MOVING AUTOMOTIVE ELECTRONICS FROM RELIABILITY/DURABILITY TESTING TO VIRTUAL VALIDATION MODELING USING A PHYSICS OF FAILURE CAE APP James McLeish, DfR Solutions Russell Haeberle, Magna Electronics
MOVING AUTOMOTIVE ELECTRONICS FROM
RELIABILITY/DURABILITY TESTING
TO VIRTUAL VALIDATION MODELING USING A
PHYSICS OF FAILURE CAE APP
James McLeish, DfR Solutions
Russell Haeberle, Magna Electronics
2014 RAMS – Paper – McLeishPaper # SAE 2014-01-0233SAE INTERNATIONAL
Traditionally, Quality, Reliability, Durability (QRD) and Safety of
Vehicular Electrical/ Electronics (E/E) Systems Depended On Rounds of
Design-Built-Test-Fix (DBTF) Reliability & Durability Growth Testing.
• Requires 12-16 or more weeks of Accelerated Life Testing (ALT)
• Increasing Vehicle E/E content, increases burden on test labs & budgets
• Larger mass of electric/hybrid vehicle power modules slows test
acceleration that can extend life testing to 5-6 months
• Durability failures tend to occur late in life testing with the required root
cause investigation often stress budgets & schedules
• Physics of Failure (PoF) Reliability Assessment combines dynamic stress
analysis of usage and environmental conditions with failure mechanism
models to perform a durability simulation that identify failure susceptibilities
and calculate reliability behavior over time.
• Performed in a Computer Aided Engineering (CAE) App Environment
PoF based durability simulations and reliability assessments are
starting to reveres the burden of increasing vehicular E/E content.
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Abstract
2014 RAMS – Paper – McLeishPaper # SAE 2014-01-0233SAE INTERNATIONAL
Computer Aided Engineering (CAE)
CAE - computers programs used to perform engineering analysis tasks
• Expedites the application of scientific principles to determine the properties or
performance characteristics of a design, (a.k.a. CAA Computer Aided Analysis).
• Evolved to support many different engineering disciplines & industries:
• Mechanical, Civil/Structural, Electrical/Electronics, Thermal, Hydraulics . . .
• Automotive, Aerospace, Naval, Construction, Mining, Power Generation . . .
1. Stress analysis using FEA (Finite Element Analysis)
2. Computational Fluid Dynamics (CFD) for thermal & fluid flow analysis
3. Kinematics & Mechanical event simulation (MES)
5. Process simulation (casting, molding, and die press forming)
6. Product Optimization
7. Circuits & Electromagnetics Analysis
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2014 RAMS – Paper – McLeishPaper # SAE 2014-01-0233SAE INTERNATIONAL 4
CAE Evaluations & Optimization of Design Alternatives, as the
Design is Created has Benefited Many Aspect of Vehicle Engineering
Crashworthiness &
Safety
Vehicle Dynamics
Durability
Energy
Performance Integration
Noise & VibrationAerodynamics
Thermal
Vehicle Structure
However, E/Es have traditionally gravitated to Circuit, Electromagnetic & Software
CAE Tools & have been less interested in Hardware Structural Analysis CAE
2014 RAMS – Paper – McLeishPaper # SAE 2014-01-0233SAE INTERNATIONAL
CAE Tools & Methods
Most CAE programs are model “creation” tools
• Like a blank spread sheet or word document they enable the user to
first create every element and then run an analysis.
• But this requires a long model creation effort
and requires the user to be:
• Very experienced with the
CAE modeling program.
• Highly knowledgeable in the specific
physics and engineering discipline
of the item being analyzed.
• PhD level expertise is often required.
• Availability and cost of this level of
expertise has sometimes limited the
expansion of CAE methods from
reaching many areas where they
could be beneficial.
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A Blank Canvas
2014 RAMS – Paper – McLeishPaper # SAE 2014-01-0233SAE INTERNATIONAL
An Emerging Trend
- Application Specific CAE Apps
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• Application Specific, Customized
CAE Solutions.
• Auto guided, specific function, CAE
Apps or analysis templates are
created to provide a common,
reusable semi-automated interface
• Pre-programed, off the shelf ready,
similar to smart phone or tablet
Apps.• Regularly needed product
optimization
• Frequently encountered problems.
• Allows product teams to perform
expert level CAE analysis without a
rare, costly, CAE expert
• See Article at:” http://www.sae.org/mags/SVE/10767
2014 RAMS – Paper – McLeishPaper # SAE 2014-01-0233SAE INTERNATIONAL
Physics of Failure Reliability Assessment
Combines dynamic stress analysis of usage & environmental conditions
with failure mechanism models to perform a durability simulation
• Identifies failure susceptibilities & calculates reliability behavior over time.
