Post on 29-Mar-2015
EML 4561Introduction to Electronic Packaging
W. Kinzy Jones, Professor MME
MWF 11:00-11:50
Jones@fiu.edu
305-393-0506(mobile)
305-348-4663 (office)
Notes on the field• I am Past President and Fellow, IMAPS, The
Microelectronics and Packaging Society• Research in advanced packaging, 1st Level
Assembly, Thermal Management, Components and Electronic Materials- Funded over $7MM in past 15 years
• Electronic packaging is a application field that crosses over many disciplines. There are 80,000 ME working in the field. Conferences/journals by ASME, IEEE, ASM, IMAPS, etc.
• All former graduate student hired prior to graduation!
Outline• Technological Drivers• Design Process
– Electrical Consideration– Mechanical Constraints– Thermal Management– Material Science Fundamentals
• Interconnect Technology – Laminate technology – Ceramic Processes ( thick film, cofire ceramic)– Thin Film Deposited
Outline (Cont.)
• Components– Active components technologies– Passive Components technologies– IC Packaging ( from DIP to System-on-package (SOP))
• Assembly– First Level Assembly ( wire bonding, flip chip)– Soldering– Manufacturing Processes
• Reliability– MIL Standards– Reliability Projections
Introduction to Microsystems Packaging
Definition of Packaging
Board
IC
Packaging is a
Bridge from ICto System
It Controls:• >90% size
• Performance
• Cost
• Reliability
Packaging Hierarchy
Microsystems Technologies
System Packaging Involves Electrical, Mechanical and Materials Technologies
Analogy Between Human and Electronics
Trend to Convergent Microsystems
Discrete Systems
Past Future
Packaging
MEMS
Microelectronics Photonics
RF
Bioelectronics
ConvergentMicrosystems
Building Block of Microsystems Packaging
1975 1995 2015
Year
1
10
100
1000
10000WW S/C Revenue ($B)
Trend to Convergent Systems
BusinessesHost-based computingMainframeDumb terminalFew vendors / architecture
Mainframes
Transistors / chip
1B
1M
10M
100M
10B
100K
10K
1K
100B
PCs
PCs / Servers
Businesses & some peopleClient-server computingLocal area connectionText/graphical interfaceMany vendors / few architectures
Today
All businesses, people, objectsNetwork computingWide area / bandwidthGraphical, voice, multimedia, etc.Many vendors / platforms
Internet
Source: Russ Lange, IBM Microelectronics
• Wireless• Wired
Convergent Systems
What are Convergent Microminiaturized Microsystems (CMM)?
• Convergent: Two or more functions• Microminiaturized: >1000x volume
reductions• Microsystems: systems with micro-scale
technologies
Trend to Convergent Microminiaturized Systems (CMM)
• Functional – Data and Voice
• Technology – Digital, RF, Analog
and Optical
• Product– Computer, consumer
and telecom
Video Cell Phone
CONSUMERELECTRONICS
Medical Implant/ Diagnostic Monitor/
Communicator
MEDICAL
The Invention of the First IC
Moore ’s Law: Doubles Every 18 Months
Source: Hal Lasky, IBM Microelectronics
CMOS with Copper Wiring and Silk
Silicon- on- Insulator (SOI)
Conventional Bulk CMOS
Silicon on Insulator (SOI)
Source: Hal Lasky, IBM Microelectronics
Silicon- Germanium BICMOS
• SiGe Offers– Cost/Performance for High
Frequency Devices
– 300-500% Performance Gain
– Low Noise, High Linearity
– Lower Power than Bipolar
– Equivalent Speed to GaAs at a Fraction of the Power
Source: Hal Lasky, IBM Microelectronics
SOC Advances
SOI
SiGe
Cu - low KMoore’s Law
SOC Presents Integration Limits in RF RF is Bottleneck for Highly Integrated
Wireless Systems
• Future wireless systems have to be portable and battery-powered
• Reduction of size, weight, power cost
• High level of integration
• Passive components in RF front-end are difficult to integrate, expensive and bulky
