1. Conductive Nanoparticle Inks for
Flexible and Printed Electronics
Zhihao Yang, Ph.D. & CTO
NanoMas Technologies, Inc.
1093 Clark Street
Endicott, N
E di tt New York 13760
Y k
Phone: 607-755-4121
Fax: 866-367-1128
Website: www.nanomastech.com
3rd Annual Flexible Electronics Symposium
3rd Annual Flexible Electronics Symposium
August 17‐18, 2010, Binghamton, New York

2. Printed Electronics: Fabricating
Electronic Devices with Printing
• Low equipment cost
• Continuous roll to roll processing
• Additive deposition and p
p patterning
g

3. Application Market
(by IDTechEX projection)

4. Conductive Inks for
Printed Electronics
Highly conductive and high resolution patterns fabricated
using low cost and roll-to-roll processes (such as inkjet and
low-cost roll to roll
gravure printing) are one of the most critical technology
components in making printed electronics and displays
What are the requirements:
High performance: high conductivity (close to pure metal)
Low temperature processing: plastic compatible
Printability: solution processed with “high” resolution
patterning
High throughput: R2R and fast curing
Mechanically robust: adhesion to substrates, tolerance to
mechanical deformation
Low cost

5. Nanoparticle Inks for
Printed Electronics
• Nanoparticles can be stabilized in ink solutions by organic ligand shells,
which can be removed after printing.
• N
Nanoparticles can b f th cured or sintered t hi hl conductive fil
ti l be further d i t d to highly d ti films
at low temperatures.
70-90°C
70 90°C 100-150°C
100 150°C
Deposited Ag nanoparticles
Conductive Ag film on PET cured
from printed nanoparticle inks
150°C
200 nm

6. NanoMas Proprietary Technology:
Producing High Quality Nanoparticles with
Large-Scale and Low-Cost Processes
g
NanoMas
silver
nanoparticles
with 5 6 nm
ith 5-6
in size (SEM)
50L pilot production
reactor at NanoMas NanoMas Ag nanoparticle powders and inks

7. NanoMas Conductive Nanoparticle
Inks Technology
gy
• Patented unique nanoparticle synthesis technology, widely
q p y gy y
compatible with the low cost production processes in the
chemical industry
• Low cost and fully scalable to large scale mass production
• Ultra-small nanoparticle size (2 to 10 nm) with specially designed
surface chemistry allows low annealing temperature, short
process time, and high conductivity
• Variety of surface chemistry for different solvent dispersion and
applications
• Low resistivity (as low as ~2.4 μΩ-cm, 1.5x of pure Ag)
• Low process temperature (as low as ~70°C) compatible with most
p ast c substrates
plastic subst ates
• Also curable by laser or UV light at room temperature

8. Fully Scalable Process
y
• NanoMas patented process
built around traditional wet
chemistry manufacturing
– Lowest cost method of nanoparticle
production
– Superior quality and reproducibility
p q y p y
2000L HV Production
8

9. NanoMas Metal Nanoparticles
(Ag, Au, Pd, Pt)
Silver (~5 nm) Gold ( 3-4 nm)
Platinum ( ~2 nm)
Palladium ( ~3 nm)

10. Thermal Curing Profile of NanoMas
Silver & Gold Nanoparticles
40
NanoMas NanoSilver Ink (~5 nm)
NanoMas NanoGold Ink (3-4 nm)
30
m)
Resistiv (μΩ-cm
20
vity
10
Bulk Silver Resistivity
0
80 100 120 140 160 180 200
Annealing Temperature (C)

11. In-Situ Resistance
Measurements
The measurements show the evolution of the electrical resistance of Ag‐NP films over
more than 5 decades upon sintering.
The final resistance is relatively invariant, whereas kinetics vary dramatically.
Three characteristic times, the onset, the peak rate, and the terminal times, have been
identified. Arrhenius analysis reveals an activation energy of ca. 600 meV.

12. Morphology of Sintered
Silver NP Films
5s 10 s 20 s
30 s 60 s 300 s
Ag-NP thin films sintered at 120oC

13. Control Film Morphology by
Formulation and Processing
g
Film processed
with normal
NanoSilver ink
formulation
Film processed
with a special
NanoSilver ink
formulation

14. Mechanical Performance
of NanoSilver Films
Stretching apparatus Printed Ag-NP films before & after stretching
~ 6 inch
6 inch
3 inch
II
Regime
Regime
IV
III
I Regio
n II
Resistance increases with elongation
Still conducting with >200% elongation
PET substrate fails first

15. NanoSilver Ink for Inkjet Printing
Dimatix DMP2800
used for development
df d l
15

16. Inkjet Printing
Advantages Ink Jet Printing
g g Challenges
g
• Inexpensive system • Depositing thick materials
• Proven high volume • Inks require nanoparticles
production tool and for stability (free of
technology aggregations)
• Digital flexible can make
Digital, flexible, • Depositing on three-
changes on the fly dimensional objects
• 50-100 micron line
resolution with 10 pl heads

17. NanoMas Inkjet Inks
Properties Value
% Loading 10‐50%
Viscosity
Vi it 5‐ 16 cps
5 16
Surface tension 27‐35 dynes/cm
Trace height up to 400nm/per pass
Curing Temperature <180⁰C
Conductivity 5 µΩ‐cm
• Customizable to meet customer needs
17

