soluble copper anode in controlled anode surface
ratios thereby achieving the desired oxidizing medium for
maintaining appropriate plating conditions and for achieving copper
electrode posits of the desired characteristics. The insoluble
nickel-iron alloy anode is preferably of a composite construction
comprising a conductive core having an adherent nickel-iron ahoy
electrode posit bonded there over containing from about 10 percent up
to about 40 percent by weight iron in the alloy and from about
0.005 up to about 0.06 percent sulfur. ale core is comprised of
metals such as copper, aluminum, iron and other conductive alloys
of which-copper itself comprises the preferred core material. The
nickel-iron alloy coating or plating on the core is further
characterized as being substantially nonporous and may be as thin
as 1 to 2 miss (0.001 to 0.002 inch) thwack
Additional benefits and advantages of the present
invention will become apparent upon a reading of the Description of
the Preferred Embodiments considered in conjunction with the
accompanying examples.
Brief Description of the Drawing
Figure 1 is a schematic perspective view purl in
section illustrating a plating receptacle suitable for use in the
practice of the present process;
Figure 2 is a side elevation Al view of an insoluble
nickel-iron alloy anode employed in the practice of the process of
the present invention; and
Figure 3 is a magnified transverse cross-sectional view
of the anode shown in Figure 2 and taken substantially along the
line 3-3 thereof.
description of the Preferred Embodiments
A cyanide-free electrolyte suitable for use in the
practice of the pro ant invention contains as its essential
constituents, copper ions, an organo-phosphonate co~plexing agent
in an amount sufficient to complex the copper ions present, a
stabilizing and buffering agent comprising a bath soluble arid
compatible carbonate, borate and/or acetate compound, as well as
mixtures thereof, a pi of about 6 to about 10.5, and optionally, a
wetting agent.
The copper ions are introduced during makeup of the
electrolyte by employing any one or mixtures of bath soluble and
compatible copper salts such as sulfate, carbonates, oxides,
hydroxides, and the like. Of -the foregoing, copper sulfate in the
form of a pentahydrate (Quiz) is preferred. m e copper ions
are present in the bath within the range of about 3 up to about 50
g/l, typically from around 5 to about 20 g/l. For example, when
plating steel substrates, copper ion concentrations of about 15 up
to about 50 g/l are employed to achieve a high rate of copper
electrode position. In such instances in which the copper ion
concentration is above about 20 g/l, it has been found by
experimentation that electrified part entry into the bath is
preferred to attain satisfactory adhesion. Gun the other hand, when
plating zinc-base substrates such as zinc die castings, for
example, copper ion concentrations of about 3.5 to about lo g/l are
preferred and in which instant ox the part must be electrified at the
time of bath immersion to achieve an adherent deposit. During use
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I
of the electrolyte, a replenishment of the copper ions consumed
during the electrode position operation as well as those removed by
drag-out is achieved by the progressive dissolution of a copper
anode employed in electrolyzing the bath.
The completing or chelating agent comprises an
orgaro-phosphorus ligand of an alkali metal and alkaline Earth
metal salt of which calcium is not suitable due to precipitation.
Preferably, the completing salt comprises an alkali metal such as
sodium, potassium lithium and mixtures thereof of which potassium
constitutes the preferred metal. The completing agent is present
in the bath in consideration of the specific concelltration of
copper ions present.
The specific organo-phosphorus ligand suitable for use in
accordance with the practice of the present invention comprises a
ccnpound selected from the group consisting of l-hydroYyethylidene
Al, l-diphosphonic acid (HEMP) by itself present in an amount of
about 50 to about 500 g/l, a mixture of HEMP and aminotri -
(ethylene phosphoric acid) (Alp) in which HEMP is present in anam3unt of at least about 50 percent by weight of the mixture, and a
mixture of I~EDP and ethylenediamine twitter (Ethylene phosphoric
acid) (EDTMP) in which HEMP is present in an amount of at least
about 30 percent by weight of the mixture, as well as the bath
soluble and compatible salts and partial salts thereof. When
mixtures of HEMP and AMP or HEMP and EDTMP are employed as the
chelating agent instead of HEMP by itself, a reduction in the
concentration of the chelating agent can be used due to the
I
increased chelating capacity of the AMP and ZIP compounds in
comparison to that of HEMP. Commercial available pounds of
the foregoing types which can be satisfactorily employed in the
practice of the present invention include REQUEST* 2010 (HEMP),
REQUEST 2000 AMP) and REQUEST 2041 (E~rMp) available from
Monsanto Cb~pany.
As previously indicated, the HEMP chelating agent can be
employed Nat a concentration of about 50 g/l corresponding to a
copper ion concentration of about 3 g/l up to a concentration of
about 500 g/l corresponding to a copper ion concentration of about
50 g/l, with intermediate concentrations proportionately scaled in
consideration of corresponding intermediate concentrations of
ccDper ions. Zen a mixture of HEMP and AMP is employed,
preferably comprising about 70 percent HEMP and 30 percent by
weight Autumn, it has been discovered that 14 g/l HEMP and 6 g/l ASP
are satisfactory at a copper ion content of 3 g/l while 225 g/l
HEMP and 97. g/l ATOP are satisfactory at a copper ion bath.
concentration of 50 g/l. Corresponding adjustments in the
concentrations of HEMP and AMP are proportionately made when the
copper ion concentration is intermediate of the 3 and 50 g/l limits
to provide satisfactory chelation with a slight excess of chelating
agent present in the bath. Similarly, when a mixture of HFDP and
EDqMP is employed, preferably 2c~prising about 50 percent by weight
of each pound it has been discovered that 9 g/l HEMP and 10 g/l
EDqMP are satisfactory at a copper ion concentration of about 3 g/l
- while 145 g/l HEMP and 166 g/l WIMP are satisfactory at a copper
* Trade murk
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~2~25~
ion bath concern ration of about 50 g/l with proportionate
adjustments in the concentrations of these two constituents in
consideration of intermediate copper ion concentrations. It will
also be appreciated that alternative mutters of chelating agents
within the ranges specified will require proportionate adjustments
in concentration of total chelating agent present in relation to
topper ion concentration in consideration of the foregoing
concentration relationships which can be readily calculated and
confirmed by routine testing to provide optimum performance for any
given conditions in further consideration of the specific examples
hereinafter set forth.