RF is Bottleneck
Traditional Front-ends are Bulky
Several GaAs or Si bipolar RF chips
Expensive external passive RF and IF bandpass filters
Many discrete passives: inductors, capacitors, resistors
DSP
Timing recovery
demodulation symbol
decoding- - -
LNA
LO1 LO2
ADC
High-QIF BPF
Front-End ICs are Mixed ICs
Complete Single-chip Integration Not Feasible
Technology scaling allows CMOS RFBUT: lower performance than e.g. GaAs, some blocks cannot be integrated
On-chip inductorsBUT: low Q
LNA LO
ADC
Mixed-signal integration in CMOS BUT: substrate noise coupling
FIR
900
ADC FIR
DSP
Timing recovery
demodulation symbol
decoding- - -
Single chip Integration with High Performance Not Feasible
Front-End IC’s are Mixed IC’s
Traditional Front-ends are Bulky
Single Chip Integration with High Performance Not Feasible
RF is Bottleneck for Highly Integrated Wireless Systems
• Future wireless = portable, battery powered
• Reduced size, wt., power cost• Highly integrated
• Passive comp. in RF front-end: difficult integration, expensive, bulky
SOC Presents Fundamental Digital Limits
~ 100 ps~ 1 ps.05 m
~ 1 ps~ 10 ps1.0 m
Response Time
Lint = 1mm
MOFSET Intrinsic Switching Delay
Technology Generation
Results in Major Delay Problem
Del
ay (a
u)
Technology Generation
MOS Gate
Local Wire<100um
Global Wire>1 mm
SOC ChallengesMajor Delay Problems
Summary
Fundamental Digital LimitsIntegration RF Limits
• Fundamental• Design & Verification Complexity• Test Complexity• Process Complexity• Mixed Function Costs• Wafer Fab Costs• Legal Problems• Time-to-market
SOC: Integration of Two or More Mixed Functions in a Single IC
(a) (b)Slide # 26
SOC Expectations
Source: Hal Lasky, IBM Microelectronics
RF-IC
OE-IC
ASICS
U Processor
DRAMStorage
Capacitance
FlashHigh Voltage
Tunnel Oxides
SRAMDense FeaturesImaging
Light Sensitive Devices
DSPSystem Integration
VLSI is Progressing Beyond the Needs of Individual Components
Bulky Size
1970 1980 1990 2000
Year
1
2
3
4
Total System-levelPackaging
Semiconductor Cost
What is Wrong with Current Packaging for Tomorrow’s Needs?
Higher Cost
Poorer Reliability
• Active ICs 10%• Passives: 90%
• IC: PPB• Systems Pkg: PPM
Cellular PhoneWeight Trend
Barrier to all future systems
Lower Performance
What is SOP, SIP, or Board?
A.) Today’s Board: Interconnect Components
RF IC Digital IC
Substrate
Optical IC
IC
B.) SIP: Stacked Chip/Package for Reduced Form Factors
Flash
RAM
mPIC
Package
Super IC Stack (ASET) Package (Fujitsu) Stacked IC (Amkor)
C.) SOP: Optimizes Functions Between ICs and Package
RF IC Opto IC Digital IC
Package with Opto, RF, Digital Functions
RF Opto Electrical
3-D ICs
What are SOC, SIP, and SOP?• SOC: System on Chip
– Highly integrated and mixed signal IC with partial system functions in one component
• SIP: System in Package– 3-D IC or Package Assembly– Requires Systems Board
• SOP: System on Package– Microminiaturized system-level board with two or more embedded
RF, digital, analog and optical functions– Best of on-chip and package integration for cost, performance, size
and reliability– Similar to SOC but total system function in a microminiaturized
board
SOP: SIP + SOC+Systems Board
• 3 -D Stacking of ICS or Package Structures, Similar to PWB– Macro dimensions– Vertical stack up– Testable
• 3 -D Build up, similar to IC Fabrication– Micro to Nano dimensions– Sequential build up and test
similar to MCM-D and IC– Wafer to IC concept for high
yield
SIP SOP
MEMS Ga-As SIPSOC
SOCMEMS SIPGa-As
Why SOP?• SOC is complex to design and test, expensive
to Fabricate, long time-to-market and presents fundamental limits.
