Printing Flexible Electronics for Health Care Applications

Printing Flexible Electronics for health care Applications

Pit Teunissen

Eric Rubingh

Ruben Lelieveld

Marc Koetse

Juliane Gabel

Pim Groen

SVC TechCon, Providence

April 23, 2013

Presentationoverview

SVC TechCon Providence, April 23, 2013

1. Introduction Holst Centre

2. Introduction smart blister

3. Device architecture

4. Way of working

5. Results

6. Towards high volume production

7. Conclusions and outlook

© Holst Centre

Holst Centre

An ‘open innovation’ research institute for

large area flexible electronics and ultralow power wireless sensor technology

Independent, with reputed parents

founded by imec (1300 fte, Belgium)and TNO (4500 fte, The Netherlands)

located in Eindhoven, The Netherlands

established in 2005

Critical mass

own staff 180

25 nationalities

Characteristics

• perform joint research with industrial partners

• Ca. 60 industrial residents


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© Holst Centre


Open Innovation Hot-Spot

High Tech CampusEindhoven, The Netherlands

Holst CentreR2R lab

Holst Centre Offices

Thin Filmclean room

Device Processing Facilities

Mechatronics Test & Assy Lab

ReliabilityTest Centre

Analytical Labs

EMC Test Centre

Electronic TestCentre

InstrumentRental

High-Tech Campus, initiated by Philips

• Site-sharing: ~120 companies, 7000 researchers

• Facility-sharing: MiPlaza (includes >8000m² cleanrooms)

• Program Sharing: Open Innovation research (e.g. Holst Centre)

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© Holst Centre


Conductive structures for plastic electronics - Examples

OLEDs

Disposable bio-sensors

Electronic textiles

Plastic solar cells

Smart bandage

Smart packaging

Sensors

RFID tags

Flexible displays

Touch screens

Signage

Plastic batteries

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© Holst Centre

Large area flexible electronics - manufacturing

One of the key challenges: How to manufacture these products?

Large quantities and large sizes…

• roll-to-roll (R2R) manufacturing preferred

easier to make large quantities at low costs

• to be build on low cost flex foils

not on polyimide-foil: ~ 50 euro/m2

but on PET-foil: ~ 3 euro/m2

Printing preferred over lithographic patterning

• easier for roll-to-roll processing

• fine features without complicated masks

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© Holst Centre


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• Research objective

Develop R2R compatible printing and sintering technology for functional structures on flexible substrates

• Applications targetted

OLEDs: Anode structure

OPV: Electrodes

Smart blisters/packaging: Circuit

RFID: Antenna structures

• General requirements

High conductivity: ≤ 5 X bulk silver resistivity

Low sintering temperature: ≤ 130ºC, foil compatible

Short sintering time: <(<) 1 min, R2R compatible

Compatible with device stack

Potential for multiple types of materials

Conductive structures for plastic electronics – General goal






4. Way of working

5. Results



© Holst Centre

Smart Blister

• Pharmaceutical package capable of monitoring when a pill is taken out of its packaging

• Data can easily be transferred wireless via NFC

• Main purpose: To ensure that patients in clinical trials take their medicine at the time and frequency recommended to avoid non-compliance issues


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© Holst Centre

Smart blister: Partner request


• Assembled

• “3D”-system

• High cost

• Added to existing package

• Fully integrated

• 2D-System in Foil

• Low cost, mass fabrication

• Roll to Roll compatible

Request from partner: from assembled PCB to low-cost integrated system in foil

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© Holst Centre

Technological challenges

System engineering

• Simplification, cost reduction

• Optimal chip set

• Design rules

Printing

• Conductivity (Antenna)

• Multi layer (circuitry)

• Overlay precision

Assembly

• Adhesives

• Accuracy

• Reliability and durability


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2. Introduction Smart blister


4. Way of Working

5. results



© Holst Centre

Substrate selection

Substrate:

• Price

PI >50€/m2

PEN <10 €/m2

PET <1 €/m2


Preferred substrate PET

• Tg PET ~ 100°C

Processing temperature < 130 °C

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© Holst Centre

Building Blocks


sensing

logic

radio

antenna

power Thin film battery

Resistance ladder to monitor which pill was taken from package

Integrated chips for measuring and registration

Printed antenna for data transfer

Integrated chips for RFID communication and data storage

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© Holst Centre

Vacuum process vs. printingStandard Lift-off process

Substrate

Lithography mask

exposure

developing

Deposition(sputtering, ebeamevaporation…)

Lift off

Next

layer

Photo resist

vacuum

Substrate with resist pattern

Resist deposition

Substrate with structure

Standard print process

Substrate

Printing

Curing (UV, photonic, heat…)

Normal pressure

Substrate with structure

Next

layer

ink


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© Holst Centre

Printing Conventional Vacuum process

Advantages - Cost efficient / Low cost- Fast- Efficient material use- Easy R2R- Pattern on demand

(inkjet)- Non-stop production

possible- Easy to upscale

- High resolution features- Bulk conductivity

(metals)- Well established process

Disadvantages - Lower resolution- Lower conductivity

- Relatively Slow - Expensive vacuum

equipment- Waiting times for vacuum- Inefficient use of

materials - Upscaling limited

Vacuum process vs. printing


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© Holst Centre

Deposition method

Processing:

• High speed processing / large volume

R2R compatible

High speed

Resolution ~100µm features

Multi-layer 100µm overlay accuracy

High aspect ratio for high conductivity


Screen printing

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© Holst Centre


Device layers

• Five layers

1: Circuit including antenna

~100µm feature size

Good conductivity

2: Antenna

~100µm overlay accuracy

~100µm feature size

Resistance ≤40 Ω

3: Dielectric

Good insulating properties

Prevent shorts in crossing layers

4: Bridges

Make electrical contact between components

5: Printed resistors

Monitor which pill is taken out

Accurate resistance (< 5% deviation)

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© Holst Centre


Components

Components

• 3 chip solution

MC: micro controller (measure and register)

RTC: real time clock (date, time)

NFC Eeprom: RFID communication and data storage

• Thin components

Components can be integrated in foil

• Assembly

No soldering possible!

Use novel low T cure isotropic conductive adhesives (100 °C cure)

withoutpackage

thinning chipdown to 20-30 µm

chip becomesflexible

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4. Way of working

5. Results



© Holst Centre

Way of Working – Deposition method

• Screen printing: principle

Ink is applied in a patterned mesh

Mesh is positioned above substrate

Ink is pushed through the mesh and a direct image of the screen is made on the substrate


smallest feature size (lab)

30 µµµµm

smallest feature size (industrial scale)

80 µµµµm

ink viscosity range 100 – 800,000 mPas

wet layer thickness 12 – 500 µµµµm

dry layer thickness 0.5 – 50 µm

dry layer thickness accuracy

15 – 40 %

alignment/overlay accuracy

100 µµµµm

Processing time < 1 min. / sheet

Woven mesh

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© Holst Centre


Way of working – Equipment and materials

• S2S screen printer

DEK Horizon 03i

• Mesh technology

Stainless steel woven mesh

Stork Prints PlanoMesh, electroformed Nickel

• Materials

Silver paste (layer 1, 2 and 4)

1: Circuit, including antenna (DuPont 5025)

2: Antenna (DuPont PV410)

4: Bridges (DuPont 5025)

Isolator (layer 3)

3: Dielectric (DuPont 7165)

Carbon (layer 5)

5: Resistors (DuPont 7082 + DuPont 5036)

Stork Prints PlanoMesh

Dek screen printer

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© Holst Centre


Way of working – Sintering

• Sintering

Metal nano,- and micro particle need to be dried and/or sintered to become conductive

Sintering = merging particles via atomic diffusion

Fraction of the bulk melting temperature

Nanoparticle inks are ideal for conductive structures on temperature-sensitive substrates

Sintering can be done thermally, photonically, electrically, using plasma, chemically, etc.

Here we use thermal sintering in an oven at 130°C

Sintered Ag nanoparticles

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4. Way of working

5. Results



© Holst Centre

Results


• 1st layer: circuit for electrical contacts

Smallest line width: 100µm

Good Conductivity

Typical line height ~6µm

Profile measurement antenna Screen printed circuit

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© Holst Centre

Results


• 2nd layer: antenna

Extra layer is printed to improve the conductivity

Resistance 15-16 Ohm (<40 Ohm needed)

SPG PlanoMesh screens are used to print thicker in one step while maintaining resolution

Stork Antenna DuPont 5025 + PV410

-5000

0

5000

10000

15000

20000

25000

30000

35000

40000

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Position (µm)

Hei

ght (

nm)

Profile measurement antenna2 layers printed using woven mesh

Profile measurement antenna2 layers printed using plano mesh

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© Holst Centre

Results


• 3rd layer: dielectric

Al spikes in Silver should be covered

No pinholes allowed

Back scatter: White Silver; black dielectricLeft Silver; right Silver+dielectric

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Defect piercing dielectric

© Holst Centre

Results


• 3rd layer: dielectric

Depending on 1st layer, up to 4 layers needed to give optimal isolation

Pinhole in dielectric

Antenna silver lines

Cross section dielectric on Silver

Profile of antenna covered with dielectric

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© Holst Centre

Results


• 4th layer: bridges

Challenge is to print high resolution lines on multi layer stack with >30µm step height

Printed 100µm lines on top of 2 layers of silver and 4 layers of dielectric

Dielectric

Silver bridges

Profile of printed silver bridges on top of silver and dielectric

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© Holst Centre

Results


• 5th layer: printed resistors

• Results carbon resistors

Resistance accuracy < 5% within one sheet

Practical tests show that with a resistance ladder for 4 different pills pushed out all combinations can be correctly registered (DAC converter behavior)

Low value resistors have larger resistance than designed

A theoretical model was made and showed the same effect

The edges of the large carbon resistors have a relative larger contribution to the conductivity compared with small carbon resistors

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© Holst Centre

Results

• Towards lower cost materials

Use printed copper for main circuit and bridges

Antenna is still silver to get the high conductivity needed

Working blisters were made

160°C processing temperature needed

Lifetime not yet good enough


Cross section Copper-dielectric-CopperSmart blister made of screen printed Copper

