Acid Bright Copper Plating Bath

Abstract

Polymeric phenazonium compounds, their method of preparation and their use in acid electrolytes for the deposition of bright, leveling, copper coatings on surfaces.

Description

The invention relates to new polymeric phenazonium compounds, methods for their production, as well as their use in acid electrolytes for the deposition of bright, leveling copper coatings.

It has long been known that certain organic substances can be added in small quantities to acid copper electrolytes, in particular to the most widely used copper sulfate electrolytes, in order to obtain bright copper coatings instead of a crystalline-dull deposition. For this purpose there have become known, for example, polyethylene glycol, thiourea and derivatives thereof, thiohydantoin, thiocarbaminic acid ester and thiophosphoric acid ester, which, however, no longer have any practical importance since the quality of the copper coatings obtained with them does not meet today's requirements. Thus the coatings are either too brittle or they have too little luster or, within certain current density ranges, they turn out with a relief type finish.

Also the addition of certain safranines, either alone according to the proposal of German Pat. No. 947,656 or in mixture with thiourea or the substitution products thereof according to German Pat. No. 1,004,880, leads to copper coatings with such unsatisfactory properties.

Further there has been proposed the addition of thiourea-formaldehyde condensates (German Pat. Nos. 1,152,863 and 1,165,962) and of certain compounds with C=S groups in the molecule (German Pat. No. 1,218,247).

While one obtains bright copper deposits with these additions, they do not always satisfy the increased requirements of the practice either, since their leveling action is unsatisfactory.

There has been proposed moreover the addition of polyalkylenimines in conjunction with organic thio compounds (German Pat. No. 1,246,374) and polyvinyl compounds in mixture with oxygen-containing high-molecular compounds and organic thio-compounds (German Pat. application No. 1,521,062). Such copper electrolytes, however, do not permit the use of higher cathodic current densities, and the deposited copper coatings can be nickel-plated only after intermediate treatment.

It is the object of the present invention to avoid the disadvantages of the known acid copper baths and moreover to improve these baths so that they can be operated also at higher current densities and in conjunction with other known brighteners to permit the deposition of especially uniform copper deposits, which can be nickel-plated without intermediate treatment.

This is solved according to the invention by an acid copper electrolyte which is characterized by a content of at least one compound of the general formula ##SPC1##

Wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, R.sub.6, R.sub.7, R.sub.8, and R.sub.9 are identical or different and represent hydrogen, a low alkyl or possibly substituted aryl, and R.sub.5 and R.sub.8 represent moreover monomeric or polymeric phenazonium radicals, A is an acid radical, and n an integer from 2 to 100, preferably from 4 to 20.

As lower alkyl radicals there may be named for example methyl and ethyl propyl, etc.

An aryl radical may be, for example, phenyl, which may be substituted by methyl, ethyl, methoxy or ethoxy, etc.

As acid radicals there enter into consideration, for example, those of hydro-chloric acid (Cl.sup.-), sulfuric acid (HSO.sub.4 .sup.-), nitric acid (NO.sub.3 .sup.-) and acetic acid (CH.sub.3 coo.sup.-), etc.

The radicals R.sub.5 and R.sub.8 may signify moreover, for example phenazonium radicals of the parent substance.

The quantities in which the identified compounds must be added to the copper baths in order to obtain a clear improvement of the copper deposition are surprisingly very small and amount to about 0.0005 to 0.1 g/liter, preferably 0.0005 to 0.03 g/liter.

Table I contains examples for substances according to the invention and data on the preferred concentrations in the electrolyte.

The linkage points of the radicals are not fully clarified. The linkage may take place, besides through the 3-position of the phenazonium radical, also through the 5-and the 7-position. ##SPC2##

These substances can be prepared, for example, as follows:

2 moles of an amine sulfate, e.g., 2-methyl-3-amino-6-dimethylamino-9-phenyl-phenazonium sulfate, are suspended with 4.5 liter of 20 percent sulfuric acid and diazotized within 3 hours at -5.degree. C with 650 ml nitrosylsulfuric acid containing 2.2 moles of nitrous acid. The excess nitrous acid is destroyed with amino-sulfonic acid and the reaction solution is heated to 20.degree. C, nitrogen evolving vigorously. After the nitrogen evolution has come to an end, one neutralizes with a base, e.g., potash lye.

