Chapter 13 Fundamentals of RF Packaging Fundamentals of RF Packaging ECEN 5004 – Digital Packaging Mike Weimer Zach Allen
Dec 18, 2015
Chapter 13
Fundamentals of RF PackagingFundamentals of RF Packaging
ECEN 5004 – Digital Packaging
Mike WeimerZach Allen
IntroductionRF is the 2nd major technology in
microsystem revolution20th Century: Copper wire21st Century: Wireless/RF transmission
Potential to become the ultimate technology for giga/tera-bit communications
Packaging is a substantial issue
ECEN 5004 – Digital Packaging
13.1 What is RF?Radio Frequency (3 kHz – 300 GHz)
Wavelengths of 1 mm – 30 cmFirst RF transmission was in 1901 with a
message sent in Morse code from England to Newfoundland
Titanic was assisted by sending an RF transmission to the Carpathia 58 miles away, saving 705 lives (1912)
Marconi earned Nobel Prize in PhysicsFirst mobile phone introduced prior to 1946First Cell Phone Commercial
ECEN 5004 – Digital Packaging
13.2 RF ApplicationsCellular telephony, portable internet,
broadband communications, etc.Most financially significant market is in
wireless applications (duh)High-bandwidth transmission (i.e. Verizon’s
new TV service) demands improved RF devicesAll while reducing package size and cost
ECEN 5004 – Digital Packaging
13.3 Anatomy of RF SystemsBase-mobile communication is standard
VHF: Very High Frequency [30 – 300 MHz]
UHF: Ultra High Frequency [300 – 3000 MHz]
SHF: Super High Frequency [3 – 30 GHz]
EHF: Extremely High Frequency [30 – 300 GHz]
Multiple-hop autonomous system networksIndividual mobiles act as repeaters
ECEN 5004 – Digital Packaging
13.3 Anatomy of RF SystemsTransceiver
Based around Variable-frequency Oscillators (VFOs)
RepeaterIntercepts/retransmits transmissionsOperates at VHF, UHF, and microwave frequencies
DuplexerAllows duplex operation (two operators can
interrupt each other at any time)Generally uses two separate frequencies
AutopatchConnects radio transceiver to telephone control
ECEN 5004 – Digital Packaging
13.3 Anatomy of RF SystemsPortable Telephone
Portable radio transceiverLong-range (10 – 20 miles)
Cordless TelephoneOld 900 MHz technologyShort-range (600 – 800 feet)
PagerActivated by a two-tone signal from base
stationOperates at 30 – 932 MHzUses a high-gain compact antenna
ECEN 5004 – Digital Packaging
13.3 Anatomy of RF SystemsTransmission Quality
Dedicated frequency to minimize interferenceAdequate power to ensure high S/N ratioSufficient bandwidth for high voice qualityFM operation to minimize noise problems
Service QualityAccessibility and Usability
Cell Phone ExampleRF Transceiver Low-pass Filter Power
Amplifier A/D Converter D/A Converter Local oscillator Antenna
ECEN 5004 – Digital Packaging
13.3 Anatomy of RF SystemsHigh quality filtering requirements
Low-pass (noise removal)Processing performed at Intermediate
FrequencyDSP is used in most modern cellular phones
Reprogrammable, fast, low power consumption
ECEN 5004 – Digital Packaging
13.4 Fundamentals of RFRadio Wave
Radiation and propagation of waves (dropping stone into pool)
Transverse waves (wave occurs in directions perpendicular to propagation)
FrequencyNumber of cycles per secondTerm coined in 1967 after Heinrich Hertz (Hz)
In lieu of the term ‘cycles per second’ (cps) ‘cps’ is also a unit of viscosity (CentiPoise)
ECEN 5004 – Digital Packaging
13.4 Fundamentals of RFAudio Frequencies
Range: 15 Hz – 20 kHzDefined by limits of human aural ability
Radio FrequenciesRange: 3 kHz – 300 GHzLargely used in radio transmission
WavelengthSpace occupied by one full cycle of a wave at
any timeWavelengths reduced at high frequencies
Passive component size comes into play
ECEN 5004 – Digital Packaging
13.4 Fundamentals of RFVelocity
Speed of signal propagation through substrateAffected by
Barometric pressure Humidity Molecular content Density
Unaffected by frequencyFilters
Passes or rejects signals of certain frequenciesBased analog filters are Circuits II materialDSP Filtering is complex and precise
ECEN 5004 – Digital Packaging
13.4 Fundamentals of RFAntenna
Interfaces RF systems with rest of worldRadiated power is a function of distance
Power density decreases by 1/r2 in all directions Why 850KOA (Denver) is a 50 kW system, but only
fractions of a W are received at your radioConductor and dielectric losses also are
considerationsGain and directivity (uni/onmi-directional)
ECEN 5004 – Digital Packaging
Gain pattern of 9 element Yagi-Uda antenna
13.4 Fundamentals of RFBandwidth
Affect performance of communications systemIdeal resonant circuit only resonates at one
frequencyCircuit ‘quality’ affects resonanceWidth of frequency band centered around the
resonant frequency is the ‘bandwidth’Noise
Affect accurate reproduction of transmissionsReceivers must have bandpass response to
limit noise
ECEN 5004 – Digital Packaging
13.4 Fundamentals of RFExternal Noise
Generated outside of the receiverCaused by atmospheric conditions, space,
solar, cosmetic-noise, lightingMan-Made Noise
EMI traceable to non-natural sourcesIgnition and impulse noise, which originates
from car engines and electrical appliances
