CS260918B1 - Bath for arsenic-containing gold deposition - Google Patents

Abstract

Galvanic bath for gold excretion containing arsenic composed of aqueous solutions gold cyano, organic salts, or inorganic acids which may be further also contain compounds derived from hydrazine, amines and imines of the metals in which they are arsenic compounds derived from alkyl, or arylarzonic acids of the formula RASO3H2 or R1R2ASO2H. Excluded coatings they have a fine-grained structure and excel weldability with other materials. I am also expanding the field of work current densities.

Description

The present invention relates to a bath for the galvanic deposition of arsenic-containing gold.

The arsenic-containing galvanic deposition gold baths hitherto known contained arsenic in the form of arsenite in addition to the usual basic constituents. Arsenates often recommended in the patent literature do not function functionally. The desired effect of arsenic is manifested by the fine-grained coating structure, which is distinguished by its easy solderability and especially aluminum-weldability by means of ultrasound. Arsenic also greatly expands the range of usable current densities.

The conversion of arsenic was assumed a two-stage conversion, in which the first stage is an unstable AsO ⁺ cation and in the next stage the reaction of adsorbed hydrogen to the metal arsenic takes place at the cathode, according to the reaction

AsO ⁺ + 2H / ads / --- θ-> As + H 2 O

The arsenite excess in the bath also reduces arsenic to arsine at high current densities. The ease of formation of the AsO cation from arsenite, its rapid oxidation by oxygen, as well as the direct oxidation of arsenites to arsenates, which are ineffective forms, leads to a decrease in the concentration of arsenites with time. This eliminates the possibility of determining the concentration of the active ingredient arsenic, in terms of its content in both the bath and the coating. Methods for complexing arsenic with thiourea and thiosulfate according to USP 3,753,874 using citrate As according to USP 3,764,489, possibly tartrate according to Switzerland. No. 615,464, also failed to improve. In practical application the solution was chosen by the method of frequent addition of arsenites in empirically determined concentrations.

In the event of a prolonged interruption of operation it was necessary to fully renew the batch. Oxidation of arsenites to arsenates was not suppressed by the addition of other reducing agents.

The aforementioned drawbacks are overcome by the invention, which consists in the fact that the arsenic-containing galvanic deposition gold bath consists of gold cyanocomplexes, alkaline salts of organic and inorganic acids having a pH of 3 to 9, containing surfactants or complexing agents, and further comprising at least one compound of the series of alkyl- or arylarzonic acids of the formula R ₅ O _{3 3} h ₂ , or R 5A ₅ O ₃ H. In contrast to the inorganic arsenate form, organic arsenic acids, where arsenic is five-valent, undergo cathodic reduction to arsine oxides according to the reaction

RAsO ₃ H ₂ · -2RAsO

The arsine oxides may undergo cathodic reduction according to the reaction of 2RASO 4 → RA ₅ = AsR ₂ R ₅ → 2RA ₅ H _{2 in} some further steps and some of the above forms also undergo cathodic reduction to metal arsenic, a mechanism not yet described. Compared to the arsenic compounds used hitherto, the organic arzonic acids allow, by their stability and relatively low reactivity, the choice of high feed concentrations.

This limits the fluctuations in the electrolyte composition and, due to the limited solubility of arzonic acids, a self-regulating method of replenishing the solution by placing an excess of the compound in porous bags can be chosen. In the general formulas, R, R p and R _{2 are the} organic radicals -CH 1, -CH ₂ CH ₂ OH, -CH ₂ COOH, phenyl, 3-amino-4-hydroxyphenyl, or - _x > wherein X, preferably at the 2- position or

4-, is -NH ₂ , -NO ₂ , -CN, -SH, -OH, -NHR, -COOH, -RCOOH, -SO 3 H, -CONH 3, -OR, -Br, -Cl, -AsO 3 H 3, -NH -NH ₂ ((NH) CNH ₂ ). Examples of compounds generally described are alkali salts or acids: methylarzonic, phenylarzonic, 4-oxyphenylarzonic, arzonacetic, guanidarzonic, diethylarzonic, 2- (1,8-dihydroxy-3,6-disulfo-2-naphthylazo) -benzenarzonic acid, 4 1'-dimethylamino-azobenzene-4-arzone, acetophenone-4-arzone, 2-methoxy-5-vinylbenzenarzone, 4-polyethyleneimine-phenylarzone, 4-arzonophenylhydrazine.

