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University of Bolton - Glossary of electronics terms
Category: Electronics and Engineering > Electronics
Date & country: 18/12/2007, UK
Words: 755

signal coupling
See circuit coupling.

signal edge
The forward or trailing part of a signal pulse that causes a gate to change logic states.

signal flow
The movement of data through a circuit.

signal integrity
The specified purity (lack of distortion) of a signal transmitted through a circuit required for proper operation. Design of a circuit, selection of electronic parts, their physical placement on a board, and the location and physical configuration of the interconnections all have a significant effect on signal integrity, especially for high speed …

signal layer
An interconnection layer on a circuit board devoted exclusively to the routing of signal traces.

signal propagation delay
The time it takes a signal to travel (propagate) in a line, compared to its theoretically possible speed. This is mainly a function of the characteristic impedance of the line, the dielectric constant of the surrounding material, and the type and number of the components attached to the line.

signal rise and fall times
The time it takes the edge of a signal pulse to reach a value that will cause a gate to change states.

signal timing
The speed at which a signal that causes digital devices to switch (change states), travels in a circuit. See clock speed.

A non-metallic element used in the semiconductor industry as a substrate for multiple layers of material, built to form transistors and integrated circuits. Silicon is grown from a crystal to form a cylinder shaped ‘log.` Slicing the logs into sections 1/40 of an inch thick creates bare wafers.

silicon wafer
A thin, iridescent, silvery disk of silicon which contains a set of integrated circuits, prior to their being cut free and packaged.

1) The decals and reference designators in epoxy ink on a printed circuit board, so called because of their method of application: see legend. 2) A data file controlling the photoplotting of this legend.

SIMM = Single In-line Memory Module
A high-density DRAM package alternative consisting of several plastic leaded chip carriers (PLCC) connected to a single printed circuit board (PC board). SIMMs provide an upgrade vehicle for future generations of DRAMs without having to redesign the PC board.

Use of a computer program that duplicates the characteristics of an entity. Its purpose is to verify the performance of a design before committing it to a hardware implementation. See modelling.

single track
PCB design with only one route between adjacent DIP pins.

single-sided (single-layer) board
A PCB with metallised conductors on one external surface only. Any through holes are unplated.

SIP = Single-In-Line Package
A component package that has a single row of terminals, pins, or lead wires along one edge of the package.

SIR test
means a test for the maintenance of a high SIR valu under conditions of applied voltage, temperature and humidity, which is used to assess the suitability of flux materials and cleaning processes. Ionic residues lead to rapidly deteriorating values of SIR.

Describing the misalignment of a component or device to its proper mounting site.

skipping (solder skip)
Condition found in wave soldering, when adjacent conductor areas are not all coated with solder.

A spreading of material (solder paste, adhesive, thick film, etc.) after stencil printing but before curing. An excessive slump detracts from definition. If loss of definition is the result after reflow, it is cause for rework.

Chemical symbol for tin.

The return of a stencil to normal (flat plane) after its deflection by a squeegee across its surface.

That part of the solder reflow process in which internal temperature differences between components are permitted to equalize (stabilization).

Pertaining to or consisting of software.

Programs, data files, procedures, rules, and any associated documentation pertaining to the operation of a computer system or of a computer application.

SOJ = Small Outline J-Leaded
A surface-mounted IC package with two parallel rows of J-leads, with standard spacing between leads and rows. Generally used for memory devices, where the rows of leads are typically on the narrow edges. Most of these parts use finer pitches than standard SOICs, and are also substantially thinner.

A fusible alloy used to join two or more metals at temperatures below their individual melting points. Solders which melt readily are ‘soft solders`, others fusing at a higher temperature (usually taken as above 425°C) are ‘hard solders`. Solders consisting mostly of tin and lead are normally used for soldering electronic assemblies. The tin in so …

solder balls
Small spheres of solder which have separated from the main body of the solder joint and adhere to laminate, mask, or conductors. Most often associated with the use of solder paste containing excessive oxides or moisture. Baking of paste may minimise formation of solder balls, but over-baking may cause excessive balling.

solder bumps
The spherical solder materials bonded to a passive or active device contact area that serve as connections to circuit pads.

solder contact angle
See contact angle.

solder dam
A neck-down (narrowing) of a conductor that restricts the flow of molten solder. Its main purpose is to ensure that the proper amount of material remains at the solder joint that is being formed.

solder fillet
(see fillet)

solder impurities
Trace metals (other than tin and lead) and contaminants which exist in the solder. With age and continued usage, impurities become more prevalent in solder baths or pots and in wave soldering machines.

