Investigation of underwater laser drilling for brittle substrates

The aim of this paper is to present and discuss data on underwater laser drilling techniques for brittle substrates. Drilling under water reduced substrate defects that typically result from conventional laser drilling in air. In this study, the substrates were submerged 1 mm beneath the water surface. A CO2 laser was used to drill holes into LCD glass and alumina substrates. It was found that the underwater laser drilling quality for these materials is much better than that from laser drilling in air. Underwater laser drilling reduced the phenomena of micro-cracking and minimized the size of the area affected by heat from the laser. Also in this study, single-hole drilling and array-holes drilling by percussion and trepanning were conducted and analyzed both in air and underwater. The minimum distance between the two neighbour holes that can be obtained was much shorter in water than in air. The SEM photographs of the holes illustrate the contrast in drilling quality. The relationship between laser power, pulse repetition rate, and the hole quality was also evaluated.