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


A-D converter
A functional circuit element or component that converts analogue signals to digital signals.

A-stage
The stage of curing of a polymer resin where the polymer is still of relatively low molecular weight and thus both readily soluble and fusible.

above-board profile
The height that a component such as a connector stands above the top surface of the PCB

acceptance tests
A set of tests performed to determine the acceptability of a PCB.

access time
Time interval between the instant that a piece of information is sent to the memory device and the instant it returns .

activator
One or more ingredients in a flux that create a wettable surface for solder, by removing oxides and possibly other contaminants when coming into contact with the metal on the parts to be soldered. These ingredients may or may not be corrosive at room temperature, but certainly must be active at elevated temperatures in order to perform their job p …

active component
An electronic component whose parametric characteristics change while operating on an applied signal.

additive process
A process for fabricating a printed circuit board by selectively depositing conductive material to define a conductor pattern on unclad, chemically treated laminate material.

adhesive dam
A method of controlling the flow of adhesive material on inner layers of a multi layer board during lamination by providing an etched border of copper around the outer edges of the conductor layers.

Ag
Chemical symbol for silver.

aging
Mechanisms that cause degradation of properties or performance over a period of time.

alloy
Mixture of two or more metals (see binary alloy; ternary alloy)

ambient
Literally = ‘surrounding`, but usually interpreted as ‘room temperature`.

angle of attack
The angle between the squeegee face and the stencil plane.

annular ring
The portion of PWB conductor material (with through-hole designs, usually a pad) that completely surrounds a hole.

anti-wicking contacts
Contacts on components such as connectors or switches that prevent entry of either flux or solder up into the contacts during the process that solders the contacts to the PCB.

antioxidant
As used when referring to fluxes, an antioxidant is a material that prevents re-oxidation of the metal surfaces after the activator has prepared them for soldering. Often, another material such as the vehicle might also serve as an antioxidant.

aperture
A predetermined shape (round, square, oblong, etc.), size (width, diameter), and type (draw or flash) that is exposed on artwork film by a photoplotter.

aperture library
A collection of standard aperture descriptions.

aperture wheel
Contains a set of individual physical apertures (or software definitions of apertures) that are specific for plotting a type or family of circuit board artworks.

aqueous cleaning
A generic cleaning approach that uses water in combination with neutralizers, saponifiers and surfactants.

archiving data
The process of relocating all the design and data files required to produce an end product into a retrievable storage area.

array
A group of components arranged in rows and columns.

artwork (master)
A photoprocessing tool used to fabricate a printed circuit board that consists of an accurately scaled image of the required pattern on the surface of a stable transparent film base.

ASCII format (ASCII code)
Originally code which represents characters by numbers so that text can easily be transferred from one computer to another. The basic set covers only the numbers 0 to 127, of which the The ASCII character set is restrictive, and there are few variant ‘extended` sets.

aspect ratio
The ratio of the length or depth of a hole to its preplated diameter. Often used for the ratio of the thickness of the board to the diameter of its smallest via hole. Holes with high aspect ratios are difficult both to drill and plate and may be susceptible to cracking.

assembly
A number of parts or subassemblies or any combination thereof that are joined together.

assembly drawing
A document that shows the physical relation of a combination of parts and subassemblies that form a higher order assembly, giving both the locations of components and their reference designators. See Bill of Materials.

Assembly Type I-II-III
see ‘ Type I/II/III Assembly`.

ATE = Automatic Test Equipment
Programmable equipment used for various testing operations within the EDR fab and assembly process. Component ATE automatically checks individual components for correct value and operation; In-Circuit Test equipment checks assemblies for correct assembly and for short-circuit and open-circuit failures on the printed circuit board; functional test …

atmospheric variations
Changes in operational or storage conditions. See ambient.

automated assembly
Automatic component placement and attachment to a printed circuit board.

automated optical inspection (AOI)
A vision system that captures and stores an image and compares it to an expected image and/or a set of design rules, in order to detect errors on printed circuit artwork, boards, or assemblies.

autorouter
CAD layout software that automatically determines the placement of interconnections on a circuit board based upon predetermined design rules.

axial lead
A lead wire extending from a component or module body along its longitudinal axis.

azeotrope
A ‘constant boiling mixture` of two or more solvents, whose vapour has the same composition as the liquid, so that the formulation cannot be altered by distillation. Constant boiling mixtures usually have a minimum boiling point, lower than that of either of its constituents. Often azeotropes used for cleaning combine polar and non-polar solvents …