A third desirable constituent of the copper electrolyte
comprises a bath soluble and compatible stabilizing and buffering
agent including carbonate compounds, borate compounds, acetate
compounds as well as mixtures thereof. Preferably, sodium
carbonate and potassium carbonate are employed to stabilize the
electrolyte against pi fluctuations and to further serve as a
carrier for contaminating metal ions introduced in the bath as a
result of drag-in and dissolution of the parts in the electrolyte
during the electrode position operation. I've use of the
aforementioned buffering agents has further been observed,
depending upon the particular chelating agent used, to inhibit the
formation of smutty copper deposits and eliminate dark copper
deposits in the cathode low current density areas. Ammonium irons
have been found undesirable in some instances because of a loss of
adhesion of the electrcdeposit while calcium ions are undesirable
11
I
because of the tendency to form precipitates in the bath. The
concentration of the buffer can broadly range from about 3 up to
about 100 g/l calculated as the sodium salt, preferably about 10 to
about 20 g/l. Concentrations of the buffering agent belay the
recommended minimum concentrations will result in pi fluctuations
whereas concentrations above the maximum range specified do not
appear to have any adverse effects on the operation of the
electrolyte.
Since the buffering agent and completing agent are
subject to depletion by both decomposition and drag-out, a
replenishment of these two chemicals to maintain the electrolyte
within appropriate composition limits is necessary during
cc~mereial operation. This can conveniently be performed on an
intermittent or continuous basis in response to an analysis of bath
composition by adding the two constituents separately or in
admixture in appropriate proportions.
The electrolyte is adjusted to provide a pi of from about
6 up to about 10.5 with a pi of about 9 to about 10 being
preferred. Typically an operating pi of about 9.5 has been found
particularly satisfactory. The appropriate pi of the electrolyte
can be maintained by adding an alkali metal hydroxide to the
electrolyte to raise the pi of which potassium hydroxide is
preferred. In order to reduce the pi within the desired range, a
mineral acid or an alkali metal bicarbonate can be employed of
which potassium bicarbonate constitutes a preferred material. When
the operating pi decreases below the recommended level, it has been
observed that the electrolyte tends to promote poor adhesion of the
copper deposit on the substrate. On the other hand, at an
operating pi above the reccm~ended range, it has been observed in
some instances, that the copper deposit becomes grainy and of a
burnt characteristic. It has been found that at a pi of below
about 7.5 down to about 6, satisfactory adhesion and deposit
appearance can be obtained on copper and copper alloy substrates.
Hcwever,-when plating ferrous and zinc base substrates, a pi above
about 7.5 to about 10.5 has ken found to provide best results.
In addition to the foregoing constituents, the bath may
optionally further contain a wetting agent or surfactant which is
bath soluble and compatible with the other constituents therein.
When such a s~lrfactant is employed, it can he used in
concentrations up to about 0025 g/l with amounts of fry about 0.01
to about 0.1 g/l being preferred. Typical surfactants suitable for
use in the practice of the present invention include polyethylene
oxides such as CPRBCWPX *l~OO`alkyl sulfates such as 2-ethyl Huxley
sulfate provided that the bath is carbon filtered to remove
degradation products formed during operation, perfluro anionic
wetting agents, and the like.
In the practice of the process of the present invention,
the electrolyte can be operated at a temperature of from about 100
to about 160F, preferably from about.llO to about 140F with
temperatures of about 120 to about 140F being typical. The
specific temperature employed will vary depending on bath
composition such as will become apparent in the specific examples
* Trade mark
'I,
subsequently to be described. The bath can operate at a cathode
current density of from abut 1 to about 80 AS with a current
density of about 5 to about 25 AS being preferred.
- The electrode position of the copper deposit can be
performed in consideration of the other operating parameters of the
bath within a time of as little as 1 minute to as long as several
hours or even days with plating times of about 2 minutes to about
30 minutes being more usual for strike deposits. The specific time
of electrode position will vary depending upon the thickness of the
plate desired which will typically range from about 0.015 to about
5 miss.
The electroplating operation is performed by versing
the conductive substrate to be plated in the electrolyte and
connecting the substrate to the cathode of a direct current source.
It has been found that when the copper ion concentration is above
about 20 g/l, it is advantageous, and usually necessary, to
electrify the substrate prior to and during irnrersion in order to
achieve good adherence of the copper plate on ferrous-base
substrates. In the case of zinc-base substrates, it has been found
-- essential at all copper ion bath concentrations to electrify the
zinc-base substrate prior to and during entry into the bath at a
minimum potential of about 3 volts to achieve satisfactory adhesion
of the copper plate on the zinc-basis substrate.
