Abstract

Visible and UV lasers with nanosecond pulse durations, diffraction-limited beam quality and high pulse repetition rates have demonstrated micro-ablation in a wide variety of materials with sub-micron precision and sub-micron-sized heat-affected zones. The copper vapour laser (CVL) is one of the important industrial lasers for micro-ablation applications. Manufacturing applications for the CVL include orifice drilling in fuel injection components and inkjet printers, micro-milling of micromoulds, via hole drilling in printed circuit boards and silicon machining. Recent advances in higher power (100W visible, 5W UV), diffraction-limited, compact CVLs are opening new possibilities for manufacturing with this class of nanosecond laser.

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References

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  1. X. Chen and X. Liu, "Short pulsed laser machining: how short is short enough?," J. Laser Applications 11, 268-272 (1999).
    [CrossRef]
  2. M.D. Shirk and P.A. Molian, "A review of ultrashort pulsed laser ablation of materials," J. Laser Applications 10, 18-28 (1998).
    [CrossRef]
  3. D. Kapitan, D. W. Coutts and C. E. Webb, "On pulsed laser ablation of metals: comparing the relative importance of thermal diffusion in the nanosecond-femtosecond regime," Conference on Lasers and Electro-Optics - Europe paper CThH76 (1998).
  4. M.R.H. Knowles, G. Rutterford , A.I. Bell, A.J. Andrews, G. Foster-Turner and A.J. Kearsley, "Sub-micron and high precision micro-machining using nanosecond," Proceedings of ICALEO 98 85e, 112-120 (1998).
  5. H.K. Tönshoff, C. Momma, A. Ostendorf, S. Nolte and G. Kamlage, "Microdrilling of metals with ultrashort laser pulses," J. Laser Applications 12, 23-27 (2000).
    [CrossRef]
  6. M. Knowles, R. Benfield, A. Andrews and A. Kearsley, "Development of high power compact copper vapour lasers," Advanced High-Power Lasers and Applications 99 M. Osinski, H.T. Power, K.Toyoda, eds., Proc SPIE 3889, paper 3889-63, (1999).
  7. D. K Kapitan, D. W. Coutts and C. E. Webb, "Efficient Generation of near diffraction-limited beam-quality output from medium-scale copper vapour laser oscillators," IEEE J. Qu. Electronics 34, 419-426 (1998).
    [CrossRef]
  8. M.R.H. Knowles, A.I. Bell,.G. Rutterford, G. Foster-Turner and A.J. Kearsley, "Advances in copper lasers for micromachining," Proceedings of ICALEO 97 82, (1997).
  9. M.R.H. Knowles, R. Foster-Turner, A.I. Bell, A.J. Kearsley, A.P. Hoult, S.W. Lim, and H. Bisset, "Drilling of shallow angled holes in aerospace alloys using a copper laser," Proceedings of ICALEO 95 80, 321-330, (1995).
  10. M.R.H. Knowles, A.J. Kearsley., R. Foster-Turner., J.E. Abbott, J.M. Boaler., K.H. Errey, "Visualization of small hole drilling using a copper laser," Proceedings of ICALEO 94 79, 352-361, (1994).
  11. J.J. Chang, B.E. Warner, E.P. Dragon and M.W. Martinez, "Precision micromachining with pulsed green lasers," J. Laser Applications 10, 285-291 (1998).
    [CrossRef]
  12. R.I. Trickett, M.J. Withford and D.J. Brown, "4.7W, 255nm source based on second-harmonic generation of a copper vapour laser in cesium lithium borate," Opt. Lett. 23, 189-191, 1998.
    [CrossRef]
  13. A.C. Glover., D.W. Coutts, D.J. Ramsay and J.A. Piper, "Progress in high-speed UV micro-machining with high repetition rate frequency doubled copper vapour lasers," Proceedings of ICALEO 94 79, 343-351, (1994).
  14. A.C. Glover,.M.J. Withford, E.K. Illy and J.A. Piper "Ablation threshold and etch rate measurements in high-speed ultra-violent micro-machining of polymers with uv-copper vapour lasers," Proceedings of ICALEO 95 80, 361-370, (1995).
  15. C. Körner, R. Mayerhofer, M. Hartmann and H.W. Bergmann, "Physical and material aspects in using visible laser pulses of nanosecond duration for ablation," Appl. Phys. A 63, 123-131, (1996).
    [CrossRef]
  16. J.J. Chang and B.E. Warner, "Laser-plasma interaction during visible laser ablation of metals," Appl. Phys. Lett. 69, 473-475, (1996).
    [CrossRef]
  17. H.K. Tonshoff, F. von Alvensleben, A. Ostendorf, G. Kamlage, S. Nolte, "Micromachining of metals using ultrashort laser pulses," IJEM Review International Journal of Electrical Machining 4, 1-6, 1999.
  18. http:/www.oxfordlasers.demon.co.uk/movies/ddi_drilling_large.mov
  19. http:/www.oxfordlasers.demon.co.uk/movies/ddi_drilling_close.mov

