| Title |
Pulsed laser ablation for volume fabrication of micro-optical arrays on large-area substrates |
| Authors |
J.E.A. Pedder, A.S. Holmes, R. Allott, K. Boehlen |
| Abstract |
Laser micromachining by ablation is an established technique
for the production of 2.5D and 3D features in a wide variety of materials. Mask projection
techniques using excimer lasers have been used to fabricate microstructures on large
panels where diamond turning and reflow techniques have reached their limits. We have
developed 3D structuring tools based upon UV laser ablation of polymers to create large
arrays of repeating micro-optical features. Synchronisation of laser pulses with
workpiece movement allows layer-by-layer growth of deep structures with outstanding
repeatability. Here, we show recent developments in laser structuring with the combination
of half-tone and binary mask techniques. Significant improvements in surface quality
are demonstrated for a limited range of structures. |
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| Title |
High speed direct laser cutting of micro structures with submicron details |
| Authors |
K.L. Boehlen, N. Sykes, C. Lefevre |
| Abstract |
The demand on performance for displays and opto-electronics is ever increasing and the industry is looking for ways to
produce large area microoptical films to help that cause. While conventional techniques reaching their limits for large
area structuring, earlier reports show that it is possible to structure a few m2 polymer film with microoptical features (>
20 um) by direct laser ablation. By employing the same optics and hardware studies were carried out to find the
minimal feature size without compromising the area that can be processed. Looking at the sub resolution ablation
behaviour of Polycarbonate enables to modify the so called Synchronised Image Scanning (SIS) mask design to control
shape and form of 3D features only a few times bigger than the resolution limit of the laser ablation mask projection
system. Results of optical 10um and 5um features are shown and discussed. The findings show that it is realistic to
direct laser cut well defined optical 3D features into polymer film with an unprecedented feature-area-ratio in excess of
1: 10^10. |
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| Title |
Laser-assisted patterning of conjugated polymer light emitting diodes |
| Authors |
D.G. Lidzey, M. Voigt, C. Giebeler, A. Buckley, J. Wright, K. Boehlen, J. Fieret, R. Allott |
| Abstract |
We have developed a patterning procedure based on laser-ablation in combination with the use of water-soluble sacrificial-
resists that we use to pixelate different light emitting polymers (LEPs) on a surface, creating a simple array of light
emitting diodes (LEDs). We demonstrate that our patterning process is capable of high spatial resolution, with structures
having a characteristic length-scale of 10 um achieved. Importantly, we demonstrate that the patterning process has no
detrimental effect on the electronic properties of the LEPs or of the underlying polymeric anode. Our process is compatible
with a high-volume manufacturing environment and furthermore it could also be applied to pattern and integrate a wide
range of functional polymeric materials for use in other applications. |
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| Title |
Advanced Laser Micromachining Processes for MEMS and Optical Applications |
| Authors |
A.S. Holmes, J.E.A. Pedder, K.L. Boehlen |
| Abstract |
Laser micromachining has great potential as a MEMS (micro-electro-mechanical systems) fabrication technique
because of its materials flexibility and 3D capabilities. The machining of deep polymer structures with complex, well-defined
surface profiles is particularly relevant to microfluidics and micro-optics, and in this paper we review recent
work on the use of projection ablation methods to fabricate structures and devices aimed at these application areas. In
particular we focus on two excimer laser micromachining techniques that are capable of both 3D structuring and large-area
machining: synchronous image scanning (SIS) and workpiece dragging with half-tone masks. The methods used in
mask design are reviewed, and experimental results are presented for test structures fabricated in polycarbonate. Both
techniques are shown to be capable of producing accurately dimensioned structures that are significantly deeper than the
focal depth of the projection optics and virtually free from fabrication artifacts such as the steps normally associated
with multiple-mask processes. |
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| Title |
Advanced laser micro-structuring of super large area optical films |
| Authors |
K.L. Boehlen, I.B. Stassen Boehlen, R.M. Allott |
| Abstract |
A novel laser micro-machining technique to produce high density micro-structures called Synchronized Image Scanning
(SIS) was introduced a couple of years ago. Over this period of time, the technique was refined in a major effort to meet
the needs of various industries.
There is an increasing demand for micro-structuring of large and super large area optical films, e.g. for Rear Projection
TV, anti counterfeit packaging material and 3D displays. Especially in the display industry, where the screens are ever
increasing in size, established micro-structuring methods like e-beam milling, diamond turning or the reflow technique
struggle to keep up with the development.
This paper explains how it is possible to direct laser etch hundreds of millions of lenses into a 2 m x 1.5 m substrate. It
looks at the advances made in SIS in recent years regarding seam reduction, overall accuracy and precision when
structuring super large area optical films, and it presents the tools and subsystems needed to generate the features in
those films. Furthermore, the potential of this exciting laser micro-machining technique for rapid prototyping for all sorts
of optical and non-optical structures is mapped out. |
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| Title |
Laser Micromachining Techniques for Industrial MEMS Applications |
| Authors |
H.J. Booth, C.E. Abbott, R.M. Allott, K.L. Boehlen, J. Fieret, J. Greuters, P. Trimble, J. Pedder |
| Abstract |
Pulsed laser sources are widely used for the micro-processing
of materials from the structuring and patterning of surfaces to the direct machining of
devices. This paper discusses laser micro-processing techniques for the fabrication of
microstructures with high accuracy and precision. Techniques discussed include laser
mask projection techniques and direct beam micromachining using galvo-scanners and high
precision motion stages, with a variety of different lasers. Examples of the application
of these techniques to the manufacture of MEMS and MOEMS devices are discussed. |
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| Title |
Laser micromachining of high-density optical structures on large substrates |
| Authors |
K.L. Boehlen and I.B. Stassen Boehlen |
| Abstract |
A new laser mask projection technique, Synchronised Image
Scanning (SIS), has been developed for the efficient
fabrication of dense arrays of repeating microstructures on large area substrates.