solder joint contamination
The presence of foreign matter in a solder connection.

solder levelling or fusing
The process of remelting plated solder (tin-lead) on the surface of a circuit board to control its thickness, reduce granularity, and eliminate harmful oxidation.

solder mask
A coating material used to mask or protect selected areas of a pattern from the application of solder. Usually applied to a PCB to allow solder to adhere only to the pads and other unmasked areas. Also referred to as ‘solder resist`.

solder paste (cream)
A homogeneous combination of minute spherical solder particles, flux, solvent, and a gelling or suspension agent, which has the consistency and viscosity of a paste and is used in surface mount reflow soldering. Solder paste can be deposited on a substrate by solder dispensing and screen or stencil printing.

solder preforms
Special solder forms or configurations, frequently supplied as stamped washers, spheres or formed wire, that generally contain a predetermined alloy and a flux core or coating.

solder projection
An undesirable solder protrusion from a solidified joint or coating. Dependent on its shape, also referred to as ‘icicle`, ‘solder horn` or ‘peak`.

solder side
In assembly of plated through-hole components, the term refers to the soldered side of the PCB. With SMT, it means the secondary side generally is limited to passive chip parts.

solder splashes
Drops of solder in areas that should be free of solder; an undesirable condition that could cause electrical shorts.

solder voids
The absence of solder on the joint surfaces or pockets of bare spaces resulting from failure of the alloy to completely wet the joint.

solder wicking
Capillary action, caused by surface tension, leads solder to fill small spaces such as holes, between strands of wire up a pad or component lead, or under the insulation of a covered wire. The effect worsens if there are temperature differentials, because the surface tension of solder increases with temperature, causing it to travel towards a heat …

The ability of a metal surface. such as a lead, pad or trace. to be wetted by molten solder to form a strong bond.

Process by which two or more metal surfaces are bonded together via an intermediary alloy called a solder.

solids content
The weight percentage of rosin (solids) in a flux formula.

The temperature at which some components of the solder alloy begin to melt. See liquidus and pasty range.

Any solution capable of dissolving a solute. In the electronics industry, aqueous, semi-aqueous and non-ozone-depleting solvents are used. As used when referring to fluxes, the ‘solvent` is the liquid carrier for the flux ingredients, which allows even distribution of the flux material. During the pre-heating of the board the solvent is intended t …

solvent cleaning
The removal of organic and inorganic soils using a blend of polar and non-polar organic solvents.

SOT = Small Outline Transistor
A plastic surface-mounted package, for use with a transistor or diode, that has two gull wing leads on one side of the package and one on the other.

special waste
: Defined by the Environmental Protection (Special Waste) Regulations 1996 (as amended) and is broadly any waste on the European Hazardous Waste List that has one or more of fourteen defined hazardous properties.

A computer tool that is used to analyse the performance of analogue circuitry.

spring contacts
in a connector can have one, two, three, four or six cantilever or beam contacts. These are usually called single beam, twin leaf or twin beam, three, four or six leaf or finger contacts. Two-part contacts comprise a precision turned outer shell with an integral stamped and formed inner spring contact.

SQFP = Shrink Quad Flat Pack
See QFP. As with the SOP, the QFP has been developed to take up less valuable board area. ‘Shrink` is the term associated with reducing the plan dimensions of the package, and is always accompanied by a reduction in lead pitch, and usually by an overall thinning of the package.

A rubber or metal blade used in stencil printing to wipe solder paste across the stencil face, forcing the material through the patterned apertures and onto the PCB.

SRAM = Static Random Access Memory
An integrated circuit similar to a DRAM which requires no constant refreshing or recharging. It retains stored information as long as power is applied to the computer, hastening information retrieval process time.

Where a connector has its length and/or breadth narrow enough to allow two connectors to be placed together, and maintain contact pitch centres. This can be side-to-side (side stackable) or end-to-end (end stackable).

Defines the construction and lay-up of a circuit board.

stamped and formed contacts
are made from originally flat strip (usually non-ferrous materials) and are stamped out of the strip and formed up into spring contacts.

Moulded pips or bars that allow cleaning fluids to pass between the connector housing and the top face of the PCB, if is necessary after the soldering operation to remove flux residues, etc.

A metal sheet bearing a circuit pattern cut into the material. Common materials are stainless steel and brass.

strain relief
An area between a body and termination which has been formed or treated in such a way as to reduce the forces acting on the body when external forces are applied to induce separation, compaction, or sliding.

A type of high-frequency transmission line configuration that has a specific, characteristic impedance value. It consists of a conductor placed in a precise relationship between two parallel ground planes and surrounded by a dielectric material.