• Based on Research into “CAUSE & EFFECT” Relationships in Failure Mechanisms
& The variable factors that makes them “APPEAR” to be Random Events.
• Combination of Material Science, Physics & Chemistry with
Statistics, Variation Theory & Probabilistic Mechanics.
• Failure of devices or structures (i.e. hardware) are due to:
• The gradual degradation (wearout) or
• Rapid disruption (overstress) due to encounters with “Excessive Stresses” from the loads an item is exposed to
• Thermal, Electrical, Chemical, Moisture, Vibration, Shock, Mechanical Loads . . .
• Failures can also occur prematurely due to fabrication or assemble defects, excessive variable factors or even design errors that weakens the items to reduced to endurance capabilities
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2014 RAMS – Paper – McLeishPaper # SAE 2014-01-0233SAE INTERNATIONAL
Sherlock ADA - A Tool Suite of CAE Apps for
PoF Durability Simulations & Reliability Assessments
Reliability Assessments of Electronic EquipmentFast, Semi-Automated
• Enables durability simulations to be interactive with design creation
• To rapidly evaluate the Durability/Reliability impact of design choices
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It is not at the
Iphone or Droid
App store.
But yes there
is now a
Physics of
Failure
Durability
Simulation App
2014 RAMS – Paper – McLeishPaper # SAE 2014-01-0233SAE INTERNATIONAL
4 Steps of a PoF CAE App Analysis
1) Design Capture – Circuit board CAD files provides
the inputs to the modeling software & calculation tools.
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2) Life-Cycle Definition – define the reliability/durability
objectives and expected environmental & usage conditions
(Field or Test) under which the device is required to operate.
3) Load Transformation – auto creates a Finite Element
Analysis to calculate and distribute the environmental
and operational loads across a circuit board to the
individual parts and features.
4) PoF Durability Simulation/Reliability Analysis
& Risk Assessment – Failure Mechanisms algorithms
applied to the model & stress conditions to performs a
design & application specific durability simulation to
calculates life expectations, reliability distributions &
prioritizes risks.
2014 RAMS – Paper – McLeishPaper # SAE 2014-01-0233SAE INTERNATIONAL
Step 1: Design Capture - Import PCBA Layout
(Gerber, ODB++, Eagle & Valor CAD & BOM Part Lists)
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2014 RAMS – Paper – McLeishPaper # SAE 2014-01-0233SAE INTERNATIONAL
Step 1: Design Capture - Mech. Stack up Analysis define PCB
Laminate & Layers to Calculate Substrate
Performance
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Calculates:
Thickness
Density
CTE x-y
CTE z
Modulus x-y
Modulus z
From the
material
properties
of each layer
Using the Built
in Laminate
Data Library
2014 RAMS – Paper – McLeishPaper # SAE 2014-01-0233SAE INTERNATIONAL
Step 1: Parts ID, Management & Linkage to
Built In PoF Component Model Library
Minimizes data entry through intelligent parsing and embedded
electronic components package and material databases
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2014 RAMS – Paper – McLeishPaper # SAE 2014-01-0233SAE INTERNATIONAL
Step 2: Define Life Cycle - Field or Test Environment &
Usage Condition – Use Pre-Programs Standards or Define
Your Own
Define Detail Lifetime Thermal, Vibration & Shock Stress Profiles
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2014 RAMS – Paper – McLeishPaper # SAE 2014-01-0233SAE INTERNATIONAL
Step 3: Load Transformation - Automated FEA Mesh Creation
to Calculate Stress Distribution Across the PCBA
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2014 RAMS – Paper – McLeishPaper # SAE 2014-01-0233SAE INTERNATIONAL
Step 3) Load Transformation Automated FEA Meshing & Analysis
Determines Stress Distribution Across the PCB & to Components
Automatic Mesh Generation • Days of FEA modeling and
calculations, executed in minutes
• Without a FEA modeling expert.
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1st Natural Frequency
Calculates PCB Stress
Distribution for use in
Fatigue/Fracture Analysis
- Harmonic Vibration
- Random Vibration
- Shock
2nd Natural Frequency
2014 RAMS – Paper – McLeishPaper # SAE 2014-01-0233SAE INTERNATIONAL
Step 4: PoF Durability Simulation & Reliability Risk
Assessments of a Safety Critical Module
- Thermal Cycling Solder Fatigue Example
N50 fatigue life calculated for each of 705 components (68 unique part types), with
risk color coding, prioritized risk listing and life distribution plots based on
known part type failure distributions (analysis performed in <30 seconds) after
model created. • Red - Significant portion of failure distribution within service life or test duration.
