US3666636A

US3666636A - Electrolytic codeposition of fine particles with copper

Info

Publication number: US3666636A
Application number: US834891A
Authority: US
Inventors: Thaddeus W Tomaszewski; Lillie C Tomaszewski
Original assignee: Udylite Corp
Current assignee: OMI International Corp; Udylite Corp
Priority date: 1969-06-19
Filing date: 1969-06-19
Publication date: 1972-05-30
Anticipated expiration: 1989-05-30

Abstract

FINE PARTICLES OF MANY NON-CONDUCTING MATERIALS DO NOT CODEPOSIT READILY FROM AQUEOUS ACIDIC COPPER ELECTROPLATING BATHS, UNLESS THERE IS PRESENT IN THE BATH ALIPHATIC AMINES, ESPECIALLY POLYAMINES OR IMINES, OR AMINO ACIDS SUCH AS ALANINE OR EDTA. THESE AMINO COMPOUNDS ARE ESPECIALLY EFFECTIVE IN ACID COPPER SULFATE PLATING BATHS FOR THE CODEPOSITION OF DISPERSED FINE, BATH-INSOLUBLE, NONCONDUCTING PARTICLES. THESE 2-PHASE COMPOSITE COPPER PLATES HAVE ENGINEERING USE POSSIBLITIES FOR ANTI-FRICTION AND ANTI-SEIZING PROBLEMS.

Description

United States Patent ELECTROLYTIC CODEPOSITION OF FINE PARTICLES WITH COPPER Thaddeus W. Tomaszewski and Lillie C. Tomaszewski,

Dearborn, Mich., assignors to Udylite Corporation,

Warren, Mich.

.No Drawing. Filed June 19, 1969, Ser. No. 834,891

' Int. Cl. C23b 5/48, 5/20 US. Cl. 204'16 16 Claims ABSTRACT OF THE DISCLOSURE This invention relates to the cathodic codeposition of multitudinous fine particles of bath-insoluble, non-conducting,inorganic and organic powders dispersed in aqueous acidic copper plating baths. More particularly this invention provides a means to improve and uniformly increase-the degree of codeposition of bath-dispersed inorganic and organic particles throughout the electrodeposited copper plate.

The densely codeposited inorganic fine particles in the matrix of the electrodeposited copper can increase the tensile strength of the copper and its resistance to high temperature creep, and the inorganic and organic particles can greatly decrease the tendency for copper surfaces to stick and seize, yet without causing any appreciable loss in electrical or heat conductivity.

Thus,. these copper deposits can be used for various engineering purposes either as a composite copper plate on top of a basis metal, including wire or strip, or as an electroform.

It has now been found that amines, especially aliphatic amines, promote the codeposition of bath-insoluble, nonconducting particles dispersed (for example, by air agitation) in the acidlcopper electroplating baths. The most effective aliphatic amines for promoting the codeposition are'polyamines and polyimines such as ethylene diamine, diethylene .triamine, tetraethylenepentamine, polyethylene' imine, etc. These amines when present in the standard acidic 'coppe'r plating baths of either low or high concentrations of copper ions make possible extensive codeposition of dispersed fine bath-insoluble particles such as barium sulfate, strontium sulfate, aluminum oxide, titanium oxide, zirconium' oxide, kaolin (a hydrous aluminum silicate rareearth fluorides, stannic oxide, finely powdered glass, lead sulfate, PVC, nylon, saran, polyethylene," polycarbonate, acetal; polystyrene, ABS, lead phosphate," ceric oxide, boron nitride, graphite, molybden'um-sulfide, iron silicide, silicon carbide, boron carbide, boron, silicon, silicon dioxide, etc.

The most effective aliphatic amines, as mentioned, are the polyamines. For example, 0.1 g./l. of ethylene diamine is at least as effective as 50 g./l. of ethyl amine in promoting the codeposition of the fine, insoluble particles on vertical surfaces. With 'tetraethylene pentamine, a concentration as low as 1 mg./l.- will make possible the codeposition of about 3.5 wt. percent of fine barium sulfate particles dispersed in the acid copper sulfate plating bath. Without the amines present in the bath, practically no particles of the type shown above are codeposited on a vertical surface from acid copper plating baths. This is very unlike codeposition of these fine particles dispersed in acidic nickel baths where codeposition on vertical cathode surfaces occurs without the need of special organic additives.

Besides the aliphatic amines mentioned, amino acids such as alanine, N,N-diethyl glycine, asparagine, N- methyl taurine, ethylene diamine tetra-acetic acid (-EDTA), and other amino acid and sequesterin agents, especially those with more than one amino group, give excellent results in promoting codeposition of fine, bathinsoluble, non-conducting particles in the acid copper plating baths.

