Design for reliability (DFR) is an industry-wide practice and a philosophy of considering reliability in an early stage of product design and development, to achieve a highly-reliable product while with sustainable cost. Physical of Failure (PoF) is recognized as a key approach of implementing DFR in a product design and development process. The author will present a case study to illustrate predicting and identifying product failure early in the design phase with the help of a quantitative PoF model based analysis tool.

1. Design for Reliability
g y
(DFR)
A Case Study Using A Physics
of Failure
of Failure
Dr. Haiyu Qi
©2011 ASQ & Presentation Qi
Presented live on May 10th, 2012
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3. Design for Reliability
(DFR)
- A Case Study Using A Physics of Failure
(PoF) Reliability Modeling and Analysis Tool
RelEng Technologies, Inc. 1

4. Why Design for Reliability (DFR)
• DFR is an industry-wide practice, and a philosophy as well, of
considering reliability in an early stage of product design and
development, to achieve a highly-reliable product while with
sustainable cost.
• Physical of Failure (PoF) is recognized as a key approach of
implementing DFR in a product design and development
process.
• A quantitative PoF model based analysis tool helps
 Predicting and identifying product failure early in the
design process, allowing reliability designed into the
product.
 Quantifying the test process of test design to be able to
achieve specified reliability goals.
RelEng Technologies, Inc. 2

5. Background
• Matured simulation and modeling based approach
• Increased sophistication of electronic assembly
• Inefficiency in methodology implementation
• Inaccuracy of simplified models
• Incapability of reliability modeling
• Complicated multiple modeling levels
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6. A Case Study to Conduct
Assembly Level Reliability
Assessment and Risk
Identification
RelEng Technologies, Inc. 4

7. Objectives
• To quantify the fatigue life of an assembly with
over 1,000 parts including over 150 BGA
packages and over 30,000 BGA interconnects;
• To identify BGA interconnects that can
potentially fail in field based on the product’s
life requirement.
RelEng Technologies, Inc. 5

8. Assessment Process
• Convert original design data into FEA model data
• Create a global FEA model and conduct
assembly-level stress analysis
• Create a component-level FEA model for each
BGA package and conduct component level local
stress analysis
• Conduct failure modeling and predict life of
interconnects
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9. Assembly under Investigation
• PCB with 154 BGA packages
• 7 packages with interconnects ranging from
1,217 to 2,092
• Total I/O number of the assembly over
100,000
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10. BGA Packages in the Assembly
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11. Modeling Process (Phase 1)
Note: Due to
confidential
nature of the
board, only a half
of the layout is
illustrated in the
figures.
 Convert the 2D
layout into a 3D FEA
 Import the PCB model in Reliability
design file and Software and then
create 2D layout export it to a
in Reliability commercial FEA
Software analyzer
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12. Top Side of the Board
 Converted into a 3D
FEM model
 Converted and then
simplified on RelSIMTM
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13. Modeling Process (Phase 2)  Conduct life prediction and
failure probability assessment
 Import obtained FEA analysis
results and determine local
stresses and loading conditions
1 1  Apply failure models to targeted
Nf  D c parts and locations to generate a
2 PCB analysis model
RelEng Technologies, Inc. 11

14. Product Usage Environment and Life
Requirement
• Storage environment:
Temp: -40/+70C
Humidity: 0-95%RH
• Operating environment:
Temp: 0/+45C
Humidity: 5-85%RH
• Expected Lifetime: 15yr
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15. Thermal Loading Conditions
Product
Power 14hrs 10hrs
ON
OFF
Time
Environmental
Temperature
45C
0C
Time
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16. Estimation of Power Consumption
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17. Estimated Board-level
Temperature
To be able to visually examine if there are any
internal hot spots, FEA results were all
perpendicularly projected down to the 2-
dimensional board surface with only the highest
temperature value being plotted, if there are
multiple results available at one planar spot.
RelEng Technologies, Inc. 15

