US3216913A - Copper plating bath - Google Patents

Description

United States Patent 3,216,913 COPPER PLATING BATH Anthony Debe, 18203 Canterbury Road, Cleveland, Ohio No Drawing. Filed Aug. 14, 1964, Ser. No. 389,766 21 Claims. (Cl. 20452) This application is a continuation-in-part of my copending application Serial No. 120,167 filed June 28, 1961, now abandoned, and my co-pending application Serial No. 247,361, now abandoned, filed December 26, 1962.

The present invention is directed to an improved copper plating bath and the method of making the same. The invention is particularly directed to the use of a catalytic ingredient in alkaline cyanide copper plating baths for the electrolytic deposition of copper.

It is an object of the present invention to provide an improved alkaline cyanide plating bath for the electrolytic deposition of copper in which a catalytic ingredient comprising an improved reaction product of hexamethylene tetramine and salicylic acid is used.

It is an object of the present invention to provide an improved plating bath and a method of making the same in which copper is deposited electrolytically from the bath, the bath containing an anode corroder and a smoothing and grain refining agent.

It is an object of the present invention to provide an improved alkaline cyanide copper plating bath and the method of making the same in which a catalytic ingredient is used, the catalytic ingredient being an anode corroder as well as a smoothing and grain refining agent.

It is an object of the present invention to provide an improved aqueous alkaline cyanide copper plating bath comprising copper cyanide, an alkali metal hydroxide, an alkali metal cyanide, an alkali metal tartrate, and a reaction product of salicylic acid and hexamethylene tetramlne.

These and other objects will be apparent from the specification that follows and from the appended claims.

The present invention provides an aqueous alkaline cyanide plating bath in which a reaction product of salicylic acid and hexamethylene tetramine (also called hexamine) is used as an anode corroder and a smoothing and grain refining agent for the electrolytic deposition of copper. In accordance with the present invention, the plating bath deposits a fine grained, smooth coating in which any sandpaper effect is eliminated or reduced substantially and in which the cathode performance is improved.

The amount of smoothing and grain refining agent generally used to obtain the above may be in the range of about 0.1 to 7.0 ounces per gallon (or about 0.75 to 53 grams per liter) of the reaction product of salicylic acid and hexamine as hereinafted describedalthough, for best results, it is preferred that at least about 0.4 ounces and up to as high as about 4 ounces per gallon or more, sometimes even as high as 6 ounces, of the above described smoothing agent be used. Generally, while 8 or 10 or more ounces per gallon can be used, more than 7 ounces per gallon apparently provides no additional benefits and is wasteful and uneconomical.

Suitable plating bath formulations, including the general ranges and preferred ranges of the above described reaction product used as an anode corroder and a smoothing and grain refining agent, are set forth below in Table 1.

As it will hereinafter be described in detail, the above described smoothing and grain refining agent or reaction product is an alkaline solution made by reacting hexamine and salicylic acid at a pH of 2 /2 to /2 to provide an acid reaction product and thereafter further re- 3,216,913 Patented Nov. 9, 1965 acting the acidic reaction product with an alkali hydroxide and additional hexamine to provide the final alkaline solution. Thus, the final solution contains amino derivatives of salicylic acid and hexamine as well as unreacted starting ingredients, etc., which act as buffers and the like to aid the catalytic activity of the amino derivatives.

As previously indicated, the above described amino derivatives apparently provide most of the catalytic activity and, thus, may be considered the catalytic ingredient. The amino derivatives, as the catalytic agent, are generally present in an amount of about 0.9% to about 17% by weight of the total alkaline solution used as the smoothing and grain refining agent. Thus, the amino derivatives are generally present in the range about 0.09 to 4.7 ounces per gallon (or about 0.6 to 35 grams per liter) of the plating bath. The preferred range for the amino derivatives, as previously indicated for the final alkaline solution, is about 0.1 to 1 ounce per gallon. As seen from the above discussion, it is possible, according to the present invention, to provide a concentrated solution of the above described amino derivatives and add other materials such as tartrates and alkali metal hydroxides to provide an alkaline solution for use as a smoothing and grain refining agent as well as an anode corroder. In any event however, the total amount of amino derivatives of salicylic acid made in a two-step re action with hexamine (the hexamine being used twice, while the salicylic acid is used only once) must be within the above described amounts to have an effective plating bath additive.

TABLE 1.BATH

Ingredients: General range (oz. per gal.) Copper cyanide 3 to 18 Alkali hydroxide (NaOH) /2 to 7 Alkali cyanide (potassium or sodium cyanide) 4 to 24 Reaction product of salicylic acid and hexamine made by reacting the above two ingredients to provide an intermediate reaction product which in turn is reacted again with hexamine and an alkali hydroxide 0.1 to 7.0 Alkali tartrate (potassium tartrate) 0.0 to 7.0

While the alkali hydroxide may be potassium hydroxide, it is preferred that sodium hydroxide be used as indicated in Table 1.