• IC company’s dream for decades. No complete system has been shipped to date.
• SOP optimizes the best of IC and package integration for cost, performance, size and reliability.
• Faster turn-around and faster time-to-market.• Provides full system solution today that SOC
provides tomorrow.• SIP is a 3-D IC or package, not a complete
system
Industrial &
Medical
11%
$105B
Military
9%
$ 8.7B
Automotive
5%
$ 48B
Business Equip
38%
$ 383B
Communications
26%
$ 259B
Consumer
26%
$112B
Information Technology is a Trillion $ Industry
Microsystems & Packaging is 25% of IT
Source: Prismark
MSP Market ($320 B)
Microelectronics ($165B)
Systems Packaging ($125B)
Opto & MEMS ($30B)
Information Technology and Microsystem Markets
Bil
lion
$/Y
ear
Hardware and Software Markets
Functions of Packaging
Package Interconnections
Core Technologies• Substrates, circuit boards• Interconnect• Passive components• Active components• Packaging
Traditionally these were treated as discrete elements Advanced applications require integrated approach of
System Level Packaging
Substrates and Circuit Boards• Printed Circuit Board (PCB), Printed Wiring Board (PWB)
– Epoxy-glass composite, copper– FR-4, FR = fire retardant– Advanced Resins
• Polyimide • BT = bismaleimide traizine• CE = cyanate ester
• Ceramic substrates– Aluminum oxide, aluminum nitride, beryllium oxide, glass-ceramic– Interconnect metals - W, Mo, Au, Cu, Ag
• Multichip Modules– MCM-D,C,L
• Platform – Support interconnect and components– Thermal path away from ICs– Withstand mechanical stresses and vibrations
Packaging Evolution
?
Microelectronic Density Trends
logic
microprocessors
Rent’s Rule
Packaging Evolution
I/O Density Trends
Chip
Package Evolution
Packaging Trends (Cont.)
Assembly Processes• Board Fabrication
– Single layer– Multilayer– PCB– Flex– Ceramic
• Populating the board– Pick and place– Insertion– Die attach
• Soldering– Solder paste reflow– Wave solder– Solder bump reflow
• Encapsulation
SIA Roadmap for Chip Interconnections, 1995
CMOS Device Trends
Buda et al, 42 CPMT, pp36-41, 1992
NEMI Roadmap, 1996
Packaging trends in Automotive Electronics
Packaging trends in Consumer Electronics
iNEMI Roadmap, 2009
NEMI Roadmap for Packaging Trends in High-Performance Systems
High Performance Systems, iNEMI 2009
Interconnect Density, Std. PWB
.1mm = 4 mils
Thermal Cooling Requirements
Types of First Level Packages
Chip-Scale Packages
Types of Ball Grid Arrays
Flip Chip Assembly
Chip
Substrate
Example- Controlled Collapse Chip Connection-C4 (IBM) assembly on ceramic substrate
Solder• Primary functions
– Electrical connection between component and interconnect– Mechanical attachment of component to board– Thermal path from component to board
• Alloys of various compositions and melting points• Lead-Tin solder most common
– Eutectic composition: 63% Tin, 47% Lead– 60/40 or 2% silver added
• Solder paste for screen printing, pressure dispensing– Alloy particles– Flux and activator chemicals– Vehicle to control viscosity
• Wave soldering– Foam or spray flux– Preheat board– Turbulent wave to spread solder– Laminar wave to smooth
Effect of Underfill on Temp Cycling Performance
With filler, 27ppm
Functions of a Multichip Package
Illustrations of MCM Types
Low Temperature Cofired Ceramics with Buried
Components
Packaging Efficiency
Packaging Considerations that Effect the Electrical Performance
Interconnects Worsen:
• Signal Integrity• Performance: switching, speed• Reliability• Form, fit, and function- weight, volume,
power
Interconnects Can Have Very Important Electrical Properties
• Property• Self-inductance• Capacitance to ground• transmission line
