DE1230644B - Galvanic alkaline copper pyrophosphate bath - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

C23b

German class: 48 a - 5/20 *

Number: 1230 644

File number: A 40634 VI b / 48 a

Filing date: July 5, 1962

Opening day: December 15, 1966

The present invention relates to new brighteners for galvanic alkaline copper pyrophosphate baths.

According to the methods that have been used up to now, copper is electrolytically extracted from an acidic bath such as copper sulphate deposited with sulfuric acid, or from a cyanide bath with sodium or potassium cyanide. In which In the latter bath, the sodium or potassium cyanide is present in excess, so that all of the copper is in the form of the double cyanide is bound in a complex. This excess is known as "free cyanide". The baths containing cyanide are harmful to health, and there is also a problem with them, the runoff To destroy liquids. Both types of baths have the further disadvantage that it is difficult is to obtain smooth, thick coatings. As the electrolysis progresses and the copper precipitate progresses becomes thicker, the surface of the precipitate becomes dull and irregular. Indeed can in these baths the precipitate is dull and irregular at a thickness of only 0.025 to 0.051 mm will.

It is also known that copper is electrolytically deposited from a pyrophosphate bath can, thereby becoming much thicker coatings, usually five to ten times as thick as precipitates with acidic or Cyanide baths, obtained before the surface begins to get dull and irregular. If z. B. the If the following electrolyte is used, irregularities only occur when a precipitate of approximately 0.25mm thickness is obtained:

Copper pyrophosphate

(containing water) 85 to 105 g / l

Tetrapotassium pyrophosphate

(anhydrous) 300 to 375 g / l

Potassium citrate 25 g / l

When using, the preferred pH is at

8.0 to 9.5 for this bath, although electrodeposition can be obtained with such a bath at pH 3-11. The current density is up to 80 A / 9.3 dm ² , the temperature is 55 to 60 ° C, and the bath is stirred very vigorously with air. However, these baths only produce semi-glossy coatings.

It has now been found a galvanic alkaline copper pyrophosphate bath as a brightener at least 0.5 parts / million 2-mercaptothiazole or its metal salts or 2-mercaptobenzothiazole or the 6-position of which contains 1 to 4 carbon atoms substituted alkyl derivative.

The present invention provides an aqueous solution for electroplating metal substrates with

Galvanic alkaline copper pyrophosphate bath

Applicant:

Albright & Wilson (Mfg.) Limited,
Oldbury, Birmingham, Warwickshire
(Great Britain)

Representative:

Dr.-Ing. R. Poschenrieder, patent attorney,

Munich 8, Lucile-Grahn-Str. 38

Named as inventor:

Frederick Herbert Wells,

Birmingham, Warwickshire;

Derek Martin Lyde, Stourbridge, Worcestershire

(Great Britain)

Claimed priority:

Great Britain July 14, 1961 (25 584)

Copper ready, which dissolved a copper salt, an alkali pyrophosphate in an amount that is at least sufficient to form the complex X ₆ Cu (P ₂ O ₇ ) ₂ , where X denotes an alkali metal, and the brightening agent according to the invention in a concentration of at least 0 .5 parts / million to saturation. Preferably the molar ratio of pyrophosphate to copper in the solution is greater than 2.0: 1, but not greater than 2.5: 1.

In general, the electrolyte solution is prepared by adding anhydrous tetrasodium or tetrapotassium pyrophosphate is dissolved in water and then the calculated amount of copper pyrophosphate is added so that the concentration of alkali pyrophosphate 250 to 300 g / l tetrasodium pyrophosphate or 300 to 400 g / l of tetrapotassium pyrophosphate and the concentration of copper pyrophosphate is 85 to 100 g / l. The copper can be deposited electrolytically from this bath onto all common metal substrates, and because of its low alkalinity, the electrolyte attacks light metals such as aluminum and zinc, not easy at. It is therefore possible to have smooth, luminous coatings of copper on these light metals to obtain. In addition, dense, well-adhering coatings of copper can be produced on heavier metals be e.g. B. iron, steel, copper, copper alloys, nickel and lead. Has this type of baths

609 747 ^ 275

Claims (1)

