Simple optical apparatus for trepanning and percussion microdrilling using pulsed green Nd:YAG laser

Laser microdrilling is becoming an important tool in a wide spectrum of industrial applications due to the possibility to produce microholes in almost any type of materials. The purpose of this study was to create a simple and efficient optical apparatus that could produce microdrillings by either percussion or trepanning methods. The developed system is composed by a nanosecond Nd:YAG laser operating at 532 nm and one convergent lens with off-center optical axis of 1′. For the trepanning method the lens spins in its geometrical center at constant angular speed of 350 rpm. Typical microholes diameters obtained in metallic aluminum were in the range of 22 to 95 μm and 70 to 150 μm for the percussion and trepanning methods, respectively. Typical drilling velocities were in the order of 10 μm/s for applied fluences ranging from 22 to 150 J/cm² for both methods. The values of the ratio between input and output diameters were 0.30 and 0.25 for microholes obtained by percussion and trepanning methods, respectively. The best microholes morphology was obtained using the trepanning method. The results for both methods are discussed based on the optical and thermal properties of the material processed and the constructed apparatus.