As to the alkali cyanide, it is highly preferred that potassium cyanide be used although sodium cyanide can be used. As indicated above the alkali cyanide is preferably used in amounts as low as 4 or 6 oz. per gal. up to about 24 oz. per gal.

Returning to the reaction product of salicylic acid and hexamine which has been found to be an outstanding anode corroder as well as an excellent smoothing and grain refining agent, the acid reaction product is made by reacting about 1 to 3 /2 moles of salicylic acid with about 1 mole of hexamine for at least about 4 hours and for better results, at least about 8 hours. After the reaction has proceeded for about 8 hours up to as long as several days, there is added about 0.05 to about 0.3 mole of additional hexamine. While the above range is generally satisfactory, the amount of additional hexamine preferably is about 0.1 to 0.2 mole. In addition, after mixing in the above described additional hexamine, and preferably within 1 to 4 hours thereafter; about 1 to 1.9 moles and preferably 1.2 to 1.6 moles of an alkali metal hydroxide, which is preferably potassium hydroxide, is added to the aqueous solution and the reaction continued for at least 2 and preferably 4 to 12 hours or even longer-up to several days if desired, although no additional advantages are obtained by longer reaction Generally the amount of water used when the hexamine and salicylic acid are first reacted is about 30 to 90 moles, and preferably 40 to 60 moles, although, as little as 20 moles or even as high as 90 to 95 moles or more can be used per mole of hexamine.

When adding the limited amount of additional hexamine (.05 to 0.3 mole based on one mole of hexamine starting material), about to 25 moles and preferably to 18 moles of water is used to make a premixed solution of the additional hexamine and the limited amount of caustic, namely the 1 to 1.9 moles of KOH or other alkali metal hydroxide.

As before discussed, to help stabilize the resultant solution and to increase its grain refining activity, generally about /2 to 3 /2 moles and preferably about 1 /2 to 2 /2 moles of potassium tartrate or other alkali metal tartrate is also added to the solution.

The present invention provides a product improvement over a process in which salicylic acid and hexamethylene tetramine (also called hexamine) are reacted at temperatures of 125190 F. at a pH of 2%. to 5 /2 for about 16 to 32 hours. At the end of this time, according to the present invention, the solution is further reacted with only about 1.2 to 1.9 of a mole of KOH in contrast to the former reaction in which 2 to 4 moles of KOH are used.

According to the present invention, a new catalytic composition is formed by the newly discovered process step in which only about half the previously used caustic is added to the reaction mixture. Only about 1 to 1.9 moles and preferably only 1.2 to 1.6 moles of potassium hydroxide are used. In addition, at this stage, the use of the small and limited amount of potassium hydroxide follows the addition of .05 to about 0.3 mole of hexamine (based on the use of one mole of hexamine, as the starting ingredient). The resulting reaction product and solution surprisingly provides a good anode corroder and an excellent smoothing and grain refining agent; the plate is denser and the cathode efficiency is improved over the previously described reaction product which was made alkaline with the use of a relatively large amount of caustic.

In the composition and method of the present invention, the pH of the resultant solution generally ranges from about 9 /2 to 10 /2 whereas the previous described solution using larger amounts of caustic and using no additional hexamine-the resultant pH was at least about 10 /2 and often about 11 /2 up to as high as 12. As used herein all pH measurements refer to those made with the glass electrode. No correction is made for sodium ion or ion concentrations.

Unexpectedly, the use of more hexamine at a dififerent stage of the caustic reaction produces a substantially more effective agent; apparently some reaction, not completely understood, takes place as a result of the double use of the hexamine.

Thus, in accordance with the present invention, the improved anode corroder and smoothing and grain refining agent (a solution) comprises a heterogeneous mixture of amino derivatives of salicylic acid including para and ortho derivatives by virtue of the reaction of salicylic acid with hexamethylene tetramine. As previously pointed out, the mixture also includes additional reaction products formed when the small amount of hexamine is added to the acid reaction product (pH: 2%. to 5 /2) and then reacted with the limited amount of KOH. The resultant solution provides an excellent anode corroder and a very good smoothing and grain refining agent for zinc copper and zinc alloys in alkaline cyanide plating baths.

The resultant solution contains some amino derivatives of salicylic acid including some p-amino salicylic acid, unreacted starting ingredients including unreacted salicylic acid and hexamine and has a final pH of preferably about 9 /2 to 10 /2.

In general, a temperature range of about to 190 F. may be employed to react the salicylic acid and hexamethylene tetramine. It has been found that the reaction is much too slow below 125 F. for commercial use. On the other hand, when a temperature of over 190 F. is used the reaction product has a much darker color and is generally not as acceptable for addition to a plating bath.

