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


flex circuit
Printed circuitry that utilizes flexible rather than rigid laminate material.

flexible buffer material
If devices packaged in a brittle material (such as glass diodes or ceramic ICs) are coated with rigid conformal coating material, temperature cycling may cause the packages to crack due to the difference in the CTEs of the two materials. This may be prevented by applying a resilient material (such as silicone rubber) to the part as a buffer betwee …

flip chip (device)
A leadless structure that is electrically and mechanically connected to the substrate via contact lands or solder bumps.

flip-chip (technology)
A ‘Chip-On-Board` technology in which the silicon chip is inverted (‘flipped`) and interconnected mechanically and electrically to a conductor pattern on the substrate by conductive bumps on the chip. The bumps are formed on the active surface of the chip, which is turned over for attachment.

flood bar
A device on a stencil printing system that drags solder paste back to the starting point after the squeegee has made a printing stroke.

flux
A chemically active agent that speeds the wetting process of metals with molten solder: a short-form way of describing a complex of rosin, activators and solvents. When heated, fluxes remove minor surface oxidation, minimise oxidation of the base metal, and promote the formation of an intermetallic layer between solder and base metal. Flux will no …

flux residue
A by-product of the soldering operation which may or may not need to be removed from the board, depending on the nature of the residue. Generally, highly active fluxes are corrosive and conduct electricity, so must be removed completely. Even with so-called ‘no-clean` fluxes there will usually be some residue which has an impact on the cosmetic pe …

flying probe tester
Computer-controlled In-Circuit Test system in which contacts are directed to specific nodes on a board to complete an electrical test.

foil
See conductive foil.

footprint
1) The pattern and space on a board taken up by a component. 2) The hole, pad and conductor pattern associated with a specific electronic component package configuration. A non-preferred term for land pattern. See also decal

form, fit, and function
Interchangeability classifications that determine the equivalence of products when design changes are implemented. If the physical form of an assembly, its ability to fit in the same place as the previous design, or its functional operation changes, it should be considered a new product, and given a new number.

fractured joint
A joint where the component lead has separated from the solder fillet, usually occurring during lead clipping after soldering.

functional test
An electrical test of a component, sub-assembly, or entire assembly that simulates part of the intended function of the product, verifying that the product is likely to comply with its overall function specification. Note that, for reasons of practicality and test time, it is unusual for this functional test to cover the entire range of function o …

gas-tight joint
The joint between male and female contacts, or a termination to a cable, which excludes air. This results in the connector maintaining good electrical continuity even under severe industrial atmospheric conditions.

geometric dimensioning
A method that defines the location and associated tolerances of a mechanical feature in terms of its allowable position with relation to its theoretical (true) position.

Gerber data (Gerber file)
Named after Gerber Scientific Co., who made the original vector photoplotter. A data format that converts physical feature information (location, shape etc.) into data used to control a numerically controlled photoplotter that produces printed circuit artwork.

glass transition temperature (Tg)
(pronounced “T sub g�) The temperature at which a polymer changes from a hard and relatively brittle condition to a viscous or rubber condition. This transition generally occurs over a relatively narrow temperature range. Although there is no phase transition, in this temperature region many physical properties (such as hardness, brittleness, ther …

glob top
A blob of non-conductive plastic, often black in colour, which protects the chip and wire bonds on some kinds of packages, particularly Chip-On-Board constructions. This specialized plastic has a low coefficient of thermal expansion so that ambient temperature changes will not rip loose the wire bonds it is designed to protect.

gold finger
A portion of a conductive pattern (usually gold plated) on or near any edge of a printed board that is intended for mating with an edge board connector. Also see printed contact.

gold plate removal
Thick gold plating is sometimes applied to leads as a protective measure, usually as a throwback to earlier Military Specification requirements. Unfortunately, tin and gold can form a brittle intermetallic interface, which will eventually cause the joint to fail – in fact, it is not unknown for gold-plated wires apparently firmly fixed in a solid …

gold(en) board
A component or assembly already tested as functional to spec and used, via comparisons, to test similar units. Also referred to as a ‘known good board`.