A combination of anodes are employed for electrolyzlng
the bath and effecting the deposition of a copper plating on the
cathode. me combination of anodes includes a copper anode of any
14
of the types well known in the art such as an oxygen-free
high purity copper anode which is soluble and replenishes
the copper ions consumed from the bath by
electrode position and drag-out. It has been observed that
when the concentration of copper ions falls below the
recommended minimum concentration, a reduction in cathode
efficiency occurs accompanied by burnt deposits. On the
other hand, concentrations of copper ions above the
recommended maximum range has been observed to adversely
affect the adhesion of the copper deposit. While
replenishment of copper ions can be effected by the
addition of copper salts to the electrolyte, it is
preferred to effect replenishment by dissolution of the
copper anode at a rate substantially corresponding to the
depletion rate of the copper ions by an appropriate
adjustment of the copper anode surface relative to the
insoluble anode surface, which insoluble anode may be a
ferrite anode or a nickel-iron alloy anode. The specific
copper anode surface area to ferrite anode surface area
ratio can range from about 1:2 to about 1:6 with a ratio
of about 1:3 to about 1:5 being preferred and a ratio of
about 1:4 being typical. The specific anode surface area
to nickel-iron alloy anode surface area ratio can range
from about 1:2 up to about 4-1, with a ratio of about 1:1
to about 2:1 being preferred. Moreover, the ratio of the
surface area of the cathode to the total anode surface
area can range from about 1:2 up to about 1:6, preferably
about 1:3 to about 1:5 and typically, about 1:4.
The insoluble ferrite anode employed in
controlled combination with the soluble copper anode may
comprise an integral or composite anode construction in
which the ferrite sections thereof comprise a sistered
mixture of iron oxides and at least one other
metal oxide to produce a sistered body having a spinner
crystalline structure. Particularly satisfactory
ferrite anode materials comprise a mixture of metal
oxides containing about 55 to about 90 mow percent of
iron oxide calculated as Foe and at least one other
metal oxide present in an amount of about 10 to 45 mow
percent of metals selected from the group consisting
of manganese, nickel, cobalt, copper, zinc and mixtures
thereof. The sistered body is a solid solution in which
the iron atoms are present in both the ferris and
ferrous forms.
Such ferrite electrodes can be manufactured,
for example, by forming a mixture of ferris oxide
(Foe) and one or a mixture of metal oxides selected
from the group consisting of Moo, No, Coo Cut, and
Zoo to provide a concentration of about 55 to 90 mow
percent of the ferris oxide and 10 to 45 percent of
one or more of the metal oxides which are mixed in a
ball mill. The blend is heated for about one to about
fifteen hours in air, nitrogen or carbon dioxide at
temperatures of about 700 to about 1000C. The heat-
in atmosphere may contain hydrogen in an amount up to
about 10 percent in nitrogen gas. After cooling, -the
mixture is pulverized to obtain a fine powder which
is thereafter formed into a shaped body of the desired
16
I
configuration such as by compression molding or extra-
soon. The shaped body is thereafter heated at a them-
portray of about 1100 to about 1450C in nitrogen or
carbon dioxide containing up to about 20 percent by
volume of oxygen for a period ranging from about 1 to
about 4 hours. The resultant sistered body is there-
after slowly cooled in nitrogen or carton dioxide
containing up to about 5 percent by volume of oxygen
producing an electrode of the appropriate configuration
characterized as having relatively low resistivity,
good corrosion resistance and resistance to thermal
shock.
It will be appreciated that instead of
employing ferris oxide, metal iron or ferrous oxide
can be used in preparing the initial blend. Addition-
ally, instead of the other metal oxides, compounds of
the metals which subsequently produce the correspond-
in metal oxide upon heating may alternatively be used,
such as, for example, the metal carbonate or oxalate
compounds. Of the foregoing, ferrite anodes comprised
predominantly of iron oxide and nickel oxide within
the proportions as hereinabove set forth have been
found particularly satisfactory for the practice of
the present process.
17
A ferrite anode comprising a sistered mix-
lure of iron oxide and nickel oxide suitable for use
in the practice of the present invention is cc~mercially
available from TIC, Inc. under the designation of F-21.
- By the proper proportioning of the copper
and ferrite anode surfaces, the chemistry of the elect
trolyte:is maintained with appropriate additions of
the completing and buffering agent and small additions,
if necessary, of the copper salt. Insufficient ferrite
anode surface area results in dull or grainy deposits
while an excessive ferrite anode surface area may result
in reduced cathode efficiency and progressive depletion
of copper anions requiring more frequent replenishment
of the electrolyte with copper salts.
Surprisingly, the use of alternative primary
insoluble anodes in lieu of the ferrite anode as
hereinabove described or the nickel-iron alloy anodes as
hereinafter described does not provide satisfactory I .
deposits. For example, insoluble graphite primary anodes
have been found to deteriorate producing harmful
by-products in the bath which result in smutty deposits.
The insoluble nickel-iron alloy anode employed in
controlled combination with the soluble copper anode may be of an
integral or composite construction providing at least an exterior
surface stratum which is comprised of a nickel-iron alloy
containing frock about 10 percent up to about 40 percent by weight
iron and the buoyancy essentially nickel, preferably about 15 to
18
about 30 percent iron. In accordance with a preferred form of to
present invention, the insoluble nickel-iron alloy anode is
cc~prised of an electrically conductive core having an adherent
electrode posit of the nickel-iron alloy over the surfaces thereof
of a thickness sufficient to envelop the core material preventing
wits exposure over prolonged periods of use. The nickel-iron alloy
deposit or coating is further characterized as being suos,antially
nonporous effectively sealing the internal core from exposure to
the electrolyte. In such Cousteau anode constructions, the core
material may comprise metals such as capper, alloys of copper,
ferrous-base cores including iron and steel, aluminum and alloys of
alu~in~m, nickel and the live. Of the foregoing, a high purity
Corey core similar to the copper anode employed in conjunction
with the insoluble nic~el-iron anode is preferred since inadvertent
exposure of the core as a result of damage or as a result of
progressive dissolution of the coating or plating over prolonged
port æ s of time does not adversely affect the operation of the bath
in that copper ions are introduced in a wanner similar to those
introduced by the conventional soluble copper anodes. In contrast,
when ferrous-base cores are employed, inadvertent exposure of the
core to the electrolyte results in a progressive dissolution of
iron introducing iron ions into the electrolyte which ultimately
adversely affects the quality of the copper deposit produced
rendering the process commercially unsatisfactory. It has been
observed that concentrations of iron ions in the electrolyte in
excess of about 325 ppm are detrimental and tend to produce dull,
19
simulating that of a conventional bright nickel deposit. h very
bright leveled nickel-iron deposit is not essential to toe
satisfactory operation of the insoluble nickel iron alloy anode of
the prevent invention in that the alloy deposit is of a fictional
rather than a decorative plating and accordingly, semi-bright,
satin and even relatively dull nickel-iron electrode posits can be
employed. In view of the foregoing, the particular concentration
and types of primary and secondary brighteners employed in the
aforementioned United States patents can be varied and reduced in
concentration to provide an adherent and ductile nickel-iron
plating of the desired ahoy composition.