The bath-insoluble, fine powders are kept suspended and dispersed in the acid copper plating baths by means of mechanical or air agitation. In general, air agitation is preferred, and of course, the air must not be contaminated with oil. Optimum codeposition results are usually reached with concentrations of particles of about 25 to 150 g./l., though higher concentration produce no troubles, and with some particles such as barium sulfate and strontium sulfate, concentrations of 500 g./l. can be used. It is important that the fine particles are clean. For example, some commercial grades of talc (a hydrous magnesium silicate) had to be washed with alcohol or acetone before the best codeposition results could be obtained. In general, the particle sizes may be from about 10 microns down to 0.01 micron for the inorganic particles with the preferred range of about 5 microns down to 0.01 micron. With particles much greater than about 10 microns, roughness from the inorganic particles is obtained on areas on which settling can occur. Some agglomerated powders may have apparent larger particle size than the preferred size, but with agitation in the copper bath, the larger agglomerates are usually broken down and particles of about 5 microns diameter and under may then be the predominant size. With organic resin powders the particle size may be as high as 50 microns size and still codeposit smoothly on vertical surfaces.

The pH of the acid copper plating baths unlike with nickel, does not have a profound effect on the percentage of the powder codeposited in the copper matrix. An acid copper sulfate bath having 100 or 200 g./l. of sulfuric acid and low or high concentrations of copper sulfate, yields in general very similar percentages of codeposition as does a copper bath with only 1 g./l. of sulfuric acid. This is also true for acidic copper plating such as copper sulfamate, copper methane sulfonate, and copper fiuoborate. Large variation in the temperature of the acid copper plating baths does exert a pronounced influence on the percentage of particles codeposited with the copper plate. At room temperatures or slightly lower there is maximum codeposition of the particles on vertical surfaces in the presence of the aliphatic amine promoters. As the temperature of the bath is increased, less eo-deposits, and temperatures higher than 60 C. are not desirable. Below are listed some specific examples illustrating the codeposition of particles with copper according to this invention.

EXAMPLE I Concentration in grams per liter CuSO .5H O 75-250. H 50 '0-150. Tetraethylene pentamine 0.001-1. BaSO, fine powder 10-150. Temperature60120 F. Agitationair or mechanical.

Current density 10-100 amps/sq. ft.

The maximum codeposition was about 5.5 wt. percent on vertical surfaces with higher concentrations on settling surfaces. In Example I, if fine zirconium oxide powder is used in concentrations of about 1-30() g./l. instead of the barium sulfate powder, a maximum of about 6 wt. percent was obtained on vertical surfaces. With fine titania powder the maximum codeposition on vertical surfaces was about 4%.

EXAMPLE ]1 Concentration in grams per liter CuSO .5H ,O 100-250. H 80 -100. EDTA 1-15.

Cerium oxide fine powder -150.

Temperature60l20 F. Agitationair or mechanical.

Current density 10-100 amps/sq. ft.

The maximum codeposition was about 3.5 wt. percent on vertical surfaces. If fine silicon carbide powder (0.1 to 7 microns) is used instead of the cerium oxide in Example II, the maximum codeposition on vertical surfaces was around 4 Wt. percent, but on settling surfaces it was much higher.

EXAMPLE III The procedure of Example I is repeated with the exception that finely divided polyvinyl chloride (PVC), of a particle size Within the range of about l-20 microns, is substituted for the barium sulfate. Using this procedure, comparable results are obtained.

In acidic copper fluoborate baths, the codeposition of the same dispersed inorganic particles in general proceeds very well, however, the addition of the amines or amino acids maximizes the codeposition rate. In the case of conducting and semi-conducting particles such as graphite and molybdenum sulfide, the codeposition proceeds very readily in the acidic copper plating baths, and it would seem that there is no need to use the amines or amino acid promoters. Nevertheless with these promoters present, lower concentrations of these fine particles may be used which in these cases tend to minimize roughness troubles. That is, with these powders it is difficult to get smooth plate with their codeposition, though with the use of the promoters and with the use of the finest particles, the plate is them much smoother. With fine particles of such powders as barium sulfate, titania, alumina, silicon carbide, the plates are very smooth.

In some cases mixtures of particles for codeposition are desirable, for example, barium sulfate with strontium sulfate, mica with barium sulfate, graphite or molybdenum sulfide with barium sulfate, or strontium sulfate.

Surfactants and brightening agents may be present in the acid copper plating baths which do not appreciably affect the ductility and adhesion of the deposits. When air agitation is used, the surfactants should not cause overfoaming, and preferably an eight carbon chain length should be used, such as sodium Z-ethyl hexyl sulfate, and sodium n-oetyl sulfonate.