granular solder
Solder appearance with a coarse, large grain structure, lacking in metallic lustre. Usually due to unclean conditions of the joining members, contaminated solder, or excessively high temperature of the molten solder. (Similar to cold solder)

grid origin
See datum intersection (origin).

gridless (shape-based) router
The type of CAD autorouting program that has the flexibility to find paths for conductors based on the shape of surrounding geometric features (such as conductor widths and spacings), instead of being restricted to a predefined grid.

grounding
As used by the connector industry, sending current flow to earth in the case of a short circuit.

gull-wing
A lead configuration typically used on small outline packages where the leads extend horizontally out of the package for a short distance, then drop to the pad level, then extend horizontally again away from the component to make attachment surfaces that rest on the pads. An end view of the package resembles a gull in flight.

halides
Compounds containing halogens (the elements fluorine, chlorine, bromine, iodine or astatine), most usually chlorine and bromine. Within soldering, the term is usually used to refer to halogen salts (especially ammonium chloride and methyl ammonium chloride) which are activators within the flux system. Residues of these materials are corrosive, and …

haloing
Mechanically induced fracturing or delamination on or below the surface of the base material; it is usually exhibited by a light area around holes, other machined areas, or both.

hard-wired interconnections
Circuit connections using wire as opposed to etched interconnections.

hardener
A chemical added to a thermosetting resin to assist its cure.

HASL = Hot-Air Solder Levelling
A process used to solder coat a board, in which the board is dipped first in flux and then in solder, with jets of heated high velocity air being used to blow any excess molten material from the boards, especially out of the plated through-holes, so as to provide as flat a surface as possible. There is a trade-off between solder thickness and the …

hazardous waste
: See Special waste. Defined by EU legislation as the most harmful wastes to people and the environment.

header
The portion of a connector assembly which is mounted on a printed circuit.

heat removal mechanisms
Heat may be transferred from a surface by any or all of three mechanisms: conduction, convection, and radiation.

heat sink
A device that aids in the removal of heat from electronic equipment, and is particularly important when heat is generated in a small area, or when devices such as power transistors, rectifiers and microprocessors are operated. Heat sinks may be added to components, or to complete assemblies. Typically they are made of metal with high thermal condu …

heat-and-pull
A desoldering technique using a soldering iron equipped with a device that heats, grasps and pulls component leads to be removed.

hermaphroditic connectors
Contacts and mouldings, which can be used as both male and female types (that is, they will plug into each other).

High Insertion Force
Refers to contacts, which, due to their design and function, require a high force to plug together. Used mainly in high-current or low-cost connectors.

high-density interconnect
The ‘density` of interconnections is a measure of the average amount of circuitry package in a given area of assembly. This can be in terms of the length of conductor within a given area, or the number of component/I/Os terminated in that area. Where boards have average I/O counts above 200 per square inch of area, they are currently treated as hi …

hole breakout
A condition in which a hole is not completely surrounded by its associated land.

hoods
(see covers)

hot gas
A method of rework for SMT boards which uses a stream of hot gas to melt the solder connection for component removal.

hot plugging
Adding or removing components or sub-assemblies to a system whilst it is powered up (hot). This needs to happen without causing damage to any of the circuitry and without significantly interrupting the system. Hot plugging is also called line insertion or live line connection.

housing
The insulating body, usually a plastic moulding which holds the electrical contacts. Housings are also referred to as insulators, dielectrics or shells.