The preferred temperature range is about to F. in order to obtain the best reaction product of hexamethylene tetramine and salicylic acid. However, the best results have been found at a temperature of around 158 to 168, evidently producing the best mixture of amino derivatives of salicylic acid, which heterogeneous mixture of derivatives may be part of the reason why it is so outstanding in use as an anode corroder and a smoothing and grain refining agent.

Generally, when forming the reaction product of hexamine and salicylic acid, a pH of about 2 /2 to 5 /2 should be employed. Usually, when the pH is down around 2 /2 or under, the salicylic acid is less soluble, the solution is too acidic and reacts differently. On the other hand when the pH of the reaction mixture is about 6, the result of its use as a catalytic ingredient in a plating bath is not the same as when the pH is lower, say, around 5. Apparently the same desirable reaction product is not formed at the higher pH.

The para-amino salicylic acid derivatives are apparently the most desirable reaction products and they have the basic formula of salicylic acid in which the following groups are attached to the para-amino position of the benzene ring of the salicylic acid;

NH;|; (i; NH2; 0r NH-R; or NR1 where R is a residue of the reaction of the hexamethylene tetramine with the salicylic acid and where R is preferably a short chain alkyl group such as methyl or ethyl, of which the methyl group is highly preferred, or Where R is methylol.

In combination with the temperature range of 125 to and the pH range of 2 /2 to 5 /2, the reaction time should be at least 8 hours and preferably around 20 to 40 hoursalt-hough generally for commercial use, the reaction may be run in the neighborhood of 16 to 32 hours. During the reaction the amount of each of the ingredients used is important. Per one mole of hexamine, generally at least about 1 /2 moles of salicylic acid may be used to provide at least a portion of the desired p-amino derivative, although it is preferred that about 2 /2 up to as high at 3% to 3 /2 moles of salicylic acid be used under the above reaction conditions just decribed. As previously indicated, no more than 4 moles of salicylic acid should be used to obtain a commercially useful product.

After the reaction has been completed and all the salicylic acid has been dissolved and the gassing has ceased, an additional portion of hexamine is added and then an alkaline metal hydroxide preferably potassium should be added to bring the pH of the solution up to about 9 /2 to 10 /2. Again, while a pH of 8 /2 to 10 /2 or even as high as 12 may be useful, a pH of 9 /2 to 10 /2 is highly preferred, with the best results being around 10. Likewise, the pH of 8 /2 or less does not provide sufiicient solubility or stability.

Thus, on the basis of 1200 lbs. of salicylic acid used as one of the starting ingredients, generally 300 to 600 lbs. of hexamine may be used although the preferred amount is about 380 to 500 lbs. Likewise, the preferred amount of potassium hydroxide used is about 200 lbs. although 150 to 250 lbs. may be used with the 1200 lbs. of salicylic acid. As to the amount of water used in the reaction, generally 2300 to 2600 lbs. or up to as high as 3600 lbs. is preferred.

Also in the above process, it is highly desirable to let the acidic reaction solution stand at about 8 to 32 hours and preferably 16 to 32 hours or, best 20 to 28 hours before reacting the acidic reaction product with the additional hexamine and then the potassium hydroxide.

While adding the potassium hydroxide in accordance with the present invention, it is also preferred that about 1 to 3 moles of an alkaline metal salt of tartaric acid be used, the preferred additive being potassium tartrate although other alkali tartrates may also be added. On the basis of starting with 1200 parts by weight of salicylic acid and 400 to 500 parts of hexamine, generally about 400 to 2000 parts by weight of potassium tartrate may be added although for best results about 1000 to 1500 parts should be used.

While not desiring to be strictly held to a particular theory, it is probable that formation of one or more of the amine derivatives of salicylic acid provide the solution with its anode corroding ability and its smoothing and grain refining activity. Apparently main products and side products are formed in which the following groups are attached to the benzene ring of the salicylic acid on positions para and ortho to the carbonyl group; amino, carbonyl followed :by an amino group, NHR or -NR where R is preferably methyl or even ethyl or methylol, or amino followed by methylol.

It has been found that the reaction rate between salicylic acid and hexamine to form the acidic reaction product can be greatly increased by the use of a catalyst such as iron oxide or hydrogen peroxide.

A small amount, say about M pound of iron oxide in the form of a wire coated with rust or iron oxide, speeds up the rate of reaction in a batch of approximately 1200 pounds of salicylic acid, 400 pounds of hexamine and 300 gallons of water so that the acidic reaction product is formed in about 12 to hours as compared to about 24 to hours without the iron catalyst.

Generally, the use of a catalyst such as hydrogen peroxide and iron in the amount of about 0.001 to 0.01 percent by weight of the batch enables one to prepare the acidic reaction product two to four times or more as fast as without a catalyst.

The following examples are used to illustrate the invention and not to limit it in any way.

