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University of Bolton - Glossary of electronics terms
Category: Electronics and Engineering > Electronics
Date & country: 18/12/2007, UK
Words: 758

Use of materials or components in a design at less than their rated characteristics (such as power dissipation or current-carrying capacity) to enhance the long-term reliability of the end product. Part manufacturers usually specify a derating factor to be used when a part is to be operated above a certain temperature.

design cycle
The entire technical activity associated with the design fabrication, assembly, test, and integration of a PCA

design qualification
Verification through test and analysis that a PCA design will perform its required operational functions.

design reviews
Checkpoints established at critical points in the design process to verify the validity of the design and its associated data and documentation, and evaluate the producibility, testability, and projected reliability of the product.

design rules
A set of layout guidelines which is used to ensure that designs meet the criteria of electronic circuit performance, ease of board fabrication and yield/cost at assembly, test and rework. Typically these rules will establish minimum dimensions and spacing, and contain recommendations on good practice. Be aware that the design rules applied by boar …

design standards
Layout processes, guidelines, and procedures that are widely used throughout the industry.

desoldering methods
Disassembling solder parts to repair or replace by wicking, sucking, heat and pull, or solder extraction.

device geometries
Sizes within a silicon device (e.g. 0.25µm) which refer to the layout of components and interconnects on the die.

Device Under Test
Used to describe both the unit being tested and an interface board placed between the device and the computerised test equipment.

A condition that occurs when molten solder has coated a surface and then receded, leaving irregularly shaped mounds of solder separated by areas covered with a thin solder film. Voids may also be seen in the dewetted areas. Dewetting is difficult to identify since solder may be wetted at some locations and base metal exposed at others. Depending o …

Pertaining to the diameter of a circle or hole.

A single rectangular piece of semiconductor material onto which specific electrical circuits have been fabricated. Refers to a semiconductor which has not yet been packaged.

An insulating medium which occupies the region between two conductors.

dielectric constant
A property that is a measure of the ability of an insulating medium to store electrostatic energy. Numerically, the dielectric constant of an insulating material is the ratio of the capacitance value when using the material, to the capacitance value of the same geometry (area and thickness) component but using vacuum as an insulator.

dielectric material
A insulating material: one that conducts no current when voltage is applied across it.

differential pair
Conductors carrying sensitive signals that should generally be routed in parallel with matched overall lengths.

Indicates the representation of data by a series of bits or discrete values, such as 0s and 1s.

digital clock lines
Conductors that carry a continuous stream of uniform pulses (0s and 1s) that establish the timing of operation of associated digital circuitry.

digital signal processor
An integrated circuit that electronically processes signals such as sound, radio, and microwaves by converting them from analogue to digital signals.

A method of capturing the X-Y coordinates of feature locations on a PCA layout and converting that data to a digital format.

dimensional origin
See datum intersection (origin).

dimensional tolerance
The total amount that a specific dimension is permitted to vary. The tolerance defines the maximum and minimum limits of the dimension.

DIP = Dual In-line Package
An integrated circuit package that has two rows of pins or lead-wires for through-hole mounting positioned along opposing long sides of the package. The number of leads and the spacings between leads and between rows are all standardised, the most common spacing being 2.54mm (0.1in) between centres of adjacent pins.

dip soldering
A process whereby printed boards are brought in contact with the surface of a static pool of molten solder for the purpose of soldering the entire exposed conductive pattern and component leads in one operation.

discrete wire
A single cable or wire, to be terminated on to a connector contact.

dispensing (syringe)
Application of adhesives by pressurized (hydraulic or pneumatic) force for a specific period required to emit an ‘appropriate` amount of material through the needle and onto the target location.

A chemical additive to water to improve particulate removability.

dissipation factor
A measure of the absorption of electromagnetic energy passing through a dielectric material.

disturbed connection
A soldered connection where there is movement between the metal surfaces during solder solidification. The connection can have a dull, granular, rough, lumpy appearance and may have noticeable spiral cracks or a separation of the component lead from the solder fillet. The joint will also be of lower than average mechanical strength. Also referred …

Information for a PCB that explains the electromechanical design concept, types and quantities of parts and materials, special instructions, and revisions. Will include a Bill of Materials.

documentation-data release
The activity that takes place following final review and approval (signoff), when all drawings and design data are placed into a configuration/records control system.

To-scale cut-outs that represent physical parts to be mounted on a circuit board. They are used to perform component placement during a manual layout effort.

The introduction of an impurity into a semiconductor to modify its electrical properties.

DOS = Disk Operating System
A program that controls the computer`s transfer of data to and from a hard or floppy disk. Personal computers that are IBM-compatible run DOS rather than other early varieties of operating systems.

