Organic Substrate - LCP

Transcription

1 Organic Substrate - LCP Why consider LCP as a substrate? Liquid Crystal Polymer (LCP) can be used as a high performance multilayer substrate Excellent electrical properties (ε r ~ 3.10 and tanδ=0.002) Flexible (printed circuits can be rolled or molded into desired shape) Wideband (9%) UHF RFID tag on LCP to cover the global MHz band Good performance: mechanical integration compatibility and economic viability Antennas fabricated on 12 x12 in LCP Film

2 Organic Substrate - Paper Why Consider Paper as a Substrate? - Environmental Friendly and low cost (LOWEST COST MATERIAL MADE BY HUMANKIND) - Large Reel to Reel Processing - Low surface profile with appropriate coating Coated paper - Compatible for printing circuitry by direct write methodologies - Host nano-scale additives (e.g. fire retardant textiles) - Can be made hydrophobic - Dielectric constant ε r (~3) close to air s, allowing EM waves to penetrate substrate easily with minimum (5-6%) power reflection Drop of water on hydrophobic paper

3 Paper Dielectric Properties Characterization The down shifted TEmnp mode resonant frequency between an empty and a lorded cavity gives the information of the sample dielectric constant. Empty Cylinder (unloaded) Paper Sample Inserted (loaded) TE011 f=2.2% peak shifting

4 Inkjet-printing Technology - Printer Characteristics: Piezo-driven jetting device to preserve polymeric properties of ink 10 pl drops give ~ 21 µm Drop placement accuracy ±10 µm gives a resolution of 5080 dpi Drop repeatability about 0.5% Printability on organic substrates (LCP, paper ) High resolution inkjet printed copper (50 µm)

5 Inkjet-printing Technology - Ink Ink: Consisting of nano-spheres melting and sintering at low temperatures (150 C) After melting a good percolation channel is created for electron flow Provides a better result than traditional polymer thick film material approach which uses metal flakes Nano-sized Silver Ink Particle Size = 30 nm SEM Images of a Layer of Printed ink, Beore and After a 15 Minute Cure at 150ºC

6 Carbon Nanotubes as Gas Sensor CNTs structure can be conceptualized by wrapping a one-atom-thick layer of graphite into a seamless cylinder. Single-walled CNTs and Multi-walled CNTs A diameter of close to 1 nanometer, with a tube length that can be many thousands of times longer. CNTs composites have electrical conductance highly sensitive to extremely small quantities of gases, such as ammonia (NH3) and nitrogen oxide (NOx). The conductance change can be explained by the charge transfer of reactive gas molecules with semiconducting CNTs. CNT Particles : Single Walled CNT Solvent : Dimethylformamide (DMF) 1. Particle size < 215um 2. Viscosity cps 3. Surface tension 28 dynes/cm

7 Inkjet-printed SWCNT Films Formulation: - P2 sample from purified SWCNT by air oxidation and catalyst removing (aggregated at the concentration of 0.1mg/ml) - P3 sample from purified SWCNT after nitric acid processing (go up to 0.4mg/ml) - 0.4mg/ml P3 sample dispersed in DMF - 12 hours sonication to prevent aggregations of large particle residues. 10L 15L 20L 25L Silver Electrode SWCNT Film Silver electrodes were patterned before depositing the SWCNT film, followed by a 140 C sintering. The electrode finger is 2mm by 10mm with a gap of 0.8mm. SWCNT film was 2mm by 3mm. 1.1mm overlapping zone to ensure the good contact between the SWCNT film and the electrodes. 500um Overlapping Zone

8 Gas Chamber Measurement Gas chamber: gas inlet, outlet and exhaust hood 4% Ammonia gas for 30 minutes SWCNT stable response up to 1GHz 25L was used for future steps 25L 20L

9 Antenna Design and Performance EU RFID Band Conductive ink has become the major cost of an RFID tag after introducing the paper-based substrate. Minimizing the amount of ink used per antenna will save thousands of dollars in the mass production. Bandwidth 810MHz 890MHz When bended 814MHz 891MHz 2.01dBi Directivity with 94.2% efficiency.

10 Gas Detection 4π Pr = Pt + 2Gt + 2Gr 40log10 40log10 d λ ( ) + η Tag 686MHz Z ant =42.6+j11.4 Ohm η = Z Z + Ioad Z + Z ANT load ANT + 2 * SWCNT Z=51.6-j6.1 Ohm in air Z=97.1-j18.8 Ohm in NH3 Power reflection coefficient changes from -18.4dB to -7.6dB. At reader s side, this means 10.8dBi increase of the received power level. By detecting this backscattered power differnce, the sensing function is fulfilled.