Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.


  1. Advanced Patent Search
Publication numberUS3403035 A
Publication typeGrant
Publication dateSep 24, 1968
Filing dateJun 24, 1964
Priority dateJun 24, 1964
Also published asDE1521440A1, DE1521440B2
Publication numberUS 3403035 A, US 3403035A, US-A-3403035, US3403035 A, US3403035A
InventorsDuff Williamson John, Mccormack John F, Schneble Jr Frederick W, Zeblisky Rudolph J
Original AssigneeProcess Res Company
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Process for stabilizing autocatalytic metal plating solutions
US 3403035 A
Abstract  available in
Previous page
Next page
Claims  available in
Description  (OCR text may contain errors)

United States Patent 3,403,035 PROCESS FOR STABILIZING AUTOCATALYTIC METAL PLATING SOLUTIONS Frederick W. Schneble, Jr., Oyster Bay, Rudolph J. Zeblisky, Hauppague, John F. McCormack, Roslyn Heights, and John Duff Williamson, Miller Place, N .Y., assignors to Process Research Company, Glen Cove, N.Y., a partnership of New York No Drawing. Filed June 24, 1964, Ser. No. 377,471 11 Claims. (Cl. 1061) The present invention relates to electroless or autocatalytic metal plating solutions and more particularly to improving the stability and useful life of such solutions, and to autocatalytic metal plating solutions having enhanced stability and relatively long useful lives.

Chemical plating solutions for continuously depositing metals or alloys by autocatalytic chemical reduction of metal ions dissolved in the solutions and in contact with a catalytic surface of an article to be plated are well known. Such solutions, which do not utilize electricity, are sometimes referred to in the art as electroless metal plating solutions, to distinguish them from electroplating solutions, which do require the use of electricity. Electroless metal deposition is also to be distinguished from displacement metal plating of the type described in Metals Finishing Guide Book, 27th Edition, 1959, pages 469 et seq., and metal mirroring procedures, wherein the metal plating desired and achieved is only a few millionths of an inch in thickness.

Typically autocatalytic or electroless metal deposition solutions comprise an aqueous solution of water soluble salt of the metal or metals to be deposited, a reducing agent for the metal cations, and a complexing or sequestering agent for the metal cations. The function of the complexing or sequestering agent is to form a water soluble complex with the dissolved metallic cations so as to maintain the metal in solution. The function of the reducing agent is to reduce the metal cation to metal at the appropriate time, as will be made more clear hereinbelow.

For proper operation, the pH of the autocatalytic met-a1 solution will ordinarily be controlled. Solution pH will depend upon the nature of the metallic salt, the sequestering agent and the reducing agent. Depending upon the ingredients, the pH may range from strongly acid to strongly alkaline, e.g., from pH 1 to 14, and usually from pH 4 to 14.

The goal in operating electroless metal deposition solutions is to balance the ingredients so that metallic deposition will occur only at the interface formed between the solution and a catalytic surface to be metallized.

As a practical matter, however, it is not possible to completely maintain the metal in solution. There is, in other words, an inherent tendency in electroless metal deposition baths for precipitates of the metal to form. The metallic precipitate constitutes a decomposition product of the plating bath, and is particularly objectionable in that it causes the desirable deposit to be coarse, rough and frequently porous. Additionally, the fine solid particles of the metallic precipitate, once formed, become suspended in the plating baths or adhere to the walls of the plating vessel, and act as nuclei to initiate the formation of additional precipitate, thereby further enhancing the tendency of the bath to decompose.

Because of their inherent tendency to form metallic precipitates, all electroless metal solutions have a finite life. It would be very desirable to extend this life, and the principal object of this invention is to do so.

According to this invention, it has been discovered that the useful life of autocatalytic metal plating solutions may be enhanced by adding to the solution a small effective amount of a cyanide compound.

Patented Sept. 24, 1968 As the cyanide compound may be mentioned alkali cyanides, such as sodium and potassium cyanide, and nitriles such as alpha-hydroxy nitriles, e.g., glycolnitrile and lactonitrile.

The amount of cyanide compound will ordinarily range between about 5 micrograms and 500 milligrams per liter.

