DD208831A1 - ELECTROLYTE FOR GALVANIC DEPOSITION OF GLACIATING GOLD ALLOY LAYERS - Google Patents

Abstract

The invention relates to a cyanide-based electrolyte for depositing glossy gold alloy layers of functional surfaces in electronic components and for decorative applications. The object and the object of the invention is to find for a cyanidic gold electrolyte an economic brightener combination which guarantees a low level of foreign substance incorporation in the gold alloy layer and wherein the monitoring effort for the metal-free component of the brightener combination should be low. According to the invention, the object is achieved by adding in the electrolyte consisting of potassium cyanoaurate (&) and an alkali salt of a weak organic acid a complex compound of a nickel and / or cobalt halide with methenamine and a methyl derivative of xanthine, preferably a dimethylxanthine.

Description

Title of the invention

Electrolyte for the electrodeposition of shiny gold alloy layers 5

Field of application of the invention

The invention relates to a cyanide-based electrolyte for depositing bright gold alloy layers for the surface finishing of functional surfaces in electronic components and for decorative applications.

Characteristic of the known technical solutions

Known is the electrodeposition of gold alloy layers of potassium dicyanoaurate (I) electrolytes in the weakly acidic pH range with the addition of complexes of cobalt and nickel. The complexing agents for Ni and / or cobalt are EDTA, amines and aminocarboxylic acids. It is also known to use organophosphorus chelates to deposit shiny gold alloy layers.

In WP 154 615 is proposed as an additive nickel (II) L-glutamic acid.

The prior art has the disadvantage that the organic component of the brightener combination only with very

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high effort can be detected «

In addition to this very high analytical effort, large amounts of carbon and foreign metals are incorporated, which affect the functional properties. This is already the case with carbon incorporation greater than 0.2 % (mass %) and nickel greater than 0.5 % (mass %) .

Object of the invention

The aim of the invention is to find an economical brightener combination and thereby achieve a low Oberwachungsaufwand for the metal-free component of the brightener combination.

Explanation of the essence of the invention

The. The object of the invention is to find a brightener combination for a cyanidic gold electrolyte which guarantees a low level of foreign matter incorporation in the gold alloy layer in order to improve the functional properties.

This object is achieved in that an electrolyte consisting of Kaliumdicyanoaurat (I) and an alkali metal salt of a weak organic acid, a complex compound with methenamine and a methyl derivative of xanthines, preferably a dimethylxanthine added.

The methyl derivative of xanthine, preferably the dimethylxanthine, may be added in excess, so that a bottom body is present in the electrolyte, from which the metal-free component of the brightener combination can be obtained

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For the deposition of gold alloy layers of high tarnish resistance and with very low carbon incorporation (less than 0.006 %) , the compounds have NiCl ₂ . 2 Uro 12 HpO or CoCl ₂ . 2 Uro · 10 HJD each in combination with 3,7 dimethylxanthine proved to be particularly advantageous.

This gold electrolyte according to the invention makes it possible to deposit gold alloy layers having a Co / Ni content of 0.04 to 0.07 + .004 %. The incorporation of carbon in these gold alloy layers is reduced by the addition of 3/7 dimethylxanthine of 0.27% Reduced 0.06 % . This results in particularly favorable functional properties, such as high tarnish resistance, high ductility and high reliability.

embodiment

The invention will be explained below with reference to two embodiments

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example 1

electrolyte composition

25 KAu (CN) ₂ 8-30 g / i / Kl LJ \ f ^ LJ f ~ \ II »Π _Λ ι ^ \ *>^> - Π - KJ ~ -j 30 - 60 g / i NiCl ₂ . 2 Uro. 12 H ₃ O 5-15 g / i 3.7 dimethylxanthine 3-12 g / i

The electrolyte can preferably be operated in the temperature range from 20 to 60 ^° C. The cathodic current density

in Katodenbewegung is 0.2 - 5 A / dm at a pH of preferably 4.5 to 5.5 (electrometrically).

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Example 2

Electrolyte composition

KAu (CN) ₂ 8-30 g / l C ₄ -H-Na-O-. 2H ^ O 20 - 60 g / i CoCl ₂ . 2 Uro. 10 HO 3-12 g / i 3) 7 dimethylxanthine 2 - 10 g / i

In the temperature range of 20 - 60 ⁰ C and cathode or electrolyte movement, the cathodic current density is 0.2 to

ρ 3 A / dm ο The pH is preferably 4.5 to

5.5 (electrometrically).

Claims (4)

* α ^ e * turn ^ w α », invention claim 1. electrolyte for the electrodeposition of bright gold alloy layers consisting of Kaliumdicyanoaurat (I) and the alkali metal salt of a weak organic acid, characterized in that the electrolyte is a complex compound of a nickel and / or Kobalthalogenides with methenamine and a methyl derivative of xanthines, preferably before a dimethylxanthine added. 10 2. Electrolyte according to item 1, characterized in that the methyl derivative of xanthine, preferably of dimethylxanthine, is added in excess. 3. electrolyte according to item 1 and / or 2, characterized in that as a complex compound NiCl ₂ . 2 Uro · 12 H ₂ O in combination with 3/7 dimethylxanthine is added. 4. The electrolyte according to item 1 and / or 2, characterized in that as a complex compound CoCl ₂ . 2 Uro. 10 H ₂ O in combination with 3/7 dimethylxanthine is added.