Failure Analysis of Electrical and Electronic Products and Components

cobham.com

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

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