The nickel-iron alloy electrolyte contains organic sulfur
cc~pounds to introduce sulfur in the resultant ahoy deposit to
provide satisfactory operation and which also enhances the adhesion
of the plate to the anode core. It has been found that sulfur
contents in mounts of about 0.005 up to about 0.06 percent my
wright preferably about 0.01 to about 0.04 percent by weight, in
the nickel-iron alloy deposit are necessary to provide satisfactory
performance as an insoluble anode in the practice of the present
process. Typically, the sulfur content in the nickel-iron alloy
electrode posit is about 0.02 to about 0.03 percent by weight.
It has teen found that the composition of the alloy is
important in attaining the appropriate oxidizing medium in the
copper electrolyte to provide a copper electroplating process which
is commercially a ox potable from the standpoint of ease of control,
naintenan ox and replenishment and in the quality of the copter
Jo
plate produced. Nile iron concentrations of about 10 percent to
about 40 percent by weight have been found satisfactory,
particularly satisfactory results are obtained at iron
concentrations of about 15 to about 30 percent iron, especially of
about 20 to about 25 percent iron with the balance essentially
nickel. Surprisingly, an anode consisting essentially of pure iron
will not work in the practice of the present process in that it
rapidly dissolves causing a rapid increase in iron ion
! concentration rendering the bath inoperative for the reasons
previously set forth. Similarly, substantially pure nickel anodes
have been found unsatisfactory in spite of the fact they are
relatively insoluble. Substantially pure nickel anodes have been
found inadequate for providing the desired oxidizing medium to
achieve proper plating performance over prolonged time periods.
Similarly, nickel-iron alloys devoid of any sulfur have been found
unsatisfactory after relatively short periods of use such as about
8 hours. Gun the other hand, sulfur contents in excess of about
0.06 percent in the nickel-iron alloy are unsatisfactory for
sustained commercial operation.
i Referring now in detail to the drawing, and as shown in
Figure 1 thereof, a typical electroplating arrangement is
schematically illustrated suitable for use in the practice of the
present invention. As shown, the apparatus includes a tank 10
filled with the cyanide-free alkaline copper electrolyte 12 and
having an anodically charged bus bar 14 disposed there above from
which a pair of soluble copper anodes 16 and an insoluble
so
nickel-iron alloy anode 18 are suspended in electrical contest
therewith. Tie ratio of the anode surface area of the soluble and
insoluble anode or anodes is important to achieve proper operation
of the bath during sustained cc~mercial operation. By appropriate
proportioning of the copper anode surface area and nickel-iron
ahoy anode surface area within a range of about 1:2 up to about
4:1, preferably at ratios of about 1:1 up to about 2:1, the
chemistry of the electrolyte is maintained with appropriate
additions of the cc~,plexing and buffering agents and small
additions, if necessary, of the copper salt. When the ratio of the
copper anode surface area to nickel-iron alloy anode surface area
falls below about ~1:2, i.e. when the total copper anode surf ox
area falls below about 33 percent of the total anode surface area,
the copper anode has been observed to tend to polarize in which
condition it remains conductive but no longer dissolves at the
desired rate resulting in dull and grainy copper deposits. This
also necessitates increased replenishment of copper ions by the
-addition of soluble salts which is associated with the formation of
degradation products in the bath. Accordingly, while the process
can be operated for short time periods at a copper anode surface
area to nickel-iron alloy anode surface area ratio of less than
about 1:2, such operation is not commercially practical over
prolonged time periods.
Referring now to Figure 2 of the drawing, the insoluble
nickel-iron alloy anode constructed in accordance with a preferred
em~cdiment of the present invention is of a composite construction
I
comprising an elongated bar 20 securely connected at its upper end
to a hook-shaped member 22 which preferably is eo~,prised of an
inert conductive material such as titanium, for example. The
elongated bar 20 as best seen in Figure 3 is comprised of a central
conductive core 24 which may be-of a solid or tubular construction
having an adherent outer stratum or plating 26 overlying the entire
outer surface thereof. The particular configuration of the
nickel-iron alloy anode is not critical in achieving satisfactory
performance thereof and the shape as well as the cross-sectional
configuration can be varied in aeeordanee with knc~n practices to
achieve outline throwing power and uniformity in the
eharaeteristies and thickness of the copper eleetrodeposit
consistent with the nature of the substrates being plated.
During an electroplating operation, a substrate or
workups 28 to be copper plated is immersed in the electrolyte 12
in the tank 10 of Figure 1 generally supported from a suitable
eathodically charged bus bar 30 and current is passed button the
anode and the substrate for a period of tire sufficient to deposit
the desired thickness of copper on the substrate.