Care should be employed in adding the cyanide compounds to insure that an excess is not employed. Too much cyanide compound is deleterious and will cause the solution to cease functioning. Within the above range, there will be used a small effective amount of the cyanide compound which is low enough to permit the solution to function.

The invention is generally applicable to autocatalytic metal deposition solutions for copper, nickel, cobalt, cadmium, tin, and similar metals. In such baths, the sulfates, chlorides, acetates, and nitrates of such metals are ordinarily utilized as the water soluble salts. Other water soluble salts of the indicated metals may however be used, the choice being primarily a question of economics.

The reducing agents in such metal deposition baths include borohydrides, amine boranes, hydrazines, hypophosphites, hydrosulfites, hydroxyl amines, formaldehyde, and the like.

The borohydride reducing agent may consist of any water soluble borohydride having a good degree of solubility and stability in aqueous solutions. Sodium and potas sium borohydrides are preferred. In addition, substituted borohydrides in which not more than 3 hydrogen atoms of the borohydride ion have been replaced can be utilized. Sodium trimethoxy borohydride, NaB(OCH H, is illustrative of the compounds of this type.

Also may be mentioned ammonium borohydride and the amine boranes, such as isopropylamine borane, and dimethyl amine borane.

Among the hydrazines may be mentioned water soluble salts of hydrazine, such as the hydrazine sulfates, e.g., monohydrazine sulfate, di-hydrazine sulfate, hydrazine disulfate, and the like. Because of its greater solubility in Water, dihydrazine sulfate is preferred.

Among the hypophosphite and hydrosulfite reducing agents, the alkali metal, e.g., sodium, potassium and ammonium salts are preferred.

In addition to formaldehyde, polymers of the formaldehyde, e.g., paraformaldehyde, may be used as the reducing agent. Also suitable as the reducing agent is alpha-trioxymethylene.

The sequestering or complexing agent will be selected to form a strong complex with the metal ions to prevent the precipitation of metal or metallic salts. The complexing agent selected should also be capable of forming a metal complex which is soluble in the plating solution, and also which is sufliciently stable so that it will not react with the reducing agent in the main body of the plating solution, but only at or in the near vicinity of the catalytic surface.

The complexing or sequestering agents suitable for use in accordance with this invention include ammonia and organic complex-forming agents containing one or more of the following functional groups: primary amino group .(NH secondary amino group NH), tertiary amino group N), imino group (=NH), carboxy gluconates, and triethanolamine are preferred as complexing agents, but commercially available glucono 6- lactone and modified ethylenediamineacetates are also useful, and in certain instances give even better results than the pure sodium ethylenediaminetetraacetates. One such material is N hydroxyethylethylenediaminetriacetate.

In preparing the electroless metal deposition baths, it is desirable to combine the bath ingredients in such a manner as to avoid reaction between the soluble metal salt and the reducing agent.

It is therefore preferred to first add the complexing agent to the aqueous solution of the metal salt to form the water soluble complex of the metal cations. If the reducing agent is added before the metal complex is formed, there will be a tendency for it to react instantaneously with the metal salt to precipitate the metal or a salt of the metal.

The pH should also be adjusted to the proper value prior to addition of the reducing agent. Here again, failure to regulate the pH initially may lead to spontaneous decomposition of the reducing agent. In view of the foregoing, it will be appreciated that ordinarily it is preferable to add the reducing agent last.

Catalytic surfaces which may be plated with the baths of this invention include metals such as nickel, cobalt, iron, steel, palladium, platinium, copper, brass, manganese, chromium, molybdenum, tungsten, titanium, tin, silver, including mixtures thereof, and oxides thereof. All such metals are catalytic to the reduction of the metal cations dissolved in the solutions described.

Non-metallic materials such as glass, ceramic, and various plastics are, in general, non-catalytic. However, the surfaces of such non-catalytic materials can be rendered catalytic by producing a film or particles of one of the catalytic materialst thereon. This can be accomplished by a variety of techniques known to those skilled in the art. One suitable sensitization procedure involves dipping noncatalytic materials in an acidic solution of stannous chloride, washing with water, and then contacting the treated material with an acidic solution of a precious metal salt, e.g., palladium chloride. A mono-layer of precious metal is thus produced on the surface of the non-catalytic material, which mono-layer is catalytic to reduction of the metal ions in the electroless metal plating solutions described herein.