• Mutual Inductance, capacitance
• Resistance, loss
• Possible Impact• Ground bounce• Delay, power sag• Propagation delay,
reflection• Cross-talk, noise
• Damping, ringing, power sag
Drivers for Reduction of Interconnect Length
• Directly reduces inductance, capacitance, resistance and delay
• Indirectly reduces switching time, power, size, ringing, ground bounce, and power sag
Electrical Fundamentals
• Resistance ( ohms). Relates Ohms law relationship between current and voltage, V=IR. Resistivity, , is a materials property, in ohm-meters. Resistance, R = Length x / cross-sectional area of conductor
• Capacitance (farads) relates to the ability to store charge. Capacitance for a parallel plate capacitor is proportional to the dielectric constant,K, times the area of the plate/ thickness of dielectric.
• Inductance ( henry)- relates to the voltage generated to oppose a change in current
Basic Resistance Equation
• Resistance R = L / A = L /wt = L/w Rs
where Rs is defined as the sheet resistivity, is resistivity, L is the length and A is the cross sectional area of the conductor/resistor
• A square ( L=W ) for a fixed thickness of material has a fixed resistance per square, independent of size. A square anything
Capacitance is• In the insulation between more than one conductor• Orders of Magnitude higher outside the chip than
inside• The dominate determinant of digital speed
Dielectric Constants of Some Insulators
Dielectric Material Type DielectricConstant, K
FR-4 epoxy 4.8
PTFE floropolymer 2.8
Alumina ceramic 9.0
PVF2 Polymer 12.0
air 1.0
Capacitance of Electrically Short Interconnections
• Capacitance is the sum of all output capacitance of all drivers to that interconnect, the input capacitance of all receivers, and the distributed capacitance to ground of the interconnection
Switching Time, Power
• If a step voltage is applied to an RC network, the time delay is proportional to RC. If the capacitor is charged from zero to full charge, the energy dissipated, W, is independent of R and equals CV2/2. But energy is also power X time delay. If we operate twice as fast, the circuit will dissipate twice the power.
Inductance• Opposes a change in current by generating a back
voltage. If the current change is positive, the back voltage subtracts from the voltage applied, causing a power sag.
• The voltage is equal to the inductance times the rate of change of the current , VL= L di/dt
• Self inductance exists in every wire, trace, wire bond, solder joint, etc..It is minimized by large, short conductors, or a sheet conductor as a ground or power plane.
• Example: If we switch 1 amp in 5 nsec on a 1” trace with 7.8 nH, we generate a back voltage of 1.6 volts.
Crosstalk
• There is a mutual capacitance between two adjacent insulated conductors that couples a fraction of one voltage to the other
• There is also mutual inductance, functioning as a transformer by generating a voltage in each when the current changes in the other.
• This is crosstalk. Can be minimized by design (keep talkers and listeners apart) and use of ground/power traces between talkers/listeners
Ground Bounce, Power Sag
• Cause: Common-mode impedance, usually inductive• Digital devices require most of their power supply
current during switching. Clocked signals switch together, so there could be a large total surge
• The inductance in the power and ground leads causes ground bounce and power sag.
Bypass ( decoupling) Capacitors
• To reduce power sag and ground bounce, add decoupling capacitors. Value should be 20-100 nF/sq.cm of silicon. Decoupling capacitors should have low parasitic inductance.
