LASER MICROMACHINING In association with
Laser micromachining: Extreme precision, high repeatability and a quality finish
www.lasersystemseurope.com/applications/micromachining
How pulsed laser light can be wielded to manipulate material on the microscopic level
Laser micromachining involves lasers being used to machine fine structures – including holes, grooves and patterns, typically between a few microns and a few hundred microns in size – on the surfaces of materials or components. Typical laser micromachining includes drilling, cutting, milling and structuring/texturing.
Advantages of laser micromachining The use of laser-based methods to machine fine structures on parts overcomes many of the limitations associated with more traditional mechanical approaches. Although they can deliver
high throughputs at low cost, mechanical machining methods require contact to be made between the tool and the workpiece, and their efficacy is dependent on the quality and condition of the tool being used. Tools degrade with wear, affecting the consistency of the features they create and necessitating their frequent replacement. Laser-based processes, on the other hand, are non-contact by nature – and the number of consumables needed to carry them out is negligible. The fine features and
complex geometries that can
be produced through laser- based techniques can be difficult or even impossible to realise using conventional techniques, depending on their dimension and shape. In addition, when a high-quality finish is required, secondary processes such as polishing may have to be carried out following conventional techniques. This is not requred as often with laser micromachining and is sometimes not necessary at all. Furthermore, certain materials such as plastics that melt at low temperatures, and brittle or hard materials such as glass and ceramics, can also be challenging to machine using conventional methods. The precision and control guaranteed by laser-based methods makes processing these materials easier. Finally, mechanical techniques
tend to be noisy and can create waste, such as contaminated cooling water, which requires remediation and disposal. Such issues are dramatically reduced or even eliminated when laser micromachining is used.
Types of lasers used for micromachining A wide variety of lasers can be used for micromachining and work continues to improve their performance by, for instance, increasing their pulse energies and optimising their pulse durations and repetition rates, reducing their cost and size, and improving their reliability. In many cases, the spatial
resolution that can be achieved through laser micromachining is determined by the radius of the beam used, which, in turn,
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A dimple texture applied to a tool by laser micromachining firm Lightmotif: the curved flute surface of a drill is machined with a texture consisting of oblong shaped dimples with a non-symmetrical cross section
“Laser drilling can be used to create very small holes quickly, precisely and repeatedly”
is determined by the diffraction and aperture of the focusing optics employed. Depending on the circumstances, a spatial resolution of approximately 1μm or less can be generated while, in certain situations, a substantially higher resolution – creating features of around 100nm in size – can also be achieved. The lasers used in
micromachining must be able to deliver near-perfect beams to target areas so that the size of the heat-affected zone (HAZ) that they create is limited, thereby preserving the integrity of surrounding materials. This means that lasers with shorter wavelengths and narrower pulse- widths are often employed. For example, ultrashort pulse (USP)
lasers, wielding picosecond and femtosecond pulse widths, are often used for laser micromachining. These lasers generate intense peak powers that result in the instantaneous vaporisation of materials and a negligible HAZ – so-called ‘cold ablation’ processing. Being readily absorbed by a
wide range of materials, visible and ultraviolet (UV) wavelength USP lasers are being increasingly used for laser micromachining. UV lasers in particular can be focused into very tight spots for even smaller, more precisely machined features. Higher ablation rates can be achieved by increasing the average output power of USP lasers, but a balance must be struck. Excess fluence (the energy delivered per unit area), for instance, is partly imparted as heat into the material, causing a reduction in throughput and quality, while insufficient fluence results in reduced ablation rates. This is
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