Alternatively, such materials as glass, ceramic, and plastic may be sensitized or rendered catalytic by treatment with an acidic aqueous solution containing, in combination, stannous tin ions and precious metal ions.

A further sensitization procedure involves adhering to the normally non-catalytic surface, finely divided particles of metals or metal oxides which are catalytic to electroless deposition.

The term catalytic surface as used herein refers to the surface of any article composed of the catalytic materials described hereinabove or covered therewith or to the surface of a non-catalytic material which has been sensitized by producing a film or particles of said catalytic materials on its surface.

The baths of this invention will deposit metal electrolessly on the catalytic surfaces of metals, and non-metals, such as paper, glass, ceramic, synthetic resins and plastics, including but not limited to silicones, phenolics, styrenes, acrylics, vinyl chlorides, nylon, mylar, acrylonitrilebutadiene-styrene, and the like.

The following examples are intended to illustrate the manner in which the present invention may be carried out.

Example 1 A bath corresponding to the following formula was prepared:

Copper sulfate moles/l 0.05 Diethylenetriamine pentaacetate do 0.05 Sodium borohydride do 0.009

Sodium cyanide do 0.00 pH 13 Temperature C 25 As a control, a bath having the same composition but without the sodium cyanide was prepared.

The control bath decomposed spontaneously after standing for /2 hour. The bath containing 0.008 mole per liter of sodium cyanide had a useful copper plating life of greater than 4 hours.

Example 2 A bath corresponding to the following formula was prepared:

Copper sulfate moles/l 0.05 N-hydroxy-ethylethylenediaminetriacetate do 0.115 Sodium cyanide -do 0.0016 Sodium borohydride do 0.008 pH 13 Temperature C 25 As a control, a bath having the same composition but without the sodium cyanide was prepared.

The control bath decomposed spontaneously after standing /2 hour, The bath containing 0.0016 mole per liter of sodium cyanide had a useful copper plating life of 20 hours.

Example 3 A bath corresponding to the following formula was prepared:

Copper sulfate moles/l 0.05 N-hydroxyethylethylenediaminetriacetate do 0.125 Sodium cyanide -do 0.001 Hydrazine sulfate do 0.019 pH 9.8 Temperature C 43 Example 4 A bath corresponding to the following formula was prepared:

Copper oxide "moles/L- 0.05 Malic acid do 0.30 Sodium cyanide do 0.00001 Sodium hypophosphite do 0.5 pH 4-5 Temperature C 80 As controls, a bath having the same composition but without the sodium cyanide, and a bath having the same composition but containing 0.0001 mole/l. of sodium cyanide were prepared.

The control bath without cyanide decomposed spontaneously forming a reddish precipitate. The bath containing 0.0001 mole per liter of sodium cyanide did not deposit copper. The bath with 0.00001 mole per liter of sodium cyanide deposited a bright copper film.

The quantities of the various ingredients in the baths of this invention are subject to wide variation. Typically, however, the bath constituents will be as follows:

Water soluble metal salt 0.002 to 0.60 mole/l. Reducing agent 0.0002 to 2.5 moles/l. Complexing agent 0.7 to 10 times the moles of metal salt. Cyanide compound 0.00001 to 0.06 mole/l.

The amount of sequestering agent to be added to the plating solution depends upon the nature of the sequestering agent and the amount of the metal salt present in the bath. In alkaline solutions, the preferred ratio of the metal salt to complexing agent lies between about 1:1 and 1:10. A small excess of the sequestering agent, based upon the metal salt, generally is advantageous.

It should be understood that as the baths are used up in plating, the metal salt, and the reducing agent may be replenished from time to time, and also that it may be advisable to monitor the pH, and the cyanide content of the bath, and to adjust them to their optimum value as the bath is used.

