Numerical Simulation of Copper Deposition in the Hull Cell Based on Butler-Volmer Kinetics

Abstract

In industry plating baths are often characterized by visual evaluation of a Hull cell deposition. In an academic approach, kinetic parameters are determined with cyclic voltammetry to obtain a deeper understanding of reaction mechanisms. In this paper we combine both approaches and show how via numerical simulations based on the boundary element method kinetic parameters can be extracted from Hull cell experiments. This combined method enables a better understanding of industrial electroplating processes without losing important information about coating and visual appearance. The validation is done in an acidic copper system using the kinetic parameters obtained from cyclic voltammetry for simulating the current density distribution and the cell voltage of a Hull cell deposition, followed by a comparison with experimental data. As an additional insight obtained from this study, the presence of O 2 lowers the anodic transfer coefficient, while Clions in the electrolyte increase the exchange current density.

Reverse Numerical Simulation of Kinetic Parameters from Acidic Copper Hull Cell Deposition

“…The electrolyte was prepared with deionised water and reagent grade chemicals. For the experiments, the Hull cell setup with 0.25 A for 30 min and with typical pretreatments (activation of the anode and pretreatment of the cathode, for further details, see 1 ) was used at ambient temperature. The current was chosen to study the low current region and to avoid poor deposition quality at high current densities in a system without additives by reducing the influence of material transport inhibition.…”

“…2 However, due to the condition of the acidic copper electrolyte containing oxygen and chloride, the experimental results of cyclic voltammetry described by Kovácsovics et al 1 showed a deviation from the known two-step mechanism. In order to not restrict the reaction kinetics presented here by an anticipatory assumption of the mechanism and due to the negligible influence of the anode on the current density distribution in the Hull cell, the anodic transfer coefficient was set to the value of α = 1.13, a determined in a previous experiment, 1 for the subsequent studies. The necessary time for building the database depends on the selected range and step size of α c and j .…”

“…The main idea behind our approach is using the reverse of the method described by Kovácsovics et al 1 It is based on calculating a database and comparing the current density distribution of a Hull cell deposition to the best fitting counterpart in the database to estimate kinetic parameters.…”

“…The necessary time for building the database depends on the selected range and step size of α c and j . 0,eff We use the parameter = •j j 2 0,eff 0 to consider the two-step mechanism of the copper deposition, as described by Kovácsovics et al 1 For a specific current and electrolyte conductivity, the construction of the database is only necessary once. The main step of the reverse determination is calculating the minimum deviation for the electric resistance between the experimental and simulated data.…”

“…List of symbols j j j , , A combined factor of the Butler-Volmer kinetic parameters [-] In our previous paper, 1 we demonstrated how numerical simulations can be used to obtain Hull cell deposition curves based on the kinetic parameters of the Butler-Volmer equation. The thickness distribution is obtained by inserting known kinetic parameters in the simulation using the Butler-Volmer equation as a boundary condition.…”