US3054734A - Addition agent for acid copper electrolytes - Google Patents

Description

p 1962 R. E. HARROVER, JR 3,054,734

ADDITION AGENT FOR ACID COPPER ELECTROLYTES Filed Sept. 9, 1960 F i g. l

Acid Copper Electrolyte Plus on Addition Agent Fig.2.

A B F E Cathodic Cathodic 2 E D D u u "2 *2 2 5 t+ C D a X- Plating Ttme X Plating Time I Y Y Between I00 Seconds and Sec. BetweenlOO secondsundfi sec/ Y- Depicting Time at least f X WITNESSES INVENTOR 91A (M, Robert E. Horrover, Jr. 9 MMM itg 3,054,734 ADDITIGN AGENT FOR ACID COPPER ELECTROLYTES Robert E. Harrover, In, North Huntingdon Township,

Westmoreiand County, Pa, assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa, a corporation of Pennsylvania Filed ept. 9, 1960, Ser. No. 54,893 Claims. (Cl. 20452) This invention relates to the electrodeposition of cop per from acid electrolytes embodying certain addition agents to promote smoother, more ductile electrodeposits of copper.

The electrodeposition of copper from acid copper electrolytes often results in an electrodeposit that is rough, spongy, dark colored or otherwise unsuited for the purpose for which it is intended. Many addition compounds have been proposed for incorporation in acid copper electrolytes for the purpose of providing improved deposition of copper on articles therefrom. The addition compounds are often referred to in the art as addition agents.

This invention is directed to a plating bath comprising copper sulfate and sulfuric acid, and containing in solution a relatively small amount of mercury.

For a complete understanding of this invention, reference is made to the following description taken in conjunction with the accompanying drawing, in which:

FIGURE 1 is a sectional view in elevation of apparatus suitable for direct-current electroplating; and

FIG. 2 is a graph illustrating one type of periodic reverse current electroplating.

In accordance with this invention it has been discovered that fine-grained, ductile electrodeposits of copper can be obtained by the addition of mercury to an acid electrolyte plating bath comprising copper sulfate and sulfuric acid. Furthermore, the brightness and smoothness of the copper electrodeposit is enhanced substantially by employing mercury in conjunction with some of the socalled brightening addition agents.

The mercury can be added in the form of mercurous or mercuric compounds. The mercurous and mercuric compounds can be either organic or inorganic. The mercury compounds employed in carrying out this invention must be soluble in the acid copper electrolyte in an amount sufiicient to produce appreciable results.

The concentration of mercury in the bath can be in the range of from about 0.0003 to 0.01 ounce per gallon of electrolyte. As used in this specification and in the appended claims the quantities given for mercury refer to quantities calculated as the metal.

Suitable mercury compounds for use in this invention include mercuric acetate, mercuric benzoate, mercuric formate, mercuric oxalate, mercuric sulfate, p-acetoxy- .lElCLlllC aniline, mercurous sulfate, mercurous acetate, mercurous fluoride, and p-aminophenylmercuricacetate.

The mercury can be used as the sole addition agent in acid copper electroplating baths if desired. It is preferred, however, to employ the mercury in conjunction with certain brightening agents as the mercury alone has no appreciable effect on the brightness of the copper electrodeposit. It has been determined that mercury, in the range of concentration above set forth, and in conjunction with known brightening addition agents does improve substantially the brightness and smoothness of the copper electrodeposit over that obtained by using the known brightening addition agents alone. Further, the mercury addition of this invention will extend substantially the useful life of most available brightening agents.

Thus, for example, mercuric sulfate can be added to a series of acid copper baths containing such brightening agents as phenyl sulfonic acid, thiourea, N-acetyl thiourea,

3,054,734 Patented Sept. 18, 1962 N-propionyl thiourea, N-trifiuoroacetyl thiourea, N-pentafiuoropropionyl thiourea, N-furfuroyl thiourea, dimethyl thiourea, and cyanoacetyl thiourea. The brightness of the electrodeposit is improved substantially over the use of any one or more of the above brightening agents without the mercury addition. smoothness and ductility of the copper electrodeposit is improved substantially also.