Other (19)

X. Chen and X. Liu, "Short pulsed laser machining: how short is short enough?," J. Laser Applications 11, 268-272 (1999).
[CrossRef]

M.D. Shirk and P.A. Molian, "A review of ultrashort pulsed laser ablation of materials," J. Laser Applications 10, 18-28 (1998).
[CrossRef]

D. Kapitan, D. W. Coutts and C. E. Webb, "On pulsed laser ablation of metals: comparing the relative importance of thermal diffusion in the nanosecond-femtosecond regime," Conference on Lasers and Electro-Optics - Europe paper CThH76 (1998).

M.R.H. Knowles, G. Rutterford , A.I. Bell, A.J. Andrews, G. Foster-Turner and A.J. Kearsley, "Sub-micron and high precision micro-machining using nanosecond," Proceedings of ICALEO 98 85e, 112-120 (1998).

H.K. Tönshoff, C. Momma, A. Ostendorf, S. Nolte and G. Kamlage, "Microdrilling of metals with ultrashort laser pulses," J. Laser Applications 12, 23-27 (2000).
[CrossRef]

M. Knowles, R. Benfield, A. Andrews and A. Kearsley, "Development of high power compact copper vapour lasers," Advanced High-Power Lasers and Applications 99 M. Osinski, H.T. Power, K.Toyoda, eds., Proc SPIE 3889, paper 3889-63, (1999).

D. K Kapitan, D. W. Coutts and C. E. Webb, "Efficient Generation of near diffraction-limited beam-quality output from medium-scale copper vapour laser oscillators," IEEE J. Qu. Electronics 34, 419-426 (1998).
[CrossRef]

M.R.H. Knowles, A.I. Bell,.G. Rutterford, G. Foster-Turner and A.J. Kearsley, "Advances in copper lasers for micromachining," Proceedings of ICALEO 97 82, (1997).

M.R.H. Knowles, R. Foster-Turner, A.I. Bell, A.J. Kearsley, A.P. Hoult, S.W. Lim, and H. Bisset, "Drilling of shallow angled holes in aerospace alloys using a copper laser," Proceedings of ICALEO 95 80, 321-330, (1995).

M.R.H. Knowles, A.J. Kearsley., R. Foster-Turner., J.E. Abbott, J.M. Boaler., K.H. Errey, "Visualization of small hole drilling using a copper laser," Proceedings of ICALEO 94 79, 352-361, (1994).

J.J. Chang, B.E. Warner, E.P. Dragon and M.W. Martinez, "Precision micromachining with pulsed green lasers," J. Laser Applications 10, 285-291 (1998).
[CrossRef]

R.I. Trickett, M.J. Withford and D.J. Brown, "4.7W, 255nm source based on second-harmonic generation of a copper vapour laser in cesium lithium borate," Opt. Lett. 23, 189-191, 1998.
[CrossRef]

A.C. Glover., D.W. Coutts, D.J. Ramsay and J.A. Piper, "Progress in high-speed UV micro-machining with high repetition rate frequency doubled copper vapour lasers," Proceedings of ICALEO 94 79, 343-351, (1994).