Nile the replenishment of the eor~plexing agent during
operation of the electrolyte is usually done employing a
neutralized alkali metal salt thereof to avoid a drastic reduction
in the operating pi of the electrolyte, it is contemplated that the
acid form of the eornplexor can be used for original or new bath
makeup by first dissolving the acid for ecmplexor in water
followed by the addition of a base such as potassium hydroxide to
24
increase the pi to a level above about 8. Thereafter, 'he
buffering agent can be added to the preliminary solution in itch a
neutralization of the complex or has been accomplished in situ.
In order to fitrther illustrate the process and novel
anode of the present invention, the follc~7ing specific examples are
provided. It will be understood that the examples as hereinafter
set forth are provided for illustrative purposes and are not
intended to be limiting of the scope of this invention as herein
disclosed and as set forth in the subjoined claims.
EXAMPLE 1
A cyanide-free aqueous alkaline electrolyte
suitable for depositing a copper strike on ferrous-
base substrates such as steel and on copper-base sub-
striates such as brass is prepared by dissolving in
deionized water, about 60 to about 72 g/l of copper
sulfate pentahydrate (15 to 18 g/l copper ions) under
agitation. Following the complete dissolution of the
copper sulfate salt, about 81 to about 87 g/l of a come
flexing agent is dissolved comprising the neutralized
potassium salt of a 30 percent by weight aminotri
(methylene-phosphonie acid) (ATOP) and 70 percent by
weight of l-hydroxyethylidene-l, 1 diphosphonic acid
2G
HOP The pi of the solution is adjusted employing
a 50 percent aqueous solution of potassium hydroxide
to provide a pi of about 8.5. Thereafter from about
15 to about 25 g/l of potassium carbonate is added and
the solution is agitated until complete dissolution
occurs. The solution is thereafter heated to an
operating temperature of from about 110 to about 140F
and a combination of an oxygen-free, high purity copper
anode and a ferrite anode are immersed while suspended
from an anode bar to provide a ferrite anode surface
area to copper anode surface area of about 4:1.
While agitation is not critical, some agile-
lion such as mechanical, cathode rod and preferably
air agitation is employed to provide for improved
efficiency and throwing power of the plating process.
Steel and brass test panels are electroplated in the
foregoing electrolyte for periods of about 2 to 20 minutes
at a cathode current density of about 5 to lo SO and at
a cathode to anode surface area ratio of about 1:2 to
about 1:6. The bath is maintained within a pi of
about 8.5 to 9.5 and the solution is vigorously agitated
by air agitation. Substantially uniform grain-refined,
ductile adherent copper strike deposits are obtained.
The foregoing electrolyte is also suitable for
copper plating steel and brass parts in a barrel plating
operation.
27
;
~2~36~
EXAMPLE 2
An electrolyte is prepared identical to that
described in Example 1. Zinc test panels are satisfac-
gorily plated employing the same operating parameters
as described in Example 1 with the exception that the
test panels are electrified at a minimum voltage of
3 volts prior to and during immersion in the electrolyte
to provide adherent, grain-refined ductile copper strike
deposits.
EXAMPLE 3
A cyanide-free aqueous alkaline electrolyte
suitable for depositing a copper strike on ferrous-base
substrates such as steel and on copper-base substrates
such as brass is prepared by dissolving in deionized water
about 25 g/l to 35 g/l of copper sulfate pentahydrate
(6.25 to 8.75 g/l copper ion) under agitation. Following
the complete dissolution of the copper sulfate salt, about
62.5 g/l to about 78.5 g/l of l-hydroxy ethylidene-l,l,
diphosphonic acid is added. The pi of the solution is
adjusted employing a 50 percent aqueous solution of
potassium hydroxide to above pi 8Ø Thereafter, from
about 15 to about 20 g/l of sodium carbonate is added
and the solution is agitated until complete dissolution
occurs. The solution is thereafter heated to an opera-
tying temperature of from about 130F to 140F and a
combination of an oxygen-free high purity copper anode
28
so
and ferrite anode is immersed in the bath while suspended
from an anode bar to provide a ferrite anode surface
area to copper surface area of about 4:1.
- Air agitation is employed to reduce burning
and to improve throwing power of the process steel and
brass panels or parts are electroplated in the foregoing
electrolyte for periods of about 2 to 20 minutes at
cathode- current densities of about 20 to 30 AS and at
a cathode to anode surface area ratio of about 1:2 to
about 1:6. The bath is maintained within a pi of about
8.5 to 10.2 and the solution is vigorously agitated by
air agitation. Uniform, fine-grained, ductile and
adherent copper strike deposits are obtained.
EXAMPLE 4
An electrolyte is prepared identical to that
described in Example 3. Zinc test panels or parts are
satisfactorily plated employing the same operating
parameters described in Example 3 with the exception
that the cathode (work) are electrified at a minimum
voltage of 3 volts prior to and during immersion in the
electrolyte, to provide adherent, fine-grained, ductile
copper deposits.
EXPEL 5
A cyanide-free aqueous alkaline electrolyte
suitable for depositing a copper deposit on ferrous-
base substrates such as steel and on copper-base substrates
such as brass is prepared by dissolving in deionized
water, about 55 g/l to about 88 g/l of copper sulfate
pentahydrate (13.5 to 22 g/l of copper ions) under ago-
station. Following the complete dissolution of the copper
sulfate salt, about 100 to about 122 g/l of l-hydroxy-
ethylidene-1,1, diphosphonic acid are added. The pi
of the solution is adjusted employing a 50 percent
aqueous solution of potassium hydroxide to provide a pi
of about 8Ø Thereafter from about 15 to 25 g/l of
sodium carbonate is added and the solution is agitated
until complete dissolution occurs. The solution is
thereafter heated to about 130 to 150F and a combination
of an o~ygen-free high purity copper anode and ferrite
anode is immersed while suspended from an anode bar to
provide a ferrite anode surface area to copper anode
surface area ratio of about 4:1.
