DE1055314B - Cyanide bath and process for the galvanic deposition of shiny copper coatings - Google Patents

Description

GERMAN

The invention relates to a method for the electrodeposition of bright copper and a method for this Suitable cyanide bath containing six-membered heterocyclic thioalcohols as brighteners.

When applying nickel-chromium coatings, a galvanic base coating made of copper is often used, wherein the copper replaces part of the nickel in terms of achieving corrosion resistance. At the For example, galvanizing injection molded parts made of zinc is almost done before the nickel coating is applied generally a copper layer of substantial thickness (0.005 to 0.02 mm) is applied. One of the advantages of Invention lies in the fact that the copper deposit is exceptionally ductile and that nickel is excellent adheres to him. Another advantage is that a bright copper deposit is obtained. Be known Significant polishing costs are saved if gloss deposits are obtained directly during electroplating.

The use of gloss-forming sulfur and / or nitrogen-containing additives to acidic copper baths is known. However, experience has shown that the knowledge gained with acidic copper baths cannot be resolved cyanide baths transferred. So far, aliphatic mercaptans and thioethers have been used for cyanide baths sulfur-containing gloss additives became known.

The brighteners according to the invention are six-membered heterocyclic mercaptans in which the mercapto group (- S H) or its equivalent (- S X) is bonded to a ring carbon atom of a triazine nucleus. Here in X is an ionizable element, such as Na or K, which can replace the hydrogen of the mercapto group. At alkyl, aryl, acyl, alkoxy, fluorine, chlorine, nitro and other substituents can also be bonded to the core which do not interfere with the gloss-forming property of the connection, for example by making the connection make insoluble in the bathroom. Usually a substituent of the aforementioned type interferes with less than about 6 carbon atoms does not significantly affect the solubility of the mercaptan. In most cases an amino substituent is desirable because it gives an increased gloss. In the context of the invention, derivatives of triazine are also included understand where the substituent is relatively inactive and the gloss-forming ability of the basic ingredients the connection is not affected.

The brighteners according to the invention can be represented by the following formula:

C; ^ c-SX
ζ

Here, X denotes hydrogen or an ionizable element such as Na or K, Y denotes hydrogen or one or several relatively inactive substituents, such as alkyl, acyl, alkoxy or aryl radicals with 6 or less Cyanide bath

and method of galvanic

Deposition of shiny copper coatings

Applicant:

The Harshaw Chemical Company, Cleveland, Ohio (V. St. A.)

Representative: Dr.-Ing W. Abitz, patent attorney, Munich 27, Gaußstr. 6th

Claimed priority: V. St. v. America January 19, 1956

C atoms or chlorine, fluorine or a nitro group, Z hydrogen, an amino group or a secondary group Amino group to which another ring of the type

is bound in what

- (-; c -sx

Cc-

is a triazine ring.

It is essential that a mercapto group be present and directly attached to a ring carbon atom of the triazine nucleus is bound.

A special feature of the compounds with which, according to the invention, a bright copper deposit is formed from copper cyanide baths is deposited, lies in the fact that certain individual groups within the general class of compounds according to the invention have a different gloss-forming capacity. In general an amino substituent on the ring gives the starting mercaptan its ability to produce gloss elevated. An amino-substituted mercaptobenzene, for example, has a greater ability to produce gloss than non-substituted mercaptobenzene Mercaptobenzene. In a corresponding manner, an N atom in the ring increases the gloss-forming ability of the heterocyclic thioalcohol compared to that of the unsubstituted carbocyclic thioalcohol. For example, mercaptotriazine has a greater gloss-forming power than mercaptobenzene. A synergistic one Effect is obtained when an amino substitution is combined with a nitrogen heterocycle is. So creates an amino substituted mercaptotriazine

809 790/441

a precipitate of higher gloss than an unsubstituted mercaptotriazine.

Specific examples of the brighteners according to the invention are given in Table I. Furthermore, it results from it, within what limits and in what preferred proportions the individual substances in cyanide baths and what relative gloss is normally obtained.

Table I.

