Porous air bearing techniques for contactless handling ...Porous air bearing technology ....
Transcript of Porous air bearing techniques for contactless handling ...Porous air bearing technology ....
Porous air bearing techniques for contactless handling, flattening and stabilization of webs
Teunis van Dam – IBS Precision Engineering
www.ibspe.com
Content
1. Why contactless web handling for flexible electronics 2. Porous air bearing technology introduction 3. Experiments and results:
1. Air turn for contactless web transport 2. Air table for contactless web support and stabilization
4. Application examples 5. Outlook
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Why contactless web handling Reasons for developing contactless web handling solutions: • Clean, damage free R2R production critical for yield and lifetime of
flexible electronic devices • Web handling equipment major source of particles & scratches,
contact with foil (especially front side) should be avoided
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Porous air bearing technology Background: • Air bearing technology first
published in 1828 • Widely used in precision
machines, e.g. in semiconductor industry
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Working principle: • Pressurized air layer between
two surfaces for contactless support and motion
Advantage porous air bearing vs. orifice air bearing • More uniform pressure distribution • Enhanced stiffness, stability and load capacity
Porous air bearing technology
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Single orifice Multiple orifices and grooves
Porous material
Experiments and results: air turn Air turn: cylindrical porous air bearing • Up to 360° cylindrical air bearing surface • Can be used to replace idler rollers in R2R processes
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Experiments and results: air turn Measurement setup • Closed loop foil between two air turns • One of the air turns used as preload to generate web tension • Foil height above air bearing surface measured by capacitive
displacement sensor
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Experiments and results: air turn
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Measurement results: fly height above cylindrical surface • Fly height 50-150 μm depending on settings • No contact between foil and air turn • Wrinkle is flattened above air turn surface
Experiments and results: air turn
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Measurement results: fly height vs. web tension • Fly height decreases to asymptotical value • Stiff and stable air layer
Experiments and results: air table Air table: flat porous air bearing containing vacuum grooves • Air bearing supports substrate • Vacuum grooves pull substrate towards air
bearing surface for higher stability • Current application: flat panel industry • New application: flexible substrates
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Experiments and results: air table Measurement setup - Stationary foil supported by air table - Foil height above air bearing surface measured by displacement
sensor
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Experiments and results: air table Measurement results: single position • Stable fly height when bearing pressure and vacuum are both on
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Experiments and results: air table Measurement results: flatness over length of foil • < 5 µm flatness over 55 mm length at optimal settings
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Bearing pressure 2 bar, vacuum pressure varied
Experiments and results: air table Measurement results: flatness over width of foil • < 15 µm flatness over 200 mm width (< 5 μm over 20 mm) at optimal
settings • Without air table support this was > 75 μm
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Bearing pressure 2 bar, vacuum pressure varied
Foil edges
Experiments and results: air table Measurement results: stability of moving web over an air table • Without air table, 250 μm foil vibrations (peak to peak) @ 1 m/min • With air table this was reduced to 9 μm (peak to peak) • No significant difference between 1 m/min and 5 m/min web velocity
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Experiments and results: contamination
• Experiments are done to verify the contactless web handling equipment is really clean (no particle increase on supported foil)
• Initial tests show no statistically significant increase, additional tests needed for quantitative analysis
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Experiments and results: conclusion
• Air turn allows contactless web transportation on 50-150 μm air film • Air table generates very flat web without making contact:
– < 5 μm over 55 mm web length and 20 mm width – < 15 μm over 250 mm width
• Air table generates very stable web: < 9 μm vibrations at 5 m/min
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Applications Air turn: • No contact, therefore useful if foil damage and contamination is critical
(e.g. if sensitive coated side of foil needs to be supported) • No contact friction, therefore 90° change of web path direction allowed • No inertia, therefore better web control when accelerating/decelerating
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Applications Air table: • Excellent web flatness and stability allows in-line (optical) inspection • Web support in R2R drying ovens, where the web should be horizontal
and stable for drying quality
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Outlook • More testing in full-scale R2R production lines for better understanding
of possible advantages of contactless web handling • Support of paper webs • Specific areas for further development:
– Investigate wrinkling behavior – Web support in high temperature environments (R2R ovens)
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Acknowledgement • The research leading to these results has received funding from the
European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement n° 281027
• Air table stability tests were done in cooperation with Eight19 Ltd, Cambridge, UK
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IBS Precision Engineering bv, Esp 201, 5633 AD Eindhoven, The Netherlands
Tel : + 31 40 290 1270
www.ibspe.com