Modelling for fabrication of microelectrodes by localized electrochemical deposition for micro-electrodischarge machining

Abstract

This paper presents the theoretical modelling and experimental investigation on the effect of different localized electrochemical deposition (LECD) parameters for fabricating a variety of microstructures. In order to estimate the rate of the deposition and the condition of the deposited structure, a set of mathematical relations is developed with the help of Faraday's laws of electrolysis and the Butler–Volmer equation. Mathematical simulation results are validated by experimental results. In this experimental process copper was deposited on the cathode surface. The variation in structure of the deposited electrode is achieved by changing the shape of a non-conductive mask. This mask is fabricated by an on-machine micromilling process and it is kept in contact with the cathode surface. The whole system is immersed in an acidified copper sulphate plating solution. This study gives a clear indication of the optimized operating range for the LECD process in order to fabricate high aspect ratio microstructures. Futhermore, the performance of the LECD electrode is evaluated by the fabrication of microholes on high-melting-point material such as a stainless steel workpiece.

Microelectrochemical Deposition

“…For a frequency value higher than 100 kHz, the deposition rate is comparatively lower than the lower frequencies. In contrast, for frequency values lower than 100 kHz, the deposition rate is comparatively higher than the lower frequencies (17). It is well known that the frequency has an inverse relationship with the pulse period.…”

“…For a voltage value lower than 1.5 V, the deposition rate is comparatively lower than the higher voltages. The results indicate that below 1.5 V, the supplied energy is not sufficient to deposit the material at a higher rate (17).…”

“…It is probable that the area surrounding the anode becomes depleted of ions for discharging the anode. At the same time, a high volume of hydrogen gas is produced at the anode (17). …”

“…Owing to the increased deposition energy, the number of ions also increases for deposition, which causes the deposition rate to increase. Alternatively, when the frequency increases, the condition will be the reverse (17). …”

“…A reasonable explanation is that this study is conducted on a fixed pulse frequency where the pulse period is fixed and the duty ratio is the ratio of pulse on time and pulse period. This is why, due to the decrease of duty ratio, the pulse on time also decreases (17). If the pulse on time is much less than the double-layer time constant, then there will be strong damping in the system.…”