Example 1 A reaction product of salicylic acid and hexamine was made by mixing 1200 lbs. of salicylic acid and 400 lbs. of hexamethylene tetramine (hexamine) in an aqueous solution of 300 gallons of the solvent comprising about 2490 lbs. of water. The salicylic acid and hexamine were heated at a temperature of about 160 F. for a period of 24 hours to produce some derivatives of hexamine and salicylic acid. The temperature of the reaction was held within 3 of 160 F. at a pH of 4.3 to 4.5. The batch was vigorously stirred for the first 15 minutes and thereafter the reaction allowed to proceed with intermittent stirring. The reaction was allowed to proceed for 24 hours, the 24 hour period including an 8 hour period of cooling to room temperature.

Thereafter a premixed solution of 200 lbs. of potassium hydroxide and lbs. of hexamine dissolved in 800 lbs. of water was added with stirring to the solution to bring the pH to 9.5 and the resultant mixture reacted for 8 hours.

The resultant solution was found to be an excellent anode corroder and smoothing and grain refining agent for copper cyanide plating baths as hereinafter illustrated in detail.

A reaction product of salicylic acid and hexamine Was prepared as above described except that a rusted iron wire weighing about Mr pound was used to catalyze the reaction. The acidic reaction product was prepared in only 15 hours instead of 24 hours, and thereafter, the acidic reaction product was treated as above described to obtain an equivalent smoothing and grain refining agent and anode corroder.

6 Example 2 A copper cyanide plating bath was made using the following ingredients.

Ingredients: Ounces per gal. Copper cyanide 9 Sodium hydroxide 2 Potassium cyanide 14 Potassium tartrate 1.5 Reaction product of salicylic acid and hexamine prepared as described in Example 1 3.0

Steel sheets were plated in the above described bath using a bath temperature of F. and using a current density of 30 amperes per square foot on the anodes. The resultant coating was smooth, evenly distributed throughout the low and high current density ranges, fine grained and no sandpaper effect was visible. The anodes were smooth and no loose particles were found to be present. The bath was stable.

Steel plates were also plated in a control bath containing all the ingredients of the bath just described except for the reaction product of salicylic acid and hexamine. The resultant deposit was uneven, and coarser grained. The control :bath required continually larger additions of copper cyanide than that of Example 2.

Example 3 A bath was made up using 8 ounces per gallon of copper cyanide, 2 ounces per gallon of sodium hydroxide, 13 ounces per gallon of potassium cyanide and 4 ounces per gallon of potassium tartrate, and 8 ounces per gallon of a reaction product of salicylic acid and hexamine. The reaction product was made as described in Example 1 except 420 lbs. total of hexamine (380 initially and 40 later) was used and the reaction temperature was F. during both the hexamine reacting steps.

The resultant coating, when deposited from the bath with a current density of 40 ASP and a temperature of 150 F. was excellent, but not economical of operation.

Copper was deposited from a bath made from the same ingredients as above described (Example 3) and using the same amounts thereof except that 2 ounces per gallon of the reaction product of salicylic acid and hexamine was used. Again, the current density was 40 ASP and the bath temperature was 140 F. The bath with 2 ounces per gallon of the catalytic agent produced a commercially satisfactory coating, the coating being smooth and fine grained.

In the above examples, the temperatures of the copper plating bath may be generally from about 138 to 178 F. in order to provide good coatings. The current density may be varied all the way from slightly above 0 to as high as about 30 amperes per square foot on the anodes.

In the above working examples, equivalent ingredients as described in the previous part of the specification, may be used in whole or part for the ingredients actually used to provide similar results. For instance, sodium hydroxide can be substituted for potassium hydroxide in the baths shown in Examples 2 and 3. Also, sodium tartrate can be substituted for potassium tartrate. In addition, the reaction product made (as previously described) from a reaction temperature range from about 125 F. to F. and at a pH of about 2 /2 to 5 /2 and then reacted with additional hexamine and alkali metal hydroxide can be used in place of the particular reaction product of salicylic acid and hexamethylene tetramine used in the above examples to provide similar results.

In the above examples, methylene di-salicylic acid can be substituted in Whole or part for the salicylic acid to provide nearly equivalent results. However, for the best results, it is preferred that of the total amount mixture of acid used, the majority, and preferably at least 70% by weight, be salicylic acid.

Although, as previously indicated, the use of methylene di-salicylic acid with salicylic acid is beneficial, it is highly preferred that the amounts thereof of methylene di-salicylic acid be about /3 to mole per mole of hexamine for the best smoothing action.

It is to be understood that other modifications of this invention may be made without departing from the spirit and scope thereof.

