Cleaning Techniques for OLED and OPV Adding Value by Reducing Defects TU Delft Summer School 1 3/5/2019
Cleaning Techniques for
OLED and OPV
Adding Value by Reducing
Defects
TU Delft Summer School 13/5/2019
Outline
• Introduction
• Clean4Yield
• Cleaning Technologies
• The Theory of Small Particle Adhesion
• Empirical Evaluation
• The Cleaning Outcomes
• New Applications
• Summary3/5/2019 TU Delft Summer School 2
INTRODUCTION - TEKNEK
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Who are we?
• Company formed 1984
• Acquired by ITW (Illinois Tool Works) in July 2011.
- $18billion sales
• Inventors & world leaders in the manufacture & design of roller
contact cleaning systems
• Global footprint
• Distribution world-wide
• Over 20,000 machines manufactured and delivered to diverse range
of industries
• Produces its own cleaning rollers & adhesives
– 10,000 cleaning rollers per year
– Design and Produce in UK, adhesive centres in UK, USA & UK
– Use around 1.2 million sq. metres of adhesive product per year
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Primary Converting
Secondary Converting
FPD and BLU Assembly
Cleaning Applications
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CLEAN4YIELD PROJECT
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Clean4Yield
• Clean4Yield is a collaborative EU funded project which is tackling
one of the most pressing issues in organic electronics – ensuring
high enough yields for cost-effective manufacturing.
• Objectives
• The objective of the Clean4Yield research project is the
development and demonstration of a holistic concept for the
detection/inspection, cleaning, prevention, and repair of defects and
contaminations in nano-scale layers applied in OLED and OPV as
well as high end moisture barrier films, which are deposited on
flexible substrates by R2R (roll-to-roll) coating and printing
techniques. This will lead to increased yield, better performance,
longer operational device lifetimes and reduced production costs.
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Clean4Yield WP3 Objectives
• Removal of particles down to 100nm
• No damage to substrate or underlying layers
• No unwanted change in surface energy
• No cross contamination
• In atmospheric coating and vacuum deposition
• Substrates of PET and PEN foils, glass and
coated substrates
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CLEANING TECHNOLOGIES
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Technology Drivers
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• Films are getting thinner – easier to damage by
particles in the wind of the roll
• Coatings are getting thinner – even nanoscale
particles can cause pinholes
• The functional requirements on coatings are
becoming more demanding
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Issues
• Particles of contamination on substrates cause
defects in processes used in Flat Panel Display
manufacturing and Organic and Flexible
Electronics
• Defects cause significant yield loss
• Removal of particles is essential for high
functionality and reliability
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R2R compatible cleaning techniquesTechnique
Particle removal efficiency indication / %Remark
0.1 - 1 1 - 10 10 - 40 > 40 µm
Contact cleaning
Rotary wet wipe ? > 90 > 90 > 90 risk of damage of soft layers and cross
contamination
Rotary brush + vacuum 0 0 > 50 > 90 risk of damage of soft layers and cross
contamination
Tacky rollers
metal particles
organic particles
50 - 90
?
> 90
< 50
> 90
50 - 90
> 90
> 90
depending strongly on substrate and
particle material and humidity
Non contact – traditional
Air knife 0 0 < 50 > 50 no small particles
Air + ultrasound 0 0 > 50 > 90 no small particles
High velocity + vacuum 0 < 10 < 50 > 90 no small particles
Non contact – new
narrow gap (liquid or gas) ? ? ? ?new technology
only for rigid substrates so far
high velocity nano spray > 50 > 90 > 90 > 90 only DI water needed, no damage
CO2 snow ? > 50 > 90 > 90high gas consumption, cooling down of
substrates
Plasma
Plasma
(only organic particles)> 10 < 10 < 10 < 10
only organic thin film contaminants and
small particles
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100 75 50 30 25 10 5 1 0.5 0.2
Air Knife
Brush & Vac
High Velocity Vacuum
Ultrasonic
Contact Clean Machine
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Particle Size, Microns
Efficiency of Cleaning Methods
Comparison of cleaning efficiency's
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Contact Cleaning Technology
The Teknek Cleaning Core
PPT 7 / 21
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THE THEORY
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Basic Theory
• Adhesion force applied by elastomer to particle
must be greater than the force holding the
particle onto the substrate
• Force exerted on the particle by the adhesive
must be greater than the adhesion force of the
elastomer
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Cleaning Scenario
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Adhesion Forces
• Adhesion describes how a particle and a surface
are held together
• A number of different forces will act together to
produce the adhesion force combination
• Two bodies in contact, an attractive force occurs
that requires a mechanical load to separate
them
• Strength of adhesion is determined by how
strong the interactions are
Adhesion forces
• At least 15 types of adhesion force, including 38
variables
• Analysis done on the force equations and
variables
• Two key variables identified, namely particle size
and contact area
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Conceptual Model
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Contact Area
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EMPIRICAL EVALUATION
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Initial Research
• Focus on measuring adhesion forces
• Using AFM
• Particle size 10micron
• Particle types – Silica, gold and
polystyrene latex
• Substrates – Elastomers and standard
films
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Shore Hardness vs PPU
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Elastomer properties
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Substrate Adhesion
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Particle measurement
‘PMC’ tool - a method using adhesive cards from forensic technologies
(developed with TNO-D) used to measure surface contamination (> 2mu)
levels
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Cleaning Efficiency
0
100
200
300
400
500
600
700
800
0 1 2 3 4
Par
ticl
es/c
m2
Number of cleaning strokes
Particle removal with manual Nanocleen roller from PET foil
Copper 3-10 micron Copper 3-10 micron
PSL 10 micron PSL 10 micron
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Other Collaborations
• The Holst Institute
• The Fraunhofer Institute
• Technical University Dresden
• Technical University Delft
• Korean Institute of Machinery and Materials3/5/2019 TU Delft Summer School 29
CONTACT CLEANING
OUTCOMES
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Silicone Free Cleaning Engine
• Silicone free cleaning rollers
• Silicone free adhesive
• Silicone free confirmed by – FTIR,
– Edx (Energy-dispersive X-ray spectroscopy)
– RGA (residual gas analysis)
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Nanocleen RGA
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Static Dissipating Elastomer
• Nanocleen
– Static dissipating NO conductive particles – clever
polymers not cheap additives
– Dyne Neutral, contact angle (Measurements on PET)
• Uncleaned contact angle 71.57, SD +/- 1.49
• Cleaned with Nanocleen 71.80, SD +/- I.46
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Static Trials - Japan
Traditional
Rollers
Static
1000 volts
Nanocleen™
Static
100 volts
Static Bars – switched OFF
Traditional
Rollers
Static
100 volts
Nanocleen™
Static
10 volts
Static Bars – switched ON
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