On standing, 800 g of a blue reaction product of substance No. 3 (Table I) crystallize out. After drying, and after proper dilution, this product can be charged immediately into acid copper electrolyte. The molecular weight is about 8,000.

In the following, the preparation of some other substances according to the invention is described.

Preparation of substance No. 1

1 mole of 3-amino-5-methyl-6-dimethylamino-9-phenyl-phenazonium-hydrogen sulfate is suspended in 2 liters of 25 percent sulfuric acid and diazotized within 4 hours at -10.degree. C with 300 ml nitrosylsulfuric acid containing 1.1 mole of nitrous acid. The excess nitrous acid is destroyed with urea and the reaction solution slowly heated to 30.degree. C, nitrogen evolving vigorously. After the nitrogen evolution has come to an end, one neutralizes with gaseous ammonia. On standing, 350 g of a polymeric blue phenyl phenazonium salt crystallize out. After drying, this polymeric dye, which has a mean molecular weight of about 5,000, can be charged in proper dilution directly into acid copper electrolyte.

Preparation of substance No. 2

1 mole of 2-methyl-3-amino-6-diethylamino-9-phenyl-phenazonium chloride is suspended in 2 liters of 30% HCl and carefully diazotized within 5 hours at 10.degree. C with 1.1 mole NaNo.sub.3 .sub.' dissolved in 250 ml of water. The excess nitrous acid is destroyed with aminosulfonic acid and the reaction solution heated to 20.degree. C, nitrogen evolving vigorously. After the nitrogen evolution has come to an end, one neutralizes with potassium hydroxide. After letting stand, 300 g of the blue polymeric dye having a mean molecular weight of 4,000 can be suctioned off.

Preparation of substance No. 4

0.1 mole of 3-amino-6-dimethylemino-9-methyl-phenazonium acetate is suspended in 250 ml of glacial acetic acid and carefully diazotized at -5.degree. C with 0.12 mole of sodium nitrite, dissolved in 50 ml of water. The excess nitrous acid is destroyed with urea and the reaction solution briefly heated to boiling. After concentrating to 100 ml and cooling, the precipitated polymeric dye of a mean molecular weight of about 8,000 can be suctioned off. The yield is: 20g.

Preparation of substance No. 5

0.1 mole of 2-m35hyl-3-amino-6-phenylamino-9-phenyl-phenazonium-hydrogen sulfate is suspended in 250 ml of 35 percent sulfuric acid and diazotized at -20.degree. C with 30 ml of nitrosylsulfuric acid containing 0.12 mole of nitrous acid. The excess nitrous acid is destroyed with aminosulfonic acid and the reaction mixture slowly heated to 50.degree. C. After the nitrogen evolution has come to an end, one neutralizes with soda lye, and the polymeric dye contaminated with some sodium sulfate and having a mean molecular weight of about 300 is suctioned off. The yield is: 15g.

Preparation of substance No. 6

0.05 mole of 2-methyl-3-amino-6-dimethylamino-phenazonium hydrogen sulfate is suspended in 50 ml of 40 percent sulfuric acid and diazotized at -5.degree. C with 15 ml of nitrosylsulfuric acid containing 0.06 mole of nitrous acid. The excess nitrous acid is destroyed with aminosulfuric acid and the acid neutralized with ammonia. After standing for a short time, a blue polymeric dye having a mean molecular weight of about 10,000 can be suctioned off. The yield is: 5g.

Preparation of substance No. 7

0.05 mole of 3-amino-6-methylamino-9-phenylphenazonium acetate is suspended in 200 ml of glacial acetic acid and diazotized at -10.degree. C with 0.06 mole of sodium nitrite, dissolved in little water. After destruction of the excess nitrous acid with urea, the reaction solution is heated to 40.degree. C, concentrated, and the precipitated dye having a mean molecular weight of about 5,000 is suctioned off. The yield is 8g.