Structural formula I. 11 SH SH description general Meng
emein e, g / l
preferred shine
of the coating HS. N 2,4,6-trimercaptotriazine 0.15 until 10 2 to 6 glittering γ NH ₂ SH HS, .N _x ,
V- / \ s
Il Dithioammelide 0.15 until 10 2.5 to 6 high gloss N _c / ^N
I. SH H ₂ N, [
NH ₂ Thioammelin 0.15 until 10 2.5 to 6 high gloss

The brighteners according to the invention are limited to baths in which the ionizable copper salt Is copper cyanide. Attempts to obtain a gloss formation in other copper baths do relatively little Shown success. A potassium cyanide bath is preferably chosen as the bath, although the thioalcohols are also in Sodium cyanide baths show a gloss-forming ability.

In Table II, the lower and upper limits, as well as the preferred values of the concentration, are the Basic components of the preferred copper cyanide bath and the working conditions specified under which optimal results are obtained with the thioalcohols.

Tabel II More preferred bath More general area area 100 to 120 Copper cyanide (CuCN), g / l 85 to 225 4 to 10 free cyanide (KCN), g / l *) 3.5 to 25 145 to 175 Potassium cyanide (KCN), g / l **) 125 to 325 until ge Potassium hydroxide (KOH) until ge wish wish PH value PH value working conditions Il, 5 to 12.5 Dw value 9 to 14 60 to 7 1 Temperature, ⁰ C .... 54 to 82 2.2 to 3.8 Current density, A / dm ² 1.1 to 6.5

*) The content of free cyanide should not drop below approx. 2.5 g / l and should not rise above approx. 18 g / l.

**) The amounts of copper cyanide and potassium cyanide are preferably assigned to one another in such a way that a potassium copper cyanide complex with the approximate composition K ₂ Cu (CN) ₃ is formed. The potassium cyanide concentration is then about 1.46 times the copper cyanide concentration.

Has to buffer the bath against pn fluctuations Potassium citrate in amounts of generally about 35 to 75 g / l have proven particularly suitable. The potassium citrate also increases the cathodic current yield and promotes the formation of a finer grain in the precipitation. The potassium citrate is preferably used in amounts of about 45 to 65 g / l and acts in these Share not only as a buffer, but also promotes the creation of an even shine. Of course Other buffers, such as Rochelle salt, can also be used, albeit when Rochelle salt is used the thioalcohols do not always fully develop their gloss-forming properties.

Shiny deposits can indeed be obtained with an uninterrupted supply of direct current, a current interruption but is preferred. Such a power interruption helps avoid polarization and prevents the formation of film-like deposits on the anode. In general it is a periodic Power interruption in 8/2 second cycles, d. H. 8 seconds power supply and 2 seconds shutdown, adequate for most deposition processes.

It has been found that, in general, higher current densities can be used if small amounts of formaldehyde are added. For example, when about 1 to 20 g of formaldehyde are added per liter of bath, current densities can be used which are about 1.1 A / dm ² above the current density possible without the addition of formaldehyde.

In the context of the invention, wetting agents known per se can also be added to the bath.

Due to the stronger shine that is obtained with dithioammelide or thioammiline, these

Claims (1)

