RU2282682C1 - Method and electrolyte for copper plating - Google Patents

Abstract

FIELD: electroplating processes, possibly electrochemical copper deposition onto steel surfaces of parts without applying additional sub-layer.

SUBSTANCE: electrolyte contains, mol/l: copper compound, 0.1 - 0.5; alkali metal hydroxide, 1.5 -5.0; potassium or sodium nitrate, 0.2 -0.8; propylene glycol, 0.6 - 2.5; hydroxide of tetraalkyl ammonium, 0.0002 -0.0006. Method comprises steps of preparation of parts and realizing electrolytic deposition of copper from such electrolyte at cathode electric current density 0.5 - 3.0 A/dm² and temperature of electrolyte 20 - 40°C.

EFFECT: improved micro-hardness, increased cohesion of highly uniform coating with base, protection capability of coating due to its lowered porosity, lowered probability of reduction of copper complexes in electrolyte mass.

5 cl, 3 ex, 1 tbl

Description

The invention relates to the field of electroplating and can be used for electrochemical copper plating of the steel surface of parts without applying an additional sublayer.

For copper plating, sulfate and cyanide electrolytes were widely used in industry. Copper cyanide electrolytes have a high dissipation ability, allow copper to be deposited directly on steel parts. Precipitation obtained from these electrolytes is characterized by a fine-crystalline structure, however, cyanide electrolytes are toxic, insufficiently stable, and have a complex multicomponent composition and are expensive.

To replace cyanide electrolytes, pyrophosphate and ammonia electrolytes deserve the most attention. They are very simple in composition, non-toxic and contain commonly available and cheap components. Their disadvantage is the narrow range of working current densities. In pyrophosphate electrolytes based on K ₄ P ₂ O _{7, the} permissible current density does not exceed 1.5 A / dm ² . In existing ammonia electrolytes, the working range of current densities is 1.2-1.8 A / dm ² . Electroplated coatings in mechanical engineering. Handbook Ed. M.A.Shlugera, Moscow, Mechanical Engineering, 1985, v. 1, pp. 93-100.

The closest analogue of the proposed electrolyte and copper plating method are the electrolyte and the method disclosed in SU 1035097 A, IPC 7 C 25 D 3/38, publ. 08/15/1983. The electrolyte contains, g / l: copper sulfate 40-60, sodium hydroxide 90-110, glycerol 40-60, melamine (2,4,6-triamino-1,3,5-triazine) 0,4-0,6 and water. Preparation of parts before copper plating is carried out in the usual way. The coating is applied at an electrolyte temperature of 10-30 ° C and a cathodic current density of 0.5-2.0 A / dm ² .

The electrolyte has a good scattering power of 50-70%, a high current efficiency of 85-95%, however, is unstable due to the recovery properties of glycerol. Coatings obtained from this electrolyte at low thicknesses have low microhardness and high porosity.

The objective of the invention is to expand the range of domestic cyanide-free copper plating electrolytes, allowing to obtain high-quality copper coatings on steel products, including complex ones.

The technical result is to increase the microhardness, the adhesion strength of the coating to the base, its uniformity, protective ability by reducing porosity, as well as reducing the likelihood of copper complexes recovering in the electrolyte volume.

The specified technical result is achieved in that the copper plating electrolyte of the steel surface of the parts includes a copper compound, an alkali metal hydroxide, a polyhydric alcohol, a nitrogen-containing organic additive and water, while the electrolyte additionally contains potassium or sodium nitrate, and the electrolyte contains sulfate or nitrate or hydroxide as a copper compound copper, propylene glycol as a polyhydric alcohol, and tetraalkylammonium hydroxide as a nitrogen-containing organic additive in the following ratio of ENTOV mol / l:

Copper compound 0.1-0.5 Alkali metal hydroxide 1,5-5,0 Potassium or sodium nitrate 0.2-0.8 Propylene glycol 0.6-2.5 Tetraalkylammonium hydroxide 0,0002-0,0006

As an alkali metal hydroxide, the electrolyte contains sodium hydroxide and / or potassium and / or lithium. In addition, the electrolyte may further comprise sodium carbonate in an amount of up to 0.3 mol / L.

As tetraalkylammonium hydroxide, you can choose tetramethylammonium hydroxide, or tetraethylammonium hydroxide, or tetrapropylammonium hydroxide, or tetrabutylammonium hydroxide, etc.

The specified technical result is also achieved by the fact that the method of copper plating the steel surface of parts includes the preparation of parts and electrolytic deposition of copper, while the deposition is carried out from an electrolyte of the above composition at a cathodic current density of 0.5-3.0 A / dm ² and the temperature of the electrolyte 20-40 ° C.

Surface preparation includes degreasing, activation in hydrochloric acid and inter-operative washing.

The proposed electrolyte is free of toxic cyanide ions and is an alkaline solution based on tetrahydroxocupritic complexes and mixed propanediol hydroxocomplexes Cu (II).

