Numerical and experimental investigations to analyze the micro-hole drilling process in spark-assisted chemical engraving (SACE)

Abstract

With the increased utilization of glass in micro-electromechanical systems (MEMS) applications, need is generated to produce micro-features on glass with excellent surface quality, i.e., better hole circularity and less thermal cracks. Spark-assisted chemical engraving (SACE) has proven to be an emerging and reliable technology for micro-machining of glass that includes local joule heating of the work material for its removal. However, some problems need to be covered in the micro-hole drilling process such as low machining depth, low aspect ratio, high thermal cracks, and an increase in machining time with the increase in depth. Moreover, few finite element modeling (FEM) studies have been reported to analyze the material removal aspects in SACE. This present study developed the FEM-based thermal model to analyze the material removal rate (MRR) and investigated the different machining conditions to improve the micro-hole drilling process in SACE. Improvement in depth and aspect ratio can be achieved by using a different tool’s shape which variably enhances the flow of electrolytes and thereby increases the formation rate of gas film. Pointed and cylindrical tools were used for micro-drilling operations. MRR, hole entrance diameter, machining depth, aspect ratio, thermal cracks, and machining time were observed under different machining conditions. FEM study revealed that MRR improves with the increase in both the applied voltage and electrolyte concentration. The MRR was predicted by utilizing the plots of temperature distributions and was found in accordance with the experimental results of MRR. The experimental study concluded that the pointed tool produced micro-holes with a higher machining depth and aspect ratio at an improved machining rate, while the cylindrical tool produced micro-holes with a smaller number of thermal cracks and better circularity.