Preparation of substance No. 8

0.05 mole of 2-phenyl-3-amino-6-3thylamino-9-phenyl-phenazonium chloride is suspended in 400 ml of 30 percent hydrochloric acid and diazotized within 1 hour with 0.06 mole of sodium nitrite, dissolved in little water. After destruction of the excess nitrous acid with aminosulfonic acid, the temperature is raised to 30.degree. C; after the nitrogen evolution has come to an end, the product is extensively concentrated, and the precipitated dye having a mean molecular weight of about 2,000 is suctioned off. The yield is: 4g.

Preparation of Substance No. 9

0.05 mole of 1,2,5,8-6365amethyl-3-amino-6-diethylamino-9-phenyl-phenazonium hydrogen sulfate is dissolved in 500 ml of 50 percent sulfuric acid and diazotized at -10.degree. C with 15 ml of nitrosylsulfuric acid containing 0.06 mole of nitrous acid. The excess nitrous acid is destroyed with aminosulfonic acid, the diazonium salt is boiled down, and the sulfuric acid neutralized with ammonia. The precipitated dye having a mean molecular weight of about 2,000 is suctioned off. The yield is: 10g.

Preparation of substance No. 10

0.05 mole of 2,7-dimethyl-3-amino-6-diethylamino-9-tolyl-phenazonium chloride is suspended in 50 ml of 30 percent hydrochloric acid and carefully diazotized at -5.degree. C with 0.06 mole of sodium nitrite, dissolved in little water. The excess nitrous acid is destroyed with aminosulfonic acid, the reaction solution heated to 80.degree. C, extensively concentrated, and the precipitated dye having a mean molecular weight of about 4,000 is suctioned off. The yield is: 8g.

Preparation of substance No. 11

0.05 mole of 2,8-diphenyl-3-amino-5-methyl-6-dimethylamino-9-phenyl-phenazonium hydrogen sulfate is dissolved in 500 ml of 50 percent sulfuric acid and diazotized at -10.degree. C with 15 ml nitrosylsulfuric acid which contains 0.06 mole of nitrous acid, and then the excess nitrous acid is destroyed with aminosulfonic acid. After the diazonium compound has been boiled down, one neutralizes with ammonia and the precipitated blue dye having a mean molecular weight of about 1,500 is suctioned off. The yield is: 9g.

Preparation of substance No. 12

2 moles of 2,7-dimethyl-3,6-diamino-9-phenyl-phenazonium hydrogen sulfate are suspended with 4.5 liter of 20 percent sulfuric acid and diazotized within 5 hours at -10.degree. C with 650 ml of nitrosylsulfuric acid which contains 2.2 moles of nitrous acid. The excess nitrous acid is destroyed with aminosulfonic acid and the reaction solution is heated to 25.degree. C, nitrogen evolving vigorously. After the nitrogen evolution has come to an end, one neutralizes with ammonia, and the polymeric red-brown dye precipitated upon standing having a mean molecular weight of about 5,000 is suctioned off. The yield is: 750g of dye (contaminated with ammonium sulfate).

The invention, therefore, further relates to a method for the production of the compounds identified above.

As has been described, this method proceeds from compounds of the general formula ##SPC3##

in which the radicals R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, R.sub.6, R.sub.7, R.sub.8, R.sub.9 signify hydrogen, a low alkyl or possibly substituted aryl, and A is an acid radical, from which then the desired reaction products are formed by diazotizing in acid solution and subsequent boiling down of the resulting diazonium salts.

Advantageously the diazotizing of the amino compounds is effected in sulfuric acid, hydrochloric acid, or acetic acid solution. These acids then form the above-mentioned acid radical A. As diazotizing agents that are suitable are sodium nitrite or nitrosylsulfuric acid, etc.

The so-called boiling down of the formed diazonium salts may take place at temperatures of about 5.degree. to 100.degree. C, preferably about 10.degree. to 25.degree. C.

The reaction products precipitate from the acid reaction solution or can be precipitated therefrom by neutralization with bases, e.g., ammonia, soda or potash lye. Isolation is then effected by common methods.

