Failure Analysis of Electrical and Electronic Products and Components

Failure Analysis of Electrical and
Electronic Products and Components
Cobham Technical Services
Reliability and Failure Analysis
The most important thing we build is trust

Failure Analysis of Electrical and
Electronic Products and Components
Cobham Technical Services
Reliability and Failure Analysis
Maintaining reliability
Reliability in electronic systems is important,
whether you are a designer, manufacturer,
distributor or user of equipment. Cobham
Technical Services has many decades of
experience in identifying the causes of
reliability problems from product down to
component level. Cobham Technical Services
provides impartial, expert and fast diagnosis
of problems from design through to use and
failure in the field, working with you to find
a solution.
Where reliability problems arise
There are many situations where having further
information can solve reliability problems and
significantly save time and money. Here are
some typical cases which Cobham Technical
Services regularly investigates:
Thermal and/or mechanical stress
Can cause many types of failure including
internal fractures. The SEM image shows
Ball Grid Array (BGA) connections which have
fractured from thermal fatigue.
Fire
Even when fire has burned away the region
that caused it, identifying the probable cause
is often still possible; sometimes from analysing
a similar non-failed product. It is not always at the
most obvious cause. The image shows a burned
out cable connection.
� Production stoppages threatening costly
delays and losses
� Field returns, where it is essential to
know whether the fault is due to design,
assembly or use
� Conflicting insurance or legal claims
� Assessing new production techniques
� Checking whether components are
counterfeit or below acceptable quality
� Analysing a supply chain to locate the
source of a fault
� Assessing the quality of manufacture
� Determining whether a series of faults
is due to a batch of components or
a change in a process
� Assessing if there should be a product recall.
Failure analysis services
Cobham Technical Services advises across
the electronics manufacturing industry from
aerospace, automotive and rail through to
domestic, IT infrastructure and medical.
Analysis of thousands of cases over more
than 30 years at Cobham Technical Services
has generated an invaluable accumulation
of experience. This capability will help you
understand the root cause of any reliability
problem and help avoid costly repetitions.
Cobham Technical Services offers a range
of services:
� Failure analysis: a practical approach to
failure from whole equipment down to all
active and passive electronic components,
providing you with an analysis of faults,
How products fail
Continuing improvements in the reliability of electronics have led to the expectation that they will never fail. The result is a greater pressure
to correct problems, when they do occur, and to prevent repetition. There are numerous potential reasons why even the best systems or
components can fail, for example:
Poor soldering
Examination of solder joints and wetting will
indicate the quality of the soldering process,
for example on lead-free joints. The image
shows poor wetting of a component lead,
with perhaps insufficient time at temperature.
Electrical overstress
Can cause melting, breakdown, oxidation
and other effects. The image shows a power
transistor with a voltage breakdown.
Contamination and migration
Contamination can be introduced during
manufacture or use. Migration can occur under
electrical stress and is exacerbated by heat and
moisture. The SEM image shows migration of
a metal across an insulating surface.
Mechanical abrasion
Defective surface finish can:
Cause or result from abrasion and wear,
Cause mechanical malfunction or electrical failure,
Cause adhesion of coatings to fail.
Surface analysis can quantify roughness, waviness,
curl and other parameters.

