US3650915A

US3650915A - Copper electrodeposition electrolytes and method

Info

Publication number: US3650915A
Application number: US793582*A
Authority: US
Inventors: George R Quimby; Kenneth R Gray
Original assignee: Deutsche ITT Industries GmbH
Current assignee: TDK Micronas GmbH; ITT Inc
Priority date: 1969-01-23
Filing date: 1969-01-23
Publication date: 1972-03-21
Anticipated expiration: 1989-03-21
Also published as: ES375824A1; ZM17469A1

Abstract

IMPROVED ELECTRODEPOSITION OF COPPER IS ACHIEVED BY ADDING A COMBINATION OF A CATION ACTIVE ORGANIC NITROGEN COMPOUND AND A LIGNOSULFONATE MATERIAL TO A COPPER ELECTRODEPOSITION ELECTROLYTE.

Description

United States Patent US. Cl. 20452 R Claims ABSTRACT OF THE DISCLOSURE Improved electrodeposition of copper is achieved by adding a combination of a cation active organic nitrogen compound and a lignosulfonate material to a copper electrodeposition electrolyte.

The present invention relates to electrolytic deposition of copper from acid electrolytes. More particularly, this invention relates to new and improved electrolytes for use in the electrorefining of copper which will promote smoother and more efiicient plating and to new and improved additive agents to be introduced therein.

In the electrolytic refining of copper, purified cathode copper is obtained by passing an electric current from an impure copper anode through an aqueous acid electrolyte to a pure copper cathode. The copper dissolves from the anode and is deposited on the cathode in purified form. However, it has been found to be highly advantageous to introduce additives into the electrolyte in order to promote the formation of a smoth, dense deposit of copper on the cathode. Without these additive agents, the copper deposits on the cathode are soft, coarsely crystalline and prone to develop into nodules or trees. Since the spacing between the anode and the cathode is usually on the order of one to two inches, these nodules of copper can grow from the cathode to the anode and cause a short circuit. Even if a short circuit does not develop, a rough cathode deposit will cause entrainment of electrolytes in the cathode which cannot be washed out and remains as a contaminant.

Many such electrolyte additive agents have been employed in attempting to prevent the nodules or trees from forming on the cathode surface. Some of these known additive agents have, in fact, improved the character of the cathode deposit to a limited extent. But, the problem has not been solved heretofore.

It is, therefore, an object of the present invention to provide new and improved copper electrodeposition electrolytes which produce copper electrodeposits which are smooth, dense and essentially free of protrusions.

Another object is to provide new and improved additive agents for copper electrodeposition electrolytes which will improve the quality and physical characteristics of the cathode electrodeposits in the electrorefining of copper.

An additional object is to provide a new and improved combination of additive agents for use in electrodepositing copper from an aqueous electrolyte which will control the deposition of copper and increase cathode polarization and thus provide electrolytically pure cathode copper which is smooth, dense and substantially nodule-free.

Additional objects if not specifically set forth herein will be readily apparent to those skilled in the art from the following detailed description of the invention.

In general, the method of this invention involves a procedure whereby very pure cathode copper is obtained by electrodeposition techniques and whereby the formation of nodules or trees on the cathode is essentially eliminated. These results are achieved by adding to a standard acid copper electrolyte solution containing a source of copper ions and a source of hydrogen ions, additive agents comprising cation active organic nitrogen compounds and lignosulfonate materials We have found that the resulting solution when employed as the electrolyte in the electrodeposition of copper will provide cathode copper deposits of improved quality-smooth, dense and relatively free of protrusions.

More specifically, we have found that the use of cation active organic nitrogen compound selected from the group consisting of conventional water soluble cation active quaternary ammonium compounds and high molecular weight polyethylene amines in conjunction with a lignosulfonate material as an additive agent in copper electrodeposition baths will produce a dense, very uniform deposit of copper, free of protrusions. This discovery of the advantages achieved with the conjoint use of these nitrogen compounds and lignosulfonates was surprising and highly unexpected since a synergistic effect is displayed. The addition of these nitrogen compounds alone in copper electrodeposition baths produced a rough cathode deposit with voluminous growth totally unsuitable for the electrorefining of copper. Lignosulfonate materials added alone to electrodeposition baths produce a rough cathode deposit with heavy nodules. However, with conjoint use of the nitrogen compounds and lignosulfonates, an outstandingly better copper deposit was produced which was smooth, dense and essentially nodule free.