The arsenic compounds described are applied at a concentration of 0.01 to 30 g / l in a bath containing further 1 to 50 g / l of gold as a complex cyanolate, 10 to 300 g / l of salts of organic or inorganic acids, and works best at pH 5 to 6.5. The bath may further comprise hydrazine, hydroxylamine, or alkyl and aryl derivatives thereof, amines, polyamines, imines, polyimines, or quaternary bases derived therefrom. It is used at a temperature of 20 to 80 ° C, usually at 50 to 70 ° C, at a current density of 1 to 20 A / dm ² , with excellent current efficiency.

The alkyl or arylarzonic acids of the invention are not subject to further oxidation in the gold bath and thus guarantee the stability of the bath and the coating composition. The arsenic content of the coating is determined by the stability of the selected compound, the environment, additives and working conditions. The bath finds its main application in electronics, namely for the coating of high purity coatings, especially where special demands are placed on soldering properties. Alkyl- or arylarzone 2 + compounds also enhance the gloss of coatings containing other metal ions, for example Pb or Tl ⁺ , or else additional arsenic additions in the form of other known compounds, for example arsenite. During co-deposition of the mentioned metals, the hardness and porosity of the coating are monitored. The influence of undesirable metal impurities such as Ni, Co, Cu, Fe can be suppressed by complexing agents which do not have a negative effect on the added arsenic compounds, for example ethylenediaminetetraacetic nitrilotriacetic acid, ethylenediaminetetramethylenephosphonic acid.

The invention is illustrated by four examples, by which the present invention is neither limited nor exhaustive.

Example:

Potassium cyanolate 30 g / i potassium nitrate 50 g / i acidic potassium fluoride 20 May g / i 2-aminobenzenarzonic acid 0.15 g / l dihydrazooxaldiimin 0.2 g / i sodium arsenite 10 mg / l pH adjusted with KOH 8 temperature <° C) 70 current density D _k (A / dm ² ) 15 Dec Example 2: amidosulfonic acid 20 May g / i boric acid 80 g / 1 ethylenediamine 20 May ml / l Potassium cyanolate 9 g / 1 methylarzonic acid 5 g / i phenylhydrazine 0.5 g / i pH adjusted with ammonia 7 temperature <° C) 50 current density D _k (A / dm ² ) 4 Example 3: Potassium cyanolate 12 g / i citric acid 100 ALIGN! g / i ethylenediaminetetra- methylenephosphonous 30 g / i 3-nitro-4-oxyphenylarsine oxide 0.075 g / l hydrazine hydrate 40% 20 May ml / l pH adjusted with KOH 5.5

Example 4 Phosphoric acid 85%

120 g / l potassium cyanosilate 18 g / l

4- (polyethylenemine, -phenylarzonic acid 0.05 g / l pH adjusted KOH 6.2 temperature (° C) 60 current density D ^ (A / dm) 8

The coatings deposited from the baths with the above-mentioned components exhibit perfect weldability by known methods, have high thermal stability, abrasion resistance, ductility and are semi-glossy to glossy, with minimal porosity.

Claims (1)

OBJECT OF THE INVENTION Arsenic galvanic deposition bath containing cyanocomplexes of gold, organic or inorganic acids, or their alkali salts, or amines, polyamines, imines, polyimines, or hydrazine, hydrazine derivatives or quaternary bases derived therefrom, marked in that it comprises at least one arsenic compound in an amount of 0.01 g / 1 to 30 g / 1, derived from alkyl-, arylarzonových RAsOjH acids of the formula R ,,, or RjAsOjH ⁱⁿ which R, R, R ₂ are organic the radicals -CH ₃ , -CH ₂ CH ₂ OH, -CH ₃ COOH, phenyl, or wherein X, preferably at the 2- or 4- position, is -NH 3, -NO ₂ , -CN, -SH, -OH, -NHR, -COOH, -RCOOH, -SO ₃ H, -CONH ₃ , -SR, -OR, -Br, -Cl, -AsO 3 H 4 -NH-NH ₂ , - ((= NH) CNH ₂ ).