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Selective laSer etching of glaSS and Sapphire
F R A U N H O F E R I N S T I T U T E F O R L A S E R T E c H N O L O g y I LT
DQS certified by
DIN EN ISO 9001
Reg.-No.: DE-69572-01
Fraunhofer-Institut
für Lasertechnik ILT
Director
Prof. Dr. Reinhart Poprawe M.A.
Steinbachstraße 15
52074 Aachen, Germany
Phone +49 241 8906-0
Fax +49 241 8906-121
www.ilt.fraunhofer.de
Fraunhofer Institute for Laser Technology ILT
With about 420 employees and more than 11,000 m² of
usable floorspace the Fraunhofer Institute for Laser Technology
ILT is worldwide one of the most important development and
contract research institutes of its specific field. The activities
cover a wide range of areas such as the development of new
laser beam sources and components, precise laser based
metrology, testing technology and industrial laser processes.
This includes laser cutting, caving, drilling, welding and solder-
ing as well as surface treatment, micro processing and rapid
manufacturing.
Furthermore, the Fraunhofer ILT is engaged in laser plant
technology, process control, modelling and simulation as
well as in the entire system technology. We offer feasibility
studies, process qualification and laser integration in customer
specific manufacturing lines. The Fraunhofer ILT is part of the
Fraunhofer-Gesellschaft, with 67 institutes, 23,000 employees
and an annual research budget of 2 billion euros.
Subject to alterations in specifications and other technical information. 03/2014.
RWTH Aachen University. The current development of
rapid deflection systems makes the production of individual
microstructured parts of glass and sapphire possible at cost
levels that can only be achieved today by masking techniques
or molding processes for identical plastic parts manufactured
in large series.
The potential for scaling up to cycle times of just seconds will
make direct industrial implementation possible. In the medium
term this will enable low-cost glass and sapphire parts to be
produced which will be more resistant than the present plastic
parts and which will be easier to clean and sterilize. In the
long term SLE also offers enormous potential for individualized
mass production, because it does not require expensive masks
or molding tools, which means that no part-specific fixed costs
are incurred. Parts can be generated within seconds directly
from the software (CAD data). As a result the SLE technique
enables the manufacture of prototypes, small series and large
series with transferable process parameters, and customized
mechanical microsystems with completely new functional
properties to be produced more quickly and cheaply. Further-
more, SLE offers the advantage of unrestricted geometrical
freedom taking series-identical utility properties into account
for transparent parts.
Shape cutting and Drilling
For its main applications in precision mechanics and medical
engineering the SLE technique is used to cut out parts made
of sapphire and glass. The technique achieves extremely
narrow widths of cut, e. g. < 5 µm in a material thickness of
1 mm. Using a special microscanner, shapes of any configuration
can be cut to a precision of 1 micrometer, with the cut-out
part and the resulting shaped hole exhibiting a roughness of
Rz < 1 µm.
Microstructured 3D Parts
Using the SLE technique, microstructured parts are produced
in sapphire and glass for precision applications such as
watchmaking, microoptics and medical engineering. For
example a microtube made of fused silica can be produced
precisely with a length and a diameter of 1 mm, and a
wall thickness of 8 µm with a roughness Rz of 1 µm. As the
material to be removed is exposed in volume with micrometer
precision, parts which have been fitted together, for example
a toothed wheel rotating on a shaft, can be produced in
already assembled form. The SLE technique renders time-
consuming adjustment and assembly work superfluous in
the manufacture of complex micromechanical systems.
Microchannels inside glass and Sapphire
Microfluidic systems can be produced using the SLE technique
in thermally and chemically resistant materials such as fused
silica, borosilicate glass and sapphire for applications such as
those found in medical diagnosis. In fused silica the volume
modified by the laser radiation is etched 1000 times faster
than the unmodified glass. The edge angles of the channels
reflect this selectivity. Minimal channel diameters of 10 µm
with a length of a few mm are feasible. In-volume scanning
produces channels, branches and hollow structures of almost
any complexity.
New high-speed microscanners have been developed to
reduce the exposure time for microstructured parts with a
1 W laser from the few minutes to just a few seconds.
We have already demonstrated the scalability of the SLE
technique. For example, 3D microfluidics in fused silica
cylinders have been exposed in just a few seconds (picture 4).
In sapphire the selectivity is > 10.000:1, enabling a minimal
channel cross-section of 1 - 10 micrometers to be archieved
on a length of 1 centimeter.
Outlook
Experts of the Fraunhofer ILT continuously develop and
optimize the SLE technique for customer-specific applications.
The primary goals are to reduce surface roughness, to extend
the range of materials that can be processed and to increase
the feed speed using new high-power femtosecond lasers
with mean outputs of 200 - 1000 W.
contacts
Dr. Jens Gottmann
Phone +49 241 8906-406
Dipl.-Phys. Martin Hermans
Phone +49 241 8906-471
Selective laSer etching of glaSS and SapphireWith the new Selective Laser Etching (SLE) technique the Fraunhofer Institute for Laser Technology ILT provides
the first process for producing microchannels and shaped holes and cuts in transparent parts made of
fused si l ica, borosil icate glass, sapphire and ruby. Micrometer-fine structures and entire parts are produced
directly from 3D CAD data.
The Technique
Ultrashort-pulsed laser radiation is focused within a transpa-
rent workpiece and absorbed exclusively in the focus volume
by multiphoton processes. In this focus volume, optical and
chemical characteristics of the transparent material (for
example glass or sapphire) are changed without cracking
in such a way that the irradiated material can be selectively
removed by wet-chemical etching. Using a microscanner to
move the focus, areas which will subsequently be removed
by wet-chemical etching are exposed. This enables micro-
channels, shaped holes, structured parts and even complex,
assembled mechanical systems to be produced in glass or
sapphire.
Greater Efficiency for Large and Small Series
The SLE technique achieves high energy efficiency (melting
instead of vaporization), high material efficiency (kerfs of just
a few µm), great precision in three dimensions (1 µm focus,
no deposits) and it can be scaled up to high speed by laser
beam sources with high pulse repetition rates. These properties
have been achieved for the first time at the Fraunhofer ILT in
cooperation with the Chair for Laser Technology LLT at
3 51 2
Front page: Movable toothed wheel (Ø 3 mm) in fused silica.
1 Complex microfluidics in fused silica.
2 Planetary drive produced in fused silica.
4
3 Microlens blank structured
in fused silica (Ø 500 µm).
4 3D microfluidic, exposed in a few seconds.
5 1 mm fused silica micropart produced
using Selective Laser Etching.