What is claimed is:

1. An aqueous alkaline cyanide plating bath comprising about 3 to 18 ounces per gallon of a cyanide of copper, about /2 to 6 ounces per gallon of an alkali metal hydroxide, about 4 /2 to 24 ounces per gallon of an alkali metal cyanide, up to about 7.0 ounces per gallon of an alkali metal tartrate, and about 0.1 to 7.0 ounces per gallon of a reaction product of salicylic acid and hexamethylene tetra-mine in which about 1 to 4 moles of salicylic acid are reacted with 1 mole of hexamethylene tetramine in water at a temperature of about 130 to 190 F. and a pH of about 2 /2 to 5 /2 for at least about 4 hours to provide an acidic reaction mixture and thereafter reacting said acidic mixture with about 0.05 to 0.3 mole of hexamethylene tetramine and about 1 to 1% moles of an alkali hydroxide at a temperature below 190 F. to form said reaction product, said reaction product including a derivative of the following general formula:

2 E COOH where X is a member of the group consisting of -NH 0 H iiNHz, -JIIZI\IIR, l I--R, and NRq where R is a member of the group consisting of alkyl and alkylol.

2. An aqueous alkaline cyanide plating bath comprising about 3 to 18 ounces per gallon of copper cyanide, about 1 to 6 ounces per gallon of an alkali metal hydroxide, about 4 /2 to 24 ounces per gallon of an alkali metal cyanide, up to about 7.0 ounces per gallon of an alkali metal tartrate, and at least about 0.1 ounce per gallon of a reaction product of salicylic acid and hexamine, the reaction being at a temperature of about 125 to 190 F. at a pH of about 2 /2 to 5 /2 for at least about 4 hours, and the product thereafter reacted with hexamethylene tetramine and an alkali metal hydroxide and the final solution having a pH of about 8 /2 to /2, said final solution containing para-amino salicylic acid.

3. An aqueous alkaline cyanide plating bath comprising about 3 to 18 ounces per gallon of copper cyanide, about 1 to 6 ounces per gallon of an alkali metal hydroxide, about 4 /2 to 24 ounces per gallon of an alkali metal cyanide, about 0.1 to 7.0 ounces per gallon of an alkali metal tartrate, and at least about 0.1 ounce per gallon of a solution having a pH of about 8 /2 to 10 /2 and containing about 0.0009 to 4.7 ounces per gallon of a derivative of salicylic acid having the following general formula:

OH X where X is a member of the group consisting of -NH 0 0 IL l I -(,NH, NR, NR, and NR2 where R is a member of the group consisting of alkyl and alkylol.

4. An aqueous alkaline cyanide plating bath comprising about 3 to 18 ounces per gallon of copper cyanide, about 1 to 6 ounces per gallon of an alkali metal hydroxide, about 4 /2 to 24 ounces per gallon of an alkali metal cyanide, and about 0.2 to 7 ounces per gallon of a solution having a pH of about 8 /2 to 10 /2, the solution comprising an alkali metal tartrate, an alkali metal hydroxide and a derivative of salicylic acid which is a reaction product of salicylic acid and hexamine at a pH of about 4.1 to 4.6 and a temperature of about to F. for about 8 to 72 hours to provide an acidic reaction mixture and the acidic mixture further reacted with hexamine and an alkali metal hydroxide at about 70 to F. for at least about 4 hours to provide said reaction product, said derivative of salicylic acid comprising a para-substituted derivative of salicylic acid in which the substituent is a member of the group consisting of --NH 0 o H H (%NH2, l l-R, I&'R, and "NR:

where R is a member of the group consisting of alkyl and alkylol.

5. An aqueous alkaline cyanide plating bath adapted for electrolytically plating copper comprising at least about 3 ounces per gallon of copper cyanide, at least about 3 ounces per gallon of sodium hydroxide, at least about 4 /2 ounces per gallon of potassium cyanide, about .8 to 4 ounces per gallon of alkali tartrate and about 0.4 to 6 ounces per gallon of a reaction product of salicylic acid and hexamethylene tetramine in which about 1 to 4 moles of salicylic acid are reacted with 1 mole of hexamethylene tetramine in water at a temperature of about 125 to 190 F. and a pH of about 2 /2 to 5 /2 for at least about 4 hours to provide an acidic reaction mixture and thereafter reacting said acidic mixture with about 0.05 to 0.3 mole of hexamethylene tetramine and about 1 to 1% moles of an alkali hydroxide at a temperature below 190 F. to form said reaction product, said reaction product including an ortho-substituted salicylic acid in which the ortho-substituent is a member of the group consisting of NH2:

where R is a member of the group consisting of alkyl and alkylol.

6. An aqueous alkaline cyanide plating bath adapted for plating copper comprising about 5 to 16 ounces per gallon of copper cyanide about /2 to 5 ounces per gallon of sodium hydroxide, about 6 to 20 ounces per gallon of potassium cyanide, and at least about 0.1 ounce per gallon of an aqueous solution having a pH of about 8 /2 to 10 /2 and containing potassium tartrate and a reaction product of salicylic acid and hexamethylene tetramine in which about 1 to 4 moles of salicylic acid are reacted with 1 mole of hexamethylene tetramine in water at a temperature of about 125 to 190 F. and a pH of about 2 /2 to 5 /2 for at least about 4 hours to provide an acidic reaction mixture and thereafter reacting said acidic mixture with about 0.05 to 0.3 mole of hexamethylene tetramine and about 1 to 1% moles of an alkali hydroxide at a temperature below 190 F. to form said reaction product, the reaction product including para-amino salicylic acid, and a derivative of salicylic acid having the formula:

and unreacted hexamethylene tetramine.