3 4 the further advantage that it is not necessary that the electrolyte solutions according to the invention can Remove vapors, as is the case with the cyanide baths for the production of smooth, shiny coatings Case is. of up to 0.051 mm copper on metals for decorative That used as a glossy additive tive purposes and shiny, smooth and very thick Mercaptothiazole can be used in the Lö- 5 coatings of 0.051 to 25.4 mm or more on electrical Solutions in the free or bound state introduced Irish conductive surfaces for electroplating be, d. H. as such or as a salt thereof, are particularly used. The latter has no or other in the form of a copper or an alkali salt or little mechanical aftertreatment required, in the form of a compound from which it is formed, such as The following examples illustrate the invention. Bis-thiazyl sulfide or disulfide, which comes under the alka- io. lic conditions prevailing in the solution, example Forms mercaptothiazole or a salt thereof. In this example, a stainless steel cylinder ders suitable hydrocarbon derivatives of 2-mer- coated with copper, and the bath composition captothiazole are 2-mercaptobenzothiazole and alkyl- is the following: substituted derivatives thereof, especially δ-alkyl ^ -mer- x ₅ copper pyrophosphate captobenzthiazole, m which the alkyl group 1 to (containing water) 100 g / l Contains 4 carbon atoms. Tetrapotassium pyrophosphate The most effective concentration of shining <\ x / accprfrf> n ^ RQ σ / ι The addition in the solution for electroplating is ammonia 2 0 g / l 5 to 10 parts / million, although improved copper 2-mercaptobenzothiazole ...... 5 'parts / mil coatings with a concentration down to 0.5 parts / million can be obtained and the additives. The pH of the bath is 8.7 that used can also be used in excess up to the saturation current density 35 A / 9.3 dm ² , the temperature 6O ⁰ C, and limit of concentration can be used. the bath is filled with air and a spinning The electrolyte solution according to the invention contains a previously stirred cathode. preferably also small amounts of other additives which under the above conditions will produce a lower an improved electrolyzing process. blow of approximately 4.8 mm thickness according to 100stün-So ammonia can be electroplated in a concentration of 1 to digem. This precipitate has to be added 3 g / l in order to obtain a better anode gloss, even and smooth and especially for the bile solution. Aliphatic carcinoplasty can also be used.
organic acids, such as citric acid, tartaric acid and oxal - Example 2
acid can be added. In addition, «-amino- The electrolytic procedure of Example 1 will be added to acids. These carboxylic acids have repeated, but the deposition time is reduced to 15 times the effect of increasing the range of current density. As a result, an electrolytic deposit in which electronic deposits with good appearance 35 copper deposit was formed, which had a thickness of only little more than 0.0127 mm and obtained good mechanical properties. This will be electrolytic. The usable range of the current density can be precipitated by the addition of nitric acid, nitrate or nitrite ions. Precipitation is an excellent base. The nitrate or or chromium in the manufacture of items for nitrite ions are usually in the form of 40 decorative purposes.
Potassium or sodium salts added. These additives Example 3
are normally used after the dissolution of the bathroom Copper salt and the pyrophosphate added. The in this example will be a small brass cylinder Thiazole additive is often used as a solution in an alkali as a cathode in a bath, the copper in hydroxyd added. 45 at a concentration of 30 g / l, pyrophosphate in one When using the electrolyte, a suitable concentration of 200 g / l, ammonia is contained in a cone in a rubber-lined vessel with a concentration of 1 g / 1 and 5 parts / million 6-methyl mild steel, a steam heating coil made of 2-mercaptobenzthiazole contains. The pH of the stainless steel and a plastic snake to the bath is 8.8, and it is used at 55 ° C.
Contains stirring with air. The concentrations of 50 The brass cylinder is then electroplated with a current bath components can in a wide range density of 30 A / 9.3 dm ^{2 for} 2 hours. It vary. The higher the metal content of the bath, the more shiny and smooth the copper deposit will be, the higher the maximum current density. The 0.076 mm thick copper content of the solution obtained on the cylinder can be less than 1 g / l up to which is a perfectly satisfactory example of saturation, but 30 g / l a 55 has been found to represent electroforming ,
is good practical value. The anodes can be off electrolytic copper. The pH claim: The value of the bath is suitably between 7 and 11, Galvanic alkaline copper pyrophosphate normally between 7.5 and 9.5 and preferably bad, characterized in that it between 8.6 and 8.9. The pH can be adjusted to 60 as a brightener at least 0.5 parts / million 2 mer- by pyrophosphoric acid, nitric acid, captothiazole or its metal salts or 2-mer- Sodium hydroxide, potassium hydroxide or ammonia captobenzothiazole or its in the 6-position with solution can be added. When using is 1 to 4 carbon atoms substituted alkyl the temperature range of the bath 35 to 60 ° C, and contains derivative. a suitable current density is up to 80 A / 9.3 dm ² , 65 ■ although in the case of irregularly shaped objects, the following pamphlets are considered: as a cathode it is difficult to achieve a current density of more German patent specification No. 852 633; as 60 A / 9.3 dm ² . U.S. Patent No. 2,663,684. 609 747/275 12.66 © Bundesdruckerei Berlin