Additionally, the mercury addition agent of this invention can be employed in combination with the brightening addition agents disclosed in U.S. Patent No. 2,700,019, assigned to the assignee of the present invention.

The addition agents disclosed in Patent 2,700,019 are employed in amounts of from about 0.0005 to 0.05 ounce per gallon of electrolyte and comprise 2-thiohydantoin and certain derivatives of 2-thiohydantoin having the following thiohydantoin structure 2 0 II S and having at least one organic substituent in any one of the 1, 3, and 5 positions. Various organic radicals can be substituted at any one or more of the 1, 3, or 5 positions, as long as the compound is not rendered so insoluble that it Will not dissolve in the acid copper electrolyte in an amount sufiicient to produce an appreciable result. Examples of suitable compounds include 1-acetyl-2-thiohydantin, 5(2-hydroxylbenzal)-2-thiohydantoin, S-furfural-2-thiohydantoin, '1-benzol-2-thiohydantoin, S-benzol-2-thiohydantoin, l-methyl-Z-thiohydantoin, and 3- acetyl-Z-thiohydantoin. r

The mercury addition agent of this invention can be used also in combination with the addition agents disclosed in U.S. Patent No. 2,853,443 to Robert E. Harrover, Jr., assigned to the assignee of the present invention.

The compounds disclosed in Patent 2,853,443 are employed in acid copper electroplating baths in amounts of from about 0.0001 to 0.5 ounce per gallon of electrolyte and are obtained by admixing and heating substantially equimolar proportions of at least one compound having the nucleus tilt and at least one alkylolamine selected from the group consisting of primary, secondary and tertiary alkylolamines in which the groups substituted on the nitrogen atom are selected from the group consisting of hydrogen, alkyl groups, and alkylol groups having from 1 to 4 carbon atoms, there being at least one alkylol group per molecule.

Examples of suitable compounds having the nucleus -C-NO II I ll 0 H s tit 3 and other suitable alkylolamines. Reference is made also to Patent 2,853,443 for the method of reacting the above compounds to provide the desired reaction product.

The mercury addition, in accordance with this invention, can be employed also in conjunction with the brightening agents disclosed in application Serial No. 770,775, filed October 30, 1958, to enhance substantially the brightening effect of the disclosed addition agents. Application Serial No. 770,775, now US. Patent 2,997,428, is assigned to the assignee of the present invention.

In application Serial No. 770,775, there are disclosed novel reaction products which, when employed in acid copper electroplating baths in amounts of from about 0.001 to 0.5 ounce per gallon of electrolyte, improve the brightness of the copper electrodeposit.

In preparing the novel reaction products disclosed in application Serial No. 770,775, any of the several compounds having the nucleus C-NC U H H s can be reacted with ammonia or cetrain derivatives thereof as will be described more fully hereinbelow. An example of a particularly suitable aliphatic compound having the nucleus GNC tit

Examples of other compounds, having the nucleus -C-NC is acetylthiourea.

are Z-thiohydantoin and substitution derivatives of Z-thiohydantoin having at least one organic substituent in the l, positions. The nucleus of these Z-thiohydantoin substituent derivatives has the following structure:

Various organic radicals can be substituted at one or both of the 1 or 5 positions, providing the resultant compound obtained upon reaction with ammonia or derivatives thereof is soluble in the acid copper electrolyte in an amount sufiicient to'produce an appreciable improvement in brightness and smoothness of the copper deposited. Examples of suitable compounds are:

Z-thiohydantoin -1-acetyl-2-thiohydantoin .5 (Z-hydroxylbenzal) -2-thiohydantoin 5 -furfural-2-thiohydantoin -5-benzal-2-thiohydantoin -.1-methyl-2-thiohydantoin Various organic radicals can be substituted for hydrogen at any one or more of the 1, 5 or 6 positions, providing the resultant compound obtained upon reaction with the ammonia or derivatives thereof is soluble in the acid electroplating bath. Examples of suitable compounds of this nature include:

Compounds which can be reacted with compounds having the nucleus lllll OHS to form the addition agents disclosed in application Serial No. 770,775 comprise compounds selected from the group consisting of (A) monocyclic unsubstituted aromatic compounds containing in the ring structure from 4 to 6 carbon atoms and from 1 to 2 nitrogen atoms per molecule and (B) compounds having the formula wherein R is a radical selected from the group consisting of hydrogen; monovalent and divalent saturated aliphatic hydrocarbon radicals having from 1 to 4 carbon atoms and in which the substitutents are NH radicals; monovalent and divalent alicyclic radicals containing from 5 to 6 carbon atoms in the ring in which the substituents are selected from the group consisting of CH and NH radicals; monovalent and divalent heterocyclic radicals having from 5 to 6 carbon atoms in the ring and in which hetero atoms occur only in the ring structure and the substituents occur only in the carbon atoms and are NH radicals; phenyl radicals; and aminophenyl radicals.

Specific examples of compounds included within the scope of the terms identified as (A) and (B) above include: ammonia, isopropylamine, ethylenediamine, dibutylarnine, methylpropylenediamine, diethylenediamine, cyclopentylamine, dicyclohexylamine, cyclopentylmethylamine, cyclopentylethylenediamine, B-methylcyclohexylamine, 1,2-diaminocycl0pentane, Z-aminothiazol, 3,5-diamino 1,2,4 triazole, aniline, p-aminoaniline, methylaniline, methyl-2-aminothiazole, 3-methylamino-5-amino- 1,2,4-triazole, 2-cyclohexylaminothiazole, ethyl-4-methylcyclohexylarnine, 4-cycloheXylamino-5amino-2-pyridine,

4 methylaminocyclohexylamine, p-aminomethylaniline,

3,3'-diisothiazolylamine, cyclohexylaniline, Z-methylcyclohexylthiazol 2, diphenylamine, 3 amino-S-phenylamino-1,2,4-triazole thiazolyl 2 phenylamine, pyridine, pyrimidine, pyrazine, phenyl-4-aminocyclohexy1amine, 4- methylcyclohexylpropylenediamine, N-(Z thiazolyD-paminoaniline, dimethylcyclohexylamine, phenylethylenediamine, di 4 aminocyclohexylamiue, N-cyclopentylaminoaniline, 3 (2' thiazolylamino)-5-amino-l,2,4-triazole, phenyl-p-aminoaniline, Z-thiaZolylethyIenediamine,

3-p-aminophenyl-5-amino-1,2,4-triazole, N (2-aminoethylene)-l,4-diaminocyclohexane, N-cyclopentyl-1,4-diaminocyclohexane, cyclohestylmethylcyclohexylamine, N- (2' thiazolyl)-1,2-diminocyclopentane, di-p-aminophenylamine, p aminophenyl 4 methylcyclohexylamine, 4-methylcyclohexylphenylamine, p-arninophenylethylenediamine, p-aminophenyl-3-aminocyclopentylamine, N- (2-aminoethylene) -3 ,5 -diaminopyridine, N-(3-amino-1,4- thiapyranyl 5) 4-methylcyclohexylamine, N (3'- methylcyclopentyl) l ,4-diaminocyclohexane, N- 3'-methylcyclohexyl) -4-aminocyclohexane, 3 -aminocyclohexyl- 3-aminopyridyl-5-amine and di-2-amino-l,4-pyranyl-4- amine.

The following specific examples illustrate the preparation of the novel addition compounds disclosed in application S.N. 770,775.

Example I About 1 mol of l-acetyl-2-thiohydantoin and one mol of ammonia (28% aqueous solution) are dissolved in three liters of ethanol and placed within a suitable reaction vessel. The resultant solution then is heated to boiling and refluxed for about 30 minutes. The solution then is evaporated to about one liter in volume. The resultant product is a viscous slurry. It is cooled, filtered, and the separated crystals are air dried. The reaction product is a light brown, crystalline solid which darkens to a reddish brown on exposure to air. This reaction product, when added to acid copper plating baths, brings about an improved brightness in copper electrodeposited therefrom.