(of magnetic data storage media, such as floppy disks.) Prepared for storage of data in such a way that DOS transfer can occur.

double-sided (board)
A printed board with a conductive pattern on both sides of the board.

Slang for fine line design with two traces between DIP pins.

DRAM = Dynamic Random Access Memory
. A type of memory component. ‘Dynamic` means that the device`s memory cells need to be periodically recharged. Information stored in the memory cells, as a positive or negative charge, can be accessed randomly.

A variant of tombstoning in which the component is at a small angle to the substrate rather than almost at right-angles.

Documentation that provides the configuration and requirements information needed to build a product.

drill data
Information that specifies X-Y locations for all drilled holes, their sizes, and their plating requirements.

drill spindle run-out
The undesirable deviation from the theoretical centre of rotation of a drill spindle due to its inherent mechanical tolerances.

A method used to modify a fabricated circuit board or assembly by drilling through a conductor (usually internal) or plated hole to break the connection.

A signal source that generates an output strong enough to change logic levels of all devices (loads) attached to its net.

Oxide and other contaminants which form on the surface of molten solder.

dry film material
A photosensitive resist or solder mask material available as a film (as opposed to a liquid) that is applied to a circuit board during fabrication, using heat and pressure. Dry film solder mask can manage the higher resolution required for fine line design and surface mount, but is more expensive than liquid photoimageable solder mask.

dual solder wave
A wave soldering process in which an initial ‘wave` of molten solder covers all PCB surfaces contacted. It is followed by a second laminar or ‘flat` wave that serves to ‘finish` the board by removing all solder bridges and icicles.

dummy traces
Added non-functional conductors that help achieve plating balance. See thieves.

: The delivery of competitively priced goods and services that satisfy human needs and bring quality of life, while progressively reducing environmental impacts and resource intensity throughout the life cycle, to a level at least in line with the earth`s estimated carrying capacity.

A document that describes and controls engineering design or documentation changes.

edge contact
See gold finger.

edge-card connector
A pluggable connector specifically used for making non-permanent interconnections to contacts plated on the edge of a circuit board.

See board extractor.

electrical noise
Variations from a nominal operational voltage or current value on a power or signal line. Circuits are usually designed to function within a noise tolerance band or allowable noise budget.

electrochemical migration
Gradual movement of corrosive or conductive materials that may create unwanted circuit paths and cause performance degradation or failure. Migration is usually caused by exposure of existing contaminant residues or bare metal surfaces to a combination of high humidity, elevated temperatures, and an electrical potential.

electroless plating
A process for chemically depositing metallic material on a nonconductive surface. It is primarily used for metallising holes in a circuit board to prepare them for addition of electroplated metal.

( electrolytic plating) Direct deposition of metallic materials on a surface using an electrolytic process. It involves passing a current between an anode and a cathode through a conductive solution containing metal ions. The conductive surface of the laminate (circuit board) to be plated is the negative electrode (cathode).

: (European) Eco-management and Audit Scheme. A European voluntary scheme for industrial sites. To register under EMAS your company should have a clearly defined strategy for environmental management, complete with quantified objectives.

Electromagnetic interference (EMI) is the detrimental effect stray radiated electromagnetic energy has on the performance of a circuit. Electromagnetic compatibility (EMC) involves the control and reduction of this energy.

A representation (hardware or software) of an electronic device or function that simulates its behaviour. It is used to verify performance of a circuit design by analysis.

1) A stable combination of two or more immiscible (unmixable) materials suspended in a surrounding medium.

end-to-end design
Integrating the inputs and outputs of CAE, CAD and CAM software packages to allow design to flow smoothly in both directions with minimal manual intervention.

energy recovery
: The recovery of useful energy in the form of heat and/or power from burning waste. Generally applied to incineration, but can also include the combustion of landfill gas and gas produced during anaerobic digestion.

The surrounding conditions in which an assembly exists and functions, including temperature, humidity, altitude, vibration, shock, etc.

Environment Agency
: The principal environmental regulator in England and Wales. Established in April 1996 to combine the functions of former waste regulation authorities, the National Rivers Authority and Her Majesty`s Inspectorate of Pollution. Intended to promote improved waste management and consistency in waste regulation across England and Wales.

environmental accounting
: Any quantitative approach to linking financial and environmental performance.

environmental footprint
: The impact of an organisation in environmental terms (resource use, waste generation, physical environmental changes etc).

Electrically Programmable Read Only Memory: a device that allows data stored in it to be erased and new data input to it, usually by exposure to ultraviolet radiation.

ESD = electrostatic discharge
The rapid transfer of a voltage potential into a circuit or component. Depending on its sensitivity to ESD, the overstress can permanently damage a component.

etch (etching)
Chemical removal of material, usually associated with defining conductor patterns on a circuit board.