18. Inkjet Printing using
NanoMas Inks
Line width
~200 μm
~100 μm
Jetting from 10pL head at 5KHz NanoSilver ink printed on glass &
cured at 150⁰C
18

19. NanoSilver Ink for
Pneumatic Aerosol Jet
Printing
Optomec Aerosol Jet Printer
used for Development
19

20. 20

21. 3D Multi‐Chip Stack Packaging
• 3D multi-chip stack packaging enables portable devices with more
functions that consumers are looking for (such as smart phones).
• Printed vertical interconnects to replace wire bonding
ertical ire
• Lower cost, higher yield, better device performance and reliability…
21

22. Aerosol Jet Printing
Advantages Aerosol Jet Printing Challenges (ink):
• Capable of depositing traces on • Loss of solvent from ink during
3-dimensional packages aerosol formation
• High deposition rates
g p • Agglomeration of p
gg particles
• High throughput tools currently during aerosol formation
being developed • Depositing thick materials
• Does not require <100nm
particles in ink
• Very high resolution can be
achieved (<10 micron)

23. Example of Target Material
Specification for Optomec Ink
Physical Property Target Spec. Formulated Ink
Particle Size <100nm 5nm
Solids Loading 50wt% (or greater required), >66%
>70wt% preferred
Resistivity <5x10‐8 ohm.m < 5x10‐8 ohm.m
Sintered trace
Sintered trace Several microns thick
Several microns thick Demonstrated several microns thick
Demonstrated several microns thick
traces
Agglomerates Very few required, none preferred None observed
Sedimentation No cake formation in 1‐2 hours None observed
required, no cake formation preferred
Multiple No preferential sedimentation Single component
Components
Pot Life
Pot Life > 12 hr shift
> 12 hr shift >8 hour operation with no measurable
>8 hour operation with no measurable
change in total dispersed solids level
Shelf Life 6 months required, Projected to be > 6months
12 months preferred (under testing)
Viscosity 1 30cP
1‐30cP 5 6cP
5‐6cP
Solvent Systems High boiling point/low evaporation BP 240 C , 0.07mmHg @ 20C
rate (e.g. BP 193C, 0.06mmHg @ 20C)
23

24. Characterization of Printing
Sintered Trace Height: 3.8µm
Width 40 µm 24

25. Cross-Section of Printed Trace
High conductive (~5
uohm‐cm), high
resolution (<30 um line
width), high aspect ratio
width), high aspect ratio
(20‐30 um height)
printing can be achieved
25

26. NanoSilver Ink for High Throughput
Commercial Gravure Printing
26

27. High Throughput Gravure
Printing of RFID Antenna
g
• Demonstrated low cost production of RFID antenna using a
commercial gravure printing press
• 25-50 m/s roll-to-roll printing
p g

28. Applications in Fabricating
Printed Electronic Devices with
NanoMas Nanoparticle Inks
28

29. Solar Cell Metallization
Advantages of using NanoMas special solar inks and pastes:
• Low temperature processing (<250˚C) compatible with most thin-film
and organic solar cell technologies
g g
• High resolution printing enables better efficiency
• Excellent electric contact and mechanical adhesion with silicon, glass
ITO, etc.
29

30. Fine Line Solar Cell Metallization
Printed with Aerosol Jet
30

31. All-Printed Hydrogen
Sensors on Plastics
• Sensing hydrogen as low as 200 ppm
• Response time less than 1s
Response time less than 1s
• Low cost for large area sensing
31

32. Printed Organic TFTs
(a)
Ag OSC Ag
(b)
Silicon dioxide gate dielectric
Single crystal silicon gate
(a) (b)
Optical microscopy of fabricated bottom-
gate-bottom-contact polythiophene
IV
I-V characterization of OTFT based on OTFTs with (a) evaporated Au and (b)
polythiophene as the organic SC and printed printed Ag as the electrode materials,
Ag electrodes. (on/off ratio ~ 103 and carrier respectively.
mobility ~ 0.02 cm2 V-1 S-1) 32

33. Printed Silver Contacts on Single
Walled Carbon Nanotube FET
Vsd
SEM on SWNT‐FET
Source
S SWCNTs Drain
D i
SiO2
P‐Si
Vgate
SWNT FET
SWNT‐FET
33

34. Summary
• NanoMas has developed a low cost process for
producing A A P and Pd nanoparticles
d i Ag, Au, Pt d i l
• The particles are some of the smallest and most stable
commercially available, while allowing low temperature
sintering compatible with most flexible substrates for
printed electronics
• The nanoparticles can be formulated into inks suited to
p
a number of printing techniques including gravure, ink-
jet, Aerosol-Jet printing.
• The printed traces can be sintered at low temperatures
p p
to produce low resistivity, adherent, mechanically
robust conductive patterns suitable for use in the
printed electronics applications.
34

35. Acknowledgements
NanoMas Technologies, Inc.
Dr. David van Heerden
Dr. Hichang Yoon
Dr. Yu Du
Dr. Jalal Salami
D J l lS l i
Binghamton University
Prof.
Prof Howard Wang
Liwei Huang
Dr. Yayong Liu (SiPix now)
Nano Material LINX‐CONSULTING
Investors, LLC
C