18. Estimated Board-level
Thermal Stress
To be able to visually examine if there are
any internal stress-concentrated locations,
FEA results were all perpendicularly
projected down to the 2-dimensional board
surface with only the highest stress value
being plotted, if there are multiple results
available at one planar spot.
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19. Multilevel Modeling
• Simplified FEA models include
 slice model
 quarter symmetry model
 octant symmetry model
• Completed FEA models face challenges on
 Different magnitudes of geometrical dimensions
 Computer capability to analyze.
• Alternative Approach – Multilevel Modeling
 Board level
 Component level
 The board level results as an input to the component level models
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20. Component-level BGA Models
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21. BGA Solder Interconnect Models
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22. Estimated Component-level
Thermal Stress at Solder
Balls
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23. Thermal
Stresses before
and after
Component
Level Stresses
are Overlapped
The board thermal stress
distribution is obtained
by combining the
analytical results from
both the board level and
component level models.
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24. Estimated Interconnect Life Distribution
Assume 1 cycle per day and 365 cycles per year
5,475 cycles  15 years
795 cycles  2.2 years
cycles
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25. Summary
• Fatigue life of all the BGA interconnects of the
assembly under investigation was analyzed and
examined in this case study.
• Due to increased geometric dimensions, those 7
BGA packages with the number of I/Os over 1,000
were the focus of the examination.
• The results indicate that the solder interconnects
on multiple BGA packages are not able to meet the
15-year life requirement of the product.
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26. Contact Us
RelEng Technologies, Inc.
12202 Braxfield Ct.
Rockville, MD 20852
Phone: 410-705-1830
Dr. Haiyu Qi
haiyuqi@relengtech.com
Dr. Jingsong Xie
jingsong.xie@relengtech.com
RelEng Technologies, Inc. 24

27. Appendix
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28. Thermal Fatigue Model -
Engelmaier-Wild Model
1
1
N f  D c
2
 360 
c  0.442  6 104 TSJ  1.74  102 ln 1  
 tD 
Nf is the number of cycles to failure;
D is the potential cyclic fatigue damage at complete stress relaxation;
tD is half-cycle dwell time in minutes;
TSJ is mean cyclic solder joint temperature;
c is fatigue ductility exponent
RelEng Technologies, Inc. 26

29. What is RelSIMTM
RelSIMTM is a physics-of-failure (PoF) model based reliability
assessment software platform for design and development of
electronic products and systems.
The platform primarily carries a knowledge-based expert system and
a failure model based quantitative analysis tool. It is built upon an
internet based data sharing and communication mechanism, which
brings together users and software technical support people as well
as behind-the-scene reliability engineering personnel, all on the same
platform across the internet, while the users can still rely on their
own local computing resources on analysis.
It includes 5 quantitative analysis modules:
• pofANTM: component level modeling and analysis
• pofPWATM: assembly level modeling and analysis
• pofESATM: environmental stress analysis
• pofSYSTM: system/equipment level modeling and analysis
• pofPHMTM: real-time analysis and prediction
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30. What makes RelSIMTM different from
other Products in the Market
Here below summarizes some key capabilities and features that
differentiates RelSIMTM from other products in the market:
• Integrated local computing and internet remote data access for
model constants, material properties, commonly used loading
conditions and design parameters;
• Availability of remote technical support on both software and
reliability data and models needed for analysis;
• Integration of a reliability expert system and PoF reliability
modeling and analysis capability;
• Interface to Cadence®, ANSYS®, AutoCAD® and other
commercial Electronic Design Automation (EDA), Finite Element
Analysis (FEA), and Computer Aided Design (CAD) data files;
• A dynamically updated pool of models including customer
specified empirical models
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31. Why choose RelSIMTM in DFR Implementation
• RelSIMTM has interface to Cadence®, Protel/Altium® and planned to
Mentor Graphics® data file format, allowing its access to design data
that are generated from commercial EDA tools and achieve the
automation of a modeling process;
• RelSIMTM utilizes commercial tools, instead of built-in codes, to
conduct FEA analysis, making it more compatible to customers’
existing engineering design environment and eliminating cost of
duplication;
• RelSIMTM is a specialized assembly-level life assessment modeling
and analysis tool, with dynamically updating capability of failure
models, including customer specified empirical models.
• RelSIMTM conforms to the Service Oriented Architecture (SOA)
design principles, allowing remote technical support on both
reliability data and models.
• RelSIMTM integrates a reliability expert system and a knowledge base
to assist modeling and analysis.
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32. Support Architecture of RelSIMTM
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