• Capacitors serve as local energy reserves and need to be close to the power/ground leads
RLC Circuit Switching
• The voltage step sent down an interconnect can be distorted badly by the R, C, and L on the interconnect
• This distortion can be removed by the right balance of the values of R,L and C. When R = 2* sqrt(L/C), critical damping occurs
• If R is above critical damping, switching slows down; if below, ringing of the signal occurs
Critical Damping
Transmission Lines• Any interconnect whose length is over a
small fraction of the wavelength of the signal it carries acts like both a transmission line and an antenna radiating or receiving noise
• As speed increase, the lumped analysis of L,R,and C components must be replaced by the distributed network of L,R, and C.
• Property shielded interconnects minimize the effect of antenna properties, but the transmission properties remain
Transmission Line Properties
• A transmission line appears as a string of small inductors and capacitors, with seven principal properties:
• length L, inductance per unit length, capacitance per unit length, impedance (Z), attenuation, propagation velocity, and time delay
Transmission Line Equations
Transmission line traces
• Matched impedance systems require containment of the electrical fields. This has lead to designs including the stripline, the microstrip, the buried microstrip. Additionally, for multilayer routing, vias must be considered
• Stripline microstrip
Microstrip Design for 50 Impedance
Traveling Waves on an Infinite Line• Switching on a DC source voltage, V, :
–draws the same current as a resistor of value Zo connected to V.
– current flows down the line at the propagation velocity, while the current progressively charges up the line capacitance to voltage V. Hence a voltage step V also travels down the line.
–Draws current indefinitely due to an infinitely long line
–The source only sees a resistive load Zo continuously drawing current
Traveling Waves on an Unterminated Line• When the line is unterminated ( R is infinite):
– Kirchoff’s current law still applies at the far end: the sum of current entering the end must equal the current leaving the end. But there is no load to draw current from the end node.
– Therefore, an equal reflected current wave is generated that travels back toward the source.
– This reflected current wave requires an extra voltage source, V, to propel it, so the voltage at the far end steps up to 2V.
– This increased voltage travels back towards the source along with the reflected current.
– What happens at the source depends on the source’s internal impedance
– The waves can on occasion reflected back and forth several times
Lines Traveling Waves Capacitively Terminated
• The problem of reflection is compounded by capacitance at the ends.
• When a transmission line drives a capacitor, the extra capacitance causes:– reflections, since the line is now mismatched– ringing for some drivers, since there is no
longer critical damping• CMOS inputs are essentially capacitive.
AC Termination
• To minimize power dissipation, a series capacitor,C, can be added to the terminating resistor
• This terminated the line only when a voltage transition occurs and allows no DC power dissipation in R
• The value of C must be selected carefully, either by simulation or experimentation to minimize the effect of capacitively terminated lines.
When Interconnections are Electrically Significant
• When interconnects degrade switching time• When the signals are not correctly damped• When large amounts of current switch• In the time domain, when the line propagation
delay approaches the driver switching time. Propagation delay is proportional to length
• In the frequency domain, when the wavelength of the signal ( including harmonics) are not long compared to the length of the interconnect ( for 100 Mhz- over a few centimeters)
Packaging• What packaging provides:
• Interconnection• Power Distribution• Thermal Management• Environmental Protection
• What the package is made from--materials, parts
• What is used to design and fabricate packages:
• Facilities and Equipment• Manufacturing and Design Tools
• Process by which the package is produced over time
Technology Drives
• Increases in semiconductor complexity from decreased feature size
• Corresponding increases in systems speed• Increase in input/output (I/O) density• Increase in power density (W/cm2)
Levels of Packaging• 1st Level Connection
– IC to Common Circuit Base– Wirebonds or solder bumps to package base
• 2nd Level Connection– Common Circuit Base to Circuit Board– Package leads soldered to PCB
• 3rd Level Connection– Assembly of multiple boards into larger assembly– Video card, modem, game port on a PC motherboard
• 4th and 5th Level Connections– System level assembly with several 3rd Level subassemblies– Motion control, visual alignment, user interface, etc. in manufacturing equipment