As mentioned, the most effective amine compounds for promoting codeposition of particles are those where the amino group is attached to an aliphatic group, that is, the aliphatic amino compounds, and this designation would apply even if an aromatic ring is in the molecule, as in benzyl amine. The most elfective amino compounds are the polyamino or polyimine compounds such as ethylene diamine, diethylene triamine, tetraethylene pentarnine, etc. The aliphatic amino acids may have carboxyl groups as in alanine and EDTA, sulfonic groups as in N-methyl taurine and phosphonic groups as in N(CH PO (OH) It is to be appreciated that as used herein, the term Saran is intended to refer to polyvinylidene chlorides; the term nylon is intended to refer to polyamides; and the terms Teflon and Kel-F are intended to refer to fluorocarbon resins, such as the polytetrafluoroethylenes.

What is claimed is:

trodepositing with copper fine bath-insoluble, substantially non-conducting particles dispersed in aqueous acidic copper electroplating baths which contain dissolved therein additionally at least one organic compound which contains at least one aliphatic amino group. 7

2. A method in accordance with claim '1 wherein said amino compound is tetraethylene peutamine in a conoentIation greater than about 1 milligram per liter. 1

3. A method in accordance with claim 1 wherein said amino compound is an amino acid in a concentration greater than about 0.1 gram per liter.

4. A method in accordance with claim 1 wherein said bath-insoluble particles are barium sulfate particles in concentrations of at least about 1 gram/liter and of particle size less than about 5 microns.

5. A method in accordance with claim tions of at least about 1 gram per literand particle size less than about 5 microns.

6. A method in accordance with claim 1 wherein said bath-insoluble particles are silicon carbide particles in concentrations of at least about 1 gram/liter and par-,

ticle size less than about 7 microns.

7. -A method in accordance with claim 1 wherein said bath-insoluble particles are aluminum oxide particles in concentrations of at least about 1 gram/liter and particle size less than about 5 microns. I

8. A method in accordance with claim 1 wherein said bath-insoluble particles are polyvinylchloride (PVC) "particles in concentrations of at least about 1 gram/liter and particle size less than about 50 microns.

9. An electroplating bath comprising anaqueous acidic copper electroplating bath containing dispersed therein fine bath-insoluble, non-conducting particles and said cop per bath containing dissolved therein additionally atleast one organic compound which contains at least one aliphatic amino group.

10. A bath in accordance with claim 9 wherein said amino compound is tetraethylene pentarnine in a concentration greater than about 1 milligram per liter.

11. A bath in accordance with claim 9 wherein said concentration amino compound is an amino acid in a greater than about 0.1 gram/liter.

12. A bath in accordance with claim 9 wherein said: bath-insoluble particles are barium sulfate particles fin concentrations of at least about 1 gram/liter and of article size less than about 5 microns.

13. A bath in accordance with claim, 9 whereinsaid bath-insoluble particles are boron particles in concentra? tions of at least about 1 gram per liter and pai ticle sizie less:

than about 5 microns.

'14. A bath in accordancewith claim 9 wheri i fsaiti bath-insoluble particles are sil icon carbide particles concentrations of at least about :1 gram/liter a'ridfpafticle size less than about 7 microns; j

1s. A bath in accordance with 'claim 9,' wherein. sa'i i' bath-insoluble particles are aluminum oxide particles, in. concentrations of at least about 1 gram/literand particle.

size less than about 5 microns.

16.. A bath in accordance withjclaim 9 iwhereinlsaidl bath-insoluble particles are polyvinylchloride {Pl/C particles in concentrations of at least about 1 ;gram/liter.

and particle size less than about 50 microns.

References Cited 3 TE ATENT? (Other references on followiiig pagej 1 wherein said bath-insoluble particles are boron particles in concentra- 5 UNITED STATES PATENTS 6 Glutamic Acid as an Addition Agent, by Adamek et aL,

p. 931, The Canadian J. Chem. 32,931, 1954. 11/1950 y n Organic Chemistry by Brewster, 1961, pp. 424-425. (U62 Gllchnst O I Trans. Electrochem. Soc., vol. 54, 1928 by Pink et aL, 1,7M,927 2/ 1929 Bezzenberger 204181 5 315 316 2,858,256 10/1958 Fahnoe t 1, 204 -181 IKiPk-Othmer Encyclopedia of Chemical Technology,

0 2 1 a 1 1 V01. 8, 1965 pp. 30 -32. 1 970 Welgel 204 Transactions of the Electrochem. Society Fink et a1.

FOREIGN PATENTS 54, 1928, pp. 315320.

580,302 7/1959 Canada 20452 R 10 589,647 12/1959 Canada 204-52 R JOHN MACK Pnmary Exammer OTHER REFERENCES Modern Electroplating by Lowenheirn, 2nd ed., 1918, pp. 178-479.

R. L. ANDREWS, Assistant Examiner US. Cl. X.R. 15 204-52 R, 181