Chemical removal of dielectric material in the barrels of holes in a multilayer board. The purpose is to increase exposure of internal conductor areas (usually pads) to enhance physical and electrical contact with metal to be plated in those holes.

EU Directive
: A European Union (formerly EC-European Community) legal instruction, binding on all Member States but which must be implemented through national legislation within a prescribed time-scale.

eutectic (alloy)
An alloy of two or more metals that has a lower melting point than either of its constituents. The alloy can pass (reversibly) from solid into the liquid state without an intermediate plastic phase. Eutectic tin-lead solder is usually regarded as having the proportion 63% tin to 37% lead.

Excellon data format
A proprietary data format structure that is used to convert physical hole data (location, diameter, etc.) into a format that a software program can use to drive a numerically controlled (NC) drilling machine. It is considered a de facto industry standard.

excess solder
A solder connection characterised by the complete obscuring of the connected metal surfaces or by the presence of solder beyond the connection area. The connection appears as a rounded, piled-up, convex solder fillet, and it is impossible to determine if a proper bond has been achieved.

exempt facility
: A waste recovery operation (also occasionally certain disposal at the waste producer and some storage activities) registered with, but not licensed by, the Environment Agency. Exempt facilities are subject to general rules (e.g. on the types and quantities of wastes received).

A short metallic tube with ends that can be formed outward to fasten it within a hole in the base laminate of a printed circuit board.

Short for fabrication. Used both for the manufacture of printed circuit boards and semiconductors.

fabrication drawing
A drawing used to aid the construction of a printed board. It shows all of the locations of the holes to be drilled, their sizes and tolerances, dimensions of the board edges, and notes on the materials and methods to be used. Called ‘fab drawing` for short. It relates the board edge to at least one hole location as a reference point, so that the …

false triggering
An incorrect change of state of a digital device due to a spurious signal received by that device.

fatigue failure
Mechanical failure of a material caused by application of repeated cycles of stress (force) and strain (movement) over a period of time. These forces may be due to vibration or caused by changes in temperature, and in PCAs may result in cracked plated through-holes, open solder joints, or board delamination.

fatigue resistance
The ability of a solder joint to resist vibration.

fault isolation
A test procedure for locating the area of a circuit that is causing a performance anomaly or failure.

A conductor that connects patterns on opposite sides of a printed circuit board, e.g. an eyelet, plated through hole or clinched jumper wire.

feed-through via
A plated-through hole in a PWB used to route a trace vertically in the board, that is, from one layer to another.

FEM = finite-element modelling
A method of using a software program to simulate the response of a PCA to various mechanical or thermal conditions. A mathematical model of an assembly is constructed, exposed to mechanical or thermal stimulation, and analysed for its response to those inputs.

female connector
Consists of an insulated moulding fitted with socket contacts that allows male and female connectors to be plugged together. (In the USA female connectors can be called receptacles).

A field-effect transistor is a unipolar device, which functions as a voltage amplifier.

fibre exposure
A condition in which reinforcing fibres within the base material are exposed in machined, abraded or chemically attacked areas.

fiducial (mark)
A geometric feature incorporated into the artwork of a printed wiring board or into a stencil.

fill area
A large conductive area such as a ground or power plane.

A general term used to describe the normally concave surface of the solder at the intersection of the metal surfaces of the solder connection that is formed with a component lead or termination and a PWB land pattern. In particular, it relates to its shape and strengthening function. Visual inspection criteria are largely based on the size and the …

find number
An item number that cross-references a part callout on an assembly drawing to its entry in a parts list or bill of materials.

fine-line design
Printed circuit design permitting two (rarely three) traces between adjacent DIP pins. It entails the use of a either dry film solder mask or liquid photoimageable solder mask, both of which are more accurate than wet solder mask.

A term which always refers to the distance between lead centres of device packages, but whose value depends on the date of the definition. Previously lead pitches below 1.27mm (0.050in) were regarded as fine pitch; in 2002, given improvements in printing and paste technology, the frontier probably lies at 0.63mm (0.025in).

See gold finger.

First-pass` yield
is a better monitor of the effectiveness of a process, but even here this may disguise planned intervention after processes such as wave soldering.

A designation assigned to a photoplotting aperture. A flash aperture is the size and shape of the feature it defines on photosensitive film; a draw aperture creates the shape on film via software move commands transmitted to a photoplotter.

A non-volatile programmable semiconductor memory product. Flash devices retain the contents of their memory when the power is turned off.

Common designator for a two or four-sided integrated circuit package with gull wing or flat leads. The component leads extend from the sides and have their termination plane on the same linear plane as the base of the package, with standard spacing between leads. Commonly, the lead pitches are at 1.27mm (0.05in) centres, but lower pitches also may …