While agitation is not critical, some agitation
such as mechanical, cathode rod and preferably air ago-
station is employed to provide efficiency and throwing
power of the process. Steel and brass substrates are
electroplated in the foregoing electrolyte for periods
of 2 to 50 minutes at a cathode current density of about
10 to 30 AS and at a cathode to anode surface area
ratio of about 1:2 to about 1:6. The bath is maintained
within a pi of about 8.5 to 10.2. Uniform, fine-grained,
ductile and adherent copper deposits are obtained.
The foregoing electrolyte is also suitable for
copper plating steel and brass work pieces in a barrel
plating operation.
EXAMPLE 6
A cyanide free aqueous alkaline electrolyte
suitable for depositing a copper deposit on ferrous-base
substrates such as steel and on copper-base substrates
such as brass is prepared by dissolving in deionized
water, about 55 g/l to about 100 g/l of copper sulfate
pentahydrate (13.5 to 25 g/1 of copper ions) under ago-
station. Following the complete dissolution of the
copper sulfate salt, about 43.5 g/l to 52 g/l of l-hydroxy-
ethylidene-l,l diphosphonic acid (HEMP) and 100 to 122
g/l of ethylene Damon twitter (ethylene phosphoric
acid) (EDTMP) are added. The pi of the solution is ad-
jutted employing a 50 percent aqueous solution of poles-
slum hydroxide to provide a pi of 8Ø Thereafter from
about 10 to 25 g/l of sodium carbonate is added and the
solution is agitated until complete dissolution occurs.
The solution is thereafter heated to an operating tempera-
lure from about 130 to about 140F and a combination of
oxygen-free high purity copper anode and a ferrite anode
is immersed while suspended from an anode bar to provide
a ferrite anode surface area to copper surface area ratio
of about 4:1.
While agitation is not critical, some agitation
such as mechanical, cathode rod and preferably air
31
So
agitation is employed. Steel and brass test panels or
parts are electroplated in the foregoing electrolyte for
periods of 2 minutes to several days (depending on thick-
news of copper required) at a cathode current density
of about 10 to 40 AS and at a cathode to anode surface
area ratio of about 1:2 to about 1:6. The bath is main-
twined within the pi range of 8.5 to 10.2. Uniform, fine-
gained, ductile and adherent copper deposits are obtained.
The foregoing electrolyte is also suitable for
copper plating steel and brass parts in a barrel plating
operation.
It will be appreciated that it is not essential
to the satisfactory practice of the process and compost-
lion of the present invention to prepare the copper elect
trolytes in the specific sequence and employing the specie
lie ingredients disclosed. For example, the completing,
agent or mixture of completing agents can be introduced
in the form of an aqueous concentrate of the potassium
salt to provide the desired concentration of the come
flexing agent. Typically, the acid form of the complex-
in agent can be first neutralized employing a 50 percent
aqueous solution of potassium hydroxide providing a con-
cent rate having a pi of about 8.
. EXILE 7
A composite nickel-iron alloy anode comprising an
electrode posited nickel-iron alloy on a solid copper ore is
prepared employing an electrolyte of the following composition:
Optimum Range
No 2 56 g/l 35-100 g/l
Fe and Fe 3 4 g/l 1-10 g/l
: Nazi] 150 g/l 50-300 g/l
Nikolai] 100 g/l 30-150 g/l
H3sO3 145 g/l - 30 - Saturation
Sodium Gluconate 20 g/1 5-100 g/l
Sodium Saccharin 2.5 g/l 0-10 g/l
Sodium Ally Sulfonate 4.0 g/l 0.5-15 g/l
Wetting Agent 0.2 g/l 0.05-1.0 g/l
pi 2.9 2.5-4.0
Agitation Air, Cathode Bar or Still
Temperature 135 F 100-160F
Cathode Current Density 40 AS 5-100 AS
Anodes Iron and Nickel
I .
The wetting agent employed includes low foaming type
wetting agents such as sodium octal sulfate when employing air
agitation and relatively high foaming wetting agents such as sodium
laurel sulfate when employing cathode bar agitation or still baths.
Sodium gluconate in the electrolyte composition comprises a
ccmplexing agent for the ferris ions and alternative satisfactory
I
completing agents or mixtures thereof can be employed for this
purpose including citrates, tart rates, glucoheptonates, Silas-
fates, asrorbates or the like.
Alternative completing agents which can be satisfacto-
rile employed include those as described in the aforementioned
United States Patents 3,806,429; 3,974,044 and 4,179,343. one
anodes employed in the nickel-iron electroplating process are in
the form of individual slabs or chips of iron and nickel in
separate basket
he cG~position of the nickel-iron electrolyte in
accordance with the optimum composition as set forth in the
foregoing table produces a nickel-iron alloy deposit containing
approximately 20 percent iron and the balance essentially nickel
using cathode bar agitation. When air agitation is employed, the
iron concentration in the electrode posit will increase to about 30
percent by weight. When no agitation is employed,`` the iron
concentration in the electrode posit will decrease to about 15
percent by weight. In accordance with a preferred practice of the
present invention, cathode bar or mild air agitation is employed in
that the electrode posit is no uniform in Roth composition as well
as in appearance.
