1. TFCG-Microsystems – Elintec Ghent University
Advanced Technologies in Fabrication and Interconnection of Flexible Displays and Substrates
Tom Bert
TFCG-Microsystems – Elintec Ghent University

2. Advanced Technologies in Fabrication and interconnection of Flexible Displays and Substrates
Overview
Flexible Display Interconnection a. Low temperature flip-chip b. Interconnection of TCPackaged driverchips to displays
2. Flexible Display Technology Electrophoretic Image Displays
3. Flexible Displays Driver Design a. Field emission large area b. High voltage drivers

3. 1a. Low temperature flip chip
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)

4. Isotropic Conductive Adhesives (ICA) +
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

5. 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
Pre-curing of ICA:
to avoid the washing out of the ICA
Dispensing of NCA: exact amount of NCA has to be dispensed in spiderweb pattern

6. 1a. NICA-technology Chip placement and thermocompression:
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

7. 1b. ACA-technology limited amount of process steps and process time
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

8. Low curing temperature needed to avoid damaging the plastic
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C Bonding time: 15 sec Bonding force: 1.5 kgf

9. Measurements NICA-technology 150 m thick chips : 80% yield
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
ACA-technology
Contact resistance from 0.6 to 7 Ω dependant on the number of particles

10. Direct Flip-Chip assembly of driverchips onto the display
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:
TCPackaged chip
Flexible substrate (PI)
Chip
Interconnection of TCPackaged (Tape Carrier) driverchips to the display
Direct Flip-Chip assembly of driverchips onto the display
Chip

11. Low temperature/pressure bonding (plastics) Flexibility
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 resistance: 4-point measurements and daisy chains

12. Advanced Technologies in Fabrication and interconnection of Flexible Displays and Substrates
1b. Interconnection of TCPackaged driverchips to displays
TCPackaged chip
Flexible substrate (PI)
Chip
Display substrate
Flexible substrate (PET/stainless steel)
Pitches: 250, 200, 150, 120, 100, 80 and 60 micron

13. Test structure on display
Advanced Technologies in Fabrication and interconnection of Flexible Displays and Substrates
1b. Teststructure
4-point measurement
daisy chains
Test structure on display u
PI foil i

14. 2. Electrophoretic Image Display
Advanced Technologies in Fabrication and interconnection of Flexible Displays and Substrates
2. Electrophoretic Image Display
Movement of colored pigments in a colored solvent
V >0
V <0

15. 2a. EPID Technology Pigments: optical response
Advanced Technologies in Fabrication and interconnection of Flexible Displays and Substrates
2a. EPID Technology
Pigments: optical response
Micelles: electrical response and …

16. 2b. EPID Modelling: electrical
Advanced Technologies in Fabrication and interconnection of Flexible Displays and Substrates
2b. EPID Modelling: electrical

17. 2b. EPID Modelling: optical
Advanced Technologies in Fabrication and interconnection of Flexible Displays and Substrates
2b. EPID Modelling: optical

18. 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

19. 3a. Flexible Large Area FED display
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

20. MicroCRT’s plugged into flexible foam to form flexible display
Advanced Technologies in Fabrication and interconnection of Flexible Displays and Substrates
MicroCRT’s plugged into flexible foam to form flexible display
microCRT
Addressing Flex
microchip
MicroCRT’s individually adressed
(microchip)
no peripheral drivers
optical sensor on chip
pixel luminance control
pixel aging compensation
Electronics help to:
Improve uniformity
Expand lifetime

21. consisting of tiles of 20 x 20 pixels resolution: 800 x 600
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
40 tiles, 800 pixels, 4 m for SVGA or any size
30 tiles
600 pixels
3 m
or smaller

22. Design of the microchip
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!

23. 3b. High Voltage Driver chips
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

24. 3b. High Voltage Driver chips
Advanced Technologies in Fabrication and interconnection of Flexible Displays and Substrates
3b. High Voltage Driver chips
Courtesy of Eastman Kodak Display and Components Division

25. 3b. High Voltage Driver chips: GUI
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

26. Visit our website: come.to/tfcg
Advanced Technologies in Fabrication and interconnection of Flexible Displays and Substrates
Conclusion
Flexible Display Interconnection a. Low temperature flip-chip: below 130°C b. TCPackaged driverchips: below 150°C
2. Flexible Display Technology EPID: electrical and optical simulation
3. Flexible Displays Driver Design a. Field emission large area: complete chip design b. High voltage driver: multifunctional tool
Visit our website: come.to/tfcg

27. Advanced Technologies in Fabrication and interconnection of Flexible Displays and Substrates
Thank you
Questions?

28. 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 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:
In August 2004 a spin -off company GEMIDIS was created for the development of LCOS imagers for HDTV, control rooms and D-cinema.