For best results, surfactants in an amount of less than about 5 grams per liter are added to the baths disclosed herein. Typical of suitable surfactants are organic phosphate esters, and oxyethylated sodium salts. Such surfactants may be obtained under the trade names Gafac RE 610 and Triton QS-lS, respectively.

The baths are ordinarily used at temperatures between 25 and 90 C., although they may be used at lower temperatures or at even higher temperatures. As the temperature is increased, it is usual to find that the rate of plating is increased.

The process of this invention permits metal to be deposited on practically any conceivable substratum and to practically any thickness desired.

Metallized surfaces produced by utilizing the autocatalytic metal deposition solutions of this invention are useful as ornamental designs, markings, and the like.

' Similarly, using these baths, metal may be deposited in pre-determined patterns on insulating substrata and serve as electrical conductors. Electrically conductive circuit patterns, e.g., printed circuits, may thus be selectively plated on the activated areas of an inexpensive sheet of a wide variety of insulating material.

The invention in its broader aspects is not limited to the specific steps, processes and compositions described but departures may be made therefrom within the scope of the accompanying claims without departing from the principles of the invention and without sacrificing its chief advantages.

What is claimed is:

1. A process for increasing the useful life of autocatalytic metal plating solution used to electrolessly deposit metal onto catalytic surfaces, in which the solution comprises water, a metal ion selected from the group consisting of cobalt, nickel and tin, a complexing agent and a reducing agent for said ion, said process comprising maintaining in said solution a small eflective amount of a water-soluble cyanide compound in a concentration of 5 micrograms to 500 milligrams per liter.

2. A process according to claim 1 in which the reducing agent is a member selected from the group consisting of borohydrides, amine boranes, hydrazines, hypophosphites, hydrosulfites, hydroxyl amines and alpha-trioxymethylene.

3. A process according to claim 1 in which the complexing agent is an organic complex forming compound having at least one functional group selected from the group consisting of amino, imino, carboxy and hydroxy radicals.

4. A process according to claim 1 in which the watersoluble cyanide compound is an alphahydroxynitrile.

5. A process according to claim 4 in which the alphahydroxynitrile is glycolnitrile.

6. A process according to claim 4 in which the alphahydroxynitrile is lactonitrile.

7. A process according to claim 1 in which the watersoluble cyanide compound is sodium cyanide.

8. A process according to claim 1 in which the watersoluble cyanide compound is potassium cyanide.

9. A process according to claim 1 in which the metal of the autocatalytic metal plating solution is cobalt.

10. A process according to claim 1 in which the metal of the autocatalytic metal plating solution is nickel.

11. A process for electrolessly depositing a metal onto a catalytic surface which comprises immersing the catalytic surface in an autocatalytic metal plating solution comprising water, a water-soluble salt of a metal selected from the group consisting of cobalt, nickel and tin, a complexing agent for said metal capable of forming a stable water-soluble complex, a reducing agent for said metal and a water-soluble cyanide compound as a stabilizing agent in a concentration of from about 5 micrograms to 500 milligrams per liter.

References Cited UNITED STATES PATENTS 3,096,182 7/1963 Berzins 106--1 3,046,159 7/ 1962 Brookshire 106-1 X 3,063,850 11/1962 Mikulski 1061 3,095,309 6/ 1963 Zeblisky et al. 106-1 3,119,709 1/ 1964 Atkinson 106-1 JAMES A. SEIDLECK, Primary Examiner.

