Development and evaluation of methods for current density and layer thickness distribution prediction in electrochemical systems
The objective of this project was to develop and evaluate numerical methods to predict the current density distribution and consequently the deposition of reacting species in electrochemical systems of various natures and industrial relevance. The obtained results yield essential design tools to many branches of the electrochemical industry: plating industry (contacts, PCB'S, Smart cards, spot plating, strip and wire plating, ...) where it is a major problem to obtain uniformly deposited layers on well defined places, etching industry, anodising industry, electrochemical machining industry (e.g. electrochemical cutting) and the electrochemical recovery industry. The partnership structure contained two universities (VUB, UE), three research centres (VKI, WIT, CNRS) and four industrials (BEKAERT, BOSCH, HOOGOVENS, PHFLIPS). Based on the results obtained within the scope of the Brite-EuRam-II programme, the following has been achieved: - two general applicable electrochemistry solvers - one based on the finite element method and one based op the boundary element method - for theoretical description of electrochemical processes in two-dimensional and axisymmetrical geometries have been made. These solvers consider mass and charge transport due to diffusion, migration and convection of multicomponent solutions with homogeneous reactions in the bulk and complex charge transfer reactions at the electrodes (e.g. to model alloy plating or adsorption) and electrode growth. - an electrochemistry solver describing dilute solutions for three-dimensional situations (up to four ions) has been made. - solvers in two dimensional and axisymmetrical systems for theoretical description of electrochemical systems where ohmic and temperature effects in electrodes, ohmic and temperature effects in the solution, temperature effects produced by electrode processes, have been made. The development of solvers considering interaction between fluid flow, heat, mass and charge transfer has been started but could not be finished. - flow, mass transport, current density, thickness, temperature and potential distributions in model cells of industrial significance have been determined for the following practical electrochemical processes: - Copper deposition in a parallel plate reactor (Philips and CNRS), - Chromium deposition in an axisymmetrical reactor (Bosch) - Ni-Co codeposition in a wafer plating reactor (Bosch and CNRS), - Sn plating in an industrial plating line (Hoogovens), - Zn plating on wires (Bekaert), - Ni plating in a tubular reactor including heat effects (Bekaert), - Mass transport in a parallel plate reactor under natural convection (Exeter), - Mass transport in a three-dimensional baffled channel reactor with forced convection (Exeter), - Mass and heat transfer in a tubular reactor (Exeter). - Measured and calculated data have been compared. Although it was not possible to compare all data, it can be concluded that the agreement between simulations and measurements is very good provided that the electrochemical system is sufficiently well described. The obtained results provided a better insight in the parameters that influence the electrochemical processes. The models will enable to improve the reactor designs.