B-stage
A stage of resin polymerisation later than A-stage, at which the resin has a higher molecular weight, so is more viscous and insoluble, but still plastic and fusible. B-stage resin is still only partially polymerised, so retains the ability to adhere to other materials and to form further cross-links. Prepreg, used for making multilayer constructi …

B-stage
A partially cured thermosetting adhesive used in multilayer boards. During lamination, the application of heat and pressure completes the curing process.

bare board test(ing)
Tests of electrical connectivity and isolation carried out by the manufacturer on the unassembled (unpopulated) circuit board. In the case of high frequency boards, can sometimes include impedance control measurements.

base (or basis) metal (or material)
A metal or material upon which coatings are deposited.

base laminate
The insulating support material (most usually epoxy-glass) used in the fabrication of printed wiring boards. (Also see ‘substrate`)

base substrate
The insulating material that forms the support for conductor patterns and components.

BAT
: Best Available Techniques, defined under Integrated Pollution Prevention and Control (IPPC). Note that BAT has many more cost and implementation issues than its predecessor BATNEEC.

BATNEEC
: Best Available Techniques Not Entailing Excessive Cost, defined under Integrated Pollution Control (IPC).

bed of nails test fixture
A fixture consisting of a frame and a holder containing an array of spring-loaded contact probes that make electrical contact with conductors at specific points on the surface(s) of a circuit. Used, primarily in volume manufacture, for bare board and in-circuit testing to identify defective parts.

BGA = Ball Grid Array
A leadless IC package with a large number of terminations arranged in a matrix on the bottom of the package. Connections are made through solder terminations on the underside of the array , either in the form of solder balls (most common) or pillars. These are reflowed onto the board, forming pillars between the board and component.

bifurcated contacts
Stamped and formed contacts, in components such as connectors, which are split into a pair of springs so giving two independent spring movements.

bilateral dimensioning
Linear dimensioning (as opposed to geometric dimensioning) that defines tolerances allowing variations from the specified dimension in both directions.

bill of material(s) (‘BOM`)
A document that lists all electronic, electrical, and mechanical components, and supporting materials that are required to manufacture an assembly, and gives the quantities used. The BOM will use reference designators that uniquely identify each component and material, including associated part/find numbers. A BOM is used for part procurement and, …

binary
Numbering system using two as a base and requiring only two symbols: 0 and 1.

binary alloy
Alloy consisting of two metals (e.g. tin/lead or tin/silver).

biodiversity
: The range of plant and animal species and communities associated with terrestrial, aquatic and marine habitats.

biological treatment
: Any biological process that changes the properties of waste (for example, anaerobic digestion, composting). Biological treatment includes landspreading activities that are licensed.

bit (memory bit)
Short for ‘binary digit.` The smallest piece of data (a ‘1` or ‘0`) that a computer recognizes. Combinations of 1s and 0s are used to represent characters and numbers.

blind via
A via that extends from an outer surface of a multilayer circuit board to at least one of the inner layers, but does not go completely through the board.

blistering (blister)
A localised swelling and separation between any of the layers of a laminated base material or between base material and the metal cladding. (A form of ‘delamination`)

blowhole
A large void in the solder connection created by outgassing during the soldering process. Volatile contaminants, air or gas trapped in the solder expand with the application of heat, leaving holes in the solder joint.

board construction
Defines the types and dimensions of materials, the layering sequence of the cross-sectional structure of a circuit board, and its finished thickness.

board detail drawing
A drawing that provides and describes all the requirements for fabricating a bare circuit board.

board extractor
A device that is used as a means of extracting a PCA from its mating connector without damage to its electrical components. It can be permanently mounted on the circuit board or provided as external tool.

board fabrication
The bare-board manufacturing process, which begins after design but before assembly. Individual processes include layer lamination, metal addition/subtraction, drilling, plating, routing and cleaning.

board routing process
) A machining process for defining the outline of a circuit board. Pin routing uses a pin-guided template for manually profiling boards; NC routing utilizes programmable equipment to define a board profile. Both methods use cutters similar to end mills.

board thickness
The overall thickness of the base laminate and the conductive pattern, usually measured at the gold fingers.

board-to-board stacking height
The distance between the two inside faces of parallel mounted PCBs.

body
The central portion of an electronic component, excluding its pins or leads.

