RU2361969C2 - Aqueous electrolyte for bright copper coating of steel backplates - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: invention relates to copper coating on steel backplate without application of intermediate layer; this invention can be used in mechanic engineering, radio engineering and instrument-making industry. Electrolyte contains 30-50 g of copper sulphate, 120-180 g of sodium pyrophosphate, 70-100 g of disubstituted sodium phosphate, 1-5 mmol/l of N-allyldiethylenetriamine chloride, 1-5 mmol/l of pyridine sulphur triethylammonium chloride and water up to 1 litre.

EFFECT: quality improvement of porous-free copper coatings with mirrored surface.

3 tbl, 3 ex

Description

The present invention relates to electroplating, in particular to the deposition of copper coatings on steel substrates without the use of an intermediate sublayer, and may find application in mechanical engineering, radio and instrument making.

Copper electrolytes based on pyrophosphate salts are known [1-3], which make it possible to obtain shiny, uniform, plastic coatings with good adhesion.

However, these electrolytes do not allow to obtain high-quality mirror coatings in a wide range of current densities without hydrogenation of the steel base.

The closest in technical solution and composition of the components is an electrolyte containing copper sulfate, sodium pyrophosphate, sodium phosphate [4].

The disadvantage of this electrolyte is the impossibility of obtaining high-quality mirror copper coatings (gloss 27-66 rel. Units) without hydrogenation of the steel base (ductility of steel samples is 75-80%), the current efficiency is 71-79%, and the dissipation capacity of the electrolyte is 29 -32%. Precipitation is sufficiently porous (the number of pores ranges from 4-12 per 1 cm ² ), which does not prevent the diffusion of hydrogen into the steel base. At DK 3-4 A / dm ^{2, the} sediments are coarse-crystalline, semi-brilliant, there is pitting and whisker dendrites, partially peeling from the base.

The objective of the invention is to improve the quality of non-porous copper coatings with a mirror surface.

This object is achieved in that the electrolyte, including copper sulfate, sodium pyrophosphate, sodium phosphate, additionally contains, as a hydrogenation inhibitor, N-allyldiethylenetriamine hydrochloride, having the structural formula:

and the brightening agent is pyridinesulfotriethylammonium chloride having the structural formula:

in the following ratio of components:

Copper sulfate, g 30-50 Sodium pyrophosphate, g 120-180 Sodium Phosphate bisubstituted, g 70-100 N-allyldiethylenetriamine hydrochloric acid, mmol / l 1-5 Pyridinesulfotriethylammonium Chloride, mmol / L 1-5 Water, l up to 1

The combined presence in the pyrophosphate electrolyte of a hydrogenation inhibitor, N-allyldiethylenetriamine hydrochloride and a brightener, pyridine sulfotriethylammonium chloride at their C = 5 mmol / L, provides high-quality galvanic precipitates that are well bonded to the base, without the use of an intermediate sublayer, with a minimum porosity and a minimum mirror hydrogenation of a steel base. The resulting electrolyte has a high dispersing ability.

To obtain pyrophosphate electrolyte, three component compositions were prepared (Table 1).

Table 1 Name of components I maximum Minimum II Preferably III Copper sulfate, g fifty thirty 40 Sodium pyrophosphate, g 180 120 150 Sodium phosphate, disubstituted, g one hundred 70 85 N-allyldiethylenetriamine hydrochloride, mmol / l 5 one 3 Pyridinesulfotriethylammonium chloride, mmol / L 5 one 3 Water, l one one one

The electrolyte is prepared as follows: each of the components is dissolved separately in distilled water at a temperature of 60 ° C, and the solutions are combined by stirring. The finished solution has a dark blue color. In order to remove impurities, the electrolyte is worked out for 4-6 hours, the hydrogenation inhibitor and brightener are filtered and added. Electrodeposition conditions: cathodic current density - 1.2.3.4 A / dm ² , pH 7.5-8.9, temperature 40-50 ° C, mechanical stirring using a magnetic stirrer.

Hydration of the steel base was studied by changing the ductility of steel, characterized by the number of revolutions when twisting wire samples of carbon steel U8A ⌀ 1 mm, length 110 mm to failure on a K-5 machine with a tensile load of 1.2 kg. Sample preparation consisted of polishing with micron skin and degreasing them with Viennese lime. This type of degreasing does not affect the mechanical properties of the steel, is accompanied by the removal of the surface layer of oxides and eliminates the hydrogenation of steel in the process of preparing the surface of the sample.

The ductility of steel samples (N) was determined by the formula N = (a / a ₀ ) · 100%, where a and a ₀ are the number of revolutions of wire samples to failure of the respectively coated and uncoated copper layer.

