CA1225064A - Cyanide-free copper plating process - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A cyanide-free electrolyte and process for depositing a ductile, fine-grained, adherent copper plate usually of a thickness of about 0.015 to about 5 mils on ferrous-base, copper-base, zinc-base and the like conductive substrates. The electrolyte contains controlled effective amounts of cupric ions complexed with an organo-phosphonate chelating agent, an alkali carbonate as a bath stabilizing and buffering agent, hydroxyl ions to provide a pH on the alkaline side and preferably, a wetting agent. The copper plate is applied by electrolyzing the aforementioned electrolyte employing a combination of a bath soluble copper anode and an insoluble ferrite anode to provide a copper to ferrite anode surface area ratio within a range of about 1:2 to about 1:6.
The invention further includes a process for depositing a ductile, fine-grained adherent copper plate on a conductive substrate employing an electrolyte containing controlled effective amounts of cupric ions, a complexing agent for the cupric ions, a bath stabilizing and buffering agent, and hydroxyl and/or hydrogen ions to provide a pH from about 6 to about 10.5 and electrolyzing the aforementioned electrolyte employing a combination of a bath soluble copper anode and an insoluble nickel-iron alloy anode containing about 10 percent to about 40 percent by weight iron and about 0.005 to about 0.06 percent sulfur to provide a copper anode area to nickel-iron alloy anode surface area ratio within a range of about 1:2 to about 4:1. The invention further contemplates a novel nickel-iron alloy anode for use in the practice of the disclosed process.

Description

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 .

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 .~,", ~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 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 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 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.

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 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, 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 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.

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 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.

;

~2~36~

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.

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 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.

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.

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.

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 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 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. -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.

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 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.

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 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.

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 ~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.

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.

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.

Claims (32)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for electrodepositing a grain refined ductile and adherent copper strike on a conductive substrate which comprises the steps of providing an aqueous alkaline cyanide-free elec-trolyte containing copper ions in an amount suffi-cient to electrodeposit copper, a complexing agent in an amount sufficient to chelate the copper ions present, said complexing agent comprising a compound selected from the group consisting of 1-hydroxyethyl-idene-1,1-diphosphonic acid, a mixture of 1-hydro-xyethylidene-1,1-diphosphonic acid and aminotri-(methylene phosphonic acid) in which said 1-hydro-xyethylidene-1,1-diphosphonic acid is present in an amount of at least about 50 percent by weight of the mixture; and a mixture of 1-hydroxyethylidene-1,1-diphosphonic acid and ethylene diamine tetro (methylene phosphonic acid) in which said 1-hydro-xyethylidene-1,1-diphosphonic acid 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, a bath soluble and compatible carbonate compound in an amount sufficient to stabilize the pH of the electrolyte, and hydroxyl ions in an amount to provide a pH of about 7.5 to about 10.5 controlling the temperature of said electrolyte between about 100° to about 160°F, immersing a conductive substrate to be plated as a cathode in said electrolyte, immersing a combination of a copper-base soluble anode and a ferrite insoluble anode in said electrolyte to provide a copper anode to ferrite anode surface area ratio of about 1:2 to about 1:6 and passing current between said anodes and said cathode for a period of time sufficient to deposit copper on said substrate to the desired thickness.

2. The process as defined in claim 1 in which said copper ions are present in an amount of about 3 to about 50 g/l.

3. The process as defined in claim 1 in which said copper ions are present in an amount of about 15 to about 50 g/l.

4. The process as defined in claim 1 in which said copper ions are present in an amount of about 3.5 to about 10 g/l.

5. The process as defined in claim 1 in which said hydroxyl ions are present in an amount to provide a pH of about 9.5 to about 10.

6. The process as defined in claim 1 further including a bath soluble and compatible wetting agent present in an amount up to about 0.25 g/l.

7. The process as defined in claim 1 further including a bath soluble and compatible wetting agent present in an amount of about 0.01 to about 0.1 g/l.

8. The process as defined in claim 1 in which said carbonate compound is selected from the group consisting of alkali metal and alkaline earth metal carbonate and bicarbonate compounds and mixtures thereof.

9. The process as defined in claim 1 in which said carbonate compound is selected from the group consisting of alkali metal carbonate and bicarbonate compounds and mixtures thereof.

10. The process as defined in claim 1 in which said carbonate compound comprises potassium bicar-bonate.

11. The process as defined in claim 1 in which said carbonate compound is present in an amount of about 3 to about 100 g/l calculated on a weight equivalent basis as sodium carbonate.

12. The process as defined in claim 1 in which said carbonate compound is present in an amount of about 10 to about 20 g/l calculated on a weight equivalent basis as sodium carbonate.

13. The process as defined in claim 1 in which said complexing agent comprises 1-hydroxyethyl-idene-1,1 diphosphonic acid present in an amount of about 50 to about 500 g/l.

14. The process as defined in claim 1 in which said complexing agent comprises a mixture containing 70 percent by weight 1-hydroxyethylidene-1,1-diphos-phonic acid and 30 percent by weight aminotri-(methylene phosphonic acid) as well as the bath soluble and compatible salts and partial salts thereof, said mixture present in an amount of about 20 to about 322 g/l.

15. The process as defined in claim 1 in which said complexing agent comprises a mixture containing about 50 percent by weight 1-hydroxyethylidene-1,1 -diphosphonic acid and about 50 percent by weight ethylene diamine tetra (methylene phosphonic acid) as well as the bath soluble and compatible salts and partial salts thereof and mixtures thereof, said mixture present in an amount of about 19 to about 311 g/l.