Example 11 One mol of acetylthiourea is dissolved in 1.1 mols of n-propyl amine by heating the components in a suitable reaction vessel. Upon cooling, a solid reaction product crystallizes from the solution. The product obtained upon air drying is a white crystalline mass suitable for addition to an acid electrolyte for the purpose of bringing about improved brightness of metal electrodeposited therefrom. The product has a melting point of 170 173 C. The melting point of this product when admixed with acetylthiourea, is 126 C.

Reference is hereby made to application S.N. 770,775, filed October 30, 1958, for a complete description of the above addition compounds and the method of preparing the same.

It has been determined that in certain plating baths improved results are obtained by incorporating a minor amount of chlorides, present as a chloride ion, in the plating bath with the known brightening addition agents described thereinabove. Commercial hydrochloric acid (37%) can be used for this purpose to provide from about 0.001 ounce per gallon to 0.06 ounce per gallon of chloride ion component depending upon the quantity of the addition agent introduced into the plating bath. Usually the amount of chloride ion component present will not exceed about 0.03 ounce per gallon. Alkali metal chloride such as sodium chloride, calcium chloride and other ionizable chloride salts can be added to introduce the chloride ions into the electrolyte.

The chloride ion in proper concentration removes the low current density discoloration that results when many of the presently available commercial brightening agents are employed in the bath. In accordance with the prior art teachings the chloride concentration is critical and must be carefully controlled. If excessive amounts of chloride ion are present in the bath, the efiect of the brightening agent employed is nullified substantially, and the copper electrodeposit will become dull and coarse grained.

It has been determined that when mercury is added to the plating bath in the amounts hereinabove defined and in accordance with this invention, the concentration of the chloride ion needs not be so carefully controlled as '6 above set forth. This is an important advantage to the electroplating art as it is presently practiced, since the chloride concentration is often increased inadvertently by drag-in from preceding electrolytes and acid dips.

Thus, for example, when the chloride ion concentration is about 0.03 ounce per gallon in acid copper baths containing certain brighteners, the copper electrodeposit will often have a dull flat appearance. After the mercury addition in accordance with this invention, the copper electrodeposit takes on its desired bright appearance.

Acid copper electrolytes suitable for plating copper are well known. Ordinarily, such electrolytes comprise an aqueous solution having dissolved therein from 20 to 40 ounces per gallon of copper sulfate and from 1.3 to 13 ounces per gallon of sulfuric acid. In industry at the present time, one widely used acid copper plating bath comprises a solution of 28 ounces per gallon of copper sulfate crystals and 8 ounces per gallon of sulfuric acid (98% Mercury in the desired amount is added to the bath in the form of a soluble mercury compound or mixtures of two or more as above set forth. It will be appreciated that as the electrolyte is used in plating, additions of the soluble mercury compound must be made from time to time to maintain the desired mercury concentration.

With the desired mercury concentration in the plating bath, very satisfactory copper plating will result when the bath is at any temperature of from about 60 F. up to about 120 F. Excellent copper deposits have been secured using baths operating at temperatures of from about F. to about F., which temperatures appear to define the optimum range.

Current densities can be varied depending on the temperature andconcentration of the bath. With bath agitation, current densities of from about 10 to 200 amperes per square foot can be used and from about 10 to 50 amperes per square foot without agitation. Control of current density is within the skill of those versed in the art.

Aqueous acid copper electroplating electrolytes with the desired mercury concentration, with or without organic acids, dextrin, dextrose, or any other known additive capable of extending the useful life of the bath or otherwise improving the copper electrodeposition, as will be set forth hereinafter, can be employed for plating metal by passing either continuous direct-current or periodically reversed electrical current, or other suitable electrical current therethrough. Excellent results have been obtained with direct-current plating of such electrolytes. Periodic reverse current plating will give satisfactory electrodeposits also.

Other plating current such as interrupted direct current and alternating current superimposed on direct current can be employed if desired.

