US3492135A - Stabilized bath for deposition of copper by chemical reduction - Google Patents

Description

U.S. Cl. 106-1 United States Patent ABSTRACT OF THE DISCLOSURE Spontaneous precipitation of copper from an electroless copper plating solution is prevented by the addition of small amounts of selenium bearing organic or inorganic compounds in which the selenium is in the oxidation stage 1 or 2.

This invention relates to electroless copper plating, and particularly to the stabilizing of an aqueous bath containing a source of copper ions and a reducing agent capable of reducing the ions to. metallic copper on the surface of an object immersed in the bath.

Processes for applying metallic coatings on diverse base materials in which the metals are precipitated from solutions by chemical reduction without external sources of current are gaining increasing acceptance. Methods of depositing copper by reduction have become increasingly important during recent years because copper precipitates formed by chemical reduction are particularly suitable for producing conductive coatings on plastic sheets and plates, for example, in the electronic industry for the production of printed circuits.

The bath compositions for depositing copper by chemical reduction known heretofore have the disadvantage of being quite unstable so that they have to be used in very high concentrations if a high rate of deposition is to be achieved, and have to be discarded after a single use.

It has become known to admix addition agents, particularly sulfur-bearing compounds to the baths in order to improve their stability, but these stabilizing agents may be added only in small amounts because higher concentrations strongly reduce the deposition rate of the metal or may even prevent deposition. As a further disadvantage, it has-been found that some of the known stabilizing compounds cause a dark discoloration of the copper layer. Because the sulfur-bearing compounds often have little resistance to alkalis, particularly at elevated temperatures, copper baths intended for deposition by chemical reduction have not been capable heretofore of being stabilized over extended periods in a satisfactory manner.

It has now been found that selenium-bearing compounds in which the selenium is at the oxidation stage minus one or minus two are capable of stabilizing copper reduction baths over long periods even at higher temperatures.

The term oxidation stage, as employed herein, is to be understood to be the so-called oxidation number or the charge value, that is, the electric charge which an atom would have in a molecule composed solely of ions.

It is a particular technical effect of these compounds that they permit bright copper layers of constant thickness to be deposited from such baths.

Patented Jan. 27, 1970 Suitable selenium compounds having an oxidation stage or degree of oxidation of minus one" are compounds of the formula wherein R and R may be identical or different and may be a monovalent metal equivalent or an organic radical. Suitable selenium compounds having an oxidation stage of minus two are compounds of the formula:

wherein R and K, may be equal or different and may have the same meaning as R and R R also being hydrogen or the radical So Me, wherein Me is a monovalent metal equivalent.

Other suitable selenium compounds of the oxidation ,sta e minus two are the selenonium com unds of the wherein R R and R, may be equal or difi'erent, R and R being as defined above, R being an organic radical, and X being the radical of an acid.

Monovalent metal equivalents that may be considered are Na, K, Ca/ 2, Al/ 3, and the like; organic radicals may be aliphatic, cycloaliphatic, aromatic, and araliphatic radicals which may also be substituted and/ or interrupted by one or more hetero atoms such as oxygen, nitrogen, or sulfur, and/ or one or more groups of hetero atoms such as well as the aracyl radical and the CN group.

Suitable substituents for the afore-mentioned organic radicals include halogen atoms, such as chlorine, bromine, and others, hydroxyl radicals, alkyl radicals such as methyl, ethyl, and others, aryloxy radicals, such as phenoxy and the like; alkoxy radicals such as methoxy, ethoxy, and the like; acyloxy radicals, such as acetoxy and the like; the nitro and cyano radical; the carboxy and sulfo groups in the free form or in the form of their functional derivatives, such as esters or salts; heterocyclic radicals such as tetrahydrofuryl and the like, as well as the radicals The usual acid radicals of the onium compounds may be employed in the selenonium compounds, such as the radicals of the inorganic acids, preferablv of the hydrogen halides.

Copper baths which contain the compounds of the invention are suitable for depositing copper layers on metals or suitably pretreated and activated plastics while the copper baths are absolutely stable. Because of their particular stability, the baths do not require particular maintenance and need not be renewed after each use. It is merely necessary to replenish them for the losses caused by drag-out. The copper deposits from these baths are particularly decorative and are distinguished by bright, salmon-colored metallic luster.

Compounds which may be employed according to the invention include the following:

B. SELENIUM COMPOUNDS HAVING THE OXIDATION STAGE MINUS TWOC0ntinued Qua-011F000 CHOOCCHz-SeCHz-COOH 0-, m-, or p-ch1orophenylseifiiumcetic acid.

3,4-dimethylphepyise1eniumacetic acid.

2,4-dimethylphenylseleniumacetic acid.

Benzylseleniumacetic acid.

Ethyiseleniumacetic acid.

