Flexible tooling for localized electrochemical deposition with wire-electrodischarge grinding

Abstract

This paper describes the application of electrodes with varying diameters made by wire-electrodischarge grinding (WEDG) in the localized electrochemical deposition (LECD) of nickel micro-columns. WEDG has been widely used in the fabrication of extremely fine cylindrical pins mainly used as tool electrodes for micro-electrodischarge machining of fine holes or as contoured cores in the electroforming of micropipes. Similar to electrolysis, LECD is a new deposition technique which uses conductive tips as anode electrodes to focus the electric field that drives the process such that deposition is largely localized on the smooth cathode surface beneath the anode tip. The degree of localization depends mainly on the anode diameter, the anode-to-cathode separation, the insulation or non-insulation of the anode, and the computer-controlled motion of the anode tip during the deposition process. Considering the parameter of anode tip diameter alone, the ability to fabricate tips of differing diameters will allow a wide range in resolution of structures deposited via LECD. WEDG provides this flexible tooling for LECD at the micro to meso-scale. Experiments were carried out on a custom-built LECD rig on which nickel columns were deposited from a nickel sulphamate plating solution, using stationary and rotating WEDG-ed tips with diameters ranging from 25 to 120 μm. Aspect ratios of up to 9:1 were achieved and deposited column diameters were found to display a linear relationship with the WEDG-ed anode tip diameters. Electrode rotation was also found to improve column cross-sectional roundness and overall dimensional control for fabrication with LECD.