Automation Control for
Laser Scribing Equipment
Advantages
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Anorad Brand Engineered Solutions –
Platforms/Bases allow precision positioning,
dampen vibrations; Ultra-smooth zero friction
air bearings offer outstanding repeatability,
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resolution and velocity control
Scribing Accuracy – High-speed, high accuracy
Anorad Hercules™ Series Gantry
for Laser Scribing Applications
Anorad Granite Table
for Laser Scribing Applications
system for vision-guided processing; Scribing
accuracy better than 2µm over the entire
substrate area; Repeatability of 0.5 microns;
Overview
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X, Y-axis travels to 3m; Velocities up to 5 m/s
Crystalline and thin film solar panel manufacturing processes today are
readily adopting the use of laser technology. Typical laser applications
include scribing, drilling, doping, firing, cutting, marking and patterning.
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produce uniform scribe lines
Laser Power Intensity – Laser power level can
be coordinated with the motion profile to
High Precision Linear Stages and Gantries Micron-level accuracy and sub-micron
repeatability over full travel lengths;
Nanometer-level feedback for repeatable results
and tight process control; Variety of linear
bearing technologies for optimal system
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performance
Since laser-based tools do not come in contact with the substrate
material, they provide benefits for both crystalline and thin film solar
panel production.
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Kinetix® Integrated Motion – Direct drive
linear motors provide high speed, fast
acceleration, and quick settling times resulting
in shorter cycle times and increased
productivity; Linear guides capable of speeds
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Lasers can increase yields by reducing the risk of microcracks,
especially as material thicknesses decrease.
Laser-based tools can process material in various orientations at
high speed using highly automated inline processing techniques
resulting in increased production throughput.
Laser-based tools can simplify production lines and optimize
processes resulting in lower manufacturing costs and higher
efficiency panels.
up to 5 m/s; One development environment for
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motion and control
Crystalline Cell Manufacturing
Vision Integration - Integrate a multi-camera
Crystalline module production steps using lasers have primarily been
associated with advanced and next generation tools. Success with current
turnkey off-the-shelf equipment without lasers has end users reluctant to
change from a proven solution.
machine vision system for alignment and
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inspection
Faster Development/Troubleshooting —
Pre-built and tested Add-On-Instructions (AOI)
with Human Machine Interface (HMI) faceplates
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provide detailed diagnostics
Modular Code – Equipment Modules, Control
Modules, and State Machine structure offers
code reuse and easier troubleshooting
The most widespread application for lasers in crystalline photovoltaic (PV)
cell manufacturing is in edge isolation. After manufacturing the active
layer of a cell, a continuous edge creates a potential short circuit between
the active and back sides. Edge isolation, which involves laser scribing a
groove close to the edge of the cell surface, eliminates the shunt
pathways.
Laser scribing is one technique for isolating the active layer.
It avoids the use of chemicals, lowers the risk of damage to
the wafer and can be integrated into a continuous work
flow. It is also fast and flexible enough to allow higher
throughput.
High accuracy is important for silicon solar cells because the
location of the scribe line contributes to cell surface area
and efficiency. Scribing as closely as possible to the edge
frees up valuable surface area for exposure to the sun which
maximizes the cell output.
Thin Film Manufacturing
Thin film manufacturing, an alternative to silicon-based
manufacturing, lowers fabrication costs since it does not
rely on expensive silicon raw material substrate to build the
solar cell. Thin film predominantly uses glass as the
substrate for the solar cells which is significantly less
expensive and can provide a much larger surface area to
build the solar cells. In thin film module production,
laser-based tools represent an established and preferred
selection of tooling equipment especially for the patterning
steps.
Lasers are preferred due to the high precision and quality of
ablating thin layers of material without damaging nearby
layers or the material around the scribe line. High volume
production of panels is possible using the streamlined laser
scribing process which is faster and more reliable than
mechanical scribing.
The principle application for lasers in thin film
manufacturing is patterning. Patterning is often used to
collectively describe the three scribing steps (referred to as
P1, P2 and P3) employed to define, interconnect and isolate
the cells. A laser scriber is typically used to achieve the
electric separation and series connection of the cells known
as monolithic integration.
Lasers are used to scribe cell isolation and interconnection
lines through the layers of material deposited during
manufacturing. The first scribe (P1) divides the conductive
coating on the glass into isolated strips. The second scribe
(P2) done after deposition of the semiconductor layer,
provides the interconnect path through which the final
conductive coating contacts the first electrode. The third
scribe (P3) cuts the top electrode to isolate the cells and
completes the fabrication of the series-interconnected
structure. This three-scribe pattern is repeated across the
entire substrate area.
Accurate scribing to a width of 10-30μm helps ensure
effective insulation between each layer leading to
improved performance. Minimizing the area between the
P1 and P3 scribe lines (the dead area) is vital for
maximizing the efficiency of each module. Scribe lines
need to be narrowed and placed as close to each other as
possible with minimum offset. The use of more closely
spaced scribes requires very straight cuts that maintain
their alignment. Both resolution and precision are
important to prevent an increase in defects as scribe lines
narrow.
A turnkey solution for laser scribing equipment consists of
a number of subsystems including the following:
Material Handling
Material handling systems are used to transfer the
substrate into the work area. The substrate (wafer, glass,
etc.) will determine the type of system needed.
Vision
Advanced machine vision provides closed loop position
control relative to edges, specific reference points or
previous scribe lines. Some pieces of equipment use an
image processing system for substrate positioning while
others use an on-the-fly optical positioning system to
help assure a defined distance between previous lines
and the beginning of new lines.
Motion Control and Platform
The system’s motion platform moves and precisely locates
the laser beam delivery unit over the work surface or
locates the substrate relative to the laser. Precision motion
control and a stable platform maintain line spacing across
the large panel. Granite or polymer composite bases are
used to achieve high positioning accuracy across the
entire work space by providing stability and minimizing
vibration.
Encoders, linear motors, and programmable motion
control systems provide fast and precise motions. High
speed linear motors are used for positioning in the
x-y plane with accuracies between 5-10μm. Typical
scribing speeds range from 1-2 m/s. Some systems use air
bearings which have an advantage of less wear and tear
since there is no contact between the bearing surfaces.
Laser and Laser Beam Delivery
A laser beam is focused and used to remove material. The
laser is selected to match specific properties of the material
being processed such as absorption, melting temperature,
and thermal diffusivity. Parameters of the laser include
power, wavelength, pulse length, absorption coefficient, and
stability. Material properties and laser parameters determine
the quality and speed of material removal.
Laser beam quality and delivery are critical for process
control and speed. A laser beam delivery unit helps ensure
beam uniformity as it directs the beam from the source to
the work surface. The lasers can either be mounted on a
moving optical delivering stage or fixed to a gantry above or
below the substrate being scribed. To improve throughput,
multiple parallel operating lasers or split laser beams may be
used, allowing multiple lines to be scribed in a single pass.
Laser scribe tools are enclosed in a temperature controlled
micro-environment. Air conditioning units are needed to
control the temperature of the glass substrate as it will
expand with increasing heat thereby affecting scribing
accuracy. Enclosing the tool also helps protect workers and
the environment from harmful materials used in the
manufacturing process. Before air is exhausted from the
tool, it is processed to remove particles and contaminants
produced during the material ablation process. A fume
extraction system with multiple localized high flow
pressure/vacuum jets and a multi stage filtration system are
used to efficiently clean the air.
High speed stages and linear motors can be used to
help accurately position the substrate and the laser for
scribing. Rockwell Automation offers a portfolio of
Allen-Bradley® linear stages and linear motors that
integrate seamlessly into the Rockwell Automation
Integrated Architecture™.
Integrated Architecture brings together a powerful
multi-disciplined control engine, seamless networking,
a scalable visualization platform and the information
technologies needed to help you lower your Total Cost
to Design, Develop and DeliverSM a machine. Unlike
conventional control architectures, the Integrated
Architecture provides fully integrated, scalable
solutions using a single control platform and a single
development environment. This helps machine builders
shorten design cycles and enhance business
performance.
The Kinetix integrated servo motion control solution
can also be used to transport the substrate into and out
of the work space. Motion instructions built into the
Allen-Bradley ControlLogix® Programmable Automation
Controller (PAC) are used to command the servo drives.
The PAC is also used to maintain the proper operating
environment for repeatable, high quality scribe lines.
Substrate temperature variation can affect quality and
efficiency of the completed panels. Allen-Bradley
PowerFlex® drives integrated tightly with the PAC can
be used to safely exhaust air from the work area.
Solution
Rockwell Automation offers solutions for precision motion
control to help achieve the high accuracy required by laser
scribing equipment. Our Anorad® brand of precision motion
solutions are commonly used in today’s high-tech industries.
From building block stages and linear motors, to multi-axis
gantry and air bearing systems, Anorad brand products help
you meet the motion challenges in the solar industry.
Machine vision systems provided by Rockwell
Automation Encompass™ partners can be tightly
integrated into the Integrated Architecture over an
EtherNet/IP™ network and be used to assist in motion
positioning and alignment of the lasers. Camera images
can be incorporated into graphical user interfaces
allowing an operator to monitor equipment operation.
OEMs can use Anorad engineered systems to build on and
complete their laser scribing equipment. This starts with
platforms fabricated on granite or welded frames. Gantries
are available in both standard offerings and custom
designed solutions. All gantries are delivered as a
component ready to be installed by the OEM.
The operator control station can use a Rockwell
Automation Industrial Computer running Rockwell
Software® FactoryTalk® View HMI software. The screens
offer a user friendly, process oriented graphical
interface to view critical system functions and user
configurable parameters. Alarms and other diagnostic
information are readily available to operators.
The Anorad Microglide™ platforms feature precisely
engineered air bearing systems. These ultra-smooth
bearings glide on a pressurized thin film of air to support an
applied normal load. Repeatable precision is achieved by
maintaining a constant air gap, only microns thick, using a
variety of highly stable preloading techniques.
Additional modules from the FactoryTalk Integrated
Production and Performance Suite can be added for
historical archiving (FactoryTalk Historian), OEE
(FactoryTalk Metrics) and reporting (FactoryTalk
VantagePoint).
Typical Architecture
Laser Scribing Equipment
Rockwell Automation solutions deliver improved production capabilities and reduced total cost of ownership by providing
unparalleled functionality, flexibility and scalability. Machine builders can respond more quickly to customer or market
demands, reduce maintenance costs and downtime and easily gain access to actionable plant and production information
for improved management and decision-making.
Allen-Bradley, Anorad, Rockwell Software, Integrated Architecture, ControlLogix, Kinetix, PowerFlex, PanelView, Stratix 8000, and Total Cost to Design, Develop and Deliver are
trademarks of Rockwell Automation.
EtherNet/IP is a trademark of ODVA.
Publication OEM-AP060A-EN-P –August 2009
Copyright ©2009 Rockwell Automation, Inc. All Rights Reserved. Printed in USA.