Passive ComponentsAA 2012/2012 Lezioni di Tecnologie e Materiali per l’Elettronica Passive...

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Transcript of Passive ComponentsAA 2012/2012 Lezioni di Tecnologie e Materiali per l’Elettronica Passive...

  • AA 2012/2012 Lezioni di Tecnologie e Materiali per l’Elettronica

    Passive Components

    Danilo [email protected]

    microlab.unipv.it/microlab.unipv.it/

    Università degli Studi di Pavia

  • AA 2011/2012 Prof. D. Manstretta

    Capacitors

    Applications:

    • Supply filteringSupply filtering• Interference suppression• AC coupling

    Università degli Studi di Pavia Lezioni di Tecnologie e Materiali per l'Elettronica 2

    • AC coupling

  • AA 2011/2012 Prof. D. Manstretta

    Capacitors

    A capacitor is usually made of one dielectric layer and two conducting layerslayer and two conducting layers

    CapacitancedQC Capacitance

    Parallel plate capacitor

    dVC

    SC Parallel plate capacitor

    Dielectric properties change with temperature:

    dC

    Dielectric properties change with temperature:

    Temperature coefficientTC

    C

    1

    Università degli Studi di Pavia Lezioni di Tecnologie e Materiali per l'Elettronica 3

    TC

  • AA 2011/2012 Prof. D. Manstretta

    Capacitors A capacitor is essentially an energy storage element:

    Energy stored21

    2SE CV

    Only a limited amount of energy can be stored in a capacitor d e the ma im m oltage (ma electric field E )capacitor due the maximum voltage (max electric field ER) that the oxide can withstand before breakdown

    Maximum energy density 21SEE E

    Maximum electric field

    Maximum energy density 2v RE E

    Vol

    Electric permettivity

    Università degli Studi di Pavia Lezioni di Tecnologie e Materiali per l'Elettronica 4

    permettivity

  • AA 2011/2012 Prof. D. Manstretta

    Dielectric Electrical PropertiesElectric Permeability vs Frequency Loss tangent

    ED tjeEE 0 tjDD ''' j

    r

    tjeDD 0 '''0 j

    '''''tan

    tg

    MHz GHz 100GHz 10THz f

    interface

    dipole

    atomic Microscopic resonance ff t

    Università degli Studi di Pavia Lezioni di Tecnologie e Materiali per l'Elettronica 5

    dipole effects

  • AA 2011/2012 Prof. D. Manstretta

    Capacitors: Distributed EffectsThe capacitor can be divided into several sections in series:Each section is modeled with an RLC equivalent circuitEach section is modeled with an RLC equivalent circuit Very accurate but very complicated Can account for frequency-dependent effects

    Equivalent Circuit

    Università degli Studi di Pavia Lezioni di Tecnologie e Materiali per l'Elettronica 6

  • AA 2011/2012 Prof. D. Manstretta

    Simplified Equivalent CircuitDielectric and conductor losses

    Dielectric resistivity (DC)

    conductor losses

    GCjY 'dSC r 0 S

    dRP d S

    21 GV

    Retan

    Imdiss

    r

    Y PY P

    ● Loss tangent 2GV

    21 'C V

    ● Relaxation time constant rPCR 0

    21 '2

    C V

    Università degli Studi di Pavia Lezioni di Tecnologie e Materiali per l'Elettronica 7

  • AA 2011/2012 Prof. D. Manstretta

    Dielectric LossesIf we ignore all other sources of loss (connectors,metal plates resistive losses, etc.), the capacitor lossmetal plates resistive losses, etc.), the capacitor losstangent is given by the dielectric loss tangent (tan )

    S

    '''tan

    0 ' ''SY j C j jd

    GCjY ' 0' '

    SCd

    0 ''SGd

    2,

    1 ''2

    dissdiss vol

    PP ESd

    212diss

    P GV''P2Sd2

    21 'rP C V2

    01 'rr vol

    PP E

    ''tan'

    diss

    r

    PP

    Università degli Studi di Pavia Lezioni di Tecnologie e Materiali per l'Elettronica 8

    2r , 02r vol Sd

  • AA 2011/2012 Prof. D. Manstretta

    Capacitor Impedance vs Frequency

    Resonance frequency fRESq y RES

    The impedance magnitude |Z()| decreases as ~1/ up to theresonant frequency fRES .

    Università degli Studi di Pavia Lezioni di Tecnologie e Materiali per l'Elettronica 9

    q y RESAbove fRES the parasitic inductance dominates..

