physics of failure simulation and modeling specification webinar
TRANSCRIPT
© 2004 - 2007 © 2004 - 2010 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com © 2004 – 2010
Specifying and Satisfying Physics of
Failure Requirements
December 17th, 2015
© 2004 - 2007 © 2004 - 2010 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
o Physics of failure
o Specifications
o Use environment
o Reliability Expectations
o Complexity vs. Accuracy and Precision
o Specifying the right amount
o Thermal stresses
o Temperature Cycling
o Power Cycling
o Mechanical loads
o Vibration
o Shock
o Communicating reliability throughout product development
o Pre-layout
o Layout
o Design Finalization
o Test validation
o Field prediction
o Protecting the IP
o Verification: Quality and Testing
o Failure Analysis
o Summary and Questions
Agenda
© 2004 - 2007 © 2004 - 2010 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
o The use of science (physics, chemistry, etc.) to capture
an understanding of failure mechanisms and evaluate
useful life under actual operating conditions
o The ability of the materials to withstand stresses either once
(overstress) or repeatedly (wearout)
Physics of Failure (PoF)
© 2004 - 2007 © 2004 - 2010 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
o Stress exceeds the strength = Instant failure
Overstress
© 2004 - 2007 © 2004 - 2010 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
o Wearout mechanisms are the usual culprit
for failures
o Damage accumulation
o Reduces strength
o Stress continues
o Solder Joint Fatigue
o Mechanical Vibration
o Thermal Cycling
o Lead Fatigue
o Mechanical Vibration
o Plated Through-hole Fatigue
o Thermal Cycling
Wearout
© 2004 - 2007 © 2004 - 2010 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
o Understanding how a specific design will behave in
your specific environment
o How long will it last?
o How is it likely to fail?
o What are the goals?
o Lifetime
o Performance
o Environment
Specifying PoF
The bridge collapsing, in a frame from a 16mm
Kodachrome motion picture film taken by Barney Elliott
Wikipedia.com
© 2004 - 2007 © 2004 - 2010 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
o How long does the CUSTOMER expect the device to
perform?
o How long is the warranty?
o Is there a chance the customer would like this extended?
o Cost of replacement?
o Materials
o Downtime
o Customer confidence
Lifetime
50+ Years
Later
1957 2010
© 2004 - 2007 © 2004 - 2010 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
o Low-End Consumer Products (Toys, pedometers, gadgets, etc.) o Do they ever work?
o Consumer electronics o Cell Phones: 18 to 36 months
o Laptop Computers: 24 to 36 months
o Desktop Computers: 24 to 36 months
o Home Appliances: 7 to 15 years
o Commercial electronics o Medical (External): 5 to 10 years
o Medical (Internal): 7 years
o High End Servers: 7 to 10 years
o Industrial Controls: 7 to 15 years
o Highly regulated o Automotive: 10 to 15 years (warranty)
o Avionics (Civil): 10 to 20 years
o Avionics (Military): 10 to 30 years
o Telecommunications: 10 to 30 years
o Solar: 25 years (warranty)
Examples of Product Lifetimes
© 2004 - 2007 © 2004 - 2010 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
o Define the probability of failure during product life
o At the desired lifetime, what is an acceptable reliability?
o Define the duty cycle
o Time in use
o Cycles per day
o Flights per year
o Dormant conditions
o Intensity of use
o Power cycles
o Low power to high power
o Low data rates vs. max load
Performance
© 2004 - 2007 © 2004 - 2010 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
o Shipping
o How well is the product protected during shipping?
o Assembly, test, manufacturing, storage …
o All the things that happen before the product is even turned
on
o Do you have a good understanding of how the product
will be used?
o Life cycle
o Life cycle phases
o Events
Defining the Use Environment
© 2004 - 2007 © 2004 - 2010 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
o Life Cycles can be complex
o Use cases
o Life cycle phases
o Environmental stress types and events
o Much of environmental data is typically unstructured
o Need to organize it in a way that clearly communicates the
intended use
Communicating the Use Environment: Challenges
© 2004 - 2007 © 2004 - 2010 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
o Life cycle editor
o Handles complex environments
o Shock
o Sinusoidal vibration
o Random vibration
o Thermal Cycling
o Power Cycling
o Formats environmental stresses as inputs
for analysis
o Clear and concise transfer of information
Structuring the Environment
© 2004 - 2007 © 2004 - 2010 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
o How can I know without a doubt how long it will last?
