Advanced Technologies in Fabrication and Interconnection of Flexible Displays and Substrates

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Advanced Technologies in Fabrication and
Interconnection of Flexible Displays and
Substrates
Tom Bert TFCG-Microsystems ElintecGhent
University
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Advanced Technologies in Fabrication and
interconnection of Flexible Displays and
Substrates
Overview

• Flexible Display Interconnectiona. Low
  temperature flip-chipb. Interconnection of
  TCPackaged driverchips to displays
• 2. Flexible Display Technology Electrophoretic
  Image Displays
• 3. Flexible Displays Driver Designa. Field
  emission large areab. High voltage drivers

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Advanced Technologies in Fabrication and
interconnection of Flexible Displays and
Substrates
1a. Low temperature flip chip
Demands for use inside a smart-card ?
flexibility, bendability? thin? transparency?
low-temperature assembly? cheap and fast
technology
Substrate polyethersulphone (PES) conductive
ITO layer Assembly use of adhesives (ICA and
ACA)
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Advanced Technologies in Fabrication and
interconnection of Flexible Displays and
Substrates
Isotropic Conductive Adhesives (ICA) Non
Conductive Adhesives (NCA) NICA

• ICA on substrate
• Pre-curing of ICA
• Dispensing of NCA
• Placing of the die
• Thermocompression

US Patent No. 6,555,414
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Advanced Technologies in Fabrication and
interconnection of Flexible Displays and
Substrates
1a. NICA-technology
Screenprinting of ICA? electroformed nickel
stencil with tapered walls? smaller stencil
holes than pads to avoid bridging
Dispensing of NCAexact amount of NCA has to be
dispensed in spiderweb pattern
Pre-curing of ICA to avoid the washing out of
the ICA
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Advanced Technologies in Fabrication and
interconnection of Flexible Displays and
Substrates
1a. NICA-technology
Chip placement and thermocompression no
self-alignment with adhesives first only
pressure, then pressure heat ? no voids
inside
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Advanced Technologies in Fabrication and
interconnection of Flexible Displays and
Substrates
1b. ACA-technology

• limited amount of process steps and process time
  
• soft conductive particles needed with high
  pressure bonding

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Advanced Technologies in Fabrication and
interconnection of Flexible Displays and
Substrates
1b. ACA-technology
Low curing temperature needed to avoid damaging
the plastic
Bonding temperature 130?CBonding time 15
secBonding force 1.5 kgf
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Advanced Technologies in Fabrication and
interconnection of Flexible Displays and
Substrates
Measurements
NICA-technology
150 ?m thick chips 80 yield 250 ?m thick chips
100 yield
Contact resistance from 0.6 to 7 Odependant on
the number of particles
ACA-technology
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Advanced Technologies in Fabrication and
interconnection of Flexible Displays and
Substrates
1b. Interconnection of TCPackaged driverchips to
displays
Two technologies, both using anisotropic
conductive adhesives
Interconnection of TCPackaged (Tape Carrier)
driverchips to the display
Direct Flip-Chip assembly of driverchips onto
the display
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Advanced Technologies in Fabrication and
interconnection of Flexible Displays and
Substrates
1b. Interconnection of TCPackaged driverchips to
displays

• Difficulties
• Small pitches
• Low temperature/pressure bonding (plastics)
• Flexibility

Measurements of contact resistance4-point
measurements and daisy chains
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Advanced Technologies in Fabrication and
interconnection of Flexible Displays and
Substrates
1b. Interconnection of TCPackaged driverchips to
displays
Pitches 250, 200, 150, 120, 100, 80 and 60 micron
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Advanced Technologies in Fabrication and
interconnection of Flexible Displays and
Substrates
1b. Teststructure
4-point measurement daisy chains
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Advanced Technologies in Fabrication and
interconnection of Flexible Displays and
Substrates
2. Electrophoretic Image Display
Movement of colored pigmentsin a colored solvent
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Advanced Technologies in Fabrication and
interconnection of Flexible Displays and
Substrates
2a. EPID Technology
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Advanced Technologies in Fabrication and
interconnection of Flexible Displays and
Substrates
2b. EPID Modelling electrical
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Advanced Technologies in Fabrication and
interconnection of Flexible Displays and
Substrates
2b. EPID Modelling optical
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Advanced Technologies in Fabrication and
interconnection of Flexible Displays and
Substrates
EPID Modelling
Complete model both electrical and optical
(even thermal) Helps understanding
contributions of the different
parameters Optimization of the display
characteristics
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Advanced Technologies in Fabrication and
interconnection of Flexible Displays and
Substrates
3a. Flexible Large Area FED display
anode
cathode
Each pixel comprises of one MicroCRT
gate
Field Emission by means of Carbon nanotubes
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Advanced Technologies in Fabrication and
interconnection of Flexible Displays and
Substrates
MicroCRTs plugged into flexible foam to form
flexible display

