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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
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
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.
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
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?
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
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
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
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
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
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!
9000 Virginia Manor Rd Ste. 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
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
9000 Virginia Manor Rd Ste. 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
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
9000 Virginia Manor Rd Ste. 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com
EDS MAPPING
o EDS mapping can reveal anomalies on die
o Depletion of indium corresponded to anomalies seen in optical and SEM images
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