5 6 bonds preferred as brighteners. You can add up to 0.5 g of methyl carboxycellulose per liter of bath Quantities of generally about 0.15 to 10 g / l discolouration of the gloss deposit more evenly. Finding a twist, although you also get optimal results. . Usually in amounts of about 2.5 to 6.0 g / l example receives. You can use these ingredients on their own or in the basic bath according to Example 1 use in combination. You can also use the gloss and, under the same conditions, as a gloss former Formers according to the invention together with other thioammelin in amounts of about 2.5 to 4 g / l. Of the known brighteners can be used. The precipitate obtained is glossy. By addition It has been found that when using about 5 g of formaldehyde and 0.1 to 0.5 g of methyl-compliant brightener, methyl carboxycellulose, the same carboxycellulose per liter bath, the current density can be increased by a moderate coloration of the precipitate and about 1.1 A / dm ² above the Maxiferner, which is possible without addition, tends to increase the gloss. The methyl mal value increases and, moreover, a more uniform carboxycellulose can be obtained in amounts of up to about 1 g / l discoloration of the precipitate.
Find a turn. At a higher concentration, the
Bad a certain precipitation that leads to rough depressions 15 beat leads. Preferably the methyl carboxy claims: cellulose used in amounts of 0.1-0.5 g / l. 1. Cyanide bath for electrodeposition The inventive method may be Verwen- _VO n bright copper coatings, characterized marked dung of soluble as well as insoluble anodes shows that it is a six-membered brightener will; soluble copper anodes are preferred. Gloss- 20 contains heterocyclic mercaptan whose mercaptan Precipitation is deposited on zinc and steel cathodes on a ring carbon atom of a triazine nucleus keep. However, other metal cathodes can also be bonded. are used as they are usually used in copper cyanide 2nd bath according to claim 1, characterized in that bathrooms find use, z. B. copper and brass that it contains a mercaptan on its triazine core cathodes. In general, the gloss-forming capacity is linked to an amino group, which in turn is linked to with regard to the thickness of the precipitate cannot be connected to a triazine ring, restricts. So can good gloss deposits from 3rd bath according to claim 1 or 2, characterized by Manufacture about 0.009 to 5.1 mm thickness and more. records that there is dithioammelide or thioammelin in The following examples explain the use of an amount of about 0.15 to 10 g / l, various brighteners according to the invention in copper 30 4th bath according to claim 1 to 3, characterized thereby cyanide baths. records that it is about 85 to 225 g / l, preferably 100 Example 1 k ' ^s ^ O g / l, copper cyanide and about 125 to 350 g / l, preferably 145 to 185 g / l, potassium cyanide A finally containing the following ingredients 2.5 to 25 g / l, preferably 4 to 10 g / l, Copper cyanide bath is made using 2,4,6-tri- 35 potassium cyanide in the form of free cyanide, mercaptotriazine as a brightener in amounts of about 2 5. Bath according to claim 4, characterized in that operated up to 4 g / l. that it also contains potassium citrate in an amount of Copper cyanide (CuCN) 100 to 120 g / l ^et ™ ^a J ⁵ j> ^{is 7} {sweetness Potassium cyanide (KCN) 145 to 175 g / l ⁶ ' ^bath " ^{according to} claim 4 or 5, characterized by free cyanide (KCN) 4 to 10 g / l * ° ^ chnet that there is also formaldehyde in a KOH up to a _pH value from about 1 contains up to 20 g / l. from 11 5 to 12 5 according to claim 4 to 6, characterized Potassium citrate .... '. 45 to 65 g / l indicates that there is also methyl carboxycellulose in in an amount up to about 1 g / l. It is made with a cathode current density of about 2.7 45.8. up to 3.8 A / dm ² and a bath temperature of about 60 to zender copper coatings using cyanide 71 ° C worked. The precipitate obtained is shiny. dic baths according to claim 1 to 7, characterized The addition of about 5 to 15 g of formaldehyde per liter indicates that with a cathode current density Bath can increase the current density by about 1.1 A / dm ² over that of about 1.1 to 6.5 A / dm ² , preferably 2.2 to Maximum value can be increased at the without formaldehyde 50 3.8 A / dm ² , a bath temperature of about 54 to in addition, no dull precipitate is formed. 82 ° C, preferably 60 to 71 ⁰ C and at a pH _π . . , "From about 9 to 14, preferably about 11.5 to 12.5, ^Bels P ^{iel 2 is being} worked on. It is used in the basic bath according to Example 1 as brightening agent dithioammelide in amounts of 2.5 to 55. Publications considered: 4 g / l. The at a bath temperature of 60 to 71 ⁰ C and German Patent Nos. 837 029, 932 709; Lower USA.-Patent Nos. 2495668, 2663684, 2700020, obtained a current density of 2.2 to 3.8 A / dm ^2, Schlag is high-gloss. By adding about 0.1 2,733,198. © 809 790/441 4. 59