L. B. HAYES, Assistant Examiner.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US3046159 *Dec 17, 1957Jul 24, 1962Hughes Aircraft CoMethod of copper plating by chemical reduction
US3063850 *Sep 11, 1959Nov 13, 1962Metal Hydrides IncMetal plating by chemical reduction with amine boranes
US3095309 *May 3, 1960Jun 25, 1963Day CompanyElectroless copper plating
US3096182 *Oct 1, 1958Jul 2, 1963Du PontChemical plating solution and process for plating therewith
US3119709 *Sep 28, 1956Jan 28, 1964Atkinson Lab IncMaterial and method for electroless deposition of metal
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3507681 *Jun 2, 1967Apr 21, 1970Mine Safety Appliances CoMetal plating of plastics
US3547818 *Apr 7, 1969Dec 15, 1970Ventron CorpAlcoholic ionic compositions containing a metal selected from hg (ii),cu (ii),ag (i),cd (ii),ni (ii),zn (ii),and co (ii)
US3637472 *Mar 16, 1970Jan 25, 1972Ventron CorpChemical plating baths containing an alkali metal cyanoborohydride
US3645749 *Jun 4, 1970Feb 29, 1972Kollmorgen CorpElectroless plating baths with improved deposition rates
US3650708 *Mar 30, 1970Mar 21, 1972Hooker Chemical CorpMetal plating of substrates
US3653953 *Jan 26, 1970Apr 4, 1972North American RockwellNonaqueous electroless plating
US3663242 *Sep 25, 1970May 16, 1972Shipley CoStabilized electroless plating solutions
US3717482 *Nov 16, 1971Feb 20, 1973Shipley CoStabilized electroless plating solutions
US3798050 *May 28, 1971Mar 19, 1974Ppg Industries IncCatalytic sensitization of substrates for metallization
US3870526 *Sep 20, 1973Mar 11, 1975Us ArmyElectroless deposition of copper and copper-tin alloys
US3881049 *Dec 5, 1972Apr 29, 1975Kalle AgProcess for depositing copper layers on shaped articles of a polyimide
US3893865 *Nov 28, 1972Jul 8, 1975Ppg Industries IncMethod for stabilizing a chemical filming composition
US3899617 *Jul 19, 1973Aug 12, 1975EnthoneProcess for conditioning ABS resin surface
US3915716 *Mar 18, 1970Oct 28, 1975Schering AgChemical nickel plating bath
US3946126 *Apr 21, 1972Mar 23, 1976Rca CorporationMethod of electroless nickel plating
US3961109 *Jul 11, 1974Jun 1, 1976Photocircuits Division Of Kollmorgen CorporationSensitizers and process for electroless metal deposition
US3963842 *Nov 6, 1974Jun 15, 1976London Laboratories Limited Co.Deposition of copper
US3992211 *Jun 11, 1971Nov 16, 1976Trans-Metals CorporationGluconic acid derivatives, hydrolyzed carbohydrates
US4036651 *Feb 26, 1974Jul 19, 1977Rca CorporationElectroless copper plating bath
US4175146 *Sep 12, 1978Nov 20, 1979Obata Industry & Commerce Co., Ltd.Coating with fluorides to harden and making surfaces chemically resistant with silicon compounds and nonionic surfactants
US4269625 *Nov 13, 1979May 26, 1981U.S. Philips CorporationMetallization of catalytic surfaces using an aqueous alkaline solution containing stannous and stannic ions and a reducing agent
US4279951 *Jul 3, 1980Jul 21, 1981Mine Safety Appliances CompanyMethod for the electroless deposition of palladium
US4305997 *Dec 26, 1979Dec 15, 1981Surface Technology, Inc.Electrolessly metallized product of non-catalytic metal or alloy
US4328266 *Mar 10, 1980May 4, 1982Surface Technology, Inc.Method for rendering non-platable substrates platable
US4355083 *Dec 26, 1979Oct 19, 1982Nathan FeldsteinElectrolessly metallized silver coated article
US4481035 *Aug 25, 1983Nov 6, 1984Siemens AktiengesellschaftChemical gilding bath
US4482596 *Aug 25, 1982Nov 13, 1984Shipley Company Inc.Nickel, copper, cobalt, phosphorous
US5091223 *Jun 27, 1990Feb 25, 1992Henkel CorporationCoating with a treatment solution containing complexing agents, metal 8 group salts and additives to form corrosion resistance film
