High Aspect Ratio Glass Micromachining by Multi-Pass Electrochemical Discharge Based Micromilling Technique

Fabrication of deep microchannels by a simple electrochemical discharge based multi-pass micromilling technique is reported. The effect of electrolyte concentration, tool feed rate, number of passes, and power supply on the geometric characteristics of the microchannel is presented. Numerical analysis was performed to predict the shapes and sizes of the microchannels, which matched quite well with the experimental values. An increment in the channel depth was observed with an increase in the machining voltage and the total number of passes. Through-channels were etched in a 400 μm thick glass substrate at machining voltages of 55 V and 60 V after the 6 th and 5 th pass respectively using a 10% KOH electrolyte. For deeper microchannels (>500μm), a higher electrolyte concentration, i.e., 30% was required, that had enhanced chemical etching, resulting in higher depth and relatively smooth channel surface. Microchannels having depth >1100 μm was obtained with a 30% KOH electrolyte concentration after the 16 th pass. The number of passes required to achieve higher channel depth depends on the combined effect of voltage and the electrolyte concentration. The tool wear rate was higher at higher machining voltages. Moderate machining voltage, pulse frequency, and higher concentration are recommended for deep glass micromachining applications.