As electrolyte for the deposition of copper coatings with addition of the substances according to the invention, there is generally used a sulfuric acid copper sulfate solution of the following composition:

Copper sulfate CuSo.sub.4 .sup.. 5 H.sub.2 O -- 125-260 g/liter

Sulfuric acid H.sub.2 SO.sub.4 -- 20-85 g/liter

Instead of copper sulfate, at least in part, other copper salts may be used. The sulfuric acid may be replaced partly or wholly by fluoroboric acid, phosphoric acid and/or other suitable acids. The electrolyte may be chloride-free, or this being usually advantageous for improving the luster and the leveling, it may contain chlorides, such as, alkali chlorides or hydrochloric acid, in quantities of 0.001 to 0.2 g/liter.

If one or more of the substances of the invention are added to such copper baths, the normally crystalline-dull precipitate turns out bright in a wide current density range. Besides, the cathodic current density may be increased by about 50 percent without the formation of flaws, in particular budding, in the range of high current densities. To attain a certain layer thickness, therefore, the time of exposure may be reduced accordingly and in a unit of given size more merchandise can be put through.

The substances according to the invention are also particularly suited for depositing haze-free and high-brighteners coatings in conjunction with other common luster-formers and/or wetting agents. Electrolytes containing the substances of Table I show also excellent ageing. Even after a current passage of 200-400 Ah/ltr and more, the copper coatings turn out just as highly lustrous, leveling and ductile as in a fresh batch of electrolyte. No harmful decomposition products of these substances are formed that would require purification, for example, with active carbon.

One obtains an especially clear and sudden improvement of the luster and of the leveling effect by adding the substances according to the invention to copper electrolytes which contain as brighteners oxygen-containing, high-molecular compounds and organic thio compounds, preferably comprising one or more water-solubilizing groups.

The quantities of these compounds to be added to the copper electrolyte are comprised approximately within the following limits:

Oxygen containing high molecular compounds--0.01-20.0 g/liter

preferably--0.02-8.0 g/liter.

Organic thio compounds with water

solubilizing groups -- 0.0005-0.2 g/liter,

preferably--0.01-0.1 g/liter.

Table II below contains examples of oxygen-containing, high-molecular compounds and their preferred concentrations.

TABLE II

No. Substance Preferred concentration g/liter 1 Polyvinyl alcohol 0.05-0.4 2 Carboxymethyl cellulose 0.05-0.1 3 Polyethylene glycol 0.1-5.0 4 Polypropylene glycol 0.05-1.0 5 Stearic acid polyglycol ester 0.5-8.0 6 Oleic acid polyglycol ester 0.5-5.0 7 Stearyl alcohol polyglycol ether 0.5-8.0 8 Nonylphenol-polyglycol ether 0.5-6.0

Table III below contains examples of organic thio compounds with water-colubilizing groups and their preferred concentrations.

TABLE III

No. Substance Preferred concentration g/liter 1 N,N-diethyl-dithiocarbaminic acid-(sulfopropyl)-ester, sodium salt 0.01-0.1 2 Sodium mercaptobenzothiazol- S-propanesulfonate 0.02-0.1 3 Sodium 3-mercaptopropane-1 sulfonate 0.005-0.1 4 Bis-(3-sodium sulfopropyl)- disulfide 0.005-0.2 5 Thiophosphoric acid-O-ethyl- bis-(sulfopropyl(-ester, disodium salt 0.01-0.15 6 Thiophosphoric acid-tris- (sulfopropyl)-ester, tri- sodium sulfonate 0.05-0.2 8 Thioglycolic acid 0.001-0.003

The addition of substances of Table I to copper electrolytes which contain brighteners of Tables II and III thus brings about two decisive technical advantages:

1. The applicable cathodic current density is increased up to 50 percent;

2. The leveling effect, i.e., the reduction of roughness of the ground material, is increased (measured at a layer thickness of 24 microns) from 40-50 percent to about 70-80 percent.

The concentration ratios of the individual compounds in the copper electrolyte may vary within wide limits. It has proved favorable to have a weight ratio of the substances, listed by way of example in Tables I, II and III, of about 1 : 10 : 2 to about 1 : 200 : 20.