ECEN 5004 – Digital Packaging
13.4 Fundamentals of RFInternal Noise
Caused by passive/active devices inside a receiver
Thermal Noise Generated in resistances or impedances
Shot Noise Generated by the shot effect present in all active
devices
Noise EvaluationSignal/noise ratio
Radio of signal power to noise power Higher is better for improved sound quality
ECEN 5004 – Digital Packaging
13.4.11 RF Components and DevicesActive, resistive, and reactive componentsPassive RF components have parasitics at raised
frequenciesUsed primarily for building filters and oscillators
Microwave Discrete Circuits (MDCs)Separate elements connected by conductive wiresMeans ‘separately discrete’
Microwave Monolithic Integrated Circuits (MMICs)Single integrated circuit of all components‘monolithic’ comes from monos (meaning single)
and ‘lithos’ (meaning stone)
ECEN 5004 – Digital Packaging
13.4.11 RF Components and DevicesMicrowave Integrated Circuits (MICs)
Combination of active/passive elements manufactured by successive diffusion processes on a semiconductor in monolithic or hybrid form
Very high integration densitiesVery useful in low-power and low-density
systems such as digital circuits and military applications
ECEN 5004 – Digital Packaging
13.4.12 Noise EvaluationSignal to Noise Ratio
Ratio of Signal Power to Noise Power
n
s
n
s
P
PN
S
P
PN
S
log10
powernoise
powersignal
13.4.13 RF CircuitsPassive RF components exhibit parasitics at
higher frequenciesInductors have stray capacitanceCapacitors have stray inductance
13.4.14 Fundamentals of RF Transmission Lines Summary of Maxwell’s Equations:
Electric charges generate electric fields Electric currents generate magnetic fields
There are no magnetic “charges” Time-varying magnetic field generates a spatially-
dependent electric field Time-varying electric field generates a spatially-
dependent magnetic field When both electric and magnetic fields vary with time,
electromagnetic waves are generated that travel in space with a velocity determined by the constitutive parameters of the medium
History of Radio1873- James Clerk Maxwell formulated
Maxwell’s Equations 1887- Heinrich Hertz proved the existence of
electromagnetic waves by using an antenna 1901- Marconi received first wireless
message to cross the Atlantic
13.4.14 Fundamentals of RF Transmission LinesWave propagation in a transmission line:
Voltage and Current assume spatial and temporal variations described by the propagating waves
Parameters of interest: Propagation velocity Wavelength
13.4.14 Fundamentals of RF Transmission Lines
13.4.14 Fundamentals of RF Transmission LinesWavelength and Conductivity in Selected
Media
Equations
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Frequency and Velocity,,Wavelength
lengthunitperecapacitanc
lengthperinductance
/
:ImpedancesticCharacteri
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L
CLZ
constant dielectricrelativeε
conductors the ofdiameter d
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impedancesticcharacteriZ
log138
Z
:ImpedanceCoaxial
r
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dD
r
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line wire-two a of ImpedancesticCharacteri
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13.4.14 Fundamentals of RF Transmission LinesUniform Transmission Lines
Include two or more conductors that maintain the same cross-sectional dimensions
Coaxial line Two-wire (twin lead) line
Planar Transmission LinesConductors lie on flat dielectric sheets
Microstrip Slot-line Fin-line
13.4.14 Fundamentals of RF Transmission LinesTypes of Transmission Lines
13.4.14 Fundamentals of RF Transmission LinesCharacteristic impedance of a two-wire line
ReflectionAny mismatch in impedance will generate a
reflectionFrom a packaging standpoint, reflections are
unwantedReflections cause non-optimized transfer of
power‘Good’ designs terminate the transmission line
with an impedance equal to the line wave impedance
Crosstalk Noise Crosstalk Noise occurs as a result of coupling energy
between two transmission lines Result of capacitive and inductive coupling between
lines Generates unwanted signals in transmission lines
resulting in false and corrupted information Coupling is proportional to the time rate of change of
signals more serious at higher frequencies Present-day high frequency designs require more
compactness that compounds noise coupling problems
Crosstalk Noise (continued)Mixed-signal analog/digital circuits on the
same substrate are susceptible to crosstalk noise from digital to analog sections
System-on-chip (SOC) or system-on-package (SOP) designs must have crosstalk noise solution in place to be viable
Crosstalk Noise (continued)
13.4.15 Transmission Line Losses and Skin Effect3 major types of losses that commonly occur
in practical transmission lines:Conductor lossDielectric lossRadiation loss
Conductor Loss I2R power dissipation due to heating that occurs in
the pure resistance of the conductor Copper loss is usually greater in a line having a low
characteristic impedance Lower-impedance higher current = higher power
