Chapter 11 Fundamentals of Passives: Discrete, Integrated, and Embedded

Presented by

Paul Kasemir and Eric Wilson

Chapter ObjectivesDefine passives and their fundamental

parametersDescribe the role of passives in

electronic products Introduce the different formsDescribe the different materials and

processes used for passives

11.1 What are Passives? Can sense, monitor, transfer, attenuate, and

control voltages Cannot differentiate between positive and

negative polarity Cannot apply gain or amplification Passives absorb and dissipate electrical

energy Ex. Resistor, inductor, capacitor, transformer,

filter, switch, relay

11.2 Role of Passives in Electronic Products

High frequency applications take smaller values (pF and nH)

Impedance matching to coax (50 ohm) Power supplies require large

capacitance Digital circuitry requires decoupling

capacitors for current surges Resistors used for termination,

filtering, timing and pull up/down

RF Passives Filters, couplers, RF crossings, impedance

matching, and antennas. Signal inductors (1-20nH) and capacitors (1-

20pF) Choke Inductors (20-100nH) Higher frequency requires smaller footprints,

or even embedded passives Mixed-Signal packages used in cell phones

and GPS in MCM

11.3 Fundamentals of PassivesResistor

Resist current flow Dissipate a power as heat V = IR Current Density, resistivity,

conductivity, and sheet resistance

Fundamentals of CapacitorStores electrical charge QDielectric between 2 metal platesCapacitance C = QV = εA/d I = C(dV/dt) DC openSeries and parallel capacitorsReactance, impedance, ESR, leakage

current

Fundamentals of InductorStores energy in magnetic fieldWire coil with or without core Inductance L = μn2AlV = L(dI/dt) DC shortMagnetic cores increase B field, and

thus inductance

Filters

Low-pass High-passBandpassBandstopSeries-parallel combination of R, L, and C

11.4 Physical Representation

Physical Representation

Discrete – single passive Integrated – multiple passives

Array SIP and DIP resistor packages

Network Filter circuits with only inputs and outputs as

package terminals

Embedded Created as part of the substrate

Passive Comparisons In a typical circuit, 80% of components

are passives50% of the PCB is taken by passives25% of solder connections go to

passives~900 billion discrete units per year

11.5 Discrete PassivesResistors

Wire-wound Nichrome wire

Film resistors Carbon or metal film deposited on substrate

Carbon-composite Graphite powder, silica and a binder

Resistor applications Bias Divider Feedback Termination Pull up/down Sense Delay Timing

Polar CapacitorsAluminum electrolyte

Uneven surface gives efficiencyTantalum

Pellet with lots of surface area Cathode material limits conductivity

Nonpolar Capacitors Film

Rolled Stacked

Ceramic Most dominant Like stacked film Used to need precious metals Now Ni and Cu can be used

High Capacitance 1-47 F

Capacitor Performance I Remember capacitors have AC effects Temperature coefficient

Typically less than 10% Some can be on order of ppm/°C Larger capacitance = worse coefficient

Capacitor Performance II Voltage coefficient Aging

Logarithmic X7R 1% per decade

hour (good) Reversible

Capacitors Becoming Inductors Caps have associated inductance Self resonant frequency

ESL dependent on physical structure

Capacitor Applications I Coupling Timing and wave shaping

Changing RC time constant Windshields

Capacitor Applications II Filtering

Low pass filters

Decoupling Mostly for digital

signals

InductorsSMT inductors looking like SMT capsCore typeValue in henries, but should also have

series resistance “Choke” roleTiming circuits using Ls are gone

11.6 Integrated Passives Increased quantity decreases price

But maybe not as much as you would thinkSmaller components = higher mounting

costs But maybe a lot more than you would think

Arrays and Networks Arrays

Many of the same type in a single package Good for R Not as much for C

Networks Different types in one package Good for RC or RLC functions

11.7 Embedded (Integral) Passives Benefits

Smaller Cheaper (???) More reliable

Costs New designs New

manufacturing processes

Integration OptionsCeramicThin film on Si IC Integration

Horrible

Barriers to Embedded Passives

RiskNo reworkabilityCost

But wait until 2004!

Embedded Passives Technology R

Thick film ~100-1M Ω/square Thin film ~25-100 Ω/square

C Typical inorganic is 50 nF/cm2

GE has gotten ~200 nF/cm2 with inorganics Polymer-ceramic components can get 4-25 nF/cm2

L Okay in embedded if <100 nH Discrete recommended for >100 nH

The End