Seleniumdiacetic acid.

Seleniumdipropionic acid.

Seleniumdibutyric acid.

Benzylseleniumbutyric acid.

Benzylseleniumundecanoic acid.

Sodium ethyiseleniumprbp'anesulionate.

Bis-(sodium sulfopropyl) selenide.

Dibenzylselenide.

Difurfurylselenide.

Bis-p-methylphenyl seienide.

Bis-p-nitrophenyl selenide.

Bis-3-pheny1prbpy1selenide.

Dipropyl-selenide.

Bis-(hydroxyethyl) -se1enide.

Sodium selenocyanate.

Potassium selenocyanate.

o, por m-nitrophenyl selenocyanate.

o-, mor p-methylphenyl selenocyanate.

p-Methoxyphenyl seienocyanate.

p-Ethyiphenyl selenocyanate.

B. SELENIUM COMPOUNDS HAVING THE OXIDATION STAGE MINUS TWOC0ntinued -o CHr-CHz-SeCN KO CILSPION @cm-swn @om-cm-cmswrq OzN-CHzSeCN p-Ethoxyphenyl selenocyanate.

Sodium 4-eyanoseleno-phenylsulfonete.

0-, mor p-ohlorophenyl selenocyanate.

2-nitro-4-ehlorophenyl selenoeyanate.

p-Carbmethoxyphenyl selenocyanate.

Potassium seleiiocyanoethane-sulionate.

Phenoxyethyl selenocyanate.

Furiuryl seienocyanate.

Benzyl seienocyanate.

Phenylpropyl selenooya'nate.

p-Nitrophenyl selenocyanate.

li-Naphthyl seienooyanate.

Phenyl seienocyanate.

Carboxymethyldimethyl-selenonium bromide Phenacyl-dimethyl-selenonium bromide.

Dimethyl-selenetin dicarboxylic acid.

Triethyiselenonium iodide.

Tribenzyiselenonium chloride.

Dimethyl-benzyl selenonium bromide.

Triphenylselenonium chloride.

Tri-p-tolylselenonium chloride.

Compounds containing a group which renders them water soluble are particularly suitable because they are readily dosed and are capable of providing lasting stability. Copper reduction baths containing one or more of these compounds are extraordinarily durable.

Further to be singled out are the selenocyantes, particularly potassium selenocyanate which are distinguished by excellent stabilizing ability and by being capable of being prepared with relative ease.

Effective stabilizers according to the present invention which have an oxidation stage of minus two are also the compounds which may be formed, for example, by hydrolysis of the selenocyanates in an alkaline medium, that is, so-called selenoles of the formula Rr-SCH wherein R is as defined above, or their metal salts.

The compounds mentioned above are known or may be prepared by methods known in themselves, as they have been described for the several classes of compounds, for example, in Methoden der Organischen Chemie (Methods of Organic Chemistry), by Houben-Weyl, vol. 9 (1955), pages 937-947 (preparation of selenocyanic acids), pages 972-1002 (preparation of selenides), page 1034 (preparation of selenonium compounds), pages 1086-1099 (preparation of diselenides), pages 1089- 1090 (preparation of selenosulfates) PREPARATION OF COMPOUNDS OF CLASS A (Selenium compounds having a stage of oxidation of minus one) (a) Di- (potassium sulfopropyl)-diselenide 10.7 g. potassium w-sulfopropylselenocyanate are dissolved in 80 ml. concentrated NH OH solution, and the solution is'left to stand for two days at room temperature in an open container. It is then evaporated to dryness in a vacuum, and the residue is recrystallized from methanol. Yield: 7.8 g.=81% of theory (white crystals).

(b) Dipotassium bicarboxyethyldiselenide 11 g. potassium w-carboxyethylselenocyanate are dissolved in 80 ml. concentrated NH OH solution, and the solution obtained is left to stand at room temperature for two days in an open container. The solution is evaporated to dryness, and the residue is recrystallized from methanol. Yield: 6.2 g.=65% of theory (white crystals).

(c) Dipotassium bis-carboxypropyl-diselenide 16 g. dipotassium carboxypropylselenosulfate are dissolved in boiling ethanol, and sufiicient iodine is added until the iodine color no longer disappears. The diselenide precipitating after cooling is filtered off with suction and recrystallized from methanol. Yield: 6 g.=59% of theory (white crystals).

(d) Dipropyl diselenide 32 g. selenium are completely dissolved with heating in mixture of 16 g. sodium hydroxide and 25 g. sodium formaldehyde sulfoxylate in 250 ml. water, and 40 g. propyl bromide are then added slowly. After heating for one hour, the reddish brown color of the solution disappears almost completely, and a heavy red oil is precipitated and is taken up in chloroform. The solution is dried over sodium sulfate and fractionated. Yield: 65% of theory. HP. at 15 mm; Hg: 103-104" C.