• Yellow - Lesser portion of failure distribution within service life or test duration.
• Green - Failure distribution well beyond service life or test duration.(Note: N50 life - # of thermal cycles where fatigue of 50% of the parts are expected to fail)
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Parts With Low Fatigue Endurance
Found In Initial Design
~84% Failure Projection
Within Service Life,
Starting at ~3.8 years.
2014 RAMS – Paper – McLeishPaper # SAE 2014-01-0233SAE INTERNATIONAL
Step 4: PoF Durability/Reliability Risk Assessment
Enables Virtual Reliability Growth
Identification of specific reliability/durability limiting or deficiencies,
of specific parts in, specific applications
• Enables the design to be revised to meet reliability/durability
objectives: WHILE STILL ON THE CAE SCREEN
Failure Risk Plot of the
same project after
fatigue susceptible
parts replaced with
electrically equivalent
parts in component
package suitable for
the application.
Life time failure risks reduced from ~84% to ~1.5%
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2014 RAMS – Paper – McLeishPaper # SAE 2014-01-0233SAE INTERNATIONAL
Step 4: PoF Durability/Reliability Capabilities
Plus Optional MIL-STD-217 Random Failure Rate Calculator
• Thermal Cycling Solder Attachment Fatigue
• Thermal Cycling PCB PTH Via Barrel Cracking Fatigue
• Vibration Solder Fatigue
• Shock Solder Fracture
• Actuarial (Constant Failure Rate/MTBF Tabulations)
• Conductive Anodic Filament Risk Assessment
• Stress load in Fracture Risk Assessments
• ICT Test Stress Analysis
• Compliant Pin Connector Insertion
• ISO-26262 Functional Safety FMECA Generator
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2014 RAMS – Paper – McLeishPaper # SAE 2014-01-0233SAE INTERNATIONAL
Step 4: PoF Durability Simulations/Failure Risk Life Curves for
each Failure Mechanism Tallied to Produce a Combined Life Curve
Detailed Design & Application Specific PoF Life Curves are Far More Useful
than a simple single point MTBF (Mean Time Between Failure) estimate.
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PTH Thermal
Cycling Fatigue
Wear Out
Thermal
Cycling
Solder
Fatigue
Wear Out
Vibration
Fatigue
Wear Out
Over All
Module
Combined
Risk
Cumulative Failures from
Generic, Actuarial, Failure Rate
Tables in MIL-HDBK-217
2014 RAMS – Paper – McLeishPaper # SAE 2014-01-0233SAE INTERNATIONAL
Step 4: PoF Durability/Reliability Risk Assessment Results
Available in 6 Different Output Formats
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2014 RAMS – Paper – McLeishPaper # SAE 2014-01-0233SAE INTERNATIONAL
Step 4: PoF Durability/Reliability Risk Assessment
- Automated Report Generation
Comprehensive reports
generated in PDF format
• Key summary points
• Detailed inputs and findings
• Result plots and tables
• User control over contents
50-100 page professionally
formatted document
produced in seconds
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2014 RAMS – Paper – McLeishPaper # SAE 2014-01-0233SAE INTERNATIONAL
A vehicle control module was developed with 750 SMD (Surface Mount Devices).
• Initial prototype thermal solder fatigue testing was successful.
• Production level testing revealed solder fatigue cracks in three QFN-32s ICs
(Quad Flat No-lead w/32 terminals).
• No process or design changes were made between prototype & process
verification testing
• However a significant difference in solder thickness was noted.
• After several investigations thin solder was the primary suspected
root cause of the fatigue cracking.
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Case Study - Simulation Aided Testing (SAT) Using the Sherlock PoF CAE App @ Magna Electronics
Solder CrackProduction QFN w/Solder Fatigue Crack Un-failed Prototype QFN
2014 RAMS – Paper – McLeishPaper # SAE 2014-01-0233SAE INTERNATIONAL
QFN ICs are designed to have thin packages & low profile solder joints • IC Packages that make thin & light portable
consumer electronics possible • But low profile solder joints have high CTE Mismatch Expansion-Contraction
shearing angle stresses which Reduces Durability Capabilities
• The IC Industry is prioritizing development of new ICs in QFN packages• The auto industry needs to be able to able to evaluation & Validate which QFN ICs
are suitable for High Reliability & Safety Critical Vehicle Applications.
