Laser cutting of thick ceramic substrates by controlled fracture technique

The laser cutting technique by controlled fracture can be used for the cutting of thick ceramic substrates by synchronously applying a Nd:YAG laser and a CO2 laser on the substrate. The focused Nd:YAG laser is used to scribe a groove-crack on the surface of substrate and the defocused CO2 laser is used to induce thermal stress. The thermal stress concentration will occur on the tip of the groove-crack and make it extend through the substrate, followed by the substrate separating controllably along the moving path of the laser beams. Under the power output of 60 W for both CO2 laser and Nd:YAG laser, the maximum cutting speed that can be reached is 1.5 mm/s for a thick alumina sample. The reasons why the laser can break the thick substrates and why the breaking is controllable are studied in this paper. The SEM photographs of the separating surface are used to analyze the micro-mechanism of the fracture process. The temperature and stress distributions are analyzed by using the finite element software ANSYS. The relationships between laser power, cutting speed, and specimen geometry are obtained from the experimental analysis, and the phenomena are also explained from the results of stress analysis.