dissipation (I2R) Reduced current in a high-impedance line results in
reduced copper loss without causing a reduction in transmitted power
Skin EffectA type of conductor lossAs frequency of applied current is increased,
more of the electron flow is on the surface (skin) of the conductor
H/cm 10 1.26 ty,permeabili
Hertz in frequency
10cm ohm in metal the of yresistivit
10
8-0
6
0
3
f
fs
Skin Effect
Skin Effect
Dielectric Loss I2R power dissipation due to heating that occurs in
the dielectric between conductors in a transmission line
Proportional to the voltage across the dielectric Standing waves of voltage on a line increase dielectric
loss Dielectric material stores energy in the form of
electric charge Naturally polarized dipoles realign by rotating in
direction of applied field Rotation causes part of electrical energy to be
converted into heat (lost)
Dielectric LossLost energy in a dielectric may be
characterized by its Dielectric Loss Tangent:
component) phase-(in energy stored'
component) phase-of-(out energylost '''
''tan
Radiation LossRadiation from circuit increases rapidly with
frequencyConfining the fields to the interior of metallic
enclosures (packaging/shielding) may prevent radiative power loss
Mode GenerationGenerated by discontinuities, unmatched
terminations, and controlled by type of feeding
Single-mode propagation is desired for higher bandwidth and optimum power transfer
Mode Generation (continued) Three types of modes:
TEM: Transverse-electromagnetic modes Often called transmission line modes Transmission lines that have at least two separate conductors
and a homogeneous dielectric can support one TEM mode Quasi-TEM Modes
Inhomogeneous dielectric such as microstrip transmission line Propagation characteristics exhibit a slight dependence with
frequency when compared with TEM Waveguide Modes
Can transport energy or information only when operated above distinct cutoff frequencies.
One of the most important aspects in the RF packaging design since any package operates as a waveguiding structure
DispersionIf phase velocity is different for different
frequencies individual frequency components will not maintain their original phase relationshipsSignal distortion will occurThis is Dispersion
Microwave FundamentalsMicrowave frequencies range from
approximately 1 GHz to 300 GHzTravel essentially straight through atmosphereNot effected by ionized layers of the
atmosphereUsed for short-range, high-reliability radio and
television linksCommonly used for satellite communication
and control
Microwave RepeatersA Microwave Repeater is a
receiver/amplifier/transmitter combination used for relaying signals at microwave frequencies
Used in long distance, overland communication links
Waveguides Used to carry microwave energy at frequencies above
3 GHz Feedline used at microwave frequencies Waveguide wall resistance is made as low as possible Are often purged with dry air or nitrogen to drive
moisture from inside Attractive option because of wide-bandwidth and low-
loss transmission characteristics
13.5.1 Digital vs. RF PackagingBy contrast with digital designs, RF
interconnects scale with frequency rather than technology (not directly subject to Moore’s Law)
RF packaging is dominated by transmission lines and reactive elements
Successful implementation of RF systems requires a departure from conventional circuit theory and design techniques
13.5.2 RF Packaging Design Problems that may arise include:
Rise-time degradation Attenuation due to losses Coupling between adjacent pins Radiation of signals
Major task: determine electrical parameters of the package at microwave frequency Lumped model consisting of inductors, capacitors, and
possibly resistors represents the package at RF frequencies
13.5.3 Flip ChipFlip chip has emerged as one of the most
successful packaging technologiesBeing used for RF systems where parasitic
minimization is essentialUsing ball arrays minimizes parasitic
inductance
13.5.4 Passive and Microwave Components Many components such as band select, channel
select, and tuning elements of the Voltage Controlled Oscillator VCO must still remain external to the chip Inductors with high quality factors are not available in
standard silicone processes Development of the following items will be a major
step toward low-cost, fully-monolithic RF and microwave transceivers: Better active device models Active inductors MEMS filter building blocks
13.6 RF Measurement TechniquesRF components, devices and systems are
measured using high frequency network analyzers
Measurements involve extraction of scattering parameters (S parameters)Describe interactions between incident and
reflected waves from device under testModern network analyzers cover frequency
range up to 110 GHz
13.7 Future TrendsCell phone manufacturing goal: reduce
power consumption and price of cell phones by 30% every year
Ubiquitous Blue Tooth
Ball Aerospace Antenna ProductsFor some really neat pictures of advanced
antenna packaging, go to this address on the Ball website:
http://www.ballaerospace.com/file/media/antennatech.pdf