  • AA 2011/2012 Prof. D. Manstretta

    Resonance Freq. vs Cap. Value

    For a given capacitor type and package size, fRES decreases for

    Università degli Studi di Pavia Lezioni di Tecnologie e Materiali per l'Elettronica 10

    increasing capacitance

  • AA 2011/2012 Prof. D. Manstretta

    Applications• Supply filtering• Interference suppression• AC coupling SUPPLY

    NOISE DC

    Several capacitors inparallel provide a smallimpedance across alarge frequency rangePOSITIVE

    SUPPLYPOWER SUPPLY

    NOISE

    HF NOISE

    DC large frequency range

    DC+- LARGE INTERM

    .SMALL

    NEGATIVE ACSUPPLY

    SIGNAL GENERATOR

    AC COUPLING

    Università degli Studi di Pavia Lezioni di Tecnologie e Materiali per l'Elettronica 11

    RF

  • AA 2011/2012 Prof. D. Manstretta

    Film Capacitors Made from high quality polymer (polycarbonate, polystyrene,

    polypropylene, polyester) or paper film, and a thin (~50m) Al foilD t 10 di l t i thi k Down to 10m dielectric thickness

    Air and humidity removed to increase max voltage Conductive resin terminals Metallization of polymer sheet

    increases energy per unit volume Improved reliabilityp y

    Capacitance values: up to ~50F Frequency range: up to a few MHz

    Università degli Studi di Pavia Lezioni di Tecnologie e Materiali per l'Elettronica 12

  • AA 2011/2012 Prof. D. Manstretta

    Mica Capacitors Muscovite mica is a natural crystal

    Easy to obtain layers (~50 m thickness) r ~5-7

    L l t t (10 4 @1MH ) Low loss tangent (10-4 @1MHz) Low temperature coefficient ~100 ppm/°C High voltage applications High voltage applications 1% accuracy: trimming done removing top-plate metallization Moderate range of capacitance values: up to ~100nF

    Università degli Studi di Pavia Lezioni di Tecnologie e Materiali per l'Elettronica 13

  • AA 2011/2012 Prof. D. Manstretta

    Ceramic Capacitors A ceramic capacitor is based on a ceramic dielectric with

    metal electrodesmetal electrodes Parameters depend on the dielectric materials:

    Stetatites =6 tan=5·10-4 Stetatites r=6 tan=5·10 4

    (TiO2)x(BaO)1-x r=37 tan=3·10-4

    TiBaO3 r~1000 tan~10-23 rPiezoelectric material

    Production steps: Ceramic dielectric firing

    El t d d iti d fi i

    15·104 pF

    Electrodes deposition and firing Multi-layer ceramic capacitors: several layers are pressed and

    fired again together

    Università degli Studi di Pavia Lezioni di Tecnologie e Materiali per l'Elettronica 14

    g g

  • AA 2011/2012 Prof. D. Manstretta

    Multi-layer Ceramic Capacitors

    Università degli Studi di Pavia Lezioni di Tecnologie e Materiali per l'Elettronica 15

  • AA 2011/2012 Prof. D. Manstretta

    Al - Electrolytic Capacitor The foil insulated by the oxide layer is the anode (+) The liquid electrolyte and the second foil act as cathode. (-) The layer of insulating aluminum oxide acts as the dielectric

    thin Al2O3 dielectric → high capacitance (~mF) in a small volumeE 109 V/m high energy density Er ~109 V/m → high energy density

    High series inductance → low frequency applications Applied voltage must have positive (Va-Vc) polarity

    Università degli Studi di Pavia Lezioni di Tecnologie e Materiali per l'Elettronica 16

  • AA 2011/2012 Prof. D. Manstretta

    Electrolytic Capacitor

    Boric acid

    O id thi kOxide thickness:

    /1 tcell eVs Hydrogen gasUniversità degli Studi di Pavia Lezioni di Tecnologie e Materiali per l'Elettronica 17

    RE

    Hydrogen gas release

  • AA 2011/2012 Prof. D. Manstretta

    Ta Electrolytic Capacitor Porous sintered Tantalum (Ta) is used as first electrode (cathode)

    Oxide Ta2O5 is formed during firing with Mn(NO3 )2 MnO2 acts as electrolyte

    Second electrode (anode) is composed of graphite

    Reduced size and values (up to several 100F) compared with Al l t l ti itelectrolytic capacitors

    Università degli Studi di Pavia Lezioni di Tecnologie e Materiali per l'Elettronica 18

  • AA 2011/2012 Prof. D. Manstretta

    Capacitor TypesPolymer

    sheetMica Ceramic Electrolytic

    (Al)sheet (Al)MAX Cap. 50F 50nF 10nF ~mF

    % % % %Accuracy 10% 2% 5% 20%

    fMAX ~MHz ~ 10MHz ~ 100MHz ~ 100kHz

    Tan 5·10-4(10kHz)

    10-4 (1MHz) 10-3 (1kHz) 10-2(100Hz)

    [ /°C] ±100 100 ±20 ±1000 [ppm/°C] ±100 100 ±20 ±1000

    EV [J/cm3] 100m 1m 1m 1

    [ M·F ] 10.000 1000 1000 50

    Università degli Studi di Pavia Lezioni di Tecnologie e Materiali per l'Elettronica 19