Electrocrystallization of Cu, Sn, and Сu-Sn alloys from sulfate electrolytes in the presence of thiourea and N-octylpyridinium bromide: Experimental and computational studies

Galvanic deposition of copper, tin and their alloys is widely used in microelectronics, printed circuit boards, anticorrosive and decorative finishing of products for various purposes. One of the main factors determining the structural and morphological characteristics of the deposited coatings is the value of cathodic polarization during the deposition, which depends on the presence of complexing ions and surfactants. Complexation is one of the most effective and widespread ways to increase the cathodic polarization, as well as the convergence of deposition potentials of copper and tin. In this work we studied the combined effect of thiourea and N-octylpyridinium bromide additives on the kinetics of Cu, Sn, and Cu-Sn electrocrystallization from sulfuric acid electrolytes. The combined presence of these additives allows obtaining homogeneous and fine-grained Cu-Sn coatings. The results of theoretical studies agree well with experimental data and show that the introduction of thiourea and N-octylpyridinium bromide leads to the inhibition of cathodic reduction of hydrated copper(II) and tin(II) ions.