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

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

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)

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

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

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

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

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

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

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

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

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

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

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

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 …

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

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

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

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

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

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

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!

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

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

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

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

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

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