Über die elektrolytische abscheidung, das wachstum und die struktur von kupferüberzügen aus sauren elektrolyten

Abstract

The influence has been studied of some surfactant and levelling addends (derivatives of polyethers of polyprolyleneglycol type—PPG; dyes of the saphronic type; sulphur-containing aliphatic organic compounds having a disulphide group R-S-S-R; and Cl -) and combinations of them on cathodic polarization, its variation during the growth process and on the structure of electrolytically deposited copper coatings from electrolytes containing sulphuric acid. A depolarizing effect was found in the presence of Cl - and R-S-S-R and a considerable increase in the overvoltage was established in the presence of PPG. The variation of η in the presence of the saphranine derivative is complex—with an increase in current density the curve η-log i passes through a maximum, after which η becomes of the order of the overvoltage of the basic electrolyte. The influence of the addends on the variation of the polarization and on the growth process during electrolytic deposition of copper was investigated in situ. A characteristic course of the ø -τ curve was found. It is shown that, when bright copper coatings are obtained, an additional threshold energy appears which regulates the nuclei growth up to definite submicro dimensions. On the basis of literature data and our results, it is concluded that 〈110〉 is the main axis of preferred orientation for copper, though 〈111〉, 〈311〉 and 〈100〉 also appear under different specific conditions. Probable explanations for the latter phenomena are proposed. It is suggested also that the internal stresses in galvanic coatings can scarcely be responsible for the change in the axis of preferred orientation in the presence of the surface-active addends under consideration. It is suggested that the nature of the action of the addends affects the mechanism of growth of the electrolytically deposited copper coatings, and as a consequence there are changes in the ratio of the growth rates in different crystallographic directions, leading to possible changes in the texture axis. The decisive role of the formation of adsorption films and of the production of exceptionally small crystallites in forming bright copper coatings has been confirmed. At least for the case studied, perfection of texture is not important in producing bright copperplating.