(e) Dibenzyl diselenide 10 g. benzyl chloride are shaken for about 6 hours with a solution prepared by briefly heating minutes) precipitated red selenium (6.5 g.) in aqueous 15% sodium hydroxide solution (100 cmfi), the black layer is separated and extracted with boiling alcohol. Yield: 60% of theory. M.P. 91-92" C.

12 (f) Diphenyldiselenide 18.2 g. phenylselenocyanate are added to an aqueous solution containing 15 g. KOH, and the mixture is stirred for about 5 hours. The selenocyanate is dissolved. The diselenide is slowly precipitated. It is recrystallized from petroleum ether. Yield: of theory. M.P. 61-62 C.

Other diselenides may be prepared in an analogous manner.

PREPARATION OF COMPOUNDS OF CLASS B (Selenium compounds having a stage of oxidation of minus two) (a) Potassium butylselenosulfate 13 g. butyl bromide are added to a freshly prepared solution of K SeSO containing 8 g. selenium, and the mixture is refluxed while nitrogen is being passed therethrough for about /2 hour until a sample does not precipitate selenium when acidified with glacial acetic acid. The aqueous solution is evaporated to dryness and exhaustively extracted with ethanol. The selenosulfate crystallizes in White crystals from the alcoholic solution. Yield: 60% of theory.

Other alkylselenosulfates are obtained in an analogous manner.

(b) Potassium p-nitrobenzylselenosulfate 2.3 grams of finely powdered selenium were boiled with a solution of 6 grams potassium sulfite in 55 ml. water for three quarters of an hour, and the hot solution was filtered to remove a small amount of residual undissolved selenium. 5 grams p-nitrobenzyl chloride, dissolved in 50 ml. alcohol were then added, and the resulting turbid solution was refluxed over an open flame. The turbidity disappeared in a very short time, but a precipitate began to form after about 5 minutes. Heating was continued for ten minutes, and the contents of the flask were then cooled rapidly. A copious precipitate consisting chiefly of potassium p-nitrobenzyl selenosulfate, but containing a small quantity of p-nitrobenzyl diselenide and some potassium chloride, sulfate, and sulfite, was thereby produced. The inorganic salts were removed by recrystallizing the precipitate several times from 95% alcohol.

Other selenosulfates are prepared in an analogous manner.

(c) Phenylselenocyanate Aniline (9.1 g.), dissolved in dilute sulfuric acid (1:4), was diazotised at 3 C., with sodium nitrite (9.5 g.). The solution, made neutral to Congo paper with sodium acetate, was added to cold aqueous potassium selenocyanate (22 g.). The odor of an aryl selenocyanate was at once produced, and the mixture, when subjected to steam distillation after 15 hours, gave a pale yellow oil. After being dried with calcium chloride, this boiled at 134 C. 10 mm. (yield: about 50% ((1) Potassium selenocyanoacetate 13.3 g. potassium monochloroacetat e were dissolved in a little water, and the solution was mixed with an alcoholic solution of 14.4 g. KSeCN. After standing for two days, the solution was evaporated to dryness, and the residue was extracted with ethanol. Potassium selenocyanoacetate crystallizes from the alcohol. Yield: 60% of theory (white crystals).

(e) Potassium selenocyanopropanesulfonate 18.3 g. propanesultone, dissolved in 70 ml. acetone, are added drop by drop at about 50 C. to a solution of 21.6 g. KSeCN in 200 ml. acetone. The selenocyanate is precipitated at once. It is filtered with suction after cooling. The product obtained is analytically pure. Yield: 35.6 g=89% of theory.

Potassium selenocyanobutanesulfonate and potassium selenocyanopropionate may be prepared in the same simple manner from butanersultone and KSeCN, and from propiolactone and KSeCN respectively.

(f) Potassium selenocyanate Method (a).7.9 g. selenium are added in small portions with stirring to a solution of 9 g. KCN in 25 ml. water. The temperature is not to exceed 30C. A small amount of undissolved selenium is removed by filtration.

Method (b).-A mixture of 210 g. (95%) potassium cyanide and 240 g. commercial gray selenium. is melted in a large porcelain evaporating dish at 150 to 160C. on a sand bath or on an electric hot plate. The melt is stirred with a porcelain spatula until all the selenium dissolves. It is then permitted to cool slowly, with continuous stirring, in order to prevent caking during solidification.

The solidified melt is crushed to a fine powder and is immediately dissolved in 1 l. of hot .acetone. A slow stream of carbon dioxide, dried over phosphorus pentoxide, is passed through the acetone solution for 2 hours. This treatment precipitates alkali metal hydroxides as insoluble carbonates. The slime, consisting of carbonates and tellurium, is collected by filtration on a Buchner funnel and is washed with warm acetone. The filtrate is transferred to a distilling flask, and two-thirds of the acetone are distilled off. The residual solution is poured into a beaker, where a large portion of the salt precipitates on cooling. The colorless needles are filtered and washed several times with anhydrous ether. Yield: 325 g. (75%).

