A Study of Microdrilling of Fused Silica Using EDMed PCD Tools

Abstract

In microbiochips and microfluidic devices, microholes are a basic and important feature. The microdrilling of glass materials without cracks is still challenging in the fabrication of glass-based microdevices. This paper investigates the characteristics of microdrilling fused silica using polycrystalline diamond (PCD) tools fabricated by electrical discharge machining (EDM). In particular, peak forces, which are observed at the beginning of drilling, are discussed because crack formations are related to peak forces. To reduce peak forces and to minimize cracks, the effects of drilling conditions, such as tool shape, the surface roughness of a tool, and axial feedrate, were therefore investigated. It was observed that D-shape tools with high surface roughness was useful to reduce the peak force. In through-hole drilling, a sacrificial layer was used to prevent exit cracks, and a variable feedrate was applied to increase drilling speeds. Finally, a dressing process using EDM was conducted to recondition the worn tool’s surface.