In the formulation of suitable nickel-iron electrolytes,
the ratio of nickel ions to iron ions is perhaps the single most
important factor in determining the composition of the final alloy
electrode posit. In accordance with the optimum formulation, a
nickel to iron ratio of about 14 1 employing cathode bar agitation
- 34
S~36~
provides an iron concentration in the alloy elect æ posit of about
20 percent by weight. At a higher nickel to iron ion ratio, a
lower iron concentration in the deposit is produced whereas at a
fewer nickel iron ratio, a higher iron concentration in the all
is produced. In either event, the electrolyte and the conditions
of operation are controlled so as to provide a nickel-iron alloy
deposit containing from about 15 percent up to about 30 percent by
weight iron.
An elongated copper core is employed for forming a
ccm~osite nickel-iron alloy anode and is subjected to a
conventional pretreatment prior to plating in the aforementioned
electrolyte. The pretreatment can typically comprise an alkaline
soak treatment for a period of about 1 to about 3 minutes followed
by a cathodic electrocleaning step for a period of about 1 to about
2 minutes followed by a cold water rinse. The rinsed copper core
is thereafter subjected to a soak treatment in a 5 to 10 percent
sulfuric acid solution for a period of about 15 to about 30 seconds
followed by a cold water rinse. The pretreated copper core is
thereafter immersed in the aforementioned nickel iron electrolyte
and is electroplated for a period of 1 to about 2 hours at an
average cathode current density of about 40 amperes per square foot
(AS) thereafter the composite anode is withdrawn, cold water
rinsed and dried. m e nickel-iron alloy electrode posit is of a
thickness of about 2 to about 4 miss and contains about 20 percent
iron by weight and about 0.025 percent sulfur by weight. In the
fabrication of such nickel-iron alloy anodes, the electrode position
O
of the nickel-iron alloy electrode posit ~11 usually range from
about 0.5 miss up to about 10 r~ls or even thicker to achieve
satisfactory operation. The ir~ortant criteria of the
electr~de~osit is that it is substantially nonporous and is
adherent to the core and is further characterized as being of goad
-ductility and of relatively few stress. The conditions as set
forth in EY~mDle 1 provide a nickel-iron electrode~osit possessed
of the foregoing desirable prc~erties.
EXPMæLE 8
A composite nickel-iron alloy anode comprising an
electrode posited nickel-iron alloy on a solid steel core is
prepared er~?loying the same procedure as set forth in Example 7
with the exception what the steel core during the pretreatment
prior to plating is subjected to an antic electrocleaning step
instead of a cathodic electrocleaning step and is subsequently
subjected to. a soak treatment employing a Gore concentrated
sulfuric acid solution at about 25 percent concentration for a
similar tire period as described in Example 7.
The resultant composite anode has a nickel-iron
electrode posit of the same characteristics as obtained in Example
7. -
EXAMPLE 9
A cyanide-free aqueous alkaline electrolyte suitable for
depositing a copper strike on ferrous base substrates such as steel
,:
So
and on copper-base substrates such as brass is prepared by
dissolving in deionized water about 25 g/l to 35 g/l of copter
sulfate pentahydrate (6.25 to 8.75 g/l copper ion) under agitation.
Following the complete dissolution of the copper sulfate salt,
about 76.1 g/l to about 84.8 g/l of l-hydroxy ethylidene-1,1,
diphosphonic acid is added. The pi of the solution is adjusted
employing a 50 percent aqueous solution of potassium hydroxide to
above pi 8Ø Thereafter, from about 15 to about 20 g/l of sodium
carbonate is added and the solution is agitated until complete
dissolution occurs. The solution is thereafter heated to an
operating temperature of from about 130F to 140F and a
combination of an oxygen-free high purity copper anode and a
nickel-iron alloy anode as obtained in accordance with Example 7 is
immersed in the bath while suspended from an anode bar to provide a
copper anode surface area to nickel-iron alloy anode Æ face area
of about 2:1.
Air agitation is employed to reduce burning and to
improve throwing power of the process. Steel and brass panels or
parts are electroplated in the foregoing electrolyte for periods of
about 2 to 20 minutes at cathode current densities of about 15 to
20 AS and at a cathode to anode surface area ratio of about 1:2 to
about 1:6. The bath is maintained within a pi of about 9.5 to 10.2
and the solution is vigorously agitated by air agitation. Uniform,
fine-grained, ductile and adherent copper strike deposits are
obtained.
EXAMPLE 10
A cyanide-free aqueous alkaline electrolyte suitable for
depositing a copper deposit on ferrous-base substrates such as
steel and on copper-base substrates such as brass is prepared by
dissolving in deionized water, about 55 g/l to about 88 g/l of
copper sulfate~pentahydrate (13.5 to 22 g/1 of copper ions) under
agitation. Following the complete dissolution of the copper
sulfate salt, about 107.9 to about 147 g/l of
l-hydroxy-ethylidene-1,1, diphosphonic acid are added. m e pi of
the solution is adjusted employing a 50 percent aqueous solution of
potassium hydroxide to provide a pi of about 8Ø Thereafter from
bout 15 to 25 g/l of sodium carbonate is added and the solution is
agitated until complete dissolution occurs. The solution is
thereafter heated to about 130 to 150F and a combination of an
oxygen-free high purity copper anode and nickel-iron alloy anode is
immersed while suspended from an anode bar to provide a copper
anode surface area to nickel iron alloy anode surface area ratio of
about 1:1.
While agitation is not critical, some agitation such as
mechanical, cathode rod and preferably air agitation is employed to
provide efficiency and throwing power of the process. Steel and
brass substrates are electroplated in the foregoing electrolyte for
periods of 2 to 60 minutes at a cathode current density of about 10
to 30 AS and at a cathode to anode surface area ratio of about 1:2
to about 1:6. me bath is maintained within a pi of about 9.5 to
38
10~2. Uniform, fine-grained, ductile and adherent copper deposits
are obtained.