NaSeCN is prepared in an analogous manner at 240- 260 C.

(g) n-Butylselenocyanate (h) Dibenzyl selenide 0.2. mol benzyl chloride was added to 0.1 mol potassium selenide in a reaction-flask which was then placed on a steam-bath for about two hours while its contents were agitated by a weak stream of hydrogen. The solution was cooled and acidified with hydrochloric acid, and the benzyl selenide was extracted with ether. The compound, when recrystallized from absolute alcohol, melted (i)' Dipropyl selenide A mixture of sodium formaldehyde sulfoxylate (90 g.; 0.76 mol), sodium hydroxide (70 g.; 1.75 mol), powdered selenium (25 g.; 0.32 mol), and water (300 ml.) was .heated to about 50 C. and propyl iodide (67.5 ml.; 0.32 mol) was slowly added. The reaction was vigorous and was completed by refluxing for 1-3 hours. The selenide was isolated by addition of water and extraction with ligroin. Distillation yielded a pure product. Yield: 54%.

-' (j) Di-w-carboxyethyl selenide=Seleniumdipropionic acid 0.2. mol w-bromobutyric nitrile dissolved in methanol are left to stand overnight with 0.1 mol K Se. After removal of the KBr formed, the liquid is barely acidified, the methanol is distilled oil, the residue is extracted with ether, and the extract is dried over Na SO The ether is 14 evaporated and the residue is recrystallized from CCl M.P. ,95 C.

The other di-fatty acid selenides are prepared in a corresponding manner. The salts of 'carboxylic acids may be employed instead of the nitriles. Propanesultone, butanesultone, and propiolactone may be employed respectively instead of the corresponding brominated fatty acids in preparing di-sulfopropyl selenide, disulfobutyl selenide, and di-carboxyethyl selenide.

(k) Diphenyl selenide A solution of NaNO; in water was added dropwise to a mixture of aniline, HCl and ice, and the diazonium salt solution was added to an aqueous solution of K Se (prepared as described). An oily layer separated from an aqueous layer. The aqueous solution was decanted, heated to boiling, and poured back on the oily layer. CHCI was then added, the mixture was filtered, and the organic layer was distilled. Yield:

(l) Phenylselenoglycolic acid Twenty grams of finely powdered selenium were added slowly to magnesium phenyl bromide prepared from 39 g. bromobenzene and -6 g. magnesium in dry ether. The mixture foamed strongly and was cooled on ice, the reaction being afterwards completed by warming on a water-bath. The mixture was again cooled and poured over ice and hydrochloric acid, whereby a small quantity of hydrogen selenide was developed and red selenium precipitated. The ether layer was extracted rapidly with 7 g. of caustic potash in 60 ml. water, and 100 ml. ethanol were added to the aqueous solution together with a solution of sodium chloroacetate. Heat was generated, and sodium glycolate was precipitated as a white powder. The reaction was completed on a water-bath, and the solution was evaporated to one-half its original volume, whereby sodium phenylselenoglycolate was crystallized in pinkish white plates.

Phenylselenoglycolic acid precipitated as a pale yellow oil when hydrochloric acid was added to an aqueous solution of its colorless, recrystallized sodium salt. The acid dissolved in a large quantity of boiling water, precipitating therefrom as a colorless oil, B.P. /75O mm., which became crystalline on standing for several days. M.P.=40 C.

The alkylselenoalkylcarboxylic acids, and the corresponding sulfonic acids, and the arylalkylselenoalkylcarboxylic acids and sulfonic acids are prepared in the same manner. The corresponding selenopropyland -butylsulfonic acids and the corresponding selenopropylcarboxylic acids are prepared in a particularly simple manner from the corresponding salts of the selenoles and ropanesultone, butanesultone, and propiolactone respectively.

(m) Triethylselenonium iodide A few colorless needles are formed after 24 hours at room temperature in an equimolecular mixture of diethyl selenide and ethyl iodide, and the entire mass solidifies in crystalline form after ten days. The triethylselenonium iodide which is stable in contact with air is washed with a little ether and dried.

(n) Dimethyl-selenetin-dicarboxylic acid Equivalent amounts of seleniumdiacetic acid and seleniumchloroacetic acid are dissolved in water, neutralized, and heated on a water bath for two hours. After cooling, the reaction mixture is acidified with sulfuric acid. The reaction product, which gradually crystallizes, may be recrystallized from water. M.P. about 177 C. Yield: about 50% of theory.

The arylalkylselenonium compounds and other alkylselenonium compounds may be prepared in an analogous manner.