This paper details the technique and
provides specific examples of the type of structures that can be produced.
SIS allows for major improvements in the
accuracy and speed with which 3D patterns can be created over large areas by
laser ablation. An add-in for CAD
software has been developed to build up linear feature arrays for the mask from 3D
designs. Feature sizes down to a few
microns can be produced with excellent surface quality. Large arrays of
microstructures have wide ranging applications
in many areas. One example is the machining of large polymer master panels that
are then electroformed to produce a
mould for replication for the manufacture of display enhancement films. |
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| Title |
CAD/CAM software for an industrial laser manufacturing tool |
| Authors |
I. Stassen Boehlen, J. Fieret, A. Holmes, K.W. Lee |
| Abstract |
A facility for rapid prototyping of MEMS devices
is crucial for the development of novel miniaturised components in
all sectors of high-tech industry, e.g. telecommunications, information
technology, micro-optics and aerospace. To
overcome the disadvantages of existing techniques in terms of cost and flexibility,
a new approach has been taken to
provide a tool for rapid prototyping and small-scale production: Complex CAD/CAM
software has been developed that
automatically generates the tool paths according to a CAD drawing of the MEMS device.
As laser ablation is a much
more complicated process than mechanical machining, for which such software has already
been in use for many years,
the generation of these tool paths relies not only on geometric considerations, but
also on a sophisticated simulation
module taking into account various material and laser parameters and micro-effects.
The following laser machining
options have been implemented: cutting, hole drilling, slot cutting, 2D area clearing,
pocketing and 2˝D surface
machining. Once the tool paths are available, a post processor translates this information
into CNC commands that
control a scanner head. This scanner head then guides the beam of a UV solid-state laser
to machine the desired
structure by direct laser ablation. |
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| Title |
New techniques for laser micromachining MEMS devices |
| Authors |
C. Abbott, R. Allott, B. Bann, K. Boehlen, M. Gower, P. Rumsby, I. Stassen Boehlen, N. Sykes |
| Abstract |
Two new laser mask projection techniques “Synchronized
Image Scanning” (SIS) and “Bow Tie Scanning” (BTS) have
been developed for the efficient fabrication of dense arrays of
repeating 3D microstructures on large area substrates.
Details of these techniques are given and examples of key industrial
applications are demonstrated. |
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| Title |
Laser Assisted Manufacture for Performance Optimised, Dielectrically Loaded GPS Antennas for Mobile Telephones |
| Authors |
O. Leisten, J. Fieret, I. Stassen Boehlen, P. Rumsby, P. McEvoy, Y. Vardaxoglou |
| Abstract |
The use of ceramic cores of high dielectric constant
is an essential part of a strategy to miniaturise GPS antennas for
mobile telephones. The core reduces the guide wavelength of the conducting structures
on the antenna, thereby creating
a need for high-resolution imaging to maintain very accurate dimensions. It is for
this principal reason that a novel laser
imaging technology has been developed using a positive electrophoretic photoresist
and UV excimer laser mask
imaging to produce the conducting features on the surface of the antenna.
Furthermore, a significant process challenge
in producing this type of antenna concerns the reproducibility of the
right-hand circular polarisation performance and
the bandwidth over which this can be achieved - which becomes progressively
smaller as antenna size is reduced. It is
therefore a vital requirement that the antennas have the option to be tuned
by a laser trimming process at an automatic
RF testing station. A galvanometer controlled Nd:YAG laser spot is used to
trim the conductive pattern on the top of the
antenna following an RF measurement to characterise the resonant frequencies
of the four helical conductors. Results
demonstrate the laser imaging and trimming techniques ensure a high-speed
method of guaranteeing the antenna
performance. The technique is appropriate for other antenna types such as
GSM, Bluetooth and Wireless LAN. |
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| Title |
Fabrication of axisymmetric ceramic micro parts using pulsed laser ablation |
| Authors |
K.L. Boehlen-Stassen, P.T. Rumsby, A. Cerezo, M. Huang |
| Abstract |
Novel methods using pulsed laser ablation
have been developed for the manufacture of micro-devices with axial
symmetry in ceramic materials. Such techniques allow the prototyping
and production of micro-parts that are very
difficult or even impossible to process by other mechanical and/or
chemical methods. To demonstrate these techniques
we have manufactured small conical counter-electrodes for use in a
Scanning Atom Probe (SAP) instrument. This paper
details all the innovative steps developed to produce the double cone
shaped electrode and demonstrates the potential for
mass production of other devices of similar shapes and dimensions. Many
different laser processing strategies for
fabricating the cones have been tried in order to achieve a result with
satisfactory accuracy and quality. High quality
devices have finally been produced in quantity using a combination of
excimer laser mask projection and UV YAG laser
cutting. The laser methods developed allow micro-parts of an overall size
down to 0.1mm and tolerances of a few
microns to be manufactured directly in ceramics, glasses, or crystalline materials. |
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