The quaternary ammonium salts to be employed herein may be represented by the following structural formula:

wherein R, R R and R are independently selected from the group consisting of alkyl and aryl radicals con taining from 1 to 20 carbon atoms, at least one of the R, R R and R must contain a minimum of 8 carbon atoms, and A- is an inconsequential anion such as Cl, Br: OH and the like. Typical quaternary ammonium salts of this class are:

methyldodecyl-benzyl trimethyl ammonium chloride methyldodecyl xylylene bis (trimethyl ammonium chloride) n-alkyl (C14, C C dimethyl benzyl ammonium chloride p-diisobutyl phenoxy ethoxy benzyl ammonium chloride ethyl hexadecyl dimethyl ammonium bromide diisobutyl-cresoxy-ethoxy ethyl dimethyl benzyl ammonium chloride (or hydroxide) soya trimethyl ammonium chloride 1 di-polyoxyethylene stearyl methyl ammonium chloride octadecyl trimethyl ammonium chloride coco trimethylquaternary ammonium chloride di-hydrogenated tallow dimethyl quaternary ammonium chloride cottonseed trimethyl quaternary ammonium chloride In the above listing of quaternary amomnium salts which may suitably be employed in the present invention, it is to be understood that by the radical coco is meant mixed alkyl groups derived from coconut oil and comprising essentially a mixture of saturated C C C C and C carbon length chains and predominating in C By the cottonseed and soya radicals are meant mixed alkyl groups derived from cottonseed oil and soybean oil respectively and comprising in each case mixtures of essentially unsaturated alkyl groups predominating in C carbon length cahins. By dihydrogenated tallow is meant mixed alkyl groups comprising essentially a mixture of saturated C and C carbon length chains.

The polyethylene amines to be employed herein are high molecular weight polyethylene polyamines (also known as polyethylene imines) and may be represented by the following structural formula:

The polyethylene polyamines to be utilized herein may be characterized as having relative viscosities of at least 1.25 (measured in aqueous solution at C. in comparison with water using a No. 100 Cannon-Fenske viscometer) with a preferred range of from about 1.25 to about 3.00.

The lignosulfonate component of the additive agent can be lignosulfonate-containing residue from the acid sulfite pulping of wood either in crude form containing wood sugars or in substantially sugar-free refined form, for example, as prepared by the process described in U.S. Pat. No. 3,271,382. In the acid sulfite pulping process, a lignocellulose material such as wood is generally cooked in a solution of sulfurous acid, part of the sulfurous acid being combined as bisulfite. The cation assosciated with the bisulfite ion is generally known as the pulping base. Pulping base cations normally used include sodium, calcium, ammonium, magnesium and the like. In acid sulfite pulping of conifer woods, the spent cooking liquors, irrespective of the base used contain approximately 65% lignosulfonates, 25% wood sugars and 10% inorganic salts and miscellaneous lay-products. For use in practicing this invention, the spent sulfite liquors may be used as such but for economic purposes, the liquor will usually be concentrated to at least about 40-50% concentration. More conveniently, such concentrated liquors would be dried to form water-soluble powders, to facilitate shipment and storage, by a suitable drying process such as spray drying, drum drying and the like. As used herein, the term lignosulfonate covers both dried liquor solids and never-dried spent sulfite liquors.

The concentration of additive agent to be introduced into any given electrofining bath will vary considerably depending on such factors as the impurities from the impure copper anode present in the electrolyte, the composition of the electrolyte, the temperature of the electrolyte, the current density and the like. However, generally, when a quaternary ammonium compound is used in conjunction with a lignosulfonate material, the ammonium compound and the lignosulfonate should be added separately to the standard acid copper electrolyte in amounts sufficient to provide concentrations therein of from about 0.5 to about 10 milligrams ammonium compound and about -100 milligrams of lignosulfonate per liter of electrolyte, and more preferably about 0.6-1.8 mg. ammonium compound and about 50 mg. lignosulfonate per liter of electrolyte. When a polyethylene amine is used in conjunction with a lignosulfonate material it is usually preferred to prepare an aqueous solution of both components in the ratio of about 1 part polyethylene amine to about 250 parts lignosulfonate and then dried to form a convenient condensate powder. This condensate powder can then be dissolved in an acid copper electrolyte in a sufficient amount to provide a concentration of about 0.1 to about 0.3 mg. polyethylene amine and about 30- 100 mg. lignosulfonate per liter of electrolyte, and more preferably about 0.18-0.20 mg. polyethylene amine and mg. lignosulfonate per liter of electrolyte.