conclusions on the mechanism of failure,
identification of the stage at which it
occurred, and recommendations on
correction and prevention.
� Analytical services: with expert
interpretation.
� Design review: assessment of the electronic
design or build quality of a product,
subassembly or component.
� Technical review: state-of-the-art reviews
of a particular technology. Previous
examples include high temperature
Data collection
It is crucial that all the samples and historic
data available is obtained. Details from
manufacturing history, or use, or previous
failures may give key information.
Non Destructive Tests
These include electrical measurements,
internal inspection, and probes such as X-ray
or Scanning Acoustic Microscopy. The microfocus
X-ray image shows a pcb via with very thin copper
at the centre.
Package Opening
Techniques include:
Mechanical lid removal
Chemical jet etching
The image shows an integrated circuit with
epoxy package material removed by jet etching
to reveal the chip and wire bonds.
Internal Examination
This includes both Optical Microscopy
and Scanning Electron Microscopy
The image shows a ‘tomb-stoned’
ceramic capacitor.
electronics, non-volatile memories and
electronics for use in satellites.
� Expert witness and investigation to
support legal actions: technical evidence
often clarifies who is at fault and in what
way. Cobham Technical Services works for
solicitors, companies and courts providing
expert witness statements and reports to
support claims. These can be for a single
party or joint witness situations.
� Financial loss engineering support:
while the direct causes of failure and
unreliability are technical, often it is the
underlying issues such as adequacy of the
design and design process, allocation of
fault and consequential financial losses
which are of central importance. Cobham
Technical Services deploys its technical
capability to provide evidence to support
claims and quantify costs.
A structured approach
Cobham Technical Services employs a multidisciplinary team from diverse backgrounds and with many years of experience of diagnosing
reliability and failure problems. Electronic components are analysed by using a consistent methodology and a careful sequence to ensure
that all the evidence is obtained and correctly used to assess the cause of failure:
Infrared Spectroscopy
helps identify materials by their characteristic
IR absorption. The image shows comparison
of IR curves of a contaminant and the
suspected source material.
Ion Chromatography
Separates and quantifies the individual
ions within a test solution. It is used to
characterise unknown ionic materials (e.g.
contaminants from a surface). The image
shows unknown contaminants against a
characterisation curve, and allows assessment
of risk from contamination.
Thermal analysis
Thermo gravimetric analysis (TGA) and
differential scanning calorimetry (DSC) can
give valuable information about the thermal
behaviour of materials and their thermal history
either during processing or since. The image
shows thermal decomposition of two supposedly
identical materials.
Postulation and testing of failure mechanisms
A hypothesis for the mechanism is developed
against the available evidence and previous
experience. The theory may be tested by
deliberate trial on new samples.

Examples of problems in different markets
Aerospace
A series of small smoke incidents in the cabin
of an aircraft lead to a large scale review.
Cobham Technical Services identified the
immediate cause to be associated with the
method of assembly of the electronics and
recommended changing the position of the
critical components on the board.
Transport
Problems had occurred with monitoring the
position of doors on an underground train.
Cobham Technical Services found that a
suspect component had inadequate
internal soldering.
www.cobham.com/technicalservices
ERA Technology Limited trading as Cobham Technical Services
Domestic
Several heating systems failed with emissions
of fumes. The root cause was located by
analysis at Cobham Technical Services in
some poor quality capacitors.
Industrial
An extensive set of accelerated life tests
generated a number of failures in high power
control systems. Some of these were analysed
at Cobham Technical Services to be caused
by an inadequate cleaning process.
Cobham Technical Services
Cobham Technical Services works at the
leading-edge of innovation by undertaking
advanced design and development,
producing high-performance custom
components and sub-systems, delivering
specialist technical consultancy services and by
providing state-of-the-art electromagnetic
and power system modelling software
products.
Expert technical teams have extensive
embedded programme management
experience, which ensures efficient project
planning, resource time management and
on-time delivery.
These capabilities provide customers with
high added-value and enhanced competitive
advantage through reduced technical and
commercial risk, faster time-to-market and
improved performance of products, systems
and engineering infrastructure assets.
Industry-leading technology is delivered
to government departments and global
companies across market sectors as diverse
as communications, aerospace, defence,
transport, electronics, medical and energy.
Cobham Technical Services is based
across four sites located in Leatherhead,
UK (ERA Technology), Abingdon, UK
(Lightning Testing and Consultancy),
Kidlington, UK (Vector Fields Software)
and Aurora, USA (Vector Fields Software).
For further information please contact:
Cobham Technical Services
ERA Technology
Cleeve Road,
Leatherhead,
FM1303
Surrey KT22 7SA UK
REF: RFA25
Tel: +44 (0)1372 367444
Fax: +44 (0)1372 367134
Email: era.info@cobham.com
Web: www.cobham.com/technicalservices