Referring to the drawing, there is illustrated in FIG. 1 an apparatus 10 for practicing the present invention. This apparatus comprises a tank 12 provided with a suitable liner 14 of rubber, glass or the like, resistant to the acid electrolyte, carrying an electrolyte 16 composed of an aqueous solution of copper sulfate, sulfuric acid and the mercury addition agent of this invention alone or together with other known addition agents.

Disposed within the electrolyte 16 is an anode 18 that can be composed of copper or lead, or separate anodes of both. If lead anodes are used, the copper must be replenished by introducing copper sulfate into the electrolyte 16 from time to time. The anode 1 8 is suspended by a support 19' from a conductor bar 20. A member 22. to be plated with copper is suspended by a support 24 from the second conductor bar 26. The conductor bars 20 and 26 are provided with electrical current from a suitable source 28 which can be a generator, a rectifier, storage batteries, or the like. Electrical current passing from the source 28 to the conductor bars 20 and 26 passes through the anode I 18. electrolyte 16 and the member 22 to cause copper to structure. The electrodeposit is extremely bright if known brightening agents are used in conjunction with the mercury addition.

Copper can be plated from the above described electrolyte containing the mercury addition in accordance with this invention by means of a periodically reversed electrical current composed of cycles, each of which passes electrical current through the member for a period of time of from 0.01 second to 100 seconds to plate copper on the base member and then the direction of flow of the current is reversed to deplate a part of the previously plated copper.

consists of smooth, dense, ductile copper upon which a second layer of copper is plated bythe plating portion of the next cycle of periodic reversed current and then a portion of this second increment is deplated by passing deplating current leaving a second increment of still smoother copper than the first increment, and so on.

"Referring to FIGURE 2 of the drawing, a graph is shown illustrating onetype of periodic reverse current as it is applied to the base member to be plated. Such periodic cycles can be produced by periodically reversing the flow of uniform direct current. base member when first immersed in the electrolyte is at a zero potential so that no current flows when the first cycle of periodically reversed current is: applied, a cathodic or plating current of a density of the value of A is applied and metal is plated for a period of time X to a point B, then the direction of flow of the current is reversed so that the current density in the member drops frorn'the value B to zero and then becomes anodic and will deplate copper, reaching a deplating current density of C. Metal is deplated for a period of time Y, which is about at least one-twelfth of the length of period X, at the current density of C to D until sufiicient coulombs of deplating current have been applied to the coulombs of from 8% to 90% of the coulombs applied during the plating period X. The cycle A-BC-D deposits an increment of sound, smooth copper base. The direction of current flow is again reversed from D through zero and then plating current of a density value of F is applied to begin another cycle which will plate ,a second increment of copper.

It will be understood that the showing in FIGURE 2 is merely schematic and that the current density is not necessarily uniform from A to B or C to D as shown, but will usually vary and be relatively non-uniform. Also, in reversing from B to C and from D to F, the time required is finite and these lines will not be vertical, as shown, but will take an appreciable period of time, depending upon the various factors involved in the plating installation. The deplating or anodic current density C-D can be equal to the plating current density-A-B, or exceeded or can be as low as 8% of the plating current density. Reference should be had to Patents 2,451,341;

2,678,909 and 2,470,775 for additional information as to periodic reverse current cycles.

In order to indicate more fully the advantages and capabilities of the present invention, the following specific examples are set forth to illustrate the utilization of the mercury addition agent of this invention in acid electrolyte plating baths.

It is assumed that the Example 111 An aqueous electroplating electrolyte of the following composition is prepared:

Ounces per gallon of electrolyte Copper sulfate (crystals) [CuS0 .5H O] 28 Sulfuric acid (98%) 8 Mercuric sulfate 0.005 Hydrochloric acid (37%) 0.006

This bath is operated at various temperatures from about 60 F. to about 120 F. with satisfactory results. Temperatures of from about F. to about 100 F. appear to give optimum plating results.

Copper is plated from the bath of this Example III on rectangular brass panels using direct current at a current density of about 50 amperes per square foot and at a temperature of about F. Copper is deposited until there is applied to the rectangular brass panel copper plate of a thicknessof about 3 mils. The copper plate has relatively good ductility, is a smooth and fine grained copper deposit and has a relatively high density.

