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


thermode
A heated bar that is used during rework/repair of a PCA to remove a component by simultaneously desoldering multiple component leads

thieves (plating thieves)
Non-functional metal areas on a surface to be electroplated. Their purpose is to balance the current density during plating to ensure uniform build-up of plated material. See dummy traces.

thin film hybrid
See hybrid circuit.

thixotropy
‘Memory` property of a fluid (especially of solder paste) whereby its viscosity (resistance to flow) depends on its recent history of flow and not just on the force applied to it. See also shear thinning.

through connection
See feed-through.

through-hole
1) (noun) A hole that extends though the entire circuit board, which may or may not be plated, depending on its function. Plated through-holes are used for the attachment and electrical connection to the printed board of component terminations, including pins and wires. 2) (adjective) (also spelt ‘thru-hole`). Of a component, having pins designed …

through-hole technology
The science applied to making electrical connection of components to and through the surface of a conductive pattern using component holes (in contrast to SMT).

through-hole via
A plated hole made to extend completely through a circuit board hole for the sole purpose of connecting conductors on one or more layers.

tinning
The application of a solder coating to a basis metal (e.g. conductive paths and terminals) to enhance solderability and minimise oxidation.

tombstoning
A soldering defect condition observed after reflow soldering, in which leadless devices such as chip resistors or capacitors stand on their end, with only one edge soldered to lands on the circuit board, resembling a tombstone. Also referred to as the Stonehenge or Manhattan effect. Tombstoning is caused by force imbalances during solder reflow, w …

tooling hole
A hole in a circuit board or fabrication panel that is used for positioning purposes; for example, at fabrication, to align the panel with the artwork; at assembly, to facilitate handling, and as a means of rough alignment for component placement. Typically tooling holes are treated in such a way as to be very accurate at the fabrication stage, wh …

top or bottom entry sockets
refer to the direction from which the connectors plug together (that is, bottom entry means that the plug connector has to pass through holes or slots in the PC board).

top side
The primary side of a PCA, usually containing the most complex or major components. The top side of a PCA having some or all through-hole components (Assembly Types II and III) is the side with the through-hole component bodies, and is also referred to as the ‘component side`. The top side of a PCA having all SMT components (Assembly Type I) is th …

TQFP
Thin Quad Flat Pack. Essentially the same as a QFP except low-profile, that is, thinner.

transmission line
A conductor that is configured to have a specific impedance value. See microstripline and stripline.

treatment
: Involves the physical, chemical or biological processing of waste to reduce their volume or harmfulness.

true position
The theoretically exact location of a feature or hole established by a basic dimension.

true positioning tolerancing
See geometric dimensioning.

TSOP = Thin Small Outline Package
As with SQFP, this term and the related TSSOP refer to fine pitch low-profile packages. Similar in style to the SOP, but substantially smaller. The term ‘shrink` refers to the reductions in the footprint of the package; ‘thin` generally means that both lead frame and package have been designed to allow a much thinner resin coat than the standard S …

tube feeder
A parts packaging method in which parts are inserted end-to-end in an anti-static plastic tube or stick. Indexing for feeding to the placement tool may be accomplished by vibration or spring action.

twist
The deformation parallel to a diagonal of a rectangular sheet such that one of the corners is not in the plane containing the other three corners.

two-part connector
A device that provides a mechanically pluggable interface for electrical terminations. One half of a connector pair is mounted on a circuit board and the mating half is electrically connected to the rest of the system.

Type I, II, III assembly
Designating PCB assemblies (I) SMDs mounted on one or both sides of the board; (II) mixed technology having leaded (through-hole) parts mounted on the primary side and SMDs on one or both sides; and (III) mixed technology featuring passive SMDs on the secondary side and leaded components mounted to the primary side.

UL = Underwriter`s Laboratory Inc.
An independent not-for-profit organisation, set up by the insurance industry for the purpose of establishing product safety standards, that evaluates and certifies the performance and safety of electrical equipment, components and materials.

ultra-fine-pitch
As with fine-pitch, a term whose value depends on the date of the definition. The term now (arguably) applies to surface mount packages with a centre-to-centre lead distance of 0.4mm (0.016in) or less.

unsupported hole
A hole in a printed board containing no plating or other type of conductive reinforcement.