7. A method of electrodepositing copper, the method comprising electrolyzing an aqueous alkaline cyanide solution containing copper cyanide and at least about 0.1 ounce per gallon of a reaction product of salicylic acid and hexamine in which about 1 to 4 moles of salicylic acid are reacted with 1 mole of hexamethylene tetramine in water at a temperature of about 125 to 190 F. and a pH of about 2 /2 to 5 /2 for at least about 4 hours to provide an acidic reaction mixture and thereafter reacting said acidic mixture with about 0.05 to 0.3 mole of hexamethylene tetramine and about 1 to 1% moles of an alkali hydroxide at a temperature below 190 to form said reaction product.

8. A method of electrodepositing copper, the method comprising electrolyzing'an aqueous alkaline cyanide solution containing copper cyanide and at least about 0.1 ounce per gallon of a reaction product of salicylic acid and hexamethylene tetrarnine and having the following general formula:

OH X I Where X is a member of the group consisting of NH o iNH2,i I IR, -l lR, and -NR: where R is a member of the group consisting of alkyl and alkylol.

9. A method of electrodepositing copper, the method comprising electrolyzing an aqueous alkaline cyanide solution containing copper cyanide and at least about 0.1 ounce per gallon of a reaction product of salicylic acid and hexamethylene tetrarnine including a compound having the formula:

0 I] OH said reaction product being the reaction product of salicylic acid and hexamine at a pH of about 4.1 to 4.6 and a temperature of about 125 to 170 F. for about 8 to 72 hours to provide an acidic reaction mixture and the acidic mixture further reacted with hexamine and an alkali metal hydroxide at about 70 to 190 F. for at least about 4 hours to provide said reaction product.

10. A method of making an alkaline cyanide plating bath adapted for electrodeposition of copper comprising (1) making a catalytic ingredient solution including the steps of (a) reacting about 1 to 4 moles of salicylic acid with about one mole of hexamiue at a temperature of about 125 to 190 F. and a pH of 2 /2 to /2 for at least about 4 hours to provide an acidic reaction mixture and (b) thereafter reacting the acidic mixture with about 0.05 to 0.3 mole of a hexamine and about 1 to 1.9 moles of an alkali metal hydroxide at a temperature below about 190 F. to provide the catalytic ingredient solution, and (2) mixing about 0.1 to 7.0 ounces per gallon of said solution with about 3 to 26 ounces per gallon of copper cyanide, about 1 to 20 ounces per gallon of an alkali metal hydroxide, and up to 7 ounces per gallon of an alkali metal tartrate to provide a plating bath.

11. An aqueous alkaline cyanide plating bath comprising at least about 3 ounces per gallon of a cyanide of copper, about /2 to 6 ounces per gallon of an alkali metal hydroxide, about 4 /2 to 24 ounces per gallon of an alkali metal cyanide, up to about 7.0 ounces per gallon of an alkali metal tartrate, and about 0.1 to 7.0 ounces per gallon of a reaction product of salicylic acid and hexamethylene tetrarnine in which about 1 to 4 moles of salicylic acid are reacted with 1 mole of hexamethylene tetrarnine in water at a temperature of about 130 to 190 F. and a pH of about 2 /2 to 5 /2 for at least about 4 hours to provide an acidic reaction mixture and thereafter reacting said acidic mixture with about 0.05 to 0.3 mole of hexamethylene tetrarnine and about 1 to 1% moles of an alkali hydroxide at a temperature below 190 F. to form said reaction product.

12. An aqueous alkaline cyanide plating bath comprising about 3 to 18 ounces per gallon of a cyanide of copper, about /2 to 6 ounces per gallon of an alkali metal hydroxide, about 4 /2 to 24 ounces per gallon of an alkali metal cyanide, up to about 7.0 ounces per gallon of an alkali metal tartrate, and about 0.1 to 7.0 ounces per gallon of a reaction product of salicylic acid and hexamethylene tetrarnine in which about 1 to 4 moles of salicylic acid are reacted with 1 mole of hexamethylene tetrarnine in water in the presence of a reaction catalyst at a temperature of about to F. and a pH of about 2 /2 to 5 /2 for at least about 4 hours to provide an acidic reaction mixture and thereafter reacting said acidic mixture with about 0.05 to 0.3 mole of hexamethylene tetrarnine and about 1 to 1% moles of an alkali hydroxide at a temperature below 190 F. to form said reaction product, said reaction product including a derivative of the following general formula:

OH X l where X is a member of the group consisting 'of NH 0 0 H i :NH Jll IR, I IR, and NR; where R is a member of the group consisting of alkyl and alkylol.

