Video Summary - Failure Analysis in Electronics - A Physics of Failure Approach

Main ideas, concepts, and lessons

1) Purpose and positioning of failure analysis (physics of failure approach)

Failure analysis in electronics is treated as a subcategory of root-cause problem solving.
It is most applicable when:
- the failed part has a physical limit reached, and
- the parts are available for examination and/or testing.
DFR Solutions frames its work around physics-of-failure research, integrating knowledge of:
- quality, reliability, durability of electronic systems/components/materials, and
- test methodologies and fabrication/assembly processes.
Key goal: identify failure mechanisms so organizations can create failure prevention strategies and avoid repeating the same failure condition in future designs.

2) Best-practice workflow: start with information, not testing

Instead of beginning with physical tests, the recommended best practice is to first collect historical and contextual data about the failed parts and the circumstances of failure:

Gather information on:

history of the failed parts
where/when/how failures occur
types of failures (and patterns across a production family)

Determine the operational/production context:

Is it a new/unproven device still in development/qualification/validation?
Is it a proven device failing in a new customer/application?
Is it a field-proven device that suddenly started failing (possible assembly or supply chain quality spill)?
Failure timing/context:
- in-line (coming off production line)
- OEM returns (e.g., dead on arrival)
- infant mortality at final user

Determine whether failures are:

unique/isolated vs epidemic (widespread)
seasonal or regional (linked to climate, usage patterns, or environmental conditions)

Lesson: capture all usable data alongside the investigation so it guides test selection and interpretation.

3) Core definitions: failure mode vs failure mechanism

Failure mode: how the problem is observed/detected (the outward symptom/behavior).
Failure mechanism: the deterministic chain of events/conditions that initiates and propagates until full failure occurs.
The approach emphasizes not using “mode” and “mechanism” interchangeably because the distinction matters for finding the true root cause and prevention strategy.

4) Service levels of failure analysis labs (and why it matters)

The video contrasts three “levels” of failure analysis capability:

Basic / highly competitive FA (lowest-cost factual physical reports)
- Lab performs limited physical evaluation of the provided remnants.
- Delivers findings like:
  - “solder crack found”
  - “electrical overstress observed”
- Often does not correlate findings to device history and typically does not produce true root cause (more of a “picture of what broke here”).
More comprehensive FA (lab + collaboration with background guidance)
- Lab experts collaborate using provided historical/contextual information.
- Performs a broader set of physical evaluations to move toward root cause identification.
Highest level: Physics-of-Failure (forensic signature identification)
- Physical evaluations focus on identifying forensic signatures that correspond to specific failure mechanisms.
- These signatures enable faster, more targeted procedure selection that increases the likelihood of root-cause identification.
- Example: a damaged vehicle wiring harness where signature analysis indicated bending (half-moon cut across strands) rather than pulling (which would form an “hourglass” narrowing pattern).

The “three general categories” of failure mechanisms (physics-of-failure framework)

A) Overstress failures

Definition: Environmental/usage/operational stresses overpower material/device strength.
Stresses can be:
- electrical, thermal, mechanical
- compressive/tensile
- vibration, etc.
Conceptual model (bell curve separation):
- stress distribution (blue) vs strength distribution (red)
- design aims to maintain sufficient separation so stresses rarely encroach into the weakest-strength tail
- includes idea of design margin / safety factor.

B) Stress-driven damage accumulation (how parts age)

Definition: stress-strain causes damage accumulation in materials over time (stress-driven aging).
Mechanism includes:
- instantaneous/material changes due to effects like:
  - thermal expansion/contraction
  - elastic deformation under load
  - piezoelectric effects, etc.
- strain ranges:
  - elastic range: temporary (rubber band behavior)
  - plastic deformation: permanent changes due to weakened molecular bonds
Progression:
- repeated cycles and/or continuous loading lead to failures at:
  - stress concentrators,
  - design weak links,
  - material/process variation induced weaknesses
Value for failure analysis:
- enables predicting mean time to failure (MTTF) and failure distribution behavior
- can estimate the “tip of the iceberg” fallout rate if the aging process continues.

C) Errors and excessive variation (quality-related hardest category)

Definition: quality problems due to excessive variation from many factors:
- interfaces, people, equipment
- materials and environments
- assembly processes
Concept: multiple small weaknesses/variations combine to form a compounded performance degradation risk.
Example:
- poor soldering process producing voids in a solder joint as a weak-link indicator.

Failure analysis technique methodology (instructions-style)

Step 1: Use a layered approach (“peel the onion”)

Failure analysis is likened to peeling layers until reaching the core cause.
Always try to progress from less risky to more risky testing.

Step 2: Start with non-destructive evaluations (NDE)

Non-destructive evaluations include:

Visual inspection / physical measurements
- optical microscopy
- optical documentation (e.g., digital camera)
- specialized lighting options:
  - UV, infrared, different illumination angles/conditions
Electrical characterization (without necessarily destroying)
- power up and measure voltages/currents/resistances when possible
- handle the common “no trouble found” / “no fault found (NFF)” issue:
  - suspected intermittent failure may require reproducing conditions (temperature, vibration, shock, humidity)
Imaging and inspection tools used non-destructively
- acoustic/ultrasonic microscopy
- X-ray microscopy / 2D or 3D X-ray
- infrared thermal imaging
- SQUID microscope (superconducting quantum interference device; limited/newer technique)

Practical lesson in the NDE stage: use simplest/lowest-cost tools first to potentially identify issues early (and avoid expensive testing).

