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

Chapter 11 Fundamentals of
Passives: Discrete, Integrated,
and Embedded
Presented by
Paul Kasemir and Eric Wilson
Chapter Objectives
 Define
passives and their fundamental
parameters
 Describe the role of passives in
electronic products
 Introduce the different forms
 Describe 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 (120pF)
 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
Passives
 Resistor
 Resist
current flow
 Dissipate a power as heat
 V = IR
 Current Density, resistivity,
conductivity, and sheet
resistance
Fundamentals of Capacitor
 Stores
electrical charge Q
 Dielectric between 2 metal plates
 Capacitance C = QV = εA/d
 I = C(dV/dt)
DC open
 Series and parallel capacitors
 Reactance, impedance, ESR, leakage
current
Fundamentals of Inductor
 Stores
energy in magnetic field
 Wire coil with or without core
 Inductance L = μn2Al
 V = L(dI/dt)
DC short
 Magnetic cores increase B field, and
thus inductance
Filters
 Low-pass
 High-pass
 Bandpass
 Bandstop
 Series-parallel
combination of R, L, and C
11.4 Physical Representation
Physical Representation
– single passive
 Integrated – multiple passives
 Discrete
 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 passives
 50% of the PCB is taken by passives
 25% of solder connections go to
passives
 ~900 billion discrete units per year
11.5 Discrete Passives
 Resistors
 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 Capacitors
 Aluminum
 Uneven
electrolyte
surface gives efficiency
 Tantalum
 Pellet
with lots of surface area
 Cathode material limits conductivity
Nonpolar Capacitors

Film



Ceramic





Rolled
Stacked
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
Inductors
 SMT
inductors looking like SMT caps
 Core type
 Value in henries, but should also have
series resistance
 “Choke” role
 Timing circuits using Ls are gone
11.6 Integrated Passives
 Increased
 But
quantity decreases price
maybe not as much as you would think
 Smaller
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 Options
 Ceramic
 Thin
film on Si
 IC Integration
 Horrible
Barriers to Embedded Passives
 Risk
 No
reworkability
 Cost
 But
wait until 2004!
Embedded Passives Technology

R



C




Thick film ~100-1M Ω/square
Thin film ~25-100 Ω/square
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