A.C. Glover,.M.J. Withford, E.K. Illy and J.A. Piper "Ablation threshold and etch rate measurements in high-speed ultra-violent micro-machining of polymers with uv-copper vapour lasers," Proceedings of ICALEO 95 80, 361-370, (1995).

C. Körner, R. Mayerhofer, M. Hartmann and H.W. Bergmann, "Physical and material aspects in using visible laser pulses of nanosecond duration for ablation," Appl. Phys. A 63, 123-131, (1996).
[CrossRef]

J.J. Chang and B.E. Warner, "Laser-plasma interaction during visible laser ablation of metals," Appl. Phys. Lett. 69, 473-475, (1996).
[CrossRef]

H.K. Tonshoff, F. von Alvensleben, A. Ostendorf, G. Kamlage, S. Nolte, "Micromachining of metals using ultrashort laser pulses," IJEM Review International Journal of Electrical Machining 4, 1-6, 1999.

http:/www.oxfordlasers.demon.co.uk/movies/ddi_drilling_large.mov

http:/www.oxfordlasers.demon.co.uk/movies/ddi_drilling_close.mov

Supplementary Material (3)

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Figures (6)

Fig. 1.
Fig. 1.

(a) A high quality CVL drilled hole in 1mm thick steel for diesel fuel injectors (P=35W, PRF=10kHz, F=200mm, w=10 microns, t=20s trepanned) and (b) a high performance gasoline swirl injector manufactured using a CVL (P=45W, PRF=10kHz, F=250mm, w=13 microns, t=60s trepanned). These holes demonstrate the exceptional hole quality (roundness, smooth walls, sharp edges and sub-micron recast layers).

Fig. 2.
Fig. 2.

Photographs of CVL drilling of a diesel fuel injector. Photograph (a) on the left shows an overview. See reference [18] for the link for the movie of this drilling (5.26MB). Photograph (b) on the right shows a close up of the drilling process and jig. See reference [19] for the link for the movie of this drilling (6.12MB). [Media 3]

Fig. 3.
Fig. 3.

An example of a CVL drilled industrial inkjet printer nozzle orifice. In fig 3(a) the hole diameter is 50mm through 100mm stainless steel and was trepanned. The recast laser is sub-micron and the diameter reproducibility is +/-0.2mm. In fig 3(b) the hole is 5mm diameter (part of a 22,000 hole array) in a medical device and was percussion drilled (20 pulses at 10kHz, w=4 microns).

Fig. 4.
Fig. 4.

(a) Low taper cutting of CVD diamond (250 micron thickness) to form heat sinks for laser diodes, reproduced with the permission of Marconi Materials Technology by a CVL (P=40W, PRF=10kHz, F=300mm, w=50 microns, v=0.5 mm/s) and (b) a vacuum chuck made from 1.6mm thick diamond/tungsten carbide for a pick-and-place tool (P=40W, F=250mm, w=13 microns, PRF=10kHz, v=0.01 mm/s).

Fig. 5.
Fig. 5.

(a) The photograph on the left shows direct writing of micro-circuits using a CVL. This example has 25mm wide tracks on a 50 mm pitch through 5mm thick nickel on ceramic. Note the lack of burr around the laser cuts. (b) Sub-micron surface patterning of polished steel (P=6W, PRF=10kHz, intensity=1J/cm2, 60 pulses). The ablated squares are 2mm wide with corner radii of less than 0.25mm [4].

Fig. 6.
Fig. 6.

Blind via drilled through polyimide down to the copper layer below using the frequency mixed 271nm line from the copper laser (P=500mW, PRF=6kHz, w=40 microns, t=20ms trepanned). Note the excellent roundness, smooth walls and flat bottom to the via.

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