US5298092 *May 17, 1990Mar 29, 1994The Boeing CompanyForming cobalt oxide film by oxidizing cobalt-111 hexammine complex
US5378293 *May 6, 1993Jan 3, 1995The Boeing CompanyNon-chromated oxide coating for aluminum substrates
US5411606 *Jun 25, 1992May 2, 1995The Boeing CompanyNon-chromated oxide coating for aluminum substrates
US5415687 *Dec 23, 1993May 16, 1995The Boeing CompanyNon-chromated oxide coating for aluminum substrates
US5419926 *Nov 22, 1993May 30, 1995Lilly London, Inc.Ammonia-free deposition of copper by disproportionation
US5468307 *Nov 21, 1994Nov 21, 1995Schriever; Matthias P.Non-chromated oxide coating for aluminum substrates
US5472524 *Mar 11, 1994Dec 5, 1995The Boeing CompanyApplying a cobalt-III mexacoordinated complex; oxidation; corrosion resistance; paint adhesion
US5551994 *Aug 9, 1994Sep 3, 1996The Boeing CompanyNon-chromated oxide coating for aluminum substrates
US5873953 *Dec 26, 1996Feb 23, 1999The Boeing CompanyNon-chromated oxide coating for aluminum substrates
US6183546Nov 2, 1998Feb 6, 2001Mccomas Industries InternationalHardness, wear and corrosion resistance
US6432225Oct 13, 2000Aug 13, 2002The Boeing CompanyNon-chromated oxide coating for aluminum substrates
US7064065Oct 15, 2004Jun 20, 2006Applied Materials, Inc.Silver under-layers for electroless cobalt alloys
US7205233Nov 7, 2003Apr 17, 2007Applied Materials, Inc.Method for forming CoWRe alloys by electroless deposition
US7256111Sep 3, 2004Aug 14, 2007Applied Materials, Inc.Pretreatment for electroless deposition
US7297190 *Jun 28, 2006Nov 20, 2007Lam Research CorporationPlating solutions for electroless deposition of copper
US7306662 *May 11, 2006Dec 11, 2007Lam Research CorporationAqueous copper salt and cobalt salt; triamine complexing agent (diethylenetriamine, dipropylenetriamine, or aminoethyl-propylenediamine); sulfuric, nitric, hydrochloric, fluoroboric, or acetic acid pH modifier; can be maintained in an acidic pH environment
US7514353Mar 20, 2006Apr 7, 2009Applied Materials, Inc.Contact metallization scheme using a barrier layer over a silicide layer
US7651934Mar 20, 2006Jan 26, 2010Applied Materials, Inc.Process for electroless copper deposition
US7659203Mar 20, 2006Feb 9, 2010Applied Materials, Inc.Electroless deposition process on a silicon contact
US8308858Jan 18, 2010Nov 13, 2012Applied Materials, Inc.Electroless deposition process on a silicon contact
DE2527096A1 *Jun 18, 1975Jan 8, 1976London LaboratoriesVerfahren zum abschneiden von metallischem kupfer an einer flaeche
DE2715850A1 *Apr 6, 1977Oct 13, 1977Kollmorgen Tech CorpVerfahren zum abscheiden von kupfer oder kupferlegierungen aus stromlos arbeitenden baedern
DE2920766A1 *May 22, 1979Nov 29, 1979Macdermid IncLoesung und verfahren zur stromlosen kupferabscheidung unter verwendung eines hypophosphit-reduktionsmittels
DE3622090C1 *Jul 2, 1986Feb 15, 1990Blasberg-Oberflaechentechnik Gmbh, 5650 Solingen, DeTitle not available
WO1995014538A1 *Oct 3, 1994Jun 1, 1995Lilly London IncAmmonia-free deposition of copper by disproportionation
WO2005038084A2 *Oct 15, 2004Apr 28, 2005Applied Materials IncSelective self-initiating electroless capping of copper with cobalt-containing alloys
WO2005038085A2 *Oct 18, 2004Apr 28, 2005Applied Materials IncSelective self-initiating electroless capping of copper with cobalt-containing alloys
U.S. Classification427/443.1, 427/305, 427/306, 106/1.25, 427/437, 427/438, 106/1.27, 427/304
International ClassificationC23C18/40, C23C18/52, C23C18/36, C23C18/16, C23C18/31
Cooperative ClassificationC23C18/52, C23C18/36, C23C18/40, C23C18/31
European ClassificationC23C18/52, C23C18/36, C23C18/31, C23C18/40