• Electronics help to
• Improve uniformity
• Expand lifetime

• MicroCRTs individually adressed
• (microchip)
• no peripheral drivers
• optical sensor on chip
• pixel luminance control
• pixel aging compensation

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Advanced Technologies in Fabrication and
interconnection of Flexible Displays and
Substrates

• Large Area Display
• consisting of tiles of 20 x 20 pixels
• resolution 800 x 600
• dimensions 4m on 3m

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Advanced Technologies in Fabrication and
interconnection of Flexible Displays and
Substrates

• Design of the microchip
• Each microchip (each pixel) is digitally
  adressable
• High Voltage analogous cathode driver (up to 100
  V)
• On-chip optical feedback-circuit

1 chip Same CMOS technology!
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Advanced Technologies in Fabrication and
interconnection of Flexible Displays and
Substrates
3b. High Voltage Driver chips

• Reflective bistable displays
• Very high voltage levels (typ. 20V to 50V rms)
• Very complex waveforms on rows and columns

Presented driver chip provides- a very compact
alternative - high degree of flexibility

• 120 rows and 160 columns (1/16 VGA resolution)
• 100V driving capability on all outputs
• Very complex multi-level HV output waveforms
• Numerous addressing schemes
• Ultra-low power consumption ( ? 2?W per output)
• 3 - 5V battery power supply

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Advanced Technologies in Fabrication and
interconnection of Flexible Displays and
Substrates
3b. High Voltage Driver chips
Courtesy of Eastman Kodak Display and Components
Division
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Advanced Technologies in Fabrication and
interconnection of Flexible Displays and
Substrates
3b. High Voltage Driver chips GUI
GUI Description of display configuration and
definition of driving scheme
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Advanced Technologies in Fabrication and
interconnection of Flexible Displays and
Substrates
Conclusion

• Flexible Display Interconnectiona. Low
  temperature flip-chip below 130Cb. TCPackaged
  driverchips below 150C
• 2. Flexible Display Technology EPID electrical
  and optical simulation
• 3. Flexible Displays Driver Designa. Field
  emission large area complete chip designb. High
  voltage driver multifunctional tool

Visit our website come.to/tfcg
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Advanced Technologies in Fabrication and
interconnection of Flexible Displays and
Substrates
Thank you Questions?
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Advanced Technologies in Fabrication and
interconnection of Flexible Displays and
Substrates
Tom Bert was born in 1979 and became a Master in
Engineering, Electronics in 2002. Since then he
works for the Thin Film Components Group (TFCG)
at the department of Electronics and Information
Systems (Elis) of the Ghent University. He works
on the physical modeling of electronic
paper. The TFCG Microsystems group is involved
in the research on design and technology of
microsystems. The research focuses on the
embedding of microelectronics in new applications
in the field of biomedics, textile, automotive,
telecom and displays. The underlying generic
technology platform comprises thin film, thick
film, laminate, flex technology and laser
structuring. The technology platform enables high
density interconnection and packaging on rigid
and flexible substrates, optical interconnect and
the fabrication of different microsystems on
rigid and flexible substrates. On the design
site the research efforts are focussed on
mixed-mode CMOS technologies looking at smart
interface technologies for automotive and display
applications. By means of Technology CAD (TCAD)
DMOS and IGBT's were succesfully integrated in
0.35 and 0.7 CMOS technologies. Using these CMOS
technologies, dedicated high voltage, low power
display drivers were developed for addressing
bistable displays. Other highlights are a fine
line technology and packaging technology for
cellular phone, a low temperature flip chip
technology for smart cards, a multilayer flex
technology for smart band-aid, and a liquid
crystal on silicon technology for high
performance high resolution displays. The group
has recently moved to new facilities at the
Technology Park of Gent University. The new 2000
m2 cleanroom building is equiped with a 600 m2
cleanroom facilities. More info can be found at
the website of TFCG Microsystems
http//www.elis.ugent.be/ELISgroups/tfcg/index.htm
l In August 2004 a spin -off company GEMIDIS
was created for the development of LCOS imagers
for HDTV, control rooms and D-cinema.