BOM
[pronounced ‘bomb`] see Bill of Materials.

bonding agent
An adhesive for bonding individual layers to form a multilayer laminate.

bonding layer
An adhesive layer for laminating the separate substrates of a multilayer board.

bottom side
The secondary side of a PCA, opposite the primary side. The bottom side of a PCA having some or all through-hole components (Assembly Types II and III) is the side accepting solder on the component leads. (Also referred to as ‘solder side`, ‘circuitry side` or ‘conductor side`)

boundary scan
A diagnostic test method that uses circuitry integrated in an IC component to facilitate testing or to monitor the performance of the component and its surrounding interfaces.

bow and twist
Deviations from flatness requirements of a circuit board. Bow is measured from the top of a smooth arc to the same surface of the board if it were flat; twist is a helical divergence from flatness. See also warp.

breadboarding
‘Quick and dirty` assembly and test of a circuit to validate its performance before committing it to implementation as a PCA.

breakaway panels
PCBs held together with breakaway tabs to make handling, placement and soldering easier and more efficient. Boards are snapped apart at the end of processing.

breakout
A condition in which a PWB hole is not completely surrounded by the land or annular ring.

bridge
( bridging) A formation of solder that connects (bridges) adjacent conductors, such as two leads, completing an unwanted connection, causing short. One of the causes of an electrical short.

bulk resistance
The resistivity (in ohm-cm or ohm-inch) through the cross-section of a conductive material.

buried via
A via that makes a circuit connection between internal layers of a multilayer board, but does not extend to either external surface of the board.

burn-in
The process of running an assembly at elevated voltage and temperature. This accelerates failure mechanisms, and makes it possible to remove assemblies which would otherwise be seen as early-life failures (‘infant mortality`). Burn-in can also be used on individual components before assembly in order to detect and remove potential failures.

burr
A thin, ragged piece of metal produced during a machining operation which has been left on the edge of a piece of metal.

bus bar
A mechanical means of providing power and ground interconnections using conductive metal (usually copper) bars rather than etched conductors.

bus structure
A routed conductor pattern, usually used for point-to-point interconnection of power and ground.

butt joint
A surface mount device lead that is sheared so that the end of the lead contacts the board land pattern without any hooks or bends; also called an ‘I-lead`.

bypass capacitor
Minimizes the effects of current variations in a power circuit caused by switching transients generated during circuit operation.

byte
A number of binary bits, usually eight, that represent one numeric or alphabetic character.

CAF =
Conductive Anodic Filament. Metal migration between two conductors or the dendritic growth seen under Temperature, Humidity and Bias test.

CAM files
are data files used directly in the manufacture of printed wiring. Typically this data is manipulated by the fabricator to meet production requirements (for example for panelisation) and to ensure the intended result is achieved.

capacitance
The property of a circuit element that permits it to store an electrical charge.

capacitor
A discrete device that stores an electrical charge on two conductors separated by a dielectric.

capillary action
The combination of force, adhesion and cohesion that prompts liquids, such as molten solder, to flow upward between closely spaced solid surfaces, e.g., lead (contact) and pad.

capture
Extract information automatically through the use of software, as opposed to hand-entering of data into a computer file.

card
another name for a printed circuit board.

card-edge connector
A connector which is fabricated as an integral portion of a printed circuit board along part of its edge. Often employed to enable a daughter or add-on card to be plugged directly into another much larger printed board, the motherboard or back-plane. See finger.

carriers
Holding devices for PCBs and other parts to facilitate handling during component placement, soldering and other processing.

castellation
Metallised semicircular radial features on the edges of LCCCs that interconnect conducting surfaces. Castellations typically are found on all four edges of a leadless chip carrier. Each lies within the termination area for direct attachment to the land patterns.

CBGA = Ceramic Ball Grid Array
(also Column BGA) Less common than the standard ball grid array, which uses balls of eutectic solder, CBGAs contacts are columns of a high-melting solder. When reflowed in contact with eutectic solder on the substrate, only a small portion of the column melts into the joint, so that the package is held off the substrate. The resultsing separation …

cell
A tiny area within the memory array that actually stores the bit in the form of an electrical charge.

centroid
A point whose coordinates are the average of an associated parts dimensions (central point).

CFC = chlorinated fluorocarbon
Causes depletion of ozone layer and scheduled for restricted use by the Environmental Protection Agency. CFCs are used in air conditioning, foam insulation and solvents.

chamfer
To bevel or round an otherwise sharp or blunt edge. (Also see ‘ bevel`)

chassis
The supporting frame or structure that houses printed circuit assemblies.