RU2113553C1 - Copper plating electrolyte - Google Patents

Abstract

FIELD: electrodeposition. SUBSTANCE: invention is related specifically to deposition of electrolytic compact smooth and glittering or dull coats of copper or its alloys and to manufacture of galvanoplastic articles. Copper plating electrolyte includes copper nitrate 24.2-96.8 g and dimethylsulphoxide up to 1.0 l. High-quality coats of pure copper with current output up to 98.1 per cent are deposited from proposed plating electrolyte at current densities of 0.2-0.5 A/sq.dm at temperatures of 15-45 C. EFFECT: improved quality of plating. 1 tbl

Description

 The invention relates to the field of electroplating, in particular, to electrolytes from non-aqueous solutions, and can be used to obtain electrolytic coatings with pure copper, electroplating with copper-based alloys, composite coatings, electroplating products from copper and its alloys, etc.

 Copper electrolytes based on non-aqueous solvents are known, such as methanol, ethanol, formamide, pyridine, etc. However, as a rule, it is not possible to obtain high-current coatings with high current output from these electrolytes (Fialkov Yu.Ya. Grishcheno V.E. Electrodeposition of metals from non-aqueous solutions - Kiev: Naukova Dumka, 1985, 255 pp .; Savenko P.V., Trachuk S.V. Electrodeposition of copper from non-aqueous solutions.Department in Ukrainian NIIINTI - Kiev: UkrNIINTI, N 856 - 4 to 88-17 s).

 Copper electrolytes based on aqueous solutions of copper nitrate (P) are known, containing nitric acid and additives of chloride ions and organic surfactants (for example, Pilite S.P., Vitko R.K., Matulis Yu.Yu. and others. / Sat. Research in the field of electrodeposition of metals. T.1 - Vilnius: Ed. AN Lit. SSR, 1973, p. 49; Donchenko M.I., Pakalyuk AT, Motronyuk T.I. et al. / Izv. universities, Chemistry and chemical engineering, 1988, t.31, N 7, p.64), additives of surface-active inorganic and organic anions (Gritsan D.N., Radchenkova A.P., Pravda A.A. et al. / Abstracts of the 7th All-Conference on Electroche Mii.V.1 - Chernivtsi, 1988, p. 351). The presence of nitric acid in the electrolyte, which causes corrosion activity, complicates the use of these electrolytes.

The closest in technical essence and the achieved results to the proposed technical solution is an electrolyte based on a mixture of an organic bipolar solvent with water: a mixture of dimethylformamide with water (50: 50), in which a donor of copper ions, namely copper chloride (67 - 269 g / l or 0.5 - 2.0 M) or bromine chloride (112 - 446 g / l or 0.5 - 2.0 M). At temperatures of 20-60 ^o C and some cathodic current densities (200 - 2200 A / m ² or 0.2 - 2.2 A / dm ² ) an opaque precipitate is deposited from this electrolyte (UK patent N 1410764). However, the dissimilarity of the anions and the difference in the nature of the organic solvent completely change the chemical properties of the solutions and make them different.

 A disadvantage of the known electrolyte is the impossibility of obtaining high-quality galvanic coatings from halide solutions of copper.

In order to precipitate a compact and dense electroplating, which is qualitative in appearance, from pure copper, which does not contain any inclusions that reduce its electrical conductivity and ductility, a copper plating electrolyte containing an organic solvent, dimethyl sulfoxide, and copper (II) nitrate as a donor of copper ions is proposed three-water, in the following ratio of components, g / l:
Copper (II) nitrate, three-water Cu (NO ₃ ) ₂ • 3H ₂ O - 24.2 - 96.8
Dimethyl sulfoxide - Up to 1 L
An analysis of the patent and scientific and technical literature shows that no information was found on the use of crystalline hydrates (three-water, six-water, etc.) of copper nitrate in copper plating electrolytes based on an organic solvent.

 However, it is known to use crystalline hydrates of copper nitrate, including and three-water, to obtain pure copper (II) oxide, copper-containing catalysts, as a fungicide, mordant for dyeing fabrics, as an energetic oxidizing agent (Chukurov P.M. // Chemical Encyclopedia, vol. 2 - M .: Sov. encyclopedia, 1990 , p. 669; Ripan R., Chityanu I. Inorganic chemistry, vol. 2 - M .: Mir, 1972, p. 715).

