Triple Rings Trepanning Technology for Holes Ablated Using Nanosecond Pulse Laser in Al2O3 Ceramics Substrate

The drilling pattern significantly impacts the quality of the holes and the efficiency of laser holes processing. This study utilized triple rings laser trepanning technology to process holes in Al2O3 ceramics substrates, which were 0.25 mm thick, using a fiber nanosecond laser. The effects of the number of laser scans, laser scanning speed, the amount of defocusing, and the laser power on the geometrical features of the holes such as the hole diameter, hole roundness, and taper angle were studied. The results show that in the case of unsaturated holes, both the entrance and exit diameters expanded as the number of laser scans increased, and the taper angle reduced. In contrast, the diameter and taper angle of saturated holes remained relatively stable as the number of laser scans increased. The diameter of the holes gradually decreased as the laser scanning speed rose. The taper angle of the holes gradually increased as the laser scanning speed rose. At a scanning speed of 50 mm/s, the hole taper angle decreased to 5.51°. With a defocusing amount of 0 mm, the laser energy density on the workpiece surface was maximized, resulting in the largest exit diameter and the smallest taper angle for the hole. It is deemed appropriate to process Al2O3 ceramics substrate at a power of 30 W. Furthermore, the average roundnesses at the entrance to the holes obtained by the laser triple rings trepanning technology processed in this paper were all above 0.95, and the average roundness at the exit from the holes was above 0.93. The roundness at the entrance to the holes was better than at the exit from the holes. The results of this study will find potential application in the field of ceramic manufacturing.