In a preferred embodiment of the present invention, the lignosulfonate compone of the additive agent should be introduced into the electrolyte in a concentration about 20 to times that of the quaternary ammonium compound when that component is employed in conjunction with the lignosulfonate, and about 250 times that of the high molecular weight polyethylene polya'mine when such an amine is a component of the additive agent.

The following examples are set forth for the purpose of illustration only and are not intended to be construed as being limitative in any respect.

EXAMPLE I A series of copper electrodepositiontests were conducted to determine the effectiveness of the additive agents of the present invention. The tests were conducted under the following electrodeposition conditions which were held constant for all the samples tested:

Temperature C 30 Time, hours 47 Cathode current, density, amps per square foot 17 Agitation, cycles per minute 40 Plating area, square inches 5.2

The electrolytic apparatus was set up in the same manner for each sample tested. For each sample to be tested, a 32 oz. jar was utilized. The jars were placed in a constant temperature bath. Each jar was equipped with holders for tWo anodes and a cathode, a vertical reciprocating stirring device and a D.C. regulated current supply. The two anodes were positioned one on each side of the oathode and each anode was spaced one inch from the cathode. Prior to testing, the copper anodes and the cathodes were washed 24 hours in carbon tetrachloride for degreasing and the cathodes were pickled one hour in a 5% sulfuric acid chromerge solution. The copper sheet used was electrolytic refined copper.

The basic electrolyte introduced into each of the jars was prepared from Bakers Analytical Grade cu ric sulfate pentahydrate g./l.), C. P. sulfuric acid (125 g./l.) and hydrochloric acid (10 mg/l.). The particular additive agent under test was added to the electrolyte in a given jar and the effect of the additive agent on the electrodeposition of copper was determined by visual observation of the plating at the cathode. The results of this testing are tabulated in the following table:

Amount Description of reof additive suiting copper agent eleetrodepesit at Additive agent employed (mg/l.) the cathode Control None Heavy nodules,

treed on surface. 'lcst Number:

1 Sodium-base spent sulfite liquor solids 50 Heavy nodules,

gut less than cenr 2 Di-isobuty1 crcsoxy ethoxy ethyl dimethyl benzyl anuno- 0.6 Heavy nodules.

nium chloride.

5 Di-isobutyl-cresoxyethoxy-ethyl dinlethyl benzyl ammonium chloride.

Di-isobutyl-eresoxy-ethoxy-ethyl diinethyl henzyl ammonium chloride. 7 Sodium-base spent sulfite liquor solids {Sodiulmbase spent sulfite liquor solids 50 Smooth, only 1 or U. 6 2 small nodules.

30 Heavy nodules,

more than test No. 1. 1.0 Heavy nodules.

30 Smooth, slightly 0.8 rougher than test No. 3. 00 Very similar to Amount Description of reof additive sulting copper agent eleetrodeposit at Additive agent employed (mg/1.) the cathode Sodium-base spent sulfite liquor solids 90 }Similar to test 8 Di-isobugyll-ergsoxy-ethoxy-ethyl dimethyl benzyl ammo- 0.8 N o. 3.

mumc on e. 9 Dihhlydmgenated tallow dimethyl quaternary ammonium 0.6 Heavy nodules.

o Ol'l e. Sodium-base spent sulfite liquor solids 50 10 {Di-lhIydrmenated tallow dimethyl quaternary ammonium 0.6 }very small nodules c l Oll e. 11 Di hhlydiiigenated tallow dimethyl quaternary ammonium 2.0 Heavy nodules.

c on e. Sodium-base spent sulfite liquor solids 50 Ivory small nod ules, 12 Di-lhlyd ggenated tallow dimethyl quaternary ammonium 2.0 I less than test No. l.

c 1 on e. 13 Cottonseed trimethyl and dicoco dimethyl quaternary am- 1.4 Similar to test N o.

monium chlorides. 1. Sodium-base spent sulfite liquor solids 2.0 ]No nodules, small 14 Cottonseed giirmthyl and dlcoco dimethyl quaternary am- 1.4 I corner trees.

moniumc on cs. 15 Stearyl trimethyl quaternary ammonium chloride 0.8 Sufipotirer than test 0. Sodium-base spent sulfite liquor solids 5O 16 "{Stcaryl trimethyl quaternary ammonium chloride 0.8 nodules or flees 17 Cocotrimethyl quaternary ammonium chloride- 0.8 HGaV3;1110gl111l9S,t t

roug er an es d t fi d No. l. So ium-base spen sul te liquor soli s 50 18 {Cocotrimethyl quaternary ammonium chloride 0.8 ively small nodules 19 Cottonseed trimethyl quaternary ammonium chloride 0.8 Heavy; notdugesi Slml ar 0 es s d b t 1n 1 l d 0 0 iumase spen su te iquor soi s 5 2O "{Cottonseed trimethyl quaternary ammonium chloride 0.8 ivery small nodules 21-.. Calcium-base spent sulfite liquor solids 50 Hieavyt ll110d1t11e:,N

ess an es 0. 1. 22 Di-hydrogenated tallow dimethyl quaternary ammonium 1.5 Rough, similar to C elhloridie). t m 1 nd 50 test No. 1.