Example IV The following electrolyte is prepared:

Ounces per gallon of electrolyte Copper sulfate (CuSO 5H O) 28 Sulfuric acid (98%) 8 HQ (37%) 0.006 P-acetoxymercuric aniline 0.05

Copper is plated from this bath on rectangular brass panels using direct current at a current density of about 60 amperes per square toot and at a temperature of about 90 F. Copper is deposited on the panel to a thickness of about 4 mils. The copper plate has good ductility, is fine grained and smooth.

Example V The following electrolyte is prepared:

Ounces per gallon of electrolyte Copper sulfate (CuSO .5H O) 28 Sulfuric acid (98%) 8 HCl (37%) 0.006 Mercurous sulfate 0.007

Copper plated on a brass panel from the bath is ductile, smooth and fine grained.

When direct current is applied to the electrolyte, excellent deposists of copper are produced on base members at current densities of from about 5 to 200 amperes per square foot. The copper deposit is extremely bright, smooth, fine grained, dense and has good ductility.

The addition of certain water soluble carboxylic acids, dextrin, or dextrose to acid copper electrolyte baths containing the soluble mercury additive of this invention and the known primary brightening agents enables the addition agents to function under maximum efliciency for longer periods of time than is normally possible. Citric acid, malic acid, maleic acid, linoleic acid, adipic acid, aconitic acid, and oxalic acid are examples of acids that can be employed for this purpose. Any of these or mixtures of two or more are employed in amounts of from 0.001 ounce up to about 3 ounces per gallon of electrolyte Ounces per gallon of electrolyte Copper sulfate (crystals) [CuSO .5H O] 28 Sulfuric acid (98%) 8 Mercuric sulfate 0.01 Hydrochloric acid (37%) 0.006 Dextrin (yellow) 0.008

The copper deposits obtained using this electrolyte at a bath temperature of about 80 F. are fine-grained and ductile at current densities of from to 120 amperes per square foot.

Example VIII The following electrolyte is prepared:

Ounces per gallon of electrolyte Copper sulfate (crystals) [CuSO .5H O] 28 Sulfuric acid (98%) 8 P-acetoxymercuric aniline 0.05 Citric acid 0.25 Reaction product of 1-acetyl-2-thiohydantoin and monoethanolamine 0.001

The copper deposits obtained using this electrolyte are ductile, smooth and have a high luster.

Example IX The following electrolyte is prepared:

Ounces per gallon of electrolyte Copper sulfate (crystals) [CuSO .5H O] 28 Sulfuric acid (98%) 8 Mercuric sulfate 0.01 Hydrochloric acid (37%) 0.003 Dextn'n 0.004 l-acetyl-Z-thiohydantoin 0.01

Copper electrodeposited from this bath is very bright, smooth and ductile.

Example X The following electrolyte is prepared:

Ounces per gallon Copper sulfate (crystals) [CuSO .5H O] 28 Sulfuric acid (98%) 8 P-acetoxymercuric aniline 0.05 Citric acid 0.25

Reaction product of 2-thiohydantoin and pyridine 0.001

The copper electrodeposits obtained by using this bath or electrolyte are ductile, smooth, and of high luster.

Example XI The following electrolyte is prepared:

Ounces per gallon Copper sulfate (crystals) [CuSo .5H O] 28 Sulfuric acid (98%) 8 Mercuric sulfate 0.01 Hydrocholoric acid (37%) 0.003 Dextrin 0.004 Reaction product of Z-thiohydantoin and methanediamine .002

When direct current is applied to the electrolyte, excellent copper electrodeposits are produced on base members at 10 current densities of from 5 to 200 amperes per square foot.

While the present invention has been described with particular reference to preferred embodiments thereof, it will be understood, of course, that certain changes, substitutions, modifications and the like may be made therein without departing from the scope thereof.

I claim as my invention:

1. An aqueous electrolyte plating solution comprising copper sulfate, sulfuric acid, and a water soluble mercury compound in an amount sufficient to provide mercury in the range of from about 0.0003 to 0.01 ounce per gallon in solution in said bath.

