Effect of Tool Electrode-Workpiece Gap in the Microchannel Formation by Electrochemical Discharge Machining

Microchannels in a glass-based substrate are widely used in biomedical, and microfluidic devices, buried redistribution lines (RDLs), etc. Tool electrode-workpiece gap and tool feed rate are very important process parameters for the fabrication of microchannels using electrochemical discharge machining (ECDM) process. This paper reports the effect of these parameters on the material removal and geometric characteristics of the microchannels formed in soda-lime glass substrates. Microchannels were fabricated with alkaline electrolytes i.e. NaOH and KOH with varying concentrations at different tool electrode-workpiece gaps. Experiments were performed using a DC power supply with high carbon steel needles as tool electrode. Finite element based thermal model showed a similar trend between the predicted microchannel depth and width with the experimental values. Compared to KOH electrolyte, higher channel depth and width were obtained with NaOH electrolyte for a given parametric setting. At higher tool electrode-workpiece gap and tool feed rate, lower channel depths were obtained. Higher microchannel widths were obtained at a gap of 20 μ m and 10 μ m with NaOH and KOH electrolyte, respectively. Tool wear was found to be decreasing as the tool electrode-workpiece gap and the tool feed rate was increased. KOH electrolyte resulted in lower tool wear compared to NaOH electrolyte.