SWISS FOCUS | ARTICLE
Micro Manufacturing – SEEN IN A NEW LIGHT
JANKO AUERSWALD, SENIOR PROJECT MANAGER, CSEM CENTRAL SWITZERLAND
In the past decade laser sources made the step
from the lab to a mature industrial tool. To name only a few applications: powerful infrared lasers are used for cutting and welding metal sheets,
laser diodes read structures of DVDs or CDs, fibre lasers amplify signals in transatlantic data
communication and solid-state lasers drill precise holes for fuel injectors. These ‘classic’ industrial laser solutions could not be applied for fine
structuring in micro technology, up to now. Why? They create heat and melt the material. This is a show-stopper for finest components.
Powerful lasers such as CO2-, diode- or high-
power solid-state lasers are used for drilling and welding of tubes and metal sheets. On the
opposite side we find lasers with lower energy. Pulsed copper vapor lasers (CV) for drilling of fuel injector nozzles, excimer lasers for photo lithography and ablation in eye surgery, diode-
pumped solid state lasers (DPSS) and fibre lasers for marking and micro manufacturing.
Nevertheless, all these types are restricted in terms of materials which they can process or reduced ablation rates.
<< Figure 1: Common application lab for laser micro manufacturing. Hans Marfurt (left), CEO of Trumpf
Maschinen AG Switzerland, and Janko Auerswald, project manager at CSEM (photo: M. Frutig, Technica). >>
Now powerful short- and ultra-short-pulse lasers (USP) are on the way to becoming the new Swiss-knife of micro manufacturing. In only a few nano, pico or even femto seconds these lasers provide the power of a powerplant on an area of few square micrometers. The material has no time to melt and simply evaporates — ‘cold ablation’. The quality of machined surfaces and edges achieved is accordingly high.
Which laser is best? This depends on the application. The pulse length — nano, pico or femto second — is paramount. As explained above, short-pulse lasers such as DPSS, CV and excimer already cover a certain application range. Fibre lasers with high beam quality and femto second lasers are suitable for fine structuring down to 100 nm. This allows to produce highly precise optical devices such as lattice structures or Fresnel-lenses or to carry out fine cuts in the cornea of a human eye. Using dedicated photo active materials, femto second lasers enable 3D resolution even down to 10 nm. Such processes are based on two-photon polymerisation. They are used for writing optical wave guides by local modification of the refraction index or for fluorescence microscopy in molecular biology.
18 | commercial micro manufacturing international Vol 6 No.6
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