(o) Triphenylselenonium chloride 30 g. (0.22 mol) anhydrous aluminum chloride are added to 87 g. (100 ml., 1.1 moles) benzene. The suspension obtained is cooled in an ice bath, and 40 g. (0.13 mol) diphenylselenium chloride are added in portions of about 1 g. over a period of 25 minutes. The temperature should be below 10 C. prior to each addition to prevent dark discoloration of the product. When the addition of diphenylselenium chloride is completed, the reaction mixture is allowed to stand for three hours at room temperature, whereupon 200 ml. water are added cautiously. The benzene layer is discarded, and the water layer is extracted three times with 50 ml. batches of chloroform. The combined extracts are evaporated to 40 ml., and the concentrate is mixed with 120 ml. ether. A yellow oil precipitates and solidifies almost at once to a powder. The yield is 30 g. (67% of the theoretical amount).

Other arylselenonium compounds are prepared in an analogous manner.

The compounds of the invention are added as stabilizers to copper reduction baths of otherwise conventional composition in concentrations of about 0.0001 g./liter to 0.300 g./liter, the compounds of the invention being employed singly or in combination with each other. The stabilized copper reduction baths also may contain the usual ingredients, that is, copper salts, reducing agents, bufiering compounds, complexing agents, as well as wetting agents and brighteners, and the like.

Objects made, for example, of metals, plastics, or other materials may be copper coated in a manner known in itself by means of the copper baths stabilized according to this invention.

For this purpose, the materials to be copper coated are immersed in the above-described baths. Deposition is caused to take place at a bath temperature of about 20 to 60 C. until the desired coating thickness 'is achieved. Copper plating periods of more than 20 minutes are usually unnecessary. It is advisable to mix the bath vigorously by means of a stirrer in order to produce uniform copper layers.

Non-conductive materials, such as a plastics part, require a preliminary surface treatment. This is performed in a manner known in itself, for example, by chemical roughening of the surface by means of hot concentrated sulfuric acid, and by chemical activation by means of solutions of stannous chloride, silver nitrate, or palladium dichloride.

It is a necessary prerequisite for stable baths that metals, in whose presence copper deposits are formed, be absent. Vessels and containers made of plastics, such as polyvinyl chloride, polyethylene, or polypropylene, or lined with such plastics are therefore suitable for handling and storage of the baths.

The desired deposition of copper coatings begins on metal surfaces or on suitably prepared surfaces of materials not conductive in themselves only when the solutions are brought into contact with the metals or metal nuclei.

The following examples illustrate a few of the stabilized copper baths of the invention.

Example 1:

CuSO -H O g./l Disodium ethylene diaminetetraacetate g./l NaOH g./l 16 Paraformaldehyde g./ l 4 Benzylseleniumacetic acid mg./l 2

Example 2:

CuSO -5H O g./l 20 Disodium ethylene diaminetetraacetate g./l NaOH g./l 8 Paraformaldehyde g./l 12 p-Nitrophenylseleniumacetic acid mg./l 160 16 Example 3:

CuSO '5H O g./l 5 Disodium ethylene diaminetetraacetate g./l 16 NaOH g./l 8 Paraformaldehyde g./l 16 p-Methylphenylseleniumacetic acid mg./l 40 Example 4:

(311804 g./l Disodium ethylenediaminetetraacetate g./l 40 NaOH g./l 24 Paraformaldehyde g./l 16 Phenylseleniumacetic acid mg./l 70 Example 5:

CUSO SHgO g./l Triethylenetetrarnine g./l 10 NaOH g./l l6 Paraformaldehyde g./l 10 Potassiumselenocyanate mg./l 2

Example 6:

CuSO -5H O g./l 10 Triethylenetetrarnine g./l 8 NaOH g./l 16 Paraformaldehyde g./l 16 Selenocyanoacetic acid mg./l 0.1

Example 7:

CuSO -5H O g./l 10 Disodium ethylenediaminetetraacetate g./l 20 NaOH g./l 12 Paraformaldehyde g./l 8 p-Nitrophenylselenocyanate -mg./l 1

Example 8:

CuSO '5H O g./l 10 Rochelle salt (potassium sodium tartrate g./l 10 NaOH g./] 24 Paraformaldehyde g./l 12 Selenocyanoacetic acid mg./l 3

Example 9:

CuSO -5H O g./l 10 Trisodium hydroxyethyldiamino-ethylene triacetate g./l 18 NaOH g./'l 12 Paraformaldehyde g./l 8 Selenocyanocetic acid mg./l 2

Example 10:

CuSO -5H O g./l 1O Disodium ethylenediaminetetraacetate g./l 20 NaOH g./l l6 Paraformaldehyde g./l 8 Carboxymethyl-dimethylselenonium bromide mg./l 200 Example 11:

CuSO -5H O g./l 10 Disodium ethylenediaminetetraacetate g./l- 20 NaOH g./l 16 Paraformaldehyde g./l 8 Phenylacyl-dimethylselenonium bromide mg./l Example 12: G./l. CuSO -5H O 10 Disodium ethylenediaminetetraacetate 20 NaOH l6 Paraformaldehyde 4 Di- (potassiumsulfopropyl -dise1enide 0.002

Example 13:

CuSO -5H O Disodium ethylenediaminetetraacetate 25 NaOH 8 Paraformaldehyde l3 Di-(2,3-dihydroxypropyl) -diselenide 0.050

Example 14: G./l. Example 25: G./l. CUSO2'5H4O 8 C|.1S()45II2C) Disodium ethylenediaminetetraacetate 16 Disodium ethylenediaminetetraacetate 15 Sodiumhydroxyde 8 Sodiumhydroxyde 15 Paraformaldehyde 15 Paraformaldehyde 1O Dibutyldiselenide 0.020 Potassium-(p-potassiumcarboxybenzyl)- selenosulfate 0.005 Example Example 26:

Q1504 20 C SO .5 0 15 Disodium ethylenediaminetetraacetate 35 1* 2 ["T". Sodiumhydroxyde 23 isodlum ethy enediammetetraacetate 20 Sodmmhydroxyde 10 Paraformaldehyde Paraformaldehyde 10 Dlbenzyldlselemde 0'010 Potassium (p-methoxy'benzyl)-selen0sulfate 0.0009

Example 16: v m 1e 27:

4' 2 12 15 'c :1s0 -5H 0 Tnefhylenedl'amme 12 Disodium ethylenediaminetetraacetate Sodlumhydroxyde 16 Sodiumhydroxyde 15 Parafofmalehyqe 10 Paraformaldehyde 10 Potasslumdlselemde 0001 20 Potassium-(p-cyanobenzyl)-selenosulfate 0.009

Example 17: Example 28:

CuSO 5H O 10 CuSO 5H O 25 Triethylenetetramine 8 Disodium ethylenediaminetetraacetate Sodiumhydroxyde 16 Sodiumhydroxyde 18 Paraformaldehyde 16 25 Paraformaldehyde 19 BiS-(4-CaTbOXYPheIIY1)'diselenide 0100 Potassium-(p-bromobenzyl)-selenosulfate 0.150 Example 18: Example 29! CUSO2'5H4O CUSO4'5H2O Disodium ethylenediaminetetraacetate 20 30 Trisodium hydroxyethyldiaminoethylene tri- Sodiumhydroxyde 12 acetate 1 18 Paraformaldehyde 15 NaOH 12 Bis-(w-potassiumcarboxyl-decyl)-dise1enide 0.150 Paraformaldehyde 8 Potassiumbutylselenosulfate 0.005 Example 19-. 10 Example 30:

CuSO 5H O Rochelle salt (potassium sodium tartrate) 24 4 2 v 10 Sodiumhydroxyde 24 Rochelle salt (potassium sodlum tartrate) 24 Paraformaldfihyde 2,2 i ififirgaia ag i2 i B18 potasslumsulfopropy dlse e 40 Potassiumoctylselenosulfate M20 Example 20: 1

cu s02 -sH. g;;3j.- 15 Trlsodlum hydroxyethyldlammo'ethylene tn' 19 Disodium ethylenediaminetetraacetate 20 acetate g z i g Paraformaldehyde 10 ara orma e e Bis-(w-potassiulnsulfopropyl)-di e1 id 0 0 Potassium(phenoxyethyl)-selenosulfate 0.008

Example 32:

Example 21: CuSO -5H O 20 CuSO -5H O 10 Disodium ethylenediaminetetraacetate 25 Disodium ethylenediaminetetraacetate 20 NaOH 12 Sodiumhydroxyde 16 Paraformaldehyde 12 Paraformaldehyde 9 Potassium-(potassiumcarboxydecyl) -se1eno- Di-(4-sulfopheny1)-diselenide 0'030 sulfate 0.015

Example 22: Example 33:

c s0 -5 0 10' g.' z 10 Disodium ethylenediaminetetraacetate 0 Disodlum ethylenedlammetetraacetate 15 Sodiumhydroxyde 1 6 NaOH 8 Paraformaldehyde 10 Paraformaldehyde 8 P 3 h d l 1 If 0 005 Bis-(4-methoxyphenyl)-diselenide 0.010 otasslum( Y YP PY @1108 ate Example 34:

Example 231 01150 5111 0 s 4' 2 10 Disodium ethylenediaminetetraacetate 10 Disodium ethylenediaminetetraacetate 20 NaOH 8 SQdiumhydroXyde 15 Paraformaldehyde 8 Paraformaldehyde 9 Potassium-(potassium-w-carboxypropyl)-se1e- Pofassiumselenosulfate 0.010 nosulfate 5 Example 24: Example 35:

0150 SH O 12 CuSO SH O 10 Disodium ethylenediaminetetraacetate 21 Disodium ethylenediaminetetraacetate 12 Sodiumhydroxyde 18 NaOH 10 Paraformaldehyde 9 Paraformaldehyde 10 Potassiumbenzylselenosulfate 0.040 Potassium (phenyl-propyl)-selenosulfate,0 0.009

Example 36: v G./l. CuSO -5H O l2 Disodium ethylenediaminetetraacetate 15 NaOH 12 Paraformaldehyde 10 Potassium-dodecyl-selenosulfate 0.019

Example 37:

CuSO -5H O 15 Disodium ethylenediaminetetraacetate 25 Sodiumhydroxyde 19 Paraformaldehyde 15 Bis-(p-nitro-benzyl)-diselenide 0.001

Example 38:

CUSO4 Disodium ethylenediaminetetraacetate 25 Sodiumhydroxyde 10 Paraformaldehyde 13 Bis-(p-cyanobenzyl)-diselenide 0.0009

Example 39:

CuSO 51-1 20 Disodium ethylenedia'minetetraacetate 25 Sodiumhydroxyde 9 'Paraformaldehyde 15 Bis-(p-carboxy-benzyl)-diselenide 0.005

Example 40:

CUSO4'5H2O Disodium ethylenediamine tetraacetate 30 Sodiumhydroxyde 23 Paraformaldehyde 15 Bis-(p-bromobenzD-diselenide 0.010

Example 41:

CuSO SH O 19 Disodium ethylenediamine tetraacetate 25 Sodiumhydroxyde 20 Paraformaldehyde 19 Bis-(3-hydroxy-propyl)-diselenide 0.030

Example 42:

CuSO H O 25 Disodium ethylenediaminetetraacetate 30 Sodiumhydroxyde 20 Paraformaldehyde Bis-(B-phenoxy-ethyl)-diselenide 0.020

Example 43:

CuSO -5 0 10 Disodium ethylenediaminetetraacetate 20 Sodiumhydroxyde 12 Paraformaldehyde Bis-(a-tetrahydrofurylmethyl)-diselenide 0.010

Example 44:

CuSO -5H O 15 Disodium ethylenediaminetetraacetate 25 Sodiumhydroxyde 15 Paraformaldehyde 10 Bis-(cyclohexyl)-diselenide 0.008 Example 45:

CuSO -5H O Disodium ethylenediaminetetraacetate Sodiumhydroxyde 18 Para-formaldehyde 15 Bis-(cyclopentyl)-diselenide 0.003

' What is claimed is:

1. In an aqueous electroless copper plating bath containing a source of copper ions, and a reducingagent capable of reducing said ions to metallic copper on the surface of an object immersed in said bath, the improvement which consists in the presence of a stabilizing agent in said bath, the stabilizing agent being present in said bath in an amount sufficient to substantially prevent spontaneous precipitation of copper in the absence of said immersed object, and being an organic selenium compound or selenide, diselenide, selenosulfate or selenocyanate of an alkali metal, the selenium being present in said stabilizing agent in the oxidation state minus one or minus two.

2. In bath according to claim 1, said stabilizing agent being present in said bath in a concentration of approximately 0.001 to 0.300 gram per liter.

3. In a bath according to claim 1, said stabilizing agent being a compound selected from the group consisting of potassium-diselenide;

dipropyl diselenide;

di-n-butyl diselenide;

di-n-amyl diselenide;

di-n-hexyl diselenide;

di-n-heptyl diselenide; di-(2-3-dihydroxypropyl) diselenide;

di- (potassiumsulfopropyl) diselenide;

di- (potassiumsulfoethyl) diselenide; di-(sodiumsulfobutyl)diselenide; bis-(sodiumcarboxymethyl)diselenide; bis- (potassiumcarboxyethyl) diselenide; bis- (potassiumcarboxypropyl)diselenide; bis- (potassiumcarboxydecyl) diselenide; diphenyl diselenide;

di-p-tolyl diselenide; di-(p-methoxyphenyl)diselenide;

di- (p-nitrophenyl diselenide; bis-(o acetylphenyl)diselenide; di-2,2'-biphenylyl diselenide;

bis- (p-potassiumsulfophenyl) diselenide; bis- (p-chlorophenyl diselenide;

bisp-carb oxypheuyl) diselenide; diseleniumdiacetylurea;

dibenzyl diselenide;

di- N-phenyl-carbamoylmethyl) -dise1enide; bis- (p-nitrobenzyl) diselenide;

