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Accelerating Reliability Assessment with Multi-Oven Racks
and Sensor Chips for Wire Bonds
Dr. Michael Mayer
Jimy Gomes
Dept. Mechanical and Mechatronics Engineering
Centre for Advanced Materials Joining (CAMJ)
University of Waterloo, Ontario, Canada
IMAPS New England 42nd Symposium
May 5, 2015
OUTLINE
• Introduction & Motivation
• Multi-Oven Racks
Setup Overview
Novel Minioven Design
System Capabilities
• In situ Sensing
Contact Resistance Results
Stress Sensor Chips
• Conclusions & Outlook
© M. Mayer 2015
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INTRODUCTION
• Reliability testing in Electronic Packaging
•
•
Drivers: lower cost, smaller packages
ongoing requirement for novel materials,
designs, and processes
• In situ monitoring
•
•
•
•
© M. Mayer 2015
More data from tests
Higher quality data is possible
Leads to less tests required & more information
per test
Can be decisive for product success
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MOTIVATION
• Conventional reliability assessment methods
• Shear and pull test
• Etching and cross-sectioning
• Advantages of in situ methods over conventional
• Less labor intensive
• Better time resolution
• Non-destructive
• Fast, automated
© M. Mayer 2015
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M U LT I - O V E N
RACKS
S E T U P O V E RV I E W
• Ten Miniovens in five
drawers in one rack
• Interface PCBs
multimeters, power
supplies, …
Computer
with software
Multiplexer
Minioven
• Multiplexer
• Recording meters,
power supplies
• Automated and
controlled by software
• Oven controls
• Data recording
© M. Mayer 2015
Inside of a drawer
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NOVEL MINIOVEN DESIGN
Minioven Unit
Electrical Connections to
Device Under Test
Minioven
Core
Symmetric Construction
© M. Mayer 2015
Heater Module
MINIOVEN CORE
Heating element: copper with ceramic coat
with embedded heater wire
Test chip, Dual In-line Package, Socket
Test Chip Side
Heating
Element
Socket
Package
Test Chip
Pt 100 RTD Side
Pt 100
temperature
sensor
To
Power
Supply
© M. Mayer 2015
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MINIOVEN CORE CLOSED
Heating element: copper with ceramic coat
with embedded heater wire
Test chip, Dual In-line Package, Socket
Test Chip Side
Heating
Element
Pressure
Pt 100 RTD Side
Pressure
To
Power
Supply
© M. Mayer 2015
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TESTING (EXAMPLE)
programmed
profile
Highest “safe”
temperature in the
present configuration:
215 ºC
Takes less than 10 min
to reach 200 ºC
© M. Mayer 2015
Bimetal safety switch
active when
programmed to 220ºC
SYSTEM CAPABILITIES
•
C o n ti n u ous s i g n a l a n d
te m p e rature m o n i to r i ng
•
U p to te n m i n i o ve n s
s i m u l ta ne ousl y p e r r a c k
•
F l e xi b l e p r o g r amm abl e
te m p e rature p r o fi l e s
fr o m r o o m te m p e r atu re
u p to 2 0 0 º C
•
H i g h s p e e d te m p e r ature
c yc l i n g
•
H u m i d i ty a n d H i g h e r
te m p e ratures o p ti o n a l
© M. Mayer 2015
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IN SITU SENSING
Standard Method
• Daisy chain
resistance
measurements
Package terminals
Wire
Bonds
metallization
chip
© M. Mayer 2015
Ω
Newer Methods
• Contact
resistance
measurements
with four wire
method
• Stress
measurements
using integrated
sensors
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D A I S Y C H A I N R E S I S TA N C E R E S U LT S
Example signal measured
for several Ag wire bonds
obtained while bonds were
aging at 200 °C
 24 wires in series
 18 micron ∅ Pd/Ag wire
© M. Mayer 2015
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CONTACT RESISTANCE SETUP
•
•
Contact resistance
(R C ) measured for Au
ball bond
Bonds are optimized
for
•
•
•
BD C = 5 8 µ m
BH = 1 6 µ m
SS> 1 2 0 M p a
• Four Wire
Configuration
© M. Mayer 2015
Double bonds used
for RC measurement
I
V
Package
terminals
Wire Bonds
chip
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CONTACT RESISTANCE RESULTS
R C values are obtained
while bonds were aging
at 200 °C
© M. Mayer 2015
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STRESS SENSOR CHIPS
• At bond interface,
sensor chips can
continuously measure
• Stress in X, Y, and Z
• Contact resistance
• Temperature
Package
Test
Chip
• On-chip multiplexing
• 55 bonds tested per
chip
• Non-destructive signal
monitoring
© M. Mayer 2015
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TEST PAD
Stress Sensor
M. Mayer, “Non-Destructive Monitoring of Au Ball Bond Stress During High
Temperature Aging” (2008)
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SENSING PRINCIPLE FOR ON-CHIP STRESS
Stress sensors based on piezoresistive effect
Expand
Sensor Element
Shrink
M. Mayer, “Non-Destructive Monitoring of Au Ball Bond Stress During High
Temperature Aging” (2008)
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CHARACTERISTIC TIME t C FOR
RELIABILITY PERFORMANCE
J. Gomes, ECTC 2015
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BALL BONDS FOR
STRESS SENSOR RESULTS
Effect of variable geometry on Au ball bond reliability
BH = 20 μm
BH = 16 μm
BH = 12 μm
Diameter of bonded balls = 56.5 μm
J. Gomes, ECTC 2015
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CONVENTIONAL RESULTS FOR
HTS = 200°C
J. Gomes, ECTC 2015
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STRESS SENSOR RESULTS FOR
HTS = 200°C
J. Gomes, ECTC 2015
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C H A R A C T E R I S T I C T I M E C O M PA R E D
WITH SHEAR STRENGTH
J. Gomes, ECTC 2015
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CONCLUSIONS & OUTLOOK
• Demonstration of
•
•
non-destructive, automated recording of large
numbers of bond quality signals at multiple
temperatures
advanced in situ sensing technology giving more
detailed bond quality information during test
• Four wire contact resistance
• Bond pad stress
• Precise assessment of reliability performance
• Future Applications
•
•
•
© M. Mayer 2015
New bonding wire materials
Effect of bond process parameters on bond reliability
Effect of aging temperature
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ACKNOWLEDGMENTS
• Natural Sciences and Engineering Research
Council Canada (NSERC)
• Initiative for Automotive Manufacturing
Innovation (IAMI), Ontario
• Canadian Foundation for Innovation (CFI)
• Microbonds Inc., Markham, Ontario
• MK Electron Co. Ltd., Yongin, S. Korea
© M. Mayer 2015
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