o Capture all of the product’s design complexity and
manufacturing variation by building a representative
population
o Expose it to an environment exactly representative of your
use environment
o Wait 7 to 30 years
o To move things along we start making assumptions
Precision and Accuracy
Dailymail.co.uk
© 2004 - 2007 © 2004 - 2010 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
o Components conform to datasheet values
o Materials
o Dimensions
o Measurements can be used to modify models
o Assuming a uniform population
o The assembly is well manufactured
o Solder joint quality
o Plated through hole quality
o MSL processes followed
o Laminate quality etc.
o Everything behaves the way we expect it to
o For simulation, these are all reasonable assumptions
Key Assumptions for Simulation
ipctraining.org
© 2004 - 2007 © 2004 - 2010 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
o Higher levels of accuracy and precision come at a cost
o Detailed Multiphysics Models
o Engineering time
o Computational time
o Calculations
o Expert time
o Measurements
o Prototypes
o Testing
o Not enough can also come at a cost
o Striking the balance can be an art
o We can do much more than even 5 years ago with the information we already gather during product development
Cost and Approximation
© 2004 - 2007 © 2004 - 2010 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
o Ambient Temperatures
o Often more complex than single diurnal cycle
o Flight profiles, high load periods, heating from surrounding
equipment
Thermal Stresses in the Environment
o Measured values on the intended
platform
o Measured values on a similar platform
o Industry accepted average profiles
o Educated assumptions based on
estimated use environments
Acc
ura
cy
Risk
© 2004 - 2007 © 2004 - 2010 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
o Understanding what the power dissipating components are
o Thermal simulation tools o Tend to capture all components
o Flowtherm
o Icepack
o Testing o Thermal Imaging
o Thermocouples
o Ensure airflow is typical of use environment
o Hand Calculations o Tend to be more selective
o Components with self heating >5°C
o Relies on assumptions regarding component selection
o Should be verified during prototype build
Thermal Stresses in the Product: Power Dissipation
© 2004 - 2007 © 2004 - 2010 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
Thermal Stresses: PoF Reliability Prediction
Ambient
Environment
Thermal
Analysis Design Files
Non Operating Reliability
Duty Cycle
Operating Reliability
Derating Analysis, Solder Joint and PTH Predicted Lifetimes
© 2004 - 2007 © 2004 - 2010 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
Temp. Cycling: Reliability Prediction
Software Design the board
Apply the
temp. cycle
Find the failed components
© 2004 - 2007 © 2004 - 2010 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
o Shock and Vibration
o Estimate frequency of random events
o Potholes, door closure, landing, etc.
o Understand the vibration environment
o Rotating machinery, road vibration, harmonic and random
Mechanical Stresses in the Environment
o Measured values on the intended
platform
o Measured values on a similar platform
o Industry accepted average profiles
o Educated assumptions based on
estimated use environments
Acc
ura
cy
Risk
© 2004 - 2007 © 2004 - 2010 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
o Board close to resonance
o Components can shake off due to fatigue in leads or solder
o Time to failure is determined by intensity and frequency of
stress
o Component resonance
o Lead and solder fatigue
due to component motion
Concerns: Vibration
Displacement
© 2004 - 2007 © 2004 - 2010 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
o Happens as random events
o Failure mechanism
o Sensitive to intermetallic layer
thickness
o Brittle failure
o Board failures
o Pad cracking
o Lead failures
o Probabilistic
o Equally likely to fail at event
#20 as event #200
o Stress to probability of failure
Concerns: Mechanical Shock
© 2004 - 2007 © 2004 - 2010 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
Mechanical Stresses: PoF Reliability Analysis
Vibration
Environment
Lead
Modeling Design Files
Solder Joint Fatigue
Shock
Profiles
Shock Risk Analysis
Lead Fatigue Analysis
Natural Frequency
Analysis
© 2004 - 2007 © 2004 - 2010 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
Overall Life Curves
Combined PoF Reliability Analysis Outputs
Time to Failure by Component
Natural Frequency Behavior
Automated Report
© 2004 - 2007 © 2004 - 2010 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
o What can we know and how soon can we know it?
