SU1650786A1 - Electrolyte for copper plating - Google Patents

Abstract

The invention relates to electroplating, namely to sulfuric acid electrolytes of copper plating, and can be used for electrochemical copper plating of a steel surface without an additional sublayer of another metal. The goal is to reduce internal stresses and increase the plasticity of copper deposits. Copper electrolyte contains, g / l: sulfuric-acid copper 200-300, sulfuric acid 70-100, chromic anhydride 0.7-1.2, thiourea 0.02-0.2 and water. The addition of thiourea further reduces internal stresses and increases the plasticity of copper deposits by increasing their purity. 2 tab.

Description

The invention relates to electroplating, namely to sulfuric acid electrolytes of copper plating, and can be used for electrochemical copper plating of a steel surface without an additional sublayer of another metal.

The purpose of the invention is to reduce internal stresses and increase the plasticity of copper deposits.

Copper electrolyte contains, g / l: sulfuric acid copper in water 200 - 300; sulfuric acid 70-100; chromic anhydride 0.7 - 1.2; thiourea 0.02 - 0.2 and water.

The combined effect of the two additives is associated with the formation of a cathode complex, which helps to suppress the contact release of copper on the steel surface, and provides high-quality adhesion of the copper sediment to the metal surface. The recovery of copper ions proceeds through the near-electrode film along a bridge mechanism without the fate of products of intermediate reduction of thiourea, as a result of which the precipitates obtained have a higher purity and, as a result, increased pastille and small internal stresses.

At the same time, using a combination of thiourea with chromic anhydride allows the process not with a graphite anode, as in the prototype, but with soluble copper, which during electrolyte operation automatically compensates for the loss of copper ions during their recovery at the cathode, since the cathode and anode outputs current equal to each other (100%). In the absence of thiourea, chromium (III) ions formed on the cathode cannot be oxidized on the anode from the chalk, since the addition of thiourea additionally binds chromium ions in the cathode surface complex. This eliminates the need for the oxidation of chromium (III) ions to six o

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valence state as required in a known electrolyte.

The electrolyte is prepared as follows. Sulfuric acid, chromic anhydride and thiourea are introduced into an aqueous solution of sulfuric acid copper. Each new component is introduced after the previous one has completely dissolved. The electrolyte is then made up to the desired volume.

The resulting galvanic deposits of copper on a steel base have good adhesion, have a light pink surface. To obtain a uniform coating over the entire surface, the part is immersed in the electrolyte under current.

The electrolyte compositions, including the boundary composition of the components and deposition modes, the characteristics of the coatings are given in the table.

The precipitates obtained from the proposed electrolyte in the current density range from 1 to 6 A / dm are obtained by one-time semi-brightest with low roughness and good adhesion of the steel surface, which is facilitated by the introduction of thiourea, without which brittle copper precipitates are obtained. Without the addition of chromic anhydride and thiourea, it is not possible to obtain a qualitative compact sediment.

In tab. 1 shows the compositions of tested electrolytes; in tab. 2 - data of comparative tests of copper coatings to determine the value of their internal stresses and plasticity.

The process of obtaining coatings is carried out at a temperature of 23 ± 1 ° C. The magnitude of the internal stresses is measured when the thickness of the precipitate is 25 microns.

The magnitude of the internal stresses is measured by the displacement of an annealed wire cathode with a thickness of 0.5 mm. fixed by mechanotron.

The plasticity values of the resulting coatings are estimated by the proportion of plastic deformations during compression of copper coatings 25 μm thick, to a load of 8 MPa.

Claims (1)

From the table it can be seen that the proposed copper electrolyte allows to obtain coatings with a smaller amount of internal stresses and greater plasticity. The invention The copper electrolyte containing sulfuric copper, sulfuric acid, chromic anhydride and water, characterized in that, in order to reduce internal stresses and increase the plasticity of copper deposits, it additionally contains thiourea in the following ratio of components, g / l: sulfur -acid Copper copper 200 - 300 Sulfuric acid70-100 Chromic anhydride 0.7 - 1.2 Thiourea0.02 - 0.2 35 Table 1 table 2 The continuation of the table.2.