Fig. 1. Four stages of laser-material interaction at different power densities

Fig. 2. Experimental scheme

Fig. 3. FCCL first-order blind hole machining schematic. (a) Schematic diagram of copper foil etching by nanosecond laser concentric scanning method; (b) copper foil layer etching profile; (c) schematic diagram of spiral scanning method of etching and cleaning blind hole; (d) schematic diagram of the first-order blind hole section

Fig. 4. Laser etched copper layer morphology. (a) Radius measurement chart under optical microscope; (b) three-dimensional height map under laser confocal microscope

Fig. 5. Observation diagram of laser etching and cleaning blind hole. (a) Nanosecond laser etching and cleaning morphology under optical microscope; (b) picosecond laser etching and cleaning morphology under optical microscope;(c) nanosecond laser processing blind hole two-dimensional profile; (d) picosecond laser processing blind hole two-dimensional contour diagram

Fig. 6. Optimized parameters for picosecond laser etching and cleaning of blind hole. (a) Three-dimensional color map under laser confocal microscope; (b) profile color map; (c) three-dimensional height map; (d) profile height map

Table 1. Laser processing experimental equipment parameters

Table 2. Factor level table

Table 3. Orthogonal experimental factor design and results

Table 4. Range analysis

Table 5. Factor level table

Table 6. Orthogonal experimental factor design and results

Table 7. Range analysis

Table 8. Optimization process etching results