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Research Papers

Micromachining of Metals, Alloys, and Ceramics by Picosecond Laser Ablation

[+] Author and Article Information
Wenqian Hu, Yung C. Shin, Galen B. King

School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907

J. Manuf. Sci. Eng 132(1), 011009 (Jan 15, 2010) (7 pages) doi:10.1115/1.4000836 History: Received January 19, 2009; Revised December 04, 2009; Published January 15, 2010; Online January 15, 2010

Abstract

Microhole drilling and microstructure machining with a picosecond (ps) $Nd:YVO4$ laser (pulse duration of 10 ps) in metals, alloys, and ceramics are reported. Blind and through microholes are drilled by percussion drilling as well as trepanning drilling, where the diameters of the holes are in the range of $20–1000 μm$. Microfeatures are also machined and the flexibility of ps laser machining is demonstrated. The quality of drilled holes, e.g., recast layer, microcrack, and conicity, and that of the microstructures, are investigated by an optical microscope, a surface profilometer, or a scanning electron microscope. Ps laser ablation rate is studied by experiments and a simplified laser ablation model.

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Figures

Figure 6

(a) Three-dimensional and (b) two-dimensional profiles of the hole trepanned on a Ti-6Al-4V sample. The diameter of the hole is 200 μm with a depth of 15 μm. Laser parameters are the same as in Fig. 5.

Figure 7

Blind hole drilled on SiC/SiC. Hole diameter: 125 μm. Laser parameters are the same as in Fig. 5.

Figure 9

Patterns of a micro-accelerometer: (a) dimension of 5×5 mm2, cycle time of 0.374 s; (b) dimension of 3.82×3.82 mm2, cycle time of 0.312 s. Laser parameters are the same as in Fig. 5.

Figure 10

(a) Hole-array (diameter of each hole: 175 μm; depth: 75 μm); (b) pin-array (diameter of each pin: 250 μm, depth: 100 μm). Laser parameters are the same as in Fig. 5.

Figure 11

Material properties of Cu calculated based on the QEOS model in comparison with calculations based on electron DOS (39)

Figure 12

The simulated evolvement of material temperature during one pulse laser ablation at different instantaneous time (fluence: 2 J/cm2; wavelength: 1064 nm)

Figure 13

The variation of ablation rate with laser fluence for Cu (wavelength: 1064 nm; repetition rate: 100 kHz)

Figure 14

The variation in the ablation rate with laser fluence for Cu (wavelength: 1064 nm; repetition rate: 50 kHz)

Figure 15

The variation in the ablation rate with laser fluence for Cu (wavelength: 1064 nm; repetition rate: 10 kHz)

Figure 16

The variation in the ablation rate for Cu with laser fluence under different repetition rates: (a) ablation volume per pulse; (b) ablation volume per second (wavelength: 1064 nm)

Figure 8

Blind holes drilled on SiC/SiC. Hole diameter: 1 mm; depths: (a) 300 μm and (b) 800 μm. Laser parameters are the same as in Fig. 5.

Figure 5

Through hole trepanned in a 850-μm steel plate: (a) entrance side; (b) exit side (fluence: 2.0 J/cm2; focal spot size: 12.5 μm)

Figure 4

Holes drilled on SiC/SiC: (a) repetition rate: 10 kHz, fluence: 0.87 J/cm2, diameter: 30 μm; (b) repetition rate: 25 kHz, fluence: 0.82 J/cm2, diameter: 31 μm (focal spot size: 23.4 μm)

Figure 3

Sidewall profiles: (a) and (b) the hole drilled on steel; (c) and (d) the hole drilled on Si3N4 (fluence: 0.52 J/cm2; focal spot size: 15.6 μm)

Figure 2

Schematic of the laser control system

Figure 1

Schematic of the experimental setup of the ps laser micromachining system. A: ps Lumera laser, B: quarter-wave plate, C: beam expander, D: mirror, E: Scanlab scanner, F: fixture and workpiece, G: Aerotech three-axis positioning system, H: lens, and I: manual stage

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