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© Holst Centre

Results

• Current process suits for low volume production

High volume needs continuous production process


4 intermediate generations of smart blister

• Several working devices were made

Components on top Components in blister

Components in blisterComponents in blister

Final version of smart blister

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4. Way of working

5. Results



© Holst Centre

Towards high volume production

Transfer from S2S process to R2R process

• Flatbed screen printing Rotary screen printing

Similar process as flatbed screen printing

Circular formed mesh for continuous production


smallest feature size (lab)

70 µµµµm

smallest feature size (industrial scale)

100 µµµµm

ink viscosity range 100 – 80,000 mPas

wet layer thickness 12 – 500 µµµµm

dry layer thickness 500 – 50,000 nm

dry layer thickness accuracy

15 – 40 %

alignment/overlay accuracy

100 µµµµm

linear line speed >> 10 m/min, independent from resolution

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© Holst Centre

Towards high volume production

Transfer from S2S process to R2R process

• Thermal sintering Photonic sintering

Selective heating through light absorption by the ink, not by the foil

High energy densities achieved by light focusing with an elliptical reflector

Pulsed light instead of continuous radiation to prevent excessive heating and substrate deformation


300 400 500 600 7000,0

0,2

0,4

0,6

0,8

1,0N

orm

alis

ed a

bsor

ptio

n (e

mis

sion

)

λ (nm)

PENfoil

Ag np ink

Xe lamp emission

Working principle of the photonic sintering process

Light source

Ink

substrate

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© Holst Centre


• Inline temperature and resistance measurement

The temperature profile reveals the change in material properties of the conductive ink. DuPont W693 (Ag development paste) on PEN

Photonic Sintering: Process study

Thermal conductivity: LowHeat capacity: High

Thermal conductivity: HighHeat capacity: Low

Tg of PEN

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© Holst Centre


• Sequence flash sintering (Suntronic U5603)

To achieve highly conductive structures without deforming the temperature-sensitive substrate, two flash settings are used

Two stage sintering flash parameters:

Process Time Temperature Pulse settings

Solvent evaporation seconds < Tg low intensity, high frequency

Sintering milliseconds >(>) 250°C high intensity, short pulse(s)

50x

Photonic Sintering: Process study

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© Holst Centre


• Stand alone photonic sintering unit

Research tool to investigate sintering behavior of conductive inks

Elliptic shaped reflector to focus light

Inline resistance and temperature measurement (4-point)

Nitrogen atmosphere possible (copper inks)

• S2S photonic sintering unit

Research tool to upscale from single line to 30x30 cm

2 side illumination

Up to 10 lamps

Inline resistance and temp.

measurement (4-point)

Photonic sintering: Experimental setup

Stand alone photonic sintering unit

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© Holst Centre

Rotary screen printing

Material: DuPont 5064 micron Ag

Screen: RotaMesh 305 80 µm

Foil: Agfa PET, 125 µm

Print speed: 5 m/min

Sheet resistance of full printed large areas: ~30 mΩ//mil

(Process demonstration video can be found on YouTube: Holst Centre Photonic Sintering)

Photonic sintering module

6 lamps used (3 top, 3 bottom)

2 lamps at 300 Hz, 50% power

4 lamps at 10-15 Hz, 50-60% intensity

Photograph of the R2R system containing the rotary screen printer and the sintering module

R2R rotary screen printing and in-line photonic sintering


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4. Way of working

5. Results



© Holst Centre

Conclusions


• Screen printing was demonstrated as a cheap manufacturing method for smart blisters

5 different layers were printed

Good conductivity

Overlay accuracy of ~100µm; even on multi-layer stack

Printed resistance ladders to monitor which pill is removed

Thinned down components integrated in foil

• Rotary screen printing and photonic curing was shown to be a way for high volume production

Proof of principle R2R photonic curing demonstrated

With a non optimized process 10 m/min was achieved

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© Holst Centre

Roll to roll inkjet printing

Printer: SPG inkjet printer

Print head: Xaar 1001

Material: Sun Chemical EMD5603

Foil: Agfa PET, 125 µm

Print speed: 4 m/min

Outlook processing


Movie: R2R Inkjet printing and sintering

Sintering module

NIR dryer

60% Power

Photonic sintering

2 lamps used;10Hz, 60% intensity

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© Holst Centre

General purpose flexible sensor label

- demonstrated to work with humidty, temperature, amines, (ethylene)

low power

low cost

unified plug&playplatform

for different sensors

allows data logging forseveral weeks

compatiblewith NFC and RFID standards


Outlook application

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© Holst Centre

Outlook application


Skinpatch

• Wellness and healthcare application

• Demonstrated to work with monitoring skin temperature, skin humidity and skin movement

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© Holst Centre


Outlook application

Storeskin

• shelve can detect spatially resolved presence of objects

• done by integration of a ‘large area pressure sensing foil’

• electronics external, hidden in box

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© Holst Centre

Aknowledgements


• Program partners

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Thank you for your attention!

Documents

Printing Flexible Electronics for Health Care Applications