13. An aqueous alkaline cyanide plating bath adapted for electrolytically plating copper comprising at least about 3 ounces per gallon of copper cyanide, at least about 3 ounces per gallon of sodium hydroxide, at least about 4 /2 ounces per gallon of potassium cyanide, about .8 to 4 ounces per gallon of alkali tartrate and about 0.4 to 6 ounces per gallon of a reaction product of salicylic acid and hexamethylene tetrarnine in which about 1 to 4 moles of salicylic acid are reacted with 1 mole of hexamethylene tetrarnine in Water in the presence of iron oxide coated on an iron wire as a reaction catalyst at a temperature of about 125 to 190 F. and a pH of about 2 /2 to 5 /2 for at least about 4 hours to provide an acidic reaction mixture and thereafter reacting said acidic mixture with about 0.05 to 0.3 mole of hexamethylene tetrarnine and about 1 to 1%; moles of an alkali hydroxide at a temperature below 190 F. to form said reaction product, said reaction product including an ortho-substituted salicylic acid in which the ortho-sub stituent is a member of the group consisting of NH Where R is a member of the group consisting of alkyl and alkylol.

14. An aqueous alkaline cyanide plating bath adapted for electrolytically plating copper comprising at least about 3 ounces per gallon of copper cyanide, at least about 3 ounces per gallon of sodium hydroxide, at least about 4 /2 ounces per gallon of potassium cyanide, about .8 to 4 ounces per gallon of alkali tartrate and about 0.4 to 6 ounces per gallon of a reaction product of salicylic acid and hexamethylene tetrarnine in which about 1 to 4 moles of salicylic acid are reacted with 1 mole of hexamethylene tetrarnine in Water in presence of hydrogen peroxide as a reaction catalyst at a temperature of about 125 to 190 F. and a pH of about 2 /2 to 5 /2 for at least about 4 hours to provide an acidic reaction mixture and thereafter reacting said acidic mixture with about 0.05 to 0.3 mole of hexamethylene tetrarnine and about 1 to 1%, moles of an alkali hydroxide at a temperature below 190 F. to form said reaction product, said reaction product including an ortho-substituted salicylic acid in which the ortho-substituent is a member 'of the group consisting of -NH Where R is a member of the group consisting of alkyl and alkylol.

15. A method of making an alkaline cyanide plating bath adapted for electrodeposition of copper comprising (1) making a catalytic ingredient solution including the steps of (a) reacting about 1 to 4 moles of salicylic acid with about one mole of hexamine in the presence of a reaction catalyst until substantially all the salicylic acid is dissolved and gassing has stopped to provide an acidic reaction mixture and (b) thereafter reacting the acidic mixture with about 0.05 to 0.3 mole of hexamine and about 1 to 1.9 moles of an alkali metal hydroxide to provide the catalytic ingredient solution, and (2) mixing about 0.1 to 7.0 ounces per gallonof said solution with about 3 to 26 ounces per gallon of copper cyanide, about 1 to 20 ounces per gallon of an alkali metal hydroxide, and up to 7 ounces per gallon of an alkali metal tartrate to provide a plating bath.

16. A method of making an alkaline cyanide plating bath adapted for electrodeposition of copper comprising (1) making a catalytic ingredient solution including the steps of (a) reacting about 1 to 4 moles of salicylic acid with. about one mole of hexamine in the presence of hydrogen peroxide until substantially all the salicylic acid is dissolved and gassing has stopped to provide an acidic reaction mixture and (b) thereafter reacting the acidic mixture with about 0.05 to 0.3 mole of hexamine and about 1 to 1.9 moles of an alkali metal hydroxide to provide the catalytic ingredient solution, and (2) mixing about 0.1 to 7.0 ounces per gallon of said solution with about 3 to 26 ounces per gallon of copper cyanide, about 1 to 20 ounces per gallon of an alkali metal hydroxide, and up to 7 ounces per gallon of an alkali metal tartrate to provide a plating bath.

17. An aqueous alkaline cyanide plating bath comprising about 3 to 18 ounces per gallon of a cyanide of copper, about A: to 6 ounces per gallon of an alkali metal hydroxide, about 4 /2 to 24 ounces per gallon of an alkali metal cyanide, up to about 7.0 ounces per gallon of an alkali metal tartrate, and about 0.1 'to 7.0 ounces per gallon of a reaction product of an acid containing the following radical:

and hexamethylene tetramine in which about 1 to 4 moles of said acid are reacted with 1 mole of hexamethylene tetramine in water at a temperature of about 130 to 190 F. and a pH of about 2 /2 to /2 for at least about 4 hours to provide an acidic reaction mixture and thereafter reacting said acidic mixture with about 0.05 to 0.3 mole of hexamethylene tetramine and about 1 to 1 moles of an alkali hydroxide at a temperature below 190 F. to form said reaction product.

