Element 1

Factors affecting quality and reliability of electronic

products

1.1 Factors affecting quality are identified, their causes described, and methods of improvement outlined.

1.2 Sources that adversely affect reliability are described.

1.1 Factors affecting quality are identified, their causes described, and methods of improvement outlined.

Typical factors affecting the quality of electronic products are:

Interference

Noise pickup

Feedback

Distortion

User-unfriendly design

Appearance

User-unfriendly designDefinition

Design of a product which is difficult to use for intended users

Typical Cause

Lack of research / Incomplete analysis of product requirements / Inadequate testing / Failure to evaluate user response

Method of Improvement

AppearanceDefinition

The appearance of an object is the result of a complex interaction of the light incident on the object, the optical characteristics of the object, and human perception.

Typical Cause

In appropriate size / colour / shape / texture / weight; Unpleasant feel

Method of Improvement

InterferenceDefinition

Extraneous energy, from natural or man-made sources, that impedes the reception of desired signals

Typical Cause

Another transmitter at the same frequency / mains frequency (50Hz) interference

Method of Improvement

FeedbackDefinition

The return of a portion of the output of an active device or system to the input

Typical Cause

Speaker sound re-entering a microphone / coupling between the input/output circuits

Method of Improvement

DistortionDefinition

Any departure of the output signal waveform from the input signal

Typical Cause

Non-linearities in the devices such as a transistors and op-amps

Method of Improvement

Noise pickupDefinition

An incoherent emission from a natural or man-made source

Typical Cause

Lightning / Commutator noise / Ignition system noise from petrol engines

Method of Improvement

1.2 Sources that adversely affect reliability are described.

There are a number of sources which directly contribute to adverse reliability such as:

Intermittent connections

Humidity Temperature

Dust and dirt Radiation

Electronic component failure

Mechanical component failure

Electrostatic discharge

Vibration Shock Corrosion

Intermittent ConnectionsConnections which spasmodically become a high resistance current path can affect the reliability significantly.

HumidityHigh humidity can lead to a build up of moisture within equipment leading to short-circuit paths developing and causing equipment to fail.

TemperatureHigh ambient temperatures can lead to insufficient cooling of electronic components and junction temperatures exceeding their specification, leading to component failure.

Dust and DirtOften contain carbon or other conducting material, leading to short circuits and equipment failure.

RadiationCauses electrical interference, leading to distortion of analogue signals or incorrect operation of digital equipment.

Electronic component failureIf there is no parallel redundancy in the equipment design, component failure produces system failure.

Mechanical component failureOften leads to electrical failure if:

a failed mechanical joint is also an electrical connection

OR

the failed joint results in an open circuit.

Mechanical failure can result in a broken product which works electrically but cannot be used.

VibrationVibration can lead to mechanical failure of components which leads to electrical failure and system failure.

ShockCan produce sudden mechanical and electrical failure of components or connections.

CorrosionCorrosion of components or connections leads to their mechanical and electrical failure.

Electrostatic DischargeProduces electrical damage of semiconductor components and subsequent system degradation or malfunction.

Sometimes the damage is initially undetected but produces premature failure in the component.