bisp-methylb enzyl) diselenide bis- (p-cyanobenzyl)diselenide; bis-(p-carboxy-benzl)diselenide;

bis- (p-bromobenzyl) diselenide; bis-(p-phenylethyl)diselenide; bis-(3-hydroxpropyl)diselenide; bis-(a-tetrahydrofurylmethyl) diselenide; bisp-phenoxyethyl) diselenide biscyclohexyl) diselenide; bis-(cyclopentyl)diselenide; potassiumselenosulfate; p0tassiumbenzylselenosulfate;

potassium p-nitrobenzylselenosulfate; potassium p-methylbenzylselenosulfate; potassium p-potassium-carboxybenzylselenosulfate; potassium p-methoxybenzylselenosulfate; potassium p-ethoxybenzylselenosulfate; potassium p-cyanobenzylselenosulfate; potassium p-ethyl-benzylselenosulfate; potassium p-bromobenzylselenosulfate; potassium ethylselenosulfate;

potassium butylselenosulfate;

potassium octylselenosulfate;

potassium dodecylselenosulfate; potassium 1,3-dihydroxypropylselenosulfate; potassium hydroxyethylselenosulfate; potassium phenoxyethylselenosulfate; potassium tetrahydrofurfurylselenosulfate; potassium phenylethylselenosulfate; potassium phenylpropylselenosulfate; potassium 3-hydroxypropylselenosulfate; dipotassium w-carboxyethylselenosulfate; dipotassium w-carboxybutylselenosulfate; dipotassium W-carboxydecylselenosulfate; dipotassium w-sulfoethylselenosulfate; dipotassium w-sulfopropylselenosulfate; potassium cyclopentylselenosulfate; potassium selenide;

phenylseleniumacetic acid;

-, mor p-nitrophenylseleniumacetic acid; o-, mor p-methoxyphenylseleniumacetic acid; o-, mofp-chlorophenylseleniumacetic acid; 3,4-dimethylphenylseleniumacetic acid; 2,4-dimethylphenylseleniumacetic acid; benzylseleniumacetic acid; ethylseleniumacetic acid; seleniumdiacetic acid; seleniumdiproponic acid; seleniumdi'butyric acid; benzylseleniumbutyric acid; benzylseleniumundecanoic acid;

sodium ethylseleniumpropanesulfonate; bis- (sodium sulfopropyl) selenide; phenylseleniumglycolic acid;

sodium phenylseleniumpropanesulfonate; sodium benzylseleniumpropane sulfonate; bis- (phenoxyethyl) selenide; diphenylselenide;

dibenzylselenide;

difurfurylselenide; bis-p-methylphenylselenide; bis-p-nitrophenylselenide; bis-3-phenylpropylselenide; dipropylselenide;

bis- (hydoxyethyl) selenide; sodiumselenocyanate; potassiumselenocyanate;

o-, por m-nitrophenylselenocyanate;

o-, mor p-methylphenylselenocyanate; p-methoxyphenylselenocyanate; p-ethylphenylselenocyanate; p-ethoxyphenylselenocyanate;

sodium 4-cyanoseleno-phenylsulfonate; o-, mor p-chlorophenylselenocyanate; 2-nitro-4-chlorophenylselenocyanate; p-carbmethoxyphenylselenocyanate; ethylselenocyanate;

butylselenocyanate;

decylselenocyanate;

potassium selenocyanoacetate;

potassium selenocyanopropionate; potassium selenocyanoundecanoate;

potassium selenocyanopropanesulfonate; potassium selenocyanoethanesulfonate; pheiioxyethylselenocyanate; furfurylselenocyanate; benzylselenocyanate; phenylpropylselenocyanate; p-nitrophenyselenocyanate; fl-naphthylselenocyanate; phenylselenocyanate; carboxymethyldimethyl-selenoniumbromide; phenacyI-dimethyl-selenoniumbromide; dimethyl-selenetin dicarboxylic acid; triethylselenonium iodide; tribenzylselenoniumchloride; dimethyl-benzl-selenoniumbromide; triphenylselenoniumchloride; tri-p tolylselenoniumchloride.

4. In a method of depositing copper on a conductive surface or on an activated'non-conductive surface of a body by immersing said body in a bath containing a source of copper ions and a reducing agent capable of reducing said ions to metallic copper on said surface of the, immersed body, the improvement which consists in immersing said body in a bath as set forth in claim 1.

5, In a method of depositing copper on a conductive surface or on an activated non-conductive surface of a body by immersing said body in a bath containing a source of copper ions and a reducing agent capable of reducing said ions to metallic copper on said surface of the immersed body, the improvement which consists in immersing said body in a bath as set forth in claim 3.

References Cited UNITED STATES PATENTS 1/1956 OstroW 20452 4/1959 Foulke 204-S2 US. Cl. X.R. 117130, 47,