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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1

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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