The proposed electrolyte is simple in composition and due to the combination in the solvent (dimethyl sulfoxide) of surface-active and complex-forming (with ions of Cu ²⁺ and NO $\genfrac{}{}{0ex}{}{\text{-}}{\text{3}}$ properties, does not require the introduction of other additives that affect the kinetics of the recovery of copper and nitrate ions. The electrodeposition of a copper coating from the proposed electrolyte is carried out at ordinary (room, 15 - 25 ^o C) and low (below 45 ^o C) temperatures.

 The invention is illustrated by the following examples.

 Copper electrolyte is prepared by dissolving crystalline (three-water) copper (II) nitrate, continuous stirring, in dimethyl sulfoxide. Since a freshly prepared electrolyte does not have stable properties, for example, electrical conductivity, it must be kept at room temperature for 24 hours.

The electrodeposition of copper was carried out in a glass cell with a water jacket with a working volume of 100 cm ³ . A copper foil cathode with a thickness of 0.5 mm, dimensions 25 x 30 mm ² with a total working surface of 15 cm ^{2 was} hung between two parallel platinum anodes with the same dimensions.

A universal (stabilized) power source UIP-2 was used as a current source. The temperature in the electrolytic cell was maintained using a UTU-4 thermostat with an accuracy of 0.5 ^o .

The copper cathode is pre-degreased in a 10% KOH solution at room temperature, after washing with hot water (60 ^o C) it is etched in a solution of the composition, g / l:
Nitric acid - 80 - 100
Sulfuric acid - 750 - 800
Hydrochloric acid - 2 - 3
It is washed again with water and dried. Before immersion in the electrolyte, the cathode is decapitated in 15% NH ₄ OH, washed with water, ethanol and quickly dried over a hot plate.

The current efficiency of copper was determined based on the Faraday law using a copper coulometer. The copper current output (BTCu) was calculated by the formula
BTCu = (m _e / m _k ) • 100%,
Where
m _e - the mass of copper released during the electrodeposition on the cathode of the studied electrolyte;
m _k is the mass of copper released at the same time at the cathode of a copper coulometer (Workshop on Applied Electrochemistry (N.G. Bakhchisaraitsyan, Yu.V. Borisoglebsky, G.K. Burkat et al., 3rd ed., revised .- L .: Chemistry, 1990, p.271).

 The quality of the resulting electrolytic copper deposits was evaluated visually.

 The copper (II) nitrate used in the work was subjected to purification by ordinary recrystallization (Karjakin, Yu. V. Angelov, I.I. Pure Chemical Substances. Ed. , dimethyl sulfoxide - by distillation under vacuum (Knyazev D.A., Chistozvonova O.S., Klinsky GD and others. Properties, preparations and purification methods of dimethyl sulfoxide. Dep. in ONIIT Chemistry, Cherkasy, N 22 hp - D84 - 29 s. )

During the electrolysis of a solution containing 24.2 g of three-water copper nitrate dissolved in dimethyl sulfoxide, the volume of which was brought to 1 l, at a cathodic current density of 0.5 A dm ^-2 and a temperature of 45 ^o C for 60 min at the cathode of the electrolyzer and copper was released by the coulometer in quantities of 0.0898 and 0.0915 g, respectively. The current efficiency of copper is 98.1%. The electrolytic precipitate is a uniform dense copper layer of a characteristic pink color with some brilliance (table, experiment 4).

 Other experiments were carried out in a similar way. The conditions of electrodeposition, the composition of the electrolyte and the results of the experiments are presented in the table.

 The best quality electrolytic copper precipitation, as can be seen from the table, was obtained from solutions containing copper nitrate crystalline hydrate in amounts of 24.2 - 96.8 g / l. The highest quality precipitates were obtained (experiments 2–4, 6–8, 10, 11) with maximum copper current outputs of 92.8–98.1%.

 The proposed copper plating electrolyte, thus expanding the range of copper plating electrolytes, allows to obtain high-quality copper coatings with a high (up to 98.1%) metal current output. The electrolyte in comparison with the prototype has the advantages of simplicity of composition, low temperatures of release of the coating, corrosion non-aggressiveness and high purity of the resulting coating.

Claims (1)

A copper plating electrolyte containing a copper ion donor, dimethyl sulfoxide and water, characterized in that it contains three-water copper nitrate as a copper ion donor in the following ratio of components:
Copper (II) nitrate three-water, g - 24.2 - 96.8
Dimethyl sulfoxide, l - Up to 1.

Images