The physicomechanical properties of cathodic deposits were studied on 40 × 40 × 0.3 mm plates of steel 3. The non-working side was insulated with BF-2 glue. The cathode potential was determined using a R-375 potentiometer relative to a silver chloride electrode. The quality of copper precipitation was described using a microscope. The porosity of the coatings was determined according to GOST 9.302-79. The gloss of electrolytic coatings was measured using an FB-2 photoelectric gloss meter relative to uvolev glass, the brightness of which is 65 rel. units Precipitation hardness was measured by static indentation of the diamond pyramid on a PMT-3 device under a load of 20 g. The scattering capacity of the electrolyte was studied by the Hering-Blum method. The adhesion of the copper coating to the base (adhesion) was determined by bending wire samples at 180 ° C and applying scratches. Adhesion was considered good if peeling of the coating from the substrate did not occur.

The results of the experimental analysis are given in tables 2 and 3.

The bright-forming and inhibitory effect of the investigated organic additives is determined by their ability to adsorb on the cathode. This ability depends on the structure of the molecules. Organic additives adsorbed on the surface of the cathode form adsorption layers of molecules of these substances that isolate the cathode metal from the approach of hydroxonium ions or water molecules for discharge [5].

The essence of the invention is illustrated by examples.

Example 1

The electrodeposition of copper from the electrolyte of the prototype composition I, table 1, is accompanied by high cathodic polarization (φ = -0.57-0.70 V). The resulting galvanic precipitation is finely crystalline, uniform, brilliant (gloss 66-45 rel. Units), well adhered to the base at Dk = 1-2 A / dm ² . With an increase in current density up to 4 A / dm ^2, precipitation results in large-crystalline, semi-shiny, pitting, filamentous dendrites on the surface, partially peeling from the base. The hardness of the precipitation is 110-130 kgf / mm ² . The electrolyte has a good dispersing ability (29-32%). The precipitates forming are quite porous (the number of pores is from 4-12 per 1 cm ² ), and hydrogen, freely diffusing into the steel base, leads to a strong hydrogenation of the steel cathodes. The ductility of steel samples falls by 20-25%. The current efficiency decreases from 71 to 79% (Tables 2 and 3, No. 1).

Example 2

The electrodeposition of copper was carried out from an electrolyte of composition II of Table 1. The introduction of the organic additive pyridinesulfotriethylammonium chloride into the studied electrolyte allows increasing the cathodic potential from -0.82 to 0.90. The result is better precipitation. Moreover, under all electrolysis conditions, fine-crystalline precipitates are formed, well adhered to the base, with a mirror surface (gloss - 100 rel. Units). The hardness of galvanic deposits increases from 113 to 155 kgf / mm ² . The current efficiency is 78-83%. However, the cathodic precipitation is quite porous (pore number from 2.3 to 8.9 per 1 cm ² ), therefore, ductility due to hydrogenation decreases from 91 to 85%. With an increase in the additive concentration to 5 mmol / L, the quality of galvanic precipitation improves (Tables 2 and 3, No. 2).

Example 3

The electrodeposition of copper was carried out from composition I of table 1. In the presence of two additives of N-hydrochloric acid and pyridine sulfotriethylammonium chloride in the electrolyte, the effectiveness of the inhibitory and brightening action increases, i.e. the synergy of their action is manifested. The cathode potential shifts strongly to the region of negative values from 0.92 to 1.1 V. In this case, under all electrolysis conditions, fine-crystalline precipitates are formed, well adhered to the base, with a mirror surface (brightness of 93-100 rel. Units). The hardness of galvanic deposits varies from 143 to 189 kgf / mm ² . The high dissipating ability of the electrolyte (57-59%) provides uniform precipitation over the entire surface of the sample.

The current efficiency is quite high 89-93%. Precipitation is obtained with high-quality, with a minimum pore content (0.7 to 4 pores per 1 cm ² ), so the diffusion of hydrogen into the steel base is minimal, and there is practically no hydrogenation. The ductility of steel samples is 94-99% at C = 5 mmol / L and Dk 1-4 A / dm ² (Tables 2 and 3).

INFORMATION SOURCES

1. Copyright certificate of the USSR, 433242, cl. C23D.

2. Copyright certificate of the USSR, 466297, cl. C23D.

3. Copyright certificate of the USSR, 479823, cl. C23D.

4. Kudryavtsev N.T. Electrolytic coatings with metals. M .: Chemistry, 1979, p. 259-267.

5. Milushkin A.S., Beloglazov S.M. Hydrogenation and electrocrystallization inhibitors during copper plating and nickel plating. - L .: Publishing house of Leningrad State University, 1986, p.164.

Claims (1)

An aqueous electrolyte for the brilliant copper plating of steel substrates containing copper sulfuric acid, sodium pyrophosphoric acid, sodium phosphoric acid disubstituted, a hydrogenation inhibitor and a brightener, characterized in that it contains N-allyldiethylenetriamine hydrochloric acid formulas:

and as a brightening agent - pyridinesulfotriethylammonium chloride of the formula:

in the following ratio of components:
Sulfuric acid copper, g 30-50 Sodium pyrophosphoric acid, g 120-180 Sodium phosphoric acid disubstituted, g 70-100 N-allyldiethylenetriamine hydrochloric acid, mmol / l 1-5 Pyridinesulfotriethylammonium chloride, mmol / L 1-5 Water, l up to 1