2. An aqueous electrolyte plating solution comprising copper sulfate, sulfuric acid and an amount of mercury in the range of from about 0.0003 to 0.01 ounce per gallon in solution in said bath, said mercury being introduced into the bath in the form of soluble compounds of mercury.

3. An aqueous electrolyte plating solution comprising copper sulfate, sulfuric acid, from 0.001 to 0.06 ounce of chloride ion per each gallon of electrolyte, and a Water soluble mercury compound in an amount sufiicient to provide mercury in the range of from about 0.0003 to 0.01 ounce per gallon in solution in said bath.

4. An aqueous electrolyte plating solution comprising copper sulfate, sulfuric acid, from 0.0005 to 0.05 ounce per gallon of at least one Z-thiohydantoin compound, and a water soluble mercury compound in an amount sufiicient to provide mercury in the range of from about 0.0003 to 0.01 ounce per gallon in solution in said bath.

5. An aqueous electrolyte plating bath comprising copper sulfate, sulfuric acid, a water soluble mercury compound in an amount sufficient to provide mercury in the range of from about 0.0003 to 0.01 ounce per gallon in solution in the bath, and from 0.0001 to 0.5 ounce per gallon of the product obtained by admixing and heating substantially equimolar quantities of at least one compound having the nucleus II I ll with at least one compound selected from the group consisting of (A) monocyclic unsubstituted aromatic compounds containing in the ring structure from 4 to 6 carbon atoms and from 1 to 2 nitrogen atoms per molecule, (B) compounds having the formula wherein R is a radical selected from the group consisting of hydrogen, phenyl radicals, aminophenyl radicals, monovalent and divalent saturated aliphatic hydrocarbon radicals having from 1 to 4 carbon atoms and in which the substituents are -NH radicals, monovalent and divalent alicyclic radicals containing from 5 to 6 carbon atoms in the ring in which the substituents are selected from the group consisting of CH and -NH radicals, and monovalent and divalent heterocyclic radicals having from 5 to 6 carbon atoms in the ring and in which hereto atoms occur only in the ring structure and the substituents occur only in the carbon atoms and are NH radicals, and (C) alkylolamines in which the groups substiuted on the nitrogen atoms are selected from the group consising of hydrogen, alkyl groups, and alkylol groups having from 1 to 4 carbon atoms, there being at least one alkylol group per molecule.

6. An aqueous electrolyte as set forth in claim 5 which contains from 0.001 ounce to 3 ounces of at least one Water soluble carboxylic in each gallon of the electrolyte.

7. An aqueous electrolyte as set forth in claim 5 which contains from 0.001 ounce to 5.0 ounces of dextrin in each gallon of electrolyte.

8. An aqueous electrolyte as set forth in claim 5 which 1 1 contains from 0.001 ounce to 5.0 each gall-on of electrolyte.

9. In the process of plating copper on a base member from an acid electrolyte having an anode therein, said electrolyte comprising copper sulfate and sulfuric acid, the steps comprising adding a soluble mercury compound to the electrolyte in an amount sutiicient to provide an amount of mercury in the range of from about 0.0003 to 0.01 ounce per gallon in solution in said bath, and then passing a plating electrical current from the anode through the electrolyte and to the member to deposit copper on the member.

10. The process of claim 9 in which there is from 0.001 to 0.06 ounce of chloride ion in each gallon of the electrolyte.

11. The process of claim 9 in which there is from 0.0005 to 0.05 ounce per gallon of at least one 2-thiohydantoin compound in each gallon of the electrolyte.

