2. Printed electronic applications:
From concept to pilot production
Pit Teunissen
Eric Rubingh
Milan Saalmink
Jeroen Schram
Roel Kusters
Jeroen van den Brand

3. Holst Centre in a nutshell

4. © Holst Centre
an open innovation research institute, focusing on technologies for
flexible and stretchable electronics (‘system-in-foil’) and ultralow power wireless sensors
• founded in 2005
• with reputed parents
 imec (1300 people, BE) and TNO (4500 people, NL)
Holst Centre: who we are

5. © Holst Centre
Contributing to solutions for global challenges
Reduce health care cost by
wearable health monitoring
Sensor systems connected to
the cloud for monitoring food,
air, water quality
Low-cost solar cells
Low-cost, long lasting lighting
and displays
Printed electronic applications: From concept to pilot production

6. © Holst Centre
Technology Functionality Application
From technology to full applications
Printed electronic applications: From concept to pilot production
One stop shop

7. © Holst Centre
Industry
Materials
Equipment
Components
End products
Universities
Knowledge
institutes
Users (e.g.
clinical partners)
Position in the value chain
Printed electronic applications: From concept to pilot production

8. © Holst Centre
310
Own
Researchers
28
Nationalities
40
Industrial
Residents
20 PhD students
30 BSc/MSc students

9. Introduction

10. © Holst Centre
Printed electronic applications: From concept to pilot production
Origin of a concept
• Partner (external)
 Product idea which needs realization
 Market pull
• Testcase for technologies (internal)
 Learning platform (sandbox)
 Technology push

11. © Holst Centre
Printed electronic applications: From concept to pilot production
Properties
• Functionality
 Sensing
 Data logging
 Interface
 Power supply
• Form-factor
 Area dimensions
 Thickness
 Flat / Bended
 Flex / stretchable

12. © Holst Centre
Printed electronic applications: From concept to pilot production
Evolution of a demonstrator
• Technology drivers
 Smaller
 Thinner
 Increased functionality
 Lower power consumption
 Less components
 Cheaper
Evolution of a “smart blister”

13. © Holst Centre
Printed electronic applications: From concept to pilot production
Process flow
Stage 1:
Electrical
design
Stage 2:
Prototyping
Stage 3:
Process
development
& prototyping
Stage 4:
Pilot
production
Stage 5:
Production /
outsourcing
Stage 1:
 Idea to design
 PCB concept to
printable
design
Stage 2:
 Multi-layer
inkjet printing
 Evaluate
electrical design
Stage 3:
 S2S screen
printing
 Product
evaluation
Stage 4:
 R2R screen
printing
 R2R pick &
place

14. Design

15. © Holst Centre
Printed electronic applications: From concept to pilot production
Global Building blocks
• Functionality
 Determine needed kind of chips
 Type of sensors
 Interface
• Manufacturing technologies
 Flexible substrate
 Conductive circuit (screenprint, inktjet, copper etching, combination)
 Component placement (ICA bonding, embedded, flipchip)
 Printed components

16. © Holst Centre
Printed electronic applications: From concept to pilot production
Schematic Design
• Components
 Specific IC types
 Package formfactor & size
• Functionality
 Datasheets
 Communication between IC

17. © Holst Centre
Printed electronic applications: From concept to pilot production
Circuit Design
• General considerations
 Size limitations
 Electrical properties
• Circuit manufacturing
 Single-Layer / Multi-Layer
 Trace width and pitch limits
 Alignment markers
• Chip bonding
 Position of components
 Orientation
 Chip pin indicators
• Software development & testing
 Test pads
 Programming connection

18. Prototyping

19. © Holst Centre
Printed electronic applications: From concept to pilot production
Prototyping using inkjet printing
• Circuit layer
 DuPont conductive inkjet ink (development
material)
 >20% Bulk Ag @ 130°C
 Excellent printing behavior
 Good wetting on polyester films
 PixDro LP50 print platform
• Multi layer inkjet printing
 Circuit layer + dielectric layers
 Optimization on wetting properties
 Dielectric on substrate and Ag
 Ag on substrate and dielectric and Ag
 Layer compatibility
 Isolating properties
 Conductivity
 On foil
 On dielectric
Sintered Ag ink
Inkjet printed circuit

20. © Holst Centre
Printed electronic applications: From concept to pilot production
Prototyping using inkjet printing
• Chip bonding
 Surface mount ICA bonding for SMT (passive) components
 Flip chip bare die bonding
 Underfill components
Functional fully inkjet printed “FlexSmell” sensor
platform with NFC readout