The foregoing process is also suitable for copper plating
steel and brass work pieces in a barrel plating operation.
EXAMPLE 11
The process as described in Example g is repeated for
depositing a copper strike on ferrous-base substrates with the
exception that a composite nickel-iron alloy anode is employed at
the same copper to nickel-iron alloy anode surface ratio but
containing only 11 percent by weight iron and 0.02 percent sulfur.
A uniform, fine-grained, ductile and adherent copper deposit is
obtained.
The process of Example 11 is repeated except that a
composite nickel-iron alloy anode is employed containing 11 percent
by weight iron and 0.067 percent sulfur. The resultant copper
deposit is unacceptable comprising a grainy, reddish deposit
believed to be caused by the excessive sulfur content in the
nickel-iron alloy of the anode.
Example 13
The process of Example 10 is repeated with the exception
that a composite nic~el-iron alloy anode is employed in which the
39
13~i~
alloy contains 32 percent by weight iron and 0.02 percent sulfur.
An acceptable uniform, fine-grained, ductile and adherent capper
electrode posit is obtained.
EXPMæLE 14
The process of Example issue repeated with the exception
that a composite nickel-iron alloy anode is employed containing
about 32 percent by weight iron and sulfur at a concentration of
0.088 percent. An unacceptable grainy, reddish-brc~n copper
deposit is obtained.
EXAMPLE lo
- The process of Example issue repeated with the exception
that a composite nickel-iron alloy anode is employed containing 60
percent by sleight iron and 0.02 percent sulfur An unacceptable
grainy, brittle copper deposit is obtained which is believed due to
the high iron content in the nickel-iron alloy anode.
Example 16~
'the process of Example issue repeated with -the exception
that a nickel-iron alloy anode is employed containing about 25
percent iron by weight and 0.02 percent sulfur. An acceptable
uniform, fine-grained, ductile and adherent copper deposit is
obtained.
EXAMPLE 17
A cyanide-free aqueous alkaline electrolyte suitable for
depositing a copper strike on ferrous-base substrates such as steel
and on copper-base substrates such as brass is prepared by
dissolving in deionized water, about 60 to about 72 g/l of copper
sulfate pentahydrate (15 to 18 g/l copper ions under agitation.
Following the complete dissolution of the copper sulfate salt,
about 81 to about 87 g/l of a ocmplexing agent is dissolved
comprising the neutralized potassium salt of a 30 percent by weight
aminotri (methylene-phosphonic acid) (Aim) and 70 percent by
weight of 1-hydroxyethylidene-1, 1 diphosphonic acid (HEMP). m e
pi of the solution is adjusted employing a 50 percent aqueous
solution of potassium hydroxide to provide a pi of about 8.5.
m hereafter from about 15 to about 25 g/l of sodium borate is added
and the solution is agitated until complete dissolution occurs.
The solution is thereafter heated to an operating temperature of
from about 110 to about 140F and a combination of an oxygen-free,
high purity copper anode and a composite nickel-iron alloy anode
containing 25 pervert by weight iron and 0.02 percent by weight
sulfur are immersed isle suspended from an anode bar to provide a
copper anode surface art nickel-iron alloy anode surface area
ratio of about 1:1.
While agitation is not critical, some agitation such as
mechanical, cathode rod and preferably air agitation is employed to
provide for improved efficiency and throwing power of the plating
process. Steel and brass test panels are electroplated in the
41
~zz~
foregoing electrolyte for periods of about 2 to 20 minutes at a
cathode current density of about 5 to 10 AS and at a cathode to
anode surface area ratio of about 1:2 to about 1:6. The bath is
maintained within a pi of about 7.5 to 9.5 and the solution it
vigorously agitated by air agitation. Substantially uniform
grain-refined, ductile adherent copper strike deposits are
obtained
The foregoing process is also suitable for copper plating
steel and brass parts in a barrel plating operation.
Example 18
An electrolyte is prepared identical to that described in
Example 17 ! except that about 15 to about 25 g/l of potassium
carbonate was employed in place of sodium borate as a buffering
agent. Zinc test panels are satisfactorily plated employing the
same operating parameters as described in Example 17 with the
exception that the test panels are electrified at a minimum voltage
of 3 volts prior to and during immersion in the electrolyte to
provide adherent, grain-refined ductile copper strike deposits.
tie it will be apparent that the preferred e~bodin/nts
of the invention disclosed are well calculated to fulfill the
objects above stated, it will be appreciated that the invention is
susceptible to modification, variation and change without departing
from the proper scope or fair meaning of the subjoined claims.
42
foregoing electrolyte for periods of about 2 to 20 minutes at a
cathode current density of about 5 to 10 AS arid at a cathode to
ante surface area ratio of about 1:2 to about 1:6. The bath is
maintained within a pi of about 7.5 to 9.5 and the solution is
vigorously agitated by air agitation. Substantially uniform
grain-refined, ductile adherent copper strike deposits are
obtained
The foregoing process is also suitable for copper plating
steel and brass parts in a barrel plating operation.
EXILE 18
An electrolyte is prepared identical to that described in
Example 17 1 except that about lo to about 25 g/l of potassium
carbonate was employed in place of sodium borate as a buffering
agent. Zinc test panels are satisfactorily plated employing the
same operating parameters as described in Example 17 with the
exception that the test panels are electrified at a minimum voltage
of 3 volts prior to and during version in the electrolyte to
provide adherent, grain refined ductile copper strike deposits.
While it will be apparent that the preferred embodiments
of the invention disclosed are well calculated to fulfill the
objects above stated, it will be appreciated that the invention is
susceptible to modification, variation and change without departing
from the proper scope or fair meaning of the subjoined claims.
42