aciumase spen su te iquor so s 23 {Di-Il111ydrggenated tallow dimethyl quaternary ammonium 1.5 ivery Small nodules c on e. Calcium-hase spent sulfite liquor solids. 50 }No nodules, small 24 Cottonseed trlmethyl and dieoco dimethyl quaternary am- 1.4 trees.

monium chlorides.

In the above described testing the additive agents employed were lignosulfonate materials and quaternary ammonium compounds. The lignosulfonate materials employed in the instant testing were spent sulfite liquors from sodium and calcium acid sulfite pulping of predominantly hemlock wood which were concentrated and then spray dried without neutralization. However, as will be recognized by those skilled in the art, other lignosulfonate materials could be employed herein with equally outstanding results.

The weight of copper transferred was measured in each of the tests and was very consistent at from about 33 to about 33.5 grams, which approximates 100% efiiciency at 600 ma. for 47 hours. Any variations in the weight of copper deposited, which was very small, could not be correlated with the additive used.

The results of the above tabulated testing clearly illustrate the superior properties of the additive agents of the present invention to improve the physical characteristics of the cathode deposits in the electrodeposition of copper. When lignosulfonate materials were employed in conjunction with a quaternary ammonium compound as the additive agents in copper electrodeposition baths, the copper electrodeposits were uniformly smooth and essentially free of protrusions or nodules. The test results, also, clearly indicate the unexpected synergistic effect attained by the conjoint use of these materials as additive agents in reducing tree growth and nodular formation in the electrodeposition of copper.

EXAMPLE II Employing the experimental apparatus and procedures of Example I (except that the deposition was carried out over a period of hours in the instant testing), the

effect of the conjoint use of polyethylene amines and lignosulfonate materials as additive agents in electrodeposition of copper was investigated.

The polyethylene polyamines to be tested were prepared from commercially available low molecular weight polyethylene amines by condensation polymerization reaction with ethylene chloride. One such amine was prepared by reacting equal volumes of ethylene chloride and tetraethylene pentamine for 6 hours in a steam bath and is hereinafter referred to as Amine No. 1. Another amine was prepared by reacting equal volumes of ethylene chloride and diethylene triamine for 6 hours in a steam bath this product is hereinafter referred to as Amine No. 2. Additionally, a commercially available polyethylene amine (Union Carbide Corporation) having an average molecular weight of 1800 was employed and is referred to hereinafter as Amine No. 3.

Characteristics of the above prepared polyethylene polyamines were as follows:

Amine No. Relative viscosity 1 1 1.60

No. Cannon-Fenske Vise0meter-Ratio of flow time of 10% aqueous solution vs. water at 25 C.

The lignosulfonate material employed herein was spent sulfite liquor from soda acid sulfite pulping of predominantly hemlock wood which was concentrated and then spray dried without neutralizers. As will be recognized by those skilled in the art, other lignosulfonate materials could also have been used herein.

The results of the tests which were conducted employing the above identified materials, as determined by visual TABLE II Amount of additive Description of resulting copper Additive agent agent electrodeposit at employed (mg/l.) the cathode Control N Heavy modules. Test number:

1. Sodium-base spent 50 Heavy nodules,

sulfite liquor solids. less than control. 2--. Amine No. 1 O. 3 Bushy.

Sodium-base spent 50 Smooth, very 3. sulfite liquor solids. small nodules.

Amine No. 1 0.3 4 Amino No.2 0.3 Bushy.

Sodium-base spent 50 Smooth, very sulfite liquor solids. small nodules.

Amine No. 2 0.3 6. Amine No. 3 0.18 Heavy trees,

striated. Sodium-base spent 50 7.. sulfite liquor solids. No nodules.

Amine No. 3 0. 18

The results of the above tabulated testing clearly illustrate the superior properties of the additive agents of the present invention to improve the physical characteristics of the cathode deposits in the eelctrodeposition of copper. When lignosulfonate materials were employed in conjunction with polyethylene amines as the additive agents in copper electrodeposition baths, the copper electrodeposits were uniformly smooth and essentially free of protrusions or nodules. The test results, also, clearly indicate the unexpected synergistic effect attained by the conjoint use of these materials as additive agents in reducing tree growth and nodular formation in the electrodeposition of copper.