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Comparing Thermal Cycling Durability of
QFN ICs - Thermal Cycling Reliability
Laminated BGAs:
TTCL: 3,000 to 8,000FNL CSP:
TTCL: 1,000 to 3,000*TTCL = Typical Thermal Cycle Life
During -40° to +125°C TestingPackage TypeTypical Thermal Cycles to Failure
(-40C to 125C)
QFP >10,000
BGA 3,000 – 8,000
QFN 1,000-3,000
Gull Wing Leaded QFPs
TTCL: >10,000
2014 RAMS – Paper – McLeishPaper # SAE 2014-01-0233SAE INTERNATIONAL
Prototype PCBs (Printed Circuit Boards)
samples were not manufactured correctly.
• Solder mask plug protruded from the
thermal via onto the soldering surface
under the QFN, creating a standoff
• The standoff prevented extrusion of
solder from under the QFN resulting in
thicker solder under the QFN I/O pins
Production level PCB had no protrusions
of solder mask onto solder surface
resulting in thinner solder under the QFN
• Thicker solder acts like a flexing spring to absorb differences in
Thermal Cycling Expansion/Contraction between the PCB and QFN IC
• Thin QFN Solder results in a large CTE Shear Stress Angle, which Accelerated Solder Fatigue
• Thicker QFN Solder results in a smaller CTE Shear Stress Angle, which Reduces Solder Fatigue Rates
Alternative means to achieve thicker solder under the QFNs
in productions were developed to resolve to problem
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What Caused Solder Thickness Variation?
QFN Heat Slug
PCB Pad
Solder Mask
Solder
Thermal
Via
Solder Mask
Protrusion
2014 RAMS – Paper – McLeishPaper # SAE 2014-01-0233SAE INTERNATIONAL 25
Sherlock Analysis Modeling Different Solder Thickness
The Sherlock solder fatigue durability simulation illustrated the effect of solder thickness
on QFN IC fatigue life identifies: “Time to 1st Failure” & the “Failure Growth Rate”
@ 35 mm solder thickness - mean solder
fatigue life is a RED Risks at 11.5 Yrs.
@ 50 mm solder thickness - mean solder
fatigue life is GREEN Good at 21.9 Yrs.
43% Thicker 50 mm Solder
Improves Durability/Reliability• Exceeds Reliability Goal
• 0.5% Durability Extended to 15.6 Yrs.
• 11 Yr. Failure Risk
Reduced to 0.18%
Thin 35 mm Solder Thickness Misses
Programs Reliability Durability Goal • Durability Simulation Indicates that the
<0.5% Accumulated Failure Risks @ 11Yrs.
would NOT be met
• 0.5% Exceeded at 8.7 Yrs.
2014 RAMS – Paper – McLeishPaper # SAE 2014-01-0233SAE INTERNATIONAL
With a few days & rounds of QFN issue PoF durability simulations
• Life Plot Results Correlated Well with the Physical Durability Tests
• Provided insight that correctly identified and quantified the
root cause of the premature solder fatigue
• Obtaining the same results by tradition physical testing methods would
of required months of costly sample preparation and physical testing.
• The QFN incident demonstrated the value of Physics of Failure Modeling
In the development of Vehicular Electronics and was used in
validating the Sherlock CAP App at Magna Electronics
• It is now being increasing used at Magna Electronics and integrated into the
product development schedule to provide early evaluation of the durability and
reliability capabilities of new automotive electronic modules and components
while the design is still on the CAE screen.
• Allows reliability concerns to be identified and resolved
without the time and expense of tradition
physical D-B-T-F reliability growth testing
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QFN Case Study Aftermath
2014 RAMS – Paper – McLeishPaper # SAE 2014-01-0233SAE INTERNATIONAL
In Conclusion: the Sherlock ADA CAE App is a
New, Revolutionary, Awarding Winning Tool Suite For Virtual Durability/Reliability Risk Assessments of
Electronic Equipment
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March 2014
New March 2014
“Design for Reliability
with Computer Modeling”Read Full Article @
http://pcdandf.com/cms/co
mponent/content/article/17
1-current-issue/10722-
design-validation
2014 RAMS – Paper – McLeishPaper # SAE 2014-01-0233SAE INTERNATIONAL
Want to Know More – Suggested Reading
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2014 RAMS – Paper – McLeishPaper # SAE 2014-01-0233SAE INTERNATIONAL
Questions
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