12. The process of claim 9 in which there is present in an amount equal to from about 0.0001 to 0.5 ounce per gallon, the product obtained by admixing and heating substantially equimolar quantities of at least one compound having the nucleus ounces of dextrose in with at least one compound selected from the group consisting of (A) monocyclic unsubstituted aromatic compounds containing in the ring structure from 4 to 6 carbon wherein R is a radical selected from the group consisting of hydrogen, phenyl radical, aminophenyl radicals and divalent saturated aliphatic hydrocarbon radicals having from 1 to 4 carbon atoms and in which the substituents are NH radicals, monovalent and divalent alicyclic radicals containing from 5 to 6 carbon atoms in the ring in which the substituents are selected from the group consisting of CH;, and NH radicals and monovalent and divalent heterocyclic radicals having from 5 to 6 carbon atoms in the ring and in which hetero atoms occur only in the ring structure and the substituents occur only on the carbon atoms and are NH radicals, and (C) alkylolamines in which the groups substituted on the nitrogen atom are selected from the group consisting of hydrogen, alkyl groups, and alkylol groups having from 1 to 4 carbon atoms, there being at least one alkylol group per molecule.

13. The process of claim 9 in which there is present dextrin in an amount equal to from about 0.001 ounce to 5.0 ounces per each gallon of the electrolyte.

14. The process of claim 9 in which there is present dextrose in an amount equal to from about 0.001 ounce to 5.0 ounces per each gallon of electrolyte.

15. In the process of plating copper on a base member from an acid electrolyte having an anode therein, said electrolyte comprising copper sulfate and sulfuric acid, the steps comprising adding a soluble mercury compound to the electrolyte in an amount suflicient to provide an amount of mercury in the range of from about 0.0003

to 0.01 ounce per gallon in solution in said bath, and then passing cycles of periodically reversed electrical current through the base member, the aqueous electrolyte, and an anode, each cycle of current first flowing in one direction to plate copper on the basefor a period of from 0.01 second to 100 seconds, then the direction of current flow reversing for a period of time to deplate a portion of the previously plated copper, the coulombs applied during the deplating period equal to from 8% to of the coulombs applied during the plating period, the plurality of cycles of periodically reversed current electroplating smooth sound copper on the base.

16. The process of claim 15 in which there is from 0.001 to 0.06 ounce of chloride ion in each gallon of the electrolyte.

17. The process of claim 15 in which there is from 0.0005 to 0.05 ounce per gallon of at least one 2-thiohydantoin compound in each gallon of the electrolyte.

18. The process of claim 15 in which there is present in an amount equal to from about 0.0001 to 0.5 ounce per gallon of electrolyte the product obtained by admixing and heating substantially equimolar quantities of at least on compound having the nucleus with at least one compound selected from the group consisting of (A) monocyclic unsubstituted aromatic compounds containing in the ring structure from 4 to 6 carbon atoms andfrom 1 to 2 nitrogen atoms per per molecule, (B) compounds having the formula wherein R is a radical selected from the group consisting of hydrogen, phenyl radical, aminophenyl radicals, monovalent and divalent saturated aliphatic hydrocarbon radicals having from 1 to 4 carbon atoms and in which the snbstituents are NH radicals, monovalent and divalent alicyclic radicals containing from 5 to 6 carbon atoms in the ring in which the substituents are selected from the group consisting of CH and NH radicals, and monovalent and divalent heterocyclic radicals having from 5 to 6 carbon atoms in the ring and in which hetero atoms occur only in the ring structure and the substituents occur only on the carbon atoms and are NH radicals, and (C) alkylolamines in which the groups substituted on the nitrogen atom are selected from the group consisting of hydrogen, alkyl groups, and alkylol groups having from 1 to 4 carbon atoms, there being at least one alkylol group per molecule.

19. The process of claim 15 in which there is present dextrin in an amount equal to from about 0.001 ounce to 5.0 ounces per each gallon of electrolyte.

20. The process of claim 16 in which there is present dextrose in an amount equal to from about 0.001 ounce to 5.0 ounces per each gallon of electrolyte.

References Cited in the file of this patent UNITED STATES PATENTS

Claims (1)

1. AN AQUEOUS ELECTROLYTE PLATING COMPRISING COPPER SULFATE, SULFURIC ACID, AND A WATER SOLUBLE MERCURY COMPOUND IN AN AMOUNT SUFFICIENT TO PROVIDE MERCURY IN THE RANGE OF FROM ABOUT 0.0003 TO 0.01 OUNCE PER GALLON IN SOLUTION IN SAID BATH.

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