A short projection or branch from the main path of a conductor. In high-frequency operation a stub can act as a discontinuity in a circuit, causing degradation of performance.

As in ‘board-stuffing` a somewhat disparaging term which describes the activity of attaching and soldering components to make a printed circuit assembly.

A group of printed circuits (called modules) arrayed in a panel and handled by both the board house and the assembly house as though it were a single printed circuit board. The sub-panel is usually prepared at the board house by routing most of the material separating individual modules, leaving small tabs. The tabs are strong enough so that the s …

Two or more individually replaceable items integrated to form a system.

The base material which forms both the support structure of an electronic circuit and the insulating layer upon which the conductor pattern is fabricated. Provided that the material meets the manufacturing and usage design requirements, the term may refer equally to an epoxy-glass PCB laminate, a flex material, or the ceramic base for a hybrid cir …

surface mount (technology)
See SMT.

A chemical added to water to lower its surface tension to improve wetting for cleaning. Surfactants are used in fluxes to reduce surface tension at the metal/solder interface to further promote solder wetting, especially when the assembly exits the solder wave. Where the flux is to be used in a foam fluxer, surfactants can also serve as foaming ag …

sustainable development
: Development which meets the needs of the present without compromising the ability of future generations to meet their own needs.

sustainable waste management
: Using material resources efficiently to cut down on the amount of waste produced. And, where waste is generated, dealing with it in a way that actively contributes to the economic, social and environmental goals of sustainable development.

A simplified design representing a part in a schematic circuit diagram.

A computer program that allows an engineer to specify the logic operations that a design is expected to perform. The synthesizer extracts the equivalent logic circuit functions from a library and connects them together as specified by the engineer to form a complete circuit.

system integration
See integration.

TAB = Tape Automated Bonding
A process for interconnecting an integrated circuit die to the substrate surface using a fine lead frame supported by a carrier film (usually Kapton tape). The TAB process starts by bonding the IC die to the patterned inner leads on the tape, generally followed by testing. In a separate operation, the outer leads are positioned over the substrate …

Method of housing parts in separate cavities in a long continuous strip. The cavities are covered with a plastic sheet to facilitate winding the strip around a reel for component presentation or ‘feeding` to automated placement equipment.

See CTE.

= Time Domain Reflectrometry. TDR is a technique which is used for measuring the characteristic impedance of a printed circuit trace. The equipment measures the way in which a pulse is reflected from discontinuities in the transmission line created by the trace.

temperature gradient
The rate of change in temperature, which can be expressed in terms of change per unit of distance or per unit of time.

tensile strength
Ability of a solder joint to resist a force applied perpendicular (upward) from it.

tented via
a via with dry film solder mask completely covering both its pad and its plated-thru hole. This completely insulates the via from foreign objects, thus protecting against accidental shorts, but it also renders the via unusable as a test point. Sometimes vias are tented on the top side of the board and left uncovered on the bottom side to permit pr …

A point of connection for two or more conductors in an electrical circuit; one of the conductors is usually an electrical contact or lead of a component.

terminal area
See land.

terminal hole
A hole used for attachment and electrical connection of component terminations, including pins and wires, to the printed board. (Also referred to as ‘component hole`)

terminal pad
See land.

An electric input or output point of a circuit or component to which electrical connections can be made.

A device (usually resistive) attached to the end(s) of a transmission line to prevent or reduce signal reflections that could affect the performance of the circuit.

ternary alloy
Alloy consisting of three metals (e.g. tin/lead/silver).

test coupon
A portion of a printed circuit board or panel, dedicated for test purposes, that undergoes the same fabrication processes as the board, and can therefore be used to determine its acceptability. Typically test coupons are standard patterns which enable the fabricator to compare different products.

test pad
Designated points of access to a circuit or component for testing purposes.

test pattern
During testing of a PCA, patterns of signal faults are inserted into the circuitry, and its response is observed to determine if the faults were recognized appropriately. See circuit fault.

test point
Special points of access (a terminal or plug-in connector) provided in a circuit, used for electrical testing purposes or to facilitate monitoring, calibration, or trouble-shooting.

see glass transition temperature.

theory of operation
A description of how a circuit design is supposed to function.

thermal grease
A viscous material (such as silicone grease) that is inserted between two surfaces to enhance heat transfer between them.

thermal relief pad
A land configuration used for connecting plated through-holes to large conductive areas (power or ground planes) which become heat sinks during a soldering operation. It prevents excessive loss of heat of the solder in the hole, which could result in formation of an inadequate joint.

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.