Crack-free and 3-dimensional YAG laser processing of glass-ceramics

Abstract

When a YAG laser beam which has a diameter of 200 μm irradiates on a glass-ceramics surface with an energy less than 1.3 J/pulse, the glass remains unchanged, while the energy of which is more than 1.3 J/pulse, the glass breaks instantaneously by the incident. Therefore, it was usually considered impossible to process the glass-ceramics by YAG laser irradiation method. In this paper, a newly developed crack-free and 3-dimensional glass-ceramics processing method using YAG laser is studied. Firstly, the mechanism of the destruction was examined. It was found that the destruction was caused by a melting phenomenon which induced a high thermal stress in the workpiece. To overcome this problem, it was necessary to form a crack-free processing on the surface of workpiece and then to scatter the melt into the air. According to the experimental results, it was found that a crack-free drilled hole could be processed when YAG laser beam irradiated on the surface with paints applied to absorb the laser beam continuously. Secondly, the mechanism of growth of the drilled hole was examined. By the results of observation and analyses, it was found that the growth could be attained by melted layer on the bottom of a hole. Finally, a new crack-free and 3-dimensional YAG laser processing method was developed and discussed. Since holes are always drilled along the incident direction of laser, a crack-free and 3-dimensional drilled hole was realized by changing the YAG laser incident direction.