performing effective failure analyses
TRANSCRIPT
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© 2004 – 2010 9000 Virginia Manor Rd Ste. 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
Performing Effective Failure Analyses
A Brief Guide for Electronics Assemblies
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9000 Virginia Manor Rd Ste. 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
INFORMATION COLLECTION CULTURE
o Reliability culture of the organization
o Severity of product failure
o Risk aversion
o Reputation
o Regulations
o Costs
o Money
o Time
Cost$$, Time
DataQuantity and Quality
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9000 Virginia Manor Rd Ste. 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
WHY COLLECT INFORMATION?
Confidence• In root cause determination
• In interpretation of data
• In efficacy of corrective actions
DataQuantity and Quality
o Black pad
o Lots of data
o Uncertain of the exact mechanism
o But control of identified processes minimizes it
From The Root Cause of Black Pad Failure of Solder
Joints with Electroless Ni/Immersion Gold Plating
Kejun Zeng, et. al.
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9000 Virginia Manor Rd Ste. 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
ASSEMBLY HISTORY: SUPPLIER LOTS
o Assembly serialization
o Individual components
and substrates
o Manufacturer part
numbers
o Manufacturer lots
One End
Too thin! Normal
Lot Specific Manufacturing Defect
The Other End
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9000 Virginia Manor Rd Ste. 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
ASSEMBLY HISTORY: WHEN AND WHERE?
o When did failure occur?
o Manufacturing
o Final quality control
o Storage
o A customer site
o Where did the failure occur?
o The desert?
o The jungle?
o Alaska?
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9000 Virginia Manor Rd Ste. 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
ASSEMBLY HISTORY: SOURCES OF STRESS
o What stresses was the assembly exposed to?
o Thermal (high heat)
o Thermomechanical (temp cycling)
o Bending, shock, vibration
o Electrical (ESD, in-rush current)
o Humidity and condensation
o Chemical
Chip resistor failure from sulfur attack of the silver frit
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9000 Virginia Manor Rd Ste. 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
ASSEMBLY HISTORY: AMOUNT AND DURATION OF STRESS
o What was the amount and duration of the stresses?
o Short time or low amount, compared to normal: manufacturing defect?
o High amount: external source of failure?
o Long time: wear out?
Image from Wikipedia Image from Wikipedia
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9000 Virginia Manor Rd Ste. 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
FAILURE MODE AND SYMPTOMS
o Resistive, capacitive, inductive? On die?
o Stable and repeatable?
o No trouble found after reported failure?
o May require careful stress application to
replicate failure
Flex connector with delamination in the
polyimide, and dendrites growing between
plane and via within the delamination
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9000 Virginia Manor Rd Ste. 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
FINDING THE FAILURE LOCATION
o Traditionally, non-destructive analyses are first
o Better to focus on the goal: pinpoint the physical location of the failure
o Common iterative process from large to small:
o Identify
o Isolate
o Confirm
o Can be accomplished with both destructive and non-destructive methods
De-soldering of the device at a rework station, prior
to failure analysis, may have caused thermal shock
and a large crack in the active region of the die
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9000 Virginia Manor Rd Ste. 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
WHAT IF THE FAILURE LOCATION WENT UP IN SMOKE?
o Put on fire investigator hats
o Look for the area with the most heat damage
o Overlay this area with design
o Component?
o Substrate design and features?
o Brainstorm possible failure mechanisms
o Heat is typically from a short
o Select most plausible based on available information
Location of most heat damage on a failed
assembly, corresponding to design feature shown
to have relatively high electric field density
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9000 Virginia Manor Rd Ste. 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
CHOOSING THE RIGHT ANALYSIS
o What features need to be seen?
o Educated guess about failure mechanism based on information collected
o In what order can the features be seen?
o To what degree is the technique destructive: it’s not black and white!
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CROSS SECTIONS
o Benefit: lots of options for analysis after a successful cross section
o Risks: grind away actual failure, polishing not good enough to see or
properly assess failure
Lead-free Solder Ball Under Three Different Lighting Conditions
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MORE CROSS SECTIONS
o Relatively large chip resistor, 2512
o Still measured correct resistance (partial crack)
o But, grain refinement is evident in the solder
o Large void
o Conclusion:
o Low cycle solder fatigue from diurnal cycling, possibly exacerbated by large voids
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EDS MAPPING
o EDS mapping can reveal anomalies on die
o Depletion of indium corresponded to anomalies seen in optical and SEM images
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9000 Virginia Manor Rd Ste. 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
MANY OTHER TECHNIQUES
Thank you for participating! There are many other techniques that were not covered.
I’m happy to field any questions you may have!
Seth Binfield