16. The process as defined in claim 1 in which the step of controlling the temperature of said electrolyte is performed to provide a temperature of from about 110°F to about 140°F.

17. The process as defined in claim 1 in which the step of controlling the temperature of said electrolyte is performed to provide a temperature of about 120°F to about 140°F.

18. The process as defined in claim 1 in which the step of passing current between said anodes and said cathode is performed while providing a cathode current density of about 1 to about 80 ASF.

19. The process as defined in claim 1 in which the step of passing current between said anodes and said cathode is performed while providing a cathode current density of about 5 to about 25 ASF.

20. The process as defined in claim 1 including the further step of maintaining the pH of said electrolyte within a range of about 9.5 to about 10.

21. The process as defined in claim 1 wherein the copper anode to ferrite anode surface area ratio is maintained between about 1:3 to about 1:5.

22. The process as defined in claim 1 wherein the copper anode to ferrite anode surface area ratio is maintained at about 1:4.

23. The process as defined in claim 1 in which the step of passing current is controlled to provide a copper deposit on said substrate of an average thickness of about 0.015 to about 5 mils.

24. The process as defined in claim 1 in which the step of passing current is controlled for a period of time of from about 1 minute to about 1 hour.

25. The process as defined in claim 1 in which the step of passing current is controlled for a time of from about 2 to about 30 minutes.

26. The process as defined in claim 1 including the further step of replenishing said complexing agent and said carbonate compound to maintain said bath constituents within the desired operating range.

27. The process as defined in claim 1 wherein the cathode to anode surface area ratio is maintained between about 1:2 to about 1:6.

28. The process as defined in claim 1 wherein the cathode to anode surface area ratio is maintained between about 1:3 to about 1:5.

29. The process as defined in claim 1 wherein the cathode to anode surface area ratio is maintained at about 1:4.

30. A process for electrodepositing a grain refined ductile and adherent copper strike on a ferrous-base conductive substrate which comprises the steps of providing an aqueous alkaline cyanide-free electrolyte containing copper ions in an amount sufficient to electrodeposit copper, a complexing agent in an amount sufficient to chelate the copper ions present, said complexing agent comprising a compound selected from the group consisting of 1-hydroxyethylidene-1,1-diphosphonic acid, a mixture of 1-hydroxyethylidene-1,1-diphosphonic acid and aminotri-(methylene phosphonic acid) in which said 1-hydroxyethylidene-1,1-diphosphonic acid is present in an amount of at least about 50 percent by weight of the mixture, and a mixture of 1-hydroxyethyl-idene-1,1-diphosphonic acid and ethylene diamine tetro (methylene phosphonic acid) in which said 1-hydroxyethylidene-1,1-diphosphonic acid is present in amount of at least 30 percent by weight of the mixture, as well as the bath soluble and compatible salts and partial salts thereof, a bath soluble and compatible carbonate compound in an amount sufficient to stabilize the pH of the electrolyte, and hydroxyl ions in an amount to provide a pH of about 7.5 to about 10.5, controlling the copper ion concentration within a range of about 15 to about 50 grams per liter, controlling the temperature of said elec-trolyte between about 100° to about 160°F immersing a ferrous-base conductive substrate to be plated as a cathode in said electrolyte, immersing a combination of a copper-base soluble anode and a ferrite insol-uble anode in said electrolyte to provide a copper anode to ferrite anode surface area ratio of about 1:2 to about 1:6 and passing current between said anodes and said cathode for a period of time suffi-cient to deposit copper on said ferrous-base sub-strate to the desired thickness.

31. The process as defined in claim 30 inclu-ding the further step of electrifying said ferrous-base substrate prior to and during the step of immersing said substrate in said electrolyte.

32. A process for electrodepositing a grain refined ductile and adherent copper strike on a zinc-base conductive substrate which comprises the steps of providing an aqueous alkaline cyanide-free electrolyte containing copper ions in an amount sufficient to electrodeposit copper, a complexing agent in an amount sufficient to chelate the copper ions present, said complexing agent comprising a compound selected from the group consisting of 1-hydroxyethylidene-1,1-diphosphonic acid, a mixture of 1-hydroxyethylidene-1,1-diphosphonic acid and aminotri-(methylene phosphonic acid) in which said 1-hydroxyethylidene-1,1-diphosphonic acid is present in an amount of at least about 50 percent by weight of the mixture, and a mixture of 1-hydroxyethyl-idene-1,1-diphosphonic acid and ethylene diamine tetro (methylene phosphonic acid) in which said 1-hydroxyethylidene-1,1-diphosphonic acid 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, a bath soluble and compatible carbonate compound in an amount sufficient to stabilize the pH of the elec-trolyte, and hydroxyl ions in an amount to provide a pH of about 7.5 to about 10.5, controlling the copper ion concentration within a range of about 3.5 to about 10 grams per liter, controlling the temperature of said electrolyte between about 100° to about 160°F, cathodically electrifying said conductive zinc-base substrate at a voltage of at least about 3 volts and immersing the electrified said substrate in said electrolyte, immersing a combination of a copper-base soluble anode and a ferrite insoluble anode in said electrolyte to provide a copper anode to ferrite anode surface area ratio of about 1:2 to about 1:6, and passing current between said anodes and said zinc-base substrate for a period of time sufficient to deposit copper on said substrate to the desired thickness.