UUT = Unit under test
A term applied to any component or assembly being tested by automatic testing equipment.

vacuum pickup
A parts-handling instrument through which a vacuum force secures and holds them for placement.

vapour phase
A mass soldering technique in which high-temperature vapour, condensing on the solder joints of a PCB, is the heat-transfer medium.

vapour phase (reflow)
See condensation soldering.

vector photoplotter
(also ‘vector plotter`, or ‘Gerber photoplotter` after Gerber Scientific Co., which built the first commercial equipment). A CAD database is plotted on photographic film in a darkroom by drawing each line with a continuous lamp shining through an annular-ring aperture, and creating each pad by flashing the lamp through a specially sized and shaped …

vehicle
As used when referring to fluxes and solder paste, the ‘vehicle` is a thermally stable material that acts as a high temperature solvent during wave soldering. Sometimes it is also a weak activator. Depending on its properties, it can inhibit or induce corrosion.

via (hole)
A plated-through hole used to connect two or more conductor layers of a multilayer board, in which there is no intention to insert a component lead or other reinforcing material. See through-hole via, blind via, tented via and buried via.

via tenting
Covering a via with a masking material, such as a dry film polymer coating (solder mask), B-stage (prepreg), etc., in order to prevent hole access by process solutions, solder, or contamination.

void
The absence of material in a localised area.

voltage breakdown
The level of voltage potential across a normally nonconductive material where current begins to flow in the material or on its surface. This may be accompanied by a sudden electrostatic discharge, which can severely damage the material.

wafer
A thin disk (or slice) of silicon on which many separate chips can be fabricated and then cut into individual die.

warpage
) The deviation from flatness of a board characterised by an approximately cylindrical or spherical curvature. (Also referred to as ‘bow` and ‘twist`)

waste hierarchy
: The ranking of waste management options in order of sustainability.

waste management
: Management of the collection, recovery and disposal of wastes, including options for waste reduction.

waste minimisation
: The reduction of waste at source, by understanding and changing processes to reduce and prevent waste. This is also known as process or resource efficiency. Waste minimisation can include the substitution of less environmentally harmful materials in the production process.

wave soldering
A method of soldering components to printed circuit boards by moving the boards over a continuously flowing and circulating wave of molten solder in a solder bath. The process permits precise control of the depth of immersion in the molten solder and minimises heating of the board. SMDs are held in place during wave soldering with adhesives and ar …

weave exposure
A surface condition of base material in which the unbroken fibres of woven glass cloth are not uniformly covered by resin. (Also see fibre exposure)

weave texture
A surface condition of base material in which a weave pattern of glass is apparent although the broken fibres of the woven cloth are completely covered by resin.

webbing
Solder adhering to the surface of a solder mask after the soldering operation.

wedge lock
Mechanical hardware utilized for constraining the edges of a circuit board assembly in a mechanical chassis. It reduces the possibility of damage due to board vibration and improves the heat conduction path between the assembly and the chassis.

wet solder mask
Applied by means of distributing wet epoxy ink through a silk screen, a wet solder mask has a resolution suitable for single-track design, but is not accurate enough for fine-line designs.

wetting
In general, wetting is the ability of a liquid to flow across a surface as opposed to sticking to itself. Wetting occurs when the attraction between liquid and surface is greater than the surface energy of the liquid, drawing a molecularly thin layer across itself.

whisker
A slender needle-shaped growth between conductors and lands which occurs after the printed board has been manufactured.

wicking
Absorption of liquid by capillary action along the fibres of the base metal. For an alternative use, see solder wicking.

wire
Besides its usual definition of a strand of conductor, wire on a printed board also means a route or track.

wire pullout force
The force at which a cable will fracture or pull out of the termination at the back of a contact in a connector. The pull out force must be no less than the breaking strain of the plain wire.

wire wrap area
A portion of a board riddled with plated-through holes on a 100-mil grid. Its purpose is for accepting circuit changes which may be found necessary after a board has been manufactured, stuffed, tested and debugged.

wiring harness
A prefabricated bundle of wires.

workmanship requirements
A set of quality standards that must be met by a manufactured PCA.

X-raying
An inspection process used mainly for determining the alignment of internal features (pads, conductors, etc.) of a multilayer board. It may also be used to determine the quality of solder joints that cannot be inspected by direct visual means.

zener diode
A diode which is designed to work in a reverse biased condition, and is used primarily for voltage regulation.

Zero Insertion Force (ZIF)
Refers to contacts or connectors which, when unplugged have electrical contacts which remain in an open position. The plug and socket connectors can be plugged together without any force being required. The contacts are then actuated by means of a mechanical lever, and come together to make electrical contact. This is particularly useful for very …