The following examples will elucidate the use of the products according to the invention:

EXAMPLE 1

In a copper bath of the composition

220 g/liter copper sulfate (CuSO.sub.4 .sup.. 5 H.sub.2 )

50 g/liter sulfuric acid, concentrated brass sheets or pre-nickel-plated steel sheets are copper plated at an electrolyte temperature of 20.degree. to 25.degree. C with cathode movement. The deposits are crystalline-dull. When the current density exceeds 4 A/dm.sup.2, there occur at the corners of the cathode sheets loosely adhering powdery copper depositions. If one now adds to the electrolyte 0.06 g/liter of substance No. 1 (Table I), the current density can be increased to 6 A/dm.sup.2 under the same operating conditions without causing the flaws referred to above. Besides, the deposit turns out bright.

EXAMPLE 2

To a copper bath of the composition

200 g/liter copper sulfate (CuSO.sub.4 .sup.. 5 H.sub.2 O)

60 g/liter sulfuric acid, concentrated

0.05 g/liter sodium chloride

there are added as brighteners

0.6 g/liter polypropylene glycol and

0.02 g/liter sodium 3-mercaptopropane-1 sulfonate.

Although at an electrolyte temperature of 20.degree. to 25.degree. C one obtains with a current density of 6.0 A/dm.sup.2 and air agitation bright and haze-free copper coatings, the leveling of rugosities of the ground material at a layer thickness of 24 microns is only 45 percent. When adding to the bath 0.008 g/liter of substance No. 3 (Table I), the leveling increases under the same operating conditions to 76 percent, that is, it increases by 70 percent.

EXAMPLE 3

To the electrolyte according to Example 2 there are added

4.0 g/liter nonylphenol-polyglycol ether and

0.02 g/liter N,N-diethyl-dithiocarbaminic acid-(sulfopropyl)-ester, sodium salt.

At an electrolyte temperature of 20.degree. to 25.degree. C, a current density of 5.0 A/dm.sup.2 and movement of the cathode rod, the leveling effect at a layer thickness of 24 microns copper is about 50 percent. By adding 0.01 g/liter of substance No. 6 (Table I), the leveling increases to 78 percent, the increase thus being 56 percent.

Claims

What we claim is:

1. In an acid electrolyte for the deposition of bright copper coatings comprising (a) an oxygen containing high molecular weight compound selected from the group consisting of polyvinyl alcohol, carboxymethyl cellulose, polyethylene glycol, stearic acid polyglycol ester, oleic acid polycol ester, and nonylphenol polyglycol ester; (b) an organic thio compound selected from the group consisting of sodium salt of N.sub.1 N-diethyl-dithiocarbamic acid (sulfopropyl ester), sodium mercaptobenzothiazol-5-propanesulfonate, sodium 3-mercapto-propane-1-sulfonate, bis-(3-sodium sulfopropyl)-disulfide, disodium salt of thiophosphoric acid-O-ethyl-bis-(sulfopropyl) ester, trisodium salt of thiophosphoric acid-tri-(sulfopropyl) ester, and thioglycollic acid; the improvement which comprises a compound of the formula: ##SPC4##

wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, R.sub.6, R.sub.7, R.sub.8, and R.sub.9 are individually selected from the group consisting of hydrogen, lower alkyl, aryl, and substituted aryl; R.sub.5 and R.sub.8 being additionally a monomeric or polymeric phenazonium radical; A is an acid radical; and n is an interger from 2 to 100.

2. An electrolyte as set forth in claim 1, characterized in that it contains the identified compounds in quantities of 0.0005 to 0.1 g/liter, preferably 0.0005 to 0.03 g/liter.

3. An electrolyte according to claim 2, characterized in that it additionally contains oxygen-containing, high-molecular compounds and organic thio compounds with water-solubilizing groups.

4. Electrolyte according to claim 3, characterized in that it contains the oxygen-containing, high-molecular compounds in quantities of 0.01 to 20.0 g/liter, preferably 0.02 to 8.0 g/liter and the organic thio compounds with water-solubilizIng groups in quantities of 0.0005 to 0.2 g/liter, preferably 0.01 to 0.1 g/liter.

5. An electrolyte for the deposition of bright copper coatings comprising at least one compound of the structure: ##SPC5##

wherein R.sub.1 through R.sub.9 are individually selected from the group consisting of hydrogen, lower alkyl, aryl, and substituted aryl, R.sub.5 and R.sub.8 being additionally a monomeric or polymeric phenazonium radical; A is an acid radical; and n is an integer from 2 to 100.