21. Process development & prototyping

22. © Holst Centre
Printed electronic applications: From concept to pilot production
Process development & prototyping: Screen printing
• S2S screen printing
 Multi layer printing of Silver pastes and
dielectric materials
 Both nano,- and micron particles Ag pastes
 Commercial and development materials
 Alternative materials (Carbon, Copper, hybrid, …)
 Oven sintering and photonic sintering (optionally with
NIR drying)
 Screen optimization
 Woven mesh
 Electro formed
 Stencil
 Process optimization
 Process settings
– Screen type, squeegee type and angle, print speed, paste,
emulsion, substrate, snap off, etc.
 routinely print 50 µm line and spacing (100 µm pitch)
 first steps towards >30 µm line and spacing
 Overlay accuracy < 50 µm Printed resistors
Printed circuit

23. © Holst Centre
Screen printing: multilayer circuit patterns
• Layer 1: Ground layer Ag
• Single print step
Printing a “skinpatch” step by step
Skinpatch is a physical activity monitoring patch

24. © Holst Centre
Screen printing: multilayer circuit patterns
• Layer 2: Dielectric
• Printed in 3 layers to improve reliability
Printing a “skinpatch” step by step

25. © Holst Centre
Screen printing: multilayer circuit patterns
• Layer 3: circuit
• Single print step
Printing a “skinpatch” step by step

26. © Holst Centre
Screen printing: multilayer circuit patterns
• Layer 4: dielectric
• Printed 3 layers to improve reliability
Printing a “skinpatch” step by step

27. © Holst Centre
Screen printing: multilayer circuit patterns
• Layer 5: Circuit
• Single print step
Printing a “skinpatch” step by step

28. © Holst Centre
Printed electronic applications: From concept to pilot production
• Packaged IC & passive components
 Surface Mount ICA Bonding
• Naked silicon die
 Flip chip
 Foil embedded
• Assembly
 No soldering possible!
 Use novel low T cure isotropic conductive adhesives (100 °C cure)
without
package
thinning chip
down to 20-30 µm
chip becomes
flexible
Process development & prototyping: chip bonding

29. © Holst Centre
• below thicknesses of 25 μm, silicon chips becomes ‘flexible’
 can be bended down to radii of 5 mm
 but silicon remains a brittle material
• key research challenge
 how to interconnect ultrathin (but fragile) silicon chips with plastic foils
Process development & prototyping: chip bonding

30. © Holst Centre
Printed electronic applications: From concept to pilot production
• Reliability testing
 Profile / roughness
 Conductivity
 Adhesion and cohesion
 Flex testing
 Stretch testing
 Shelf life
Multi-layered screen printed
flex test sample
Process development & prototyping: evaluation

31. © Holst Centre
• several fine pitch processes and technologies available for the reliable integration of
ultrathin silicon chips and peripheral passives
• (mostly based on conductive adhesives because of low thermal stability of polyesters)
AC163 - PET - Ag
accelarated humidity (60 oC/90% RH)
time (hrs)
-100 0 100 200 300 400 500 600 700
resistance/contact(Ohm)
0,02
0,04
0,06
0,08
#opens
0
1
2
3
4
5
AC163 - PET - Ag
temperature shock (-40 - + 125 C)
time (hrs)
-100 0 100 200 300 400 500 600 700
resistance/contact(Ohm)
0,02
0,04
0,06
0,08
#opens
0
1
2
3
4
5
25 μm thick, 90 μm pitch microcontroller + 01005 components on PE foil
Process development & prototyping: evaluation

32. Pilot production

33. © Holst Centre
Printed electronic applications: From concept to pilot production
R2R equipment
• R2R multi-layer Printing & Sintering of Silver grids

34. © Holst Centre
R2R equipment
• prepilot facilities for assembly

35. Current and future research

36. © Holst Centre
Wearable sensors
Wearable sensors
• Monitor vital signs
• Monitor location, and
• Comfort, stretchable, washable, …

37. © Holst Centre
Wearable sensors
Smart shirt:
• Stretchable
• Direct printing on TPU
• One step lamination onto textile

38. © Holst Centre
• Printed Ag/AgCl sensor
Printing of sensors
• electrochemical sensor
• enables sweat analysis
• Ion detection
Printing of dry electrodes

39. © Holst Centre
Printed electronic applications: From concept to pilot production
Smart Garment:
• printed electrical sensor
• enables ECG, EMG etc.
• lamination into shirt
• using stretch technologies for reduction of motion artefacts

40. © Holst Centre
Smart textiles:
• Accelerometer
• Heart rate monitoring
• Location

41. © Holst Centre
Flex smell:
• Sensor platform on silicon
• Temperature and humidity sensor
• NFC enabled
Alternative substrates

42. © Holst Centre
Actuation: light in clothing
Designer jacket

43. © Holst Centre
Actuation: displays in clothing

44. © Holst Centre
Solar Shirt

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Reliability and applicability in manufacturing
Manufacture in 2D,
apply in 3D,
use in 4D (stretched)

46. © Holst Centre
HMI
touch switches with integrated lighting functionality
Thermo-formed electronics

47. Acknowledgement

48. © Holst Centre
Industrial partners from across the value chain
Printed electronic applications: From concept to pilot production

49. Visit us at
www.holstcentre.com