18. An aqueous alkaline cyanide plating bath comprising about 3 to 18 ounces per gallon of a cyanide of copper, about V2 to 6 ounces per gallon of an alkali metal hydroxide, about 4 /2 to 24 ounces per gallon of an alkali metal cyanide, up to about 7.0 ounces per gallon of an alkali metal tartrate, and about 0.1 to 7.0 ounces per gallon of a reaction product of methylene di-salicylic acid and hexamethylene tetramine in which about 1 to 4 moles of methylene di-salicylic acid are reacted with 1 mole of hexamethylene tetramine in water at a temperature of about to F. and a pH of about 2 /2 to 5%. for at least about 4 hours to provide an acidic reaction mixture and thereafter reacting said acidic mixture with about 0.05 to 0.3 mole of hexamethylene tetramine and about 1 to 194 moles of an alkali hydroxide at a temperature below 190 F. to form said reaction product.

19. A method of making an alkaline cyanide plating bath comprising the steps of (1) reacting about 1 to 4 moles of methylene di-salicylic acid with 1 mole of hexamethylene tetramine in water at a temperature of about 125 to 190 F. for at least about 4 hours to provide an acidic reaction mixture, (2) reacting the acidic reaction mixture with an alkali metal hydroxide to form a catalytic ingredient solution, and (3) thereafter mixing the catalytic ingredient solution with an aqueous alkaline cyanide solution containing copper cyanide to form a plating solution in which said ingredient solution is present in an amount of about 0.1 to 7 ounces per gallon of said plating solution.

20. A method of electrodepositing copper, the method comprising electrolyzing an aqueous alkaline cyanide solution containing copper cyanide and at least about 0.1 ounce per gallon of a reaction product of about 1 mole of hexamethylene tetramine and about 1 to 4 moles of methylene di-salicylic acid in water at about 125 to 190 F. and a pH of 2 /2 to 5 /2 for at least 4 hours in which an acidic reaction product is formed which, in turn, is reacted with an alkali metal hydroxide to form said reaction product.

21. A method of electrodepositing copper, the method comprising the steps of (1) reacting about 1 mole of hexamethylene tetramine and about 1 to 4 moles of an organic acid capable of reacting with said hexarnethylene tetramine containing the following radical:

in water at a temperature of about 125 to 190 F. at a pH of about 2 /2 to 5 /2 for at least 4 hours until substantially all the organic acid has dissolved and the gassing has ceased to form an acidic reaction product, (2) reacting the acidic reaction product with an alkali metal hydroxide to form an aqueous catalytic ingredient solution, (3) mixing about 0.1 to 7 ounces per gallon of said catalytic ingredient solution into an aqueous alkaline cyanide solution containing copper cyanide to form a plating bath, and (4) electrolyzing said bath to deposit copper.

References Cited by the Examiner UNITED STATES PATENTS 526,114 9/94 Placet et al. 204-105 1,824,636 9/31 Pink 260-2485 2,195,454 4/40 Greenspan 204-52 2,929,252 3/58 Fischer 204-52 JOHN H. MACK, Primary Examiner.

Claims (1)

1. AN AQUEOUS ALKALINE CYANIDE PLATING BATH COMPRISING ABOUT 3 TO 18 OUNCES PER GALLON OF A CYANIDE OF COPPER, ABOUT 1/2 TO 6 OUNCES PER GALLON OF AN ALKALI METAL HYDROXIDE, ABOUT 4 1/2 TO 24 OUNCES PER GALLON OF AN ALKALI METAL CYANIDE, UP TO ABOUT 7.0 OUNCES PER GALLON OF AN ALKALI METAL TARTRATE, AND ABOUT 0.1 TO 7.0 OUNCES PER GALLON OF A REACTION PRODUCT OF SALICYLIC ACID AND HEXAMETHYLENE TETRAMINE IN WHICH ABOUT 1 TO 4 MOLES OF SALICYLIC ACID ARE REACTED WITH 1 MOLE OF HEXAMETHYLENE TETRAMINE IN WATER AT A TEMPERATURE OF ABOUT 130* TO 190*F. AND A PH OF ABOUT 2 1/2 TO 5 1/2 FOR AT LEAST ABOUT 4 HOURS TO PROVIDE AN ACIDIC REACTION MIXTURE AND THEREAFTER REACTING SAID ACIDIC MIXTURE WITH ABOUT 0.05 TO 0.3 MOLE OF HEXAMETHYLENE TETRAMINE AND ABOUT 1 TO 1 9/10 MOLES OF AN ALKALI HYDROXIDE AT A TEMPERATURE BELOW 190*F. TO FORM SAID REACTION PRODUCT, SAID REACTION PRODUCT INCLUDING A DERIVATIVE OF THE FOLLOWING GENERAL FORMULA: