Inks and their application in Printed Electronics Results of a European Research project for SME Associations (CLIP)
Printed Electronics
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A wide range of (possible) applications
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Solar Cells
Food Sensors
Automotive sensors
RFID tags
EL Packaging
Printed Electronics
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A wide range of (possible) applications
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Displays
Lightning (OLED)
Medical Sensors
Batteries
Printed Electronics Manufacturing
Requirements Conversion of printed ink to a conductive track High Performance Cost efficient Flexible Large area / thin tracks / large area + thin tracks Various substrate (glass, paper, ceramic, plastics) Thermal compatibility with substrate and materials Defined interface formation between stacked materials Compatible with industry standard practices
Materials & Technology
Ink formulation Printing Drying Sintering Device
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Technology for Printed Electronics
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Conventional printing
Offset
Gravure
Screen
Flexo
Digital Printing
Inkjet
Aerosol Jet
Thermal transfer
magnetography
Materials & Technology
Ink formulation Printing Drying Sintering Device
Technology for Printed Electronics
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Conventional printing
Offset
Gravure
Screen
Flexo
Digital Printing
Inkjet
Aerosol Jet
Thermal transfer
magnetography
Materials & Technology
Ink formulation Printing Drying Sintering Device
Which technology will dominate?
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Depends on market and applications
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Materials & Technology
Ink formulation Printing Drying Sintering Device
Inkjet (piëzo) Aerosol Jet Flexo Screen
Resolution ~30 µm ~10 µm ~80µm 40 - 100 µm
Throughput 0,01-0,5 m2/s 10 m2/s 2-3 m2/s
Single pass layer thickness < 500 nm 25 nm -10 µm 3 - 10 µm 50 - 100 µm
Particle size Nano Nano (micro) Nano & micro Nano & Micro
Conductive ink materials
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Research focus on graphene based inks
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Conductive Material
Ink Type / Printing process
Advantage Disadvantage
Silver Flake Predominantly Screen printing
Cost effective for many applications
thick films, surface roughness, difficult to photocure
Silver Nanoparticles
Predominantly Inkjet, Aerosol jet printing
Thin films, flexibility, high conductivity, low T sintering
High cost
Copper Nanoparticles
Predominantly Inkjet, Aerosol jet printing
Same as Ag NP, but slightly lower cost
Can oxidise and lose conductivity
Polymers (PEDOT, PANI) All
Transparent, flexible, water resistant
Lower conductivity then metal based inks
Materials & Technology
Ink formulation Printing Drying Sintering Device
Drivers
Silver flake inks for screen printing will continue to dominate with largest market share (low cost)
Increasing share for inkjet, AJP and nanoparticle inks. Delicate or irregular shaped objects Low temperature sintering required to
print onto cheap flexible substrates (polymer film, paper)
Alternative needed for sputtered
transparent ITO due to cost, supply and performance issues
Barriers
Cost Nanoparticles significantly more
expensive Ink development is time consuming and
expensive Total in-use cost needs to be considered
rather than a price comparison of inks
Technical Long term stability High resolution printing Curing
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Market
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Materials & Technology
Ink formulation Printing Drying Sintering Device
2012 market size*: $2.86 billion, dominated by silver flake inks 2018 forecast*: $3.36 billion, of which $735 million is based on nano Ag and Cu
* Adapted from IDTECHEX report: Conductive Ink Markets, 2012
CLIP:Conductive Low Cost Ink Project
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Objectives Development, formulation, and feasibility of low cost inks
Development of optimized inks for screen, flexo, inkjet and aerosol jet printing
Optimization of inks for large area printing with high resolution, <50 microns
Prepare demonstrators
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Specific guidelines for the inks
Viscosity Surface Tension
Particle size
Complex composition of nanoparticles and chemicals
Nanoparticles Solvents Binders Additives
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Ink formulation
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Materials & Technology
Ink formulation Printing Drying Sintering Device
Multimodal Ag inks
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40 nm/6 nm/ <1nm Improve particle packing improved sintering and conductivity Less material Lower cost
Materials & Technology
Ink formulation Printing Drying Sintering Device
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Filtering Filtering of the inks
necessary if small nozzle cartridges are used
Nano-particles tend to agglomerate Wide variety of filters available
Materials: PP,PES,PTFE,Nylon6,… Different µ-structures Ink dependent
Cellulose PVDF PC PES
Materials & Technology
Ink formulation Printing Drying Sintering Device
Inkjet
High resolution Different printheads
Fujifilm, Xaar, Konica, Ricoh,... 1 pL to 80 pL
Planar substrates Line and area printing
AJP
Very high resolution Wide ink viscosity range Local laser sintering
Non-planar substrates possible Line printing
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Printing
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Materials & Technology
Ink formulation Printing Drying Sintering Device
Digital printing - print at wish High quality
Low cost Small waste
Non contact/sensitive substrates No masking
Flexible & Scalable
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High speed No clogging Low resolution
Limited fluids All fluids
Materials & Technology
Ink formulation Printing Drying Sintering Device
Inkjet technology
Continuous Drop on Demand
Thermal Piezoelectric Acoustic Electrostatic
Non contact AJP technology AJP Technology description
1 2
3
4
1 – Nitrogen input
2 – Mist created (1-5µm droplet)
3 – Sheath gas input
4 - Printing and Deposition
Materials & Technology
Ink formulation Printing Drying Sintering Device
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Substrates Type of substrate depends on application
Papers: good printability, good adhesion, solvents are absorbed quickly by the paper, fast drying but porosity of paper can have a negative effect on conductivity.
Plastics: good printability, longer drying and curing time, adhesion can be a problem. No interference from substrate (no porosity). If curing and sintering are good optimal conductivity
Pretreatment can enhance adhesion
Materials & Technology
Ink formulation Printing Drying Sintering Device
Untreated substrate Treated substrate
Curing: Drying and Sintering Depending on substrates and used materials
Thermal heating Standard practice / conventional approach - Silver Uniformity Wide area of practice Substrate limiting the maximum temperature Long residence time -> inert atmosphere Not usable for Cu (oxidation)
UV Curing
Wide area of processing Standard practice Lower intensity, continuous output
Materials & Technology
Ink formulation Printing Drying Sintering Device
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Drying and Sintering Depending on substrates and used materials
Broadband flash High power densities / wide area of processing Less substrate limited and curing times short Adjustable spectrum / tunable pulse lengths High capital cost for some systems
Laser
High Power densities Exposure area smaller / Fixed wavelength but targeted wavelength to match ink requirements / uniform across the beam
/ Spatial selectivity - targeted Cost / rastering
Materials & Technology
Ink formulation Printing Drying Sintering Device
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Printing results
Trimodal CLIP-ink Commercial Reference
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Reference
Sheet Resistance after sintering 150°C Low temperature better conductivity Sheet Resistance
Multimodal better conductivity
Inkjet demonstrator Chipless RFID tag
4-bit chipless RFID tags successfully demonstrated using the final trimodal ink on PEL paper and Kapton polyimide respectively.
Higher performance than reference ink thanks to its higher conductivity at lower sintering temperature
Sintering Temperature
CLIP trimodal ink Reference
200 °C 7.85E+6 S/m 5.66E+6 S/m
39% higher
Materials & Technology
Ink formulation Printing Drying Sintering Device
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AJP and inkjet demonstrator Humidity sensor
Printing of primary circuitry MCU Gluing by KTH Overprinting
Rest of component programming and placing
Hybrid Integration of printed electronics and silicon electronics by AJP-printed interconnections.
Materials & Technology
Ink formulation Printing Drying Sintering Device
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AJP printed demonstrator LED application
3D printing by AJP of conductive tracks for LED application.
Materials & Technology
Ink formulation Printing Drying Sintering Device
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Conclusions
Inkjet technology is mature and available for conductive printing Upscaling is possible to R2R with increasing printing speed Bottleneck is the ink-development to fit the requirements Cost reduction related to Cu-inks was limited because nanoparticle
production was driving factor but improving Sintering of Cu-based inks needs alternative for thermal sintering At low sintering temperatures
Multimodal Ag-based inks show lower resistance Less ink necessary for comparable conductivity as monomodal inks
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Conclusions
Aerosol technology is dedicated for the future. Direct printing on 3D substrate is easily done with AJP Due the “Aerosol” dynamic deposition, inks are easily printable AJP is very suitable for ink development.
Large range of viscosity Size particle from nano to micro
AJP is equipped with Laser sintering. Curing by laser allow us to print and cure the deposition on low melting temperature substrates.
The printing is dedicated for line printing (10µm to 100µm) not for large area printing (even in case of scaling up according to industrial requirement).
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+32 498 91 94 63
Patrick Cosemans – Senior Project Engineer Smart Coating Application Lab
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5.12.13
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