(1) P.D. / Pulse N. (μm / pulse) *
(2) Pulse N. x 150mJ / P.D. ( mJ / μm
(3) P.D. / Pulse N. × 150mJ ( μm / mJ )
(4) 1 DaudE = μm / μ
(5) 1 DaudV = μm 3/ m
where P.D. is the Penetration Depth for blind drills like to Drill Height for Passing Holes . So, a Laser Beam Drilling Efficiency unit, the Daud ( 1 DaudE = μm / mJ or 1 DaudV = μm3/ mJ ) could be adopted as a quantitative parameter to see how the process of micro-drilling, by that type of laser on that material, has been efficient. In this paper, for example, some results obtained on some different Metals and Alloys, by using a Nd- YAG Laser, λ2 ( 2nd harm. ) 532 nm - Pulse Width 11ns - E 150 mJ / pulse, Focusing Lens in BK7 (borosilicate ) - 60mm F. L. and Optical Focused Spot on the surface of the target, are considered and evaluated. A laser percussion micro-drilling, fig.1, process has been tested on 11 different Aluminium and its alloys (Series 1000 - 2000 - 5000 and 6000; in particular AA1090 - AA2024 - AA5083 - AA5754 - AA6082 and AA 8090 ), on 7 different Cu and its alloys. The thicknesses tested for Al alloys ranging on 70 - 240 - 480 - 800 and 1000 μm as well as 50 - 100 - 180 - 280 and 500 μm for Cu and Alloys. A Nd-YAG Laser Source, (QUANTEL), YG 580 type, was used for the experiments. This laser , in Q-Switch Mode, has the following characteristics :
(1) Repetition Rates ( Single Shot, 2Hz and 10Hz ), Focusing Lens BK7 - 60 mm F.L.
(2) λ2 532 nm - Pulse Width 11ns - E 150 mJ/pulse.
The aim of this work was :
(1) the possibility to obtain micro-drills on the range from 500 to 25 μm diameters with some Aspect Ratio high values. At the same time the realization of some "blind drills", "passing holes" as well as "straight and tilted holes was proved;
(2) The possible adoption of a Laser Beam Drilling Efficiency (L.B.D.E.) unit, the DaudE and / or DaudV.