Obviously, many modifications and variations of the invention as hereinbefore set forth may be made Without departing from the spirit and scope thereof, therefore, only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. An aqueous acidic copper electrodeposition electrolyte comprising as its essential ingredients a source of copper ions, a source of hydrogen ions and an amount of an additive agent effective to provide an electrolyte which produces copper electrodeposits which are smooth, dense and essentially free of protrusions, said additive agent comprising a lignosulfonate material and a cation active organic nitrogen compound selected from the group consisting of polyethylene amines and quaternary ammonium compounds having the general formula:

wherein R, R R and R are independently selected from the group consisting of alkyl and aryl radicals containing from 1 to 20 carbon atoms, at least one of R, R R and R must contain a minimum of 8 carbon atoms, and A" is an anion, and mixtures thereof.

2. The electrolyte of claim 1 wherein the cation active organic nitrogen compound is a polyethylene polyamine.

3. The electrolyte of claim 2 wherein the polyethylene polyamine has a relative viscosity of at least 1.25 measured in 10% aqueous solution at C. in comparison with water.

4. The electrolyte of claim 2 wherein the concentration of polyethylene polyamine is from about 0.1 to about 0.3 mg./l. and the concentration of lignosulfonate material is from about 30 to about mg./l.

5. The electrolyte of claim 1 wherein the lignosulfonate material is the lignosulfonate-containing residue from the acid sulfite pulping of wood.

6. The electrolyte of claim 1 wherein the concentration of quaternary ammonium compound is from about 0.5 to about 10 mg./l. and the concentration of lignosulfonate material is from about 30 to about 100 mg./l.

7. A combination of additive agents for copper electrodeposition electrolytes which improve the quality and physical characteristics of the copper electrodeposits comprising: a mixture of a cation active organic nitrogen compound selected from the group consisting of quaternary ammonium compounds, polyethylene amines and mixtures thereof, and a lignosulfonate material; said quaternary ammonium compounds having the general formula:

wherein R, R R and R are independently selected from the group consisting of alkyl and aryl radicals containing from 1 to 20 carbon atoms, at least one of R, R R and R must contain a minimum of 8 carbon atoms, and A is an anion.

8. The combination of additive agents of claim 7 wherein the cation active organic nitrogen compound is a polyethylene polyamine.

9. The combination of additive agents of claim 8 wherein the high molecular weight polyethylene polyamine has a relative viscosity of at least 1.25 measured in 10% aqueous solution at 25 C. in comparison with Water.

10. The combination of additive agents of claim 7 wherein the lignosulfonate material is the lignosulfonatecontaining residue from the acid sulfite pulping of wood.

11. In the method of electrodepositing copper from an aqueous acidic electrolyte, the electrolyte comprising as its essential ingredients a source of copper ions and a source of hydrogen ions, the steps comprising adding to the electrolyte in an amount effective to provide an electrolyte which produces copper electrodeposits which are smooth, dense and essentially free of protrusions, a cation active organic nitrogen compound selected from the group consisting of quaternary ammonium compounds having the general formula:

l R -lTI-R; A-

wherein R, R R and R are independently selected from the group consisting of alkyl and aryl radicals containing from 1 to 20 carbon atoms, at least one of R, R R and R must contain a minimum of 8 carbon atoms, and A is an anion, polyethylene amines and mixtures thereof, in conjunction with a lignosulfonate material; and then passing an electric current from an anode through the electrolyte to a cathode to deposit copper thereon.

12. The method of claim 11 wherein the cation active organic nitrogen compound added to the electrolyte comprises a polyethylene polyamine.

13. The method of claim 12 wherein the polyethylene polyamine has a relative viscosity of at least 1.25 measured in 10% aqueous solution at 25 C. in comparison with water.

14. The method of claim 11 wherein the lignosulfonate material added to the electrolyte comprises a lignosulfonate-containing residue from the acid sulfite pulping of wood.

9 15. The method of claim 11 wherein the cation active organic nitrogen compound is added in an amount of about 0.1 to about 10 mg./l. and the lignosulfonate material is added in an amount of about 30 to about 100 mg./l.

References Cited UNITED STATES PATENTS 10 2,805,194 9/1957 Beaver et al. 204-52 2,853,444 9/1958 Pye et a1. 204108 FOREIGN PATENTS 583,003 12/ 1946 Great Britain 204-106 204DIG 2 US. Cl. X.R.