PoF in the Development Cycle
Pre-layout Layout Design
Finalization Test
Validation Field
Prediction
PDR Reliability
Growth CDR
© 2004 - 2007 © 2004 - 2010 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
o What can we know? o Board geometries and estimated material stackup
o Board mounting strategies and configuration
o Major component selection
o What can we do with it? o Bare Board Harmonic Analysis
o Yes, it will change once parts are on it, but it is a good place to start
o Evaluate mounting strategies
o Define high-risk zones for large components
o Component package selection validation
o Thermal Cycling
o Board material selection validation using largest components
o How do we specify it? o As part of PDR
o Harmonic Analysis and component package risk areas
o Board material selection and component package risk
o Specified as components greater than certain size
Pre-Layout
© 2004 - 2007 © 2004 - 2010 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
o What can we know? o Preliminary design layout
o BOM
o Board stackup and approximate copper content
o What can we do with it? o Iterative analyses
o Thermal cycling reliability
o Coarse mesh mechanical analysis
o Reliability growth during the design phase
o Low cost
o High impact
o Specification o Periodic reporting for design revision reliability analysis
o Test and field environments
o Requires greater investment and involvement
o May be appropriate where higher levels of program risk are expected
Layout
© 2004 - 2007 © 2004 - 2010 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
o What can we know?
o Design files
o Material and package selection
o Thermal analysis
o What can we do with it?
o Final field environment reliability prediction
o Qualification test performance prediction
o DFMEA, Derating analysis, CAF, ICT
o Specification
o Deliverable with critical design review (CDR)
o Automated reporting
o Verifies use of proscribed environment
o Verifies use of chosen materials
o Reduces program risk when releasing to test
Design Finalization
© 2004 - 2007 © 2004 - 2010 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
o Test to “Spec” (Industry standards) o Pass/Fail: Clipboard engineering
o Uses best practices and previous success
o Design by similarity
o Different requirements for every manufacturer or industry
o Physics of failure (POF) testing o Test to failure
o Failure analysis for failure mode verification
o One test per failure mode
o Creates prediction models that feed back to industry standards
o Combined approach o Physics of failure prediction
o Industry standards
Test Plan Strategies
Source: A. MacDiarmid,
“Thermal Cycling Failures”,
RIAC Journal, Jan., 2011.
Source:nationalparts
© 2004 - 2007 © 2004 - 2010 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
o Sherlock uses a damage accumulation method to calculate probability of failure
o Can be used for both field and test conditions
o An equivalent test for that failure mechanisms induces equivalent damage
o Encourages collaborative engineering through the supply chain
o Standard tests may not represent field
o Engineering over ‘opinioneering’
Test Validation
INSERT TWO TEMP CYCLING LIFE CURVES AND DRAW HORIZONTAL
LINE TO INDICATE DAMAGE PARITY
© 2004 - 2007 © 2004 - 2010 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
o Some markets are very competitive
o High levels of distrust in the supply chain
o Automated reporting can be selective
o Inner layer details
o Component suppliers and part numbers
o Allows for more open dialog
o Communicates reliability details
o Protects the design files
Protecting the Design
lifehacker.com
© 2004 - 2007 © 2004 - 2010 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
o PoF Analysis during design is STILL simulation
o Remember those assumptions?
Verification
We still need to test!
Components Quality
Behavior
© 2004 - 2007 © 2004 - 2010 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
o Testing to specification
o Finite duration
o Likely zero failures
o Little reliability information gained
o Continue testing to failure
o Verify the failure mechanism is as expected
o Validates simulation
o Time to failure
o Dominant failure sites
o Provides confidence in field life prediction
Qualification Testing
© 2004 - 2007 © 2004 - 2010 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
o Sample selection
o Production, not prototype
o Possibly periodic
o IPC inspections plus representative destructive analysis
o PCB Quality
o Drill
o Microvias
o Laminate
o Registration
o Etching
o Assembly Quality
o Solder joint fillets
o Cleanliness
o Component Alignment
o Solder voiding
o Solder balls (BGAs)
o Bond line thickness (QFNs, etc)
o Critical Components
o Die size
o Lead-frame material
o Construction analysis
Quality Analysis
© 2004 - 2007 © 2004 - 2010 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
o When the model doesn’t match test performance
o Find out why!
o Physics of failure is a discipline to be practiced
o Was there an unexpected material/feature?
o Laminate properties, component CTE, etc?
o Was there an unexpected stress?
o Unexpected temperature rise on components?
o Can the models be adjusted to account for the cause?
o Feed the knowledge back into design activity
Failure Analysis
© 2004 - 2007 © 2004 - 2010 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
o Contact DfR Solutions
o For examples of specification language
o Can be tailored to your needs and industry
o For assistance meeting a PoF specification
o Consulting, services, software
Specification Language and Compliance