Step 3: Proceed to destructive evaluations only when needed

Destructive evaluation types described:

Decapsulation
- Dissolve away plastic protective casings around ICs to expose the die.
- May still allow power probing and microprobes.
- Used to inspect for:
  - electrical overstress (EOS),
  - ESD damage,
  - wirebond issues,
  - potential counterfeit die authenticity.
Process sectioning / cross-sectioning
- Use a diamond saw to cut at controlled plane/depth.
- Polish to inspect internal flaws (e.g., oversize voids in solder joints).
- Often guided by prior X-ray to choose the cut location.
- Requires precision because relevant structures can be only 10–20 microns deep.
Scanning Electron Microscope (SEM) + EDS
- Requires vacuum chamber sample preparation (destructive sampling).
- Used for high magnification and detailed failure signature characterization.
- EDS/energy-dispersive X-ray provides elemental identification and proportions/areas.
Focused Ion Beam (FIB) microscope
- Uses gallium ions to mill/trench very small areas.
- Enables viewing below the surface for extremely small failure features that are hard to section conventionally.
- More expensive; used when targeted forensic detail is required.

Step 4: Perform chemical/material property characterizations (often destructive)

Examples described:

Mechanical testing (e.g., wire bond / ball shear type tests)
Thermal/mechanical/material property testing:
- coefficient of thermal expansion
- micro/nano hardness testing
- thermal methods like DSC, DMA, TMA
Chemical residue analysis:
- Ion chromatography for ionic cleanliness:
  - measures ionic residues such as chlorides/bromides/sulfates/phosphates/nitrates and weak organic acids
  - explains risk: residues can attract moisture → form electrolytic pathways → dendritic growth/metal migration → short circuits.
- FTIR (Fourier transform infrared spectroscopy) for organic contaminant identification and quantification.
References to standards/examples:
- IPC test method handbook 650 is referenced for many evaluation procedures (visual, dimensional, chemical/material/mechanical/electrical/environmental).
- IPC 650 defines residue measurement procedures but may not always provide pass/fail criteria; DFR mentions developing additional criteria through physics-of-failure research.

Specific frequently-used technique examples highlighted in the webinar

Visual inspection (including counterfeit detection support)

Look for:

charring, discoloration, cracking
soldering defects, debris/contaminants
conformal coating/solder mask issues (cracking/flaking/peeling leading to moisture susceptibility)

Counterfeit parts:

visual inspection can reveal non-genuine parts
use varied lighting (UV/IR) and microscope viewing
use fiber optic tools for low-profile packages (e.g., BGA/QFN) without fully cutting them

Electrical characterization and “intermittent” strategy

Validate true failure behavior:
- ensure the part really exhibits the reported fault.
If NFF/no trouble found occurs:
- reproduce environmental stressors (temperature cycling, vibration, humidity, shock) to force intermittent conditions to appear.

Circuit board electrical tests

Use in-circuit testing/flying probe methods to locate:
- disrupted connections
- solder joints issues
- burned traces.

Acoustic microscopy (ultrasound technique)

Device is submerged in pure deionized water.
Sonic waves reveal:
- voids/air pockets vs intact regions via bounce/through signals.
Used to locate suspect internal regions so cross-sections target the right areas.

X-ray microscopy

Non-destructive imaging to:
- check internal assembly integrity
- confirm wire bond integrity
- identify detachment/blown open bonds.

Infrared imaging (thermal)

Observe hotspots during operation.
Example: localized power distribution (“ring of fire”) causing accelerated capacitor aging; response was adjusting capacitor temperature ratings.

SQUID microscopy (short-circuit current imaging)

Detect magnetic signatures from very small currents where infrared may not detect the issue.
Example: conductive filament formation causing unintended short/leakage path, guiding correction (board material upgrade).

X-ray fluorescence (handheld)

“Point and shoot” elemental detection (less accurate than SEM-level analysis).
Used to check restricted substances (e.g., lead) and help identify counterfeit components by matching material composition.

Ion chromatography (dendrite/short circuit contamination mechanism)

Board/section is dissolved in solution; solution analyzed for residue quantities.
Converts residue amounts to per-area contamination and compares to guidelines.
Uses IPC 650 to measure residues; additional pass/fail criteria are said to be developed by DFR.

Wrap-up and additional Q&A takeaways included in subtitles

Acoustic microscopy destructiveness: can be non-destructive if the entire board/component fits in the chamber; can be dried afterward and remain usable.
Alternative BGA analysis besides CT scans: mentioned a newer approach using high-frequency lasers (not detailed).
SQUID vs short circuit mapping: short-circuit location is mapped by powering circuits and observing magnetic signature intensity patterns.
Dye-and-pry vs cross-sectioning for BGA:
- dye-and-pry uses a penetrative dye to seep into cracks before removal; helps assess crack penetration severity
- cross-sectioning is typically used for corner balls where cracking is most likely under thermal cycling/vibration stress
- dye-and-pry may not work if the package is conformally coated or potted
Wettability/oxidation investigations:
- use spectral analysis for oxides and microscopy to observe oxidation; referenced wetability testing

Speakers / sources featured

Speakers

Jim McIe (presenter; referred to in subtitles as “Jim mcle the senior member of technical staff at dfr Solutions,” and also as “Jim Mich”)
Ed (co-host/questioner; appears as “Ed” who introduces questions and moderates Q&A)

Source/standards mentioned

IPC Test Method Handbook 650 (evaluation procedures and residue measurement methods)
ASM Handbook on Failure Analysis and Failure Prevention (suggested reading)
Reliability Physics and Engineering (suggested reading)
Electronic Failure Analysis Handbook (suggested reading)
ASM and other books (general references), including “Failure Modes and Mechanisms in Electronic Packaging”

Failure Analysis in Electronics - A Physics of Failure Approach

Key takeaways