The electrolyte is prepared as follows: the calculated amounts of the components are dissolved in separate portions of water heated to 30-40 ° C, and mixed at a temperature of solutions of not more than 50 ° C. For the preparation of the solution, reagents of the “analytical grade” qualifications are used. and "chemically pure", tetrabutylammonium hydroxide (TU6-09-1369-76) - qualifications of "h". Freshly prepared electrolyte is recommended to be worked out 2-3 A · h / l, then periodically adjusted for all components.

The adhesion strength of copper coatings to steel was controlled by applying a network of scratches according to GOST 9.302-88, microhardness was determined at a load of 10 g on a PMT-3 microhardness tester, coating porosity was determined according to GOST 9.302-88.

Example 1. The steel part was degreased, washed with running, then distilled water, activated in a solution of hydrochloric acid and washed again with distilled water. The electrodeposition was carried out at a temperature of 20 ° C and a cathodic current density of 0.5 A / DM ² from an electrolyte of the following composition, mol / l:

Copper hydroxide 0.1 Potassium hydroxide 1,5 Propylene glycol 0.6 Sodium nitrate 0.2 Tetramethylammonium hydroxide 0,0002

A finely crystalline pink coating was obtained with a thickness of 5 μm with a porosity of 1 pore / cm ² and a microhardness of 720 MPa. The deposition rate of the coatings under these conditions was 2.8 μm / h. The adhesion strength of the coating to steel meets the requirements of GOST 9.302-88.

Example 2. The steel part was degreased, washed with running, then with distilled water, activated in a solution of hydrochloric acid and washed again with distilled water. The electrodeposition was carried out at a temperature of 40 ° C and a cathodic current density of 3 A / DM ² from an electrolyte of the following composition, mol / L:

Sulfur Copper 0.5 Sodium hydroxide 5,0 Propylene glycol 2,5 Potassium nitrate 0.8 Tetrabutylammonium hydroxide 0,0006

A pink crystalline coating of a color 10 μm thick with a porosity of 0.2 pore / cm ² and a microhardness of 750 MPa was obtained. The deposition rate of the coating under these conditions was 12 μm / h.

The adhesion strength of the coating to steel meets the requirements of GOST 9.302-88.

Example 3. Electrodeposition was carried out at a temperature of 35 ° C and cathodic current densities from 1.0 to 3.0 A / dm ² from an electrolyte of the following composition, mol / l:

Sulfur Copper 0.4 Sodium hydroxide 3,5 Propylene glycol 2.0 Potassium nitrate 0.6 Sodium carbonate 0.25 Tetrabutylammonium hydroxide 0,0004

Fine crystalline pink coatings were obtained with a thickness of 0.5 μm to 15 μm. An increase in the thickness of copper coatings from 0.5 μm to 10 μm leads to a decrease in porosity from 5 pores / cm ² to their complete absence. At a current density of 2 A / dm ^{2, the} microhardness of copper coatings reaches a maximum of 950 MPa. 720 MPa. The adhesion strength of the coating to steel meets the requirements of GOST 9.302-88.

The effect of current density on the deposition rate of copper coatings is given in the table.

The current density, A / DM ² 1,0 1,5 2.0 2,5 3.0 The deposition rate of microns / h 9.0 10,2 10.5 9.8 10.3

The independence of the copper deposition rate on the current density ensures the application of uniformly thick copper coatings on the surface of complex profiles.

Thus, the proposed method using a cyanide-free alkaline electrolyte based on tetrahydro-cuprite and hydroxopropanediol complexes allows to obtain solid fine-crystalline coatings of high quality with low porosity at thicknesses of more than 2 μm and high uniformity of coatings on the surface of complex profiles.

Claims (5)

1. The copper plating electrolyte of the steel surface of the parts, including a copper compound, an alkali metal hydroxide, a polyhydric alcohol, a nitrogen-containing organic additive and water, characterized in that it additionally contains potassium or sodium nitrate, as the copper compound, the electrolyte contains sulfate or nitrate or hydroxide copper, as polyhydric alcohol - propylene glycol, and as a nitrogen-containing organic additive - tetraalkylammonium hydroxide in the following ratio of components, mol / l: Copper compound 0.1-0.5 Alkali metal hydroxide 1,5-5,0 Potassium or sodium nitrate 0.2-0.8 Propylene glycol 0.6-2.5 Tetraalkylammonium hydroxide 0,0002-0,0006 2. The electrolyte according to claim 1, characterized in that it contains sodium hydroxide and / or potassium and / or lithium as an alkali metal hydroxide. 3. The electrolyte according to claim 1, characterized in that it further comprises sodium carbonate in an amount of up to 0.3 mol / L. 4. The method of copper plating the steel surface of parts, including the preparation of parts and electrolytic deposition of copper, characterized in that the deposition is carried out from the electrolyte according to claim 1 at a cathodic current density of 0.5-3.0 A / dm ² and an electrolyte temperature of 20-40 ° FROM. 5. The method according to claim 2, characterized in that the surface preparation includes degreasing, activation in hydrochloric acid and inter-operative washing.