CS263437B1 - Galvanic bath for shining evil + a - Google Patents

Abstract

A bath for the galvanic deposition of shiny gold coatings from an electrolyte of pK 3 to 6 formed by an alkali metal cyanate, furthermore combining organic and inorganic acids containing pyridine-hanine as an effective functional component.

Description

The invention relates to a bath for the electroplating of shiny coatings of gold or gold alloys from acidic electrolytes.

Previously known baths for electrolytic bright gold plating from electrolytes, which contained gold as cyanogold and were used at pH 3 to 5, used to achieve bright coatings by adding metals, mainly nickel and cobalt. Their co-precipitation into the coating made it possible to achieve the desired shade of gold and increase the hardness. At the same time, however, there was coprecipitation of alloying metal compounds into the coating. The cause was found to be the released hydrogen cyanide, which converts metal ions into an ineffective or even insoluble form. The resulting ballast compounds are incorporated into the coating during electrolysis, by sorption or cataphoresis. The use of substituted forms of amides or oxamides according to Čs.AO 229 970 made it possible to achieve bright gold coatings without the addition of alloying metals or with their reduced amount. The use of the above additives without further addition of metals assumed a significant increase in the concentration of the organic additive. This resulted in a decrease in current efficiency. The required parameters were also achieved at a low additive concentration, after the addition of 0.01 to 0.05 g/l Co or Ni, and the bath was used mainly for the production of contacts and connectors. However, a decrease in gold purity is undesirable when gold plating base metals for semiconductor elements in electronics.

The described disadvantages are eliminated by the invention, the essence of which lies in a bath for the galvanic deposition of shiny gold coatings or gold alloys from acidic electrolytes containing additions of pyridine-N-imine to a bath which further contains gold cyano complexes, organic or inorganic acids or their salts, or also metal complexants or metal admixtures, e.g. Co, Ni, Sn, in which the concentration of pyridine-N-imine is 0.01 to 1 g/1 and the pH adjusted with alkali hydroxides or ammonium hydroxide is 3 to δ. In an aqueous solution of pyridine-N-imine, an equilibrium is established

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between the basic imine form I., the hydrated form II., and the dimer III.

Determining the contribution of the described forms I to III to the effect of gilding is difficult, but empirical tests given in the composition examples prove that the addition of pyridine-N-imine leads to the achievement of shiny gold coatings that have the parameters required in electronics, are well weldable and which can also be alloyed with additions of other metals if necessary.

Example 1:

potassium cyanate 3g/l citric acid 100g/l Ν,Ν,N,Ν'-tetrakishydroxypropylethylenediamine 10g/l pyridine-N-imine 0.02g/l pH adjusted with KOH 3.5 The bath is used in vibration plating device for evil valuation of small parts at 50° C and current density of 0.05 to 1 A/d Example 2: potassium cyanate .12 g/l sodium glucoheptonate 150g/l boric acid 20g/l potassium pyrophosphate 20g/l pyridine-N-imine 0.05g/l Coatings deposited at temperatures between 40 and 60°C and Λ current density 0.1 to 4 A/drn are highly glossy.

Claims (1)

SUBJECT OF THE INVENTION A bath for the galvanic deposition of shiny coatings of gold or gold alloys from acid electrolytes, pH 3 to 6, containing gold cyanocomplexes, organic or inorganic acids and bases, or salts thereof, or complexing agents, characterized in that it contains pyridine- N-imine in an amount of 0.005 g / l to 1 g / l.