HPGL
Hewlett-Packard Graphics Language, a text-based data structure of pen-plot files which are used to drive Hewlett-Packard pen plotters. Although Hewlett-Packard no longer makes pen plotters, the large-format dot matrix printers which replaced them can also be driven by HPGL.

hybrid (micro)circuit
A generic term for a range of technologies which integrate passive and active components. Most commonly refers to ceramic substrates patterned with precious metal interconnect and resistor materials, on which chip ceramic capacitors and integrated circuits are soldered, resin bonded and/or wire bonded. A frequent base for Chip-On-Board assembly.

I-O connectors
Connectors that are the interface between a PCA`s input/output signals and the outside world.

IC = integrated circuit
(may be upper or lower-case) A device in which all the interconnected electronic circuit elements that enable the component to perform a specific function are fabricated on a single substrate of semiconductor material, most commonly silicon. Produced , called a ‘chip` or ‘die`, which is placed in a plastic or metal package with terminals for exter …

icicle
A projection from a solder joint, with a conical shape and a sharp point, which is not acceptable even though it does not make contact with another conductor. (Also referred to as a ‘peak`)

In-Circuit Test
See ICT

in-line machine
The term ‘in-line` is applied to items of equipment that are arranged within a production flow line which uses conveyerised board handling. In fabrication, such conveyor systems are frequently used between etching, stripping and cleaning operations; the approach is used almost everywhere in board assembly.

induction soldering
An interconnect method in which solder, generally as preforms, is reflowed.

industry standard
Processes, procedures, guidelines, and data formats that are widely used and recognized throughout the printed circuit industry.

infant mortal(ity)
A marginal component, circuit board, or solder joint that was not detected during production test or inspection, and fails a short time after being put into operation.

ink pattern
Applied to the surface of a circuit board through a screen or stencil, ink can be used to add markings or as a resist to define an interconnection pattern.

Input-Output (I-O)
Refers to the number of interfaces (pins) on a device which receive or transmit data.

insufficient (solder)
A soldered connection where the conductors have the appearance of being tinned and wetted together without an adequate solder fillet; or there is incomplete coverage of one or more of the metal surfaces being joined.

insulation resistance
The electrical resistance between any pair of conductors which are intended to be isolated, such as connector contacts or printed wiring board conductor tracks.

insulator
A non-metallic material designed to prevent current flow.

integration
The marriage of an operational PCA with the system or product with which it is to function.

intelligent data
Electronic data that contains physical or functional information about an item (such as an electronic part), and also links to other information.

interchangeability
The characteristic of a design that allows direct replacement of one item with another without requiring any modifications.

interconnection
The physical wiring or circuit pattern between components and individual units or subassemblies.

interconnection escapes
Conductor paths provided in a device footprint to give access to the part`s terminals.

intermetallic layer
Refers to the actual bond formed in soldering from the interdiffusion of two or more metals (e.g. copper/tin). The intermetallic layer is the most brittle part of the joint, and increases in depth in logarithmic proportion to both time and temperature during the soldering process. (Staying on the joint twice as long, or with an iron twice as hot, …

internal layer
A conductive pattern which is contained entirely within a multi-layer printed board, performing an interconnection function which is not generally visible from the surface. Defects in metallisation may result in open-circuit or short-circuit conditions, so internal layers are always subject to rigorous inspection before laminating.

IPC
Until 1999 IPC was the Institute for Interconnecting and Packaging Electronic Circuits. The new name is accompanied with an identity statement – Association Connecting Electronics Industries. IPC is a leading industry association and the final US authority on how to design and manufacture printed wiring. IPC develops and distributes standards, as …

IR emitter
A source of light energy in the infrared spectrum.

IR reflow
Use of infrared energy to bring solder to its melting point.

ISO 14001
: An environmental management system (EMS) is a systematic approach to dealing with the environmental impacts of an organisation. It is a framework that enables an organisation of any size or type to control the impact of its activities, products or services on the natural environment. ISO 14001 Environmental management systems is an international …

isotropic conductive adhesive (ICA)
The term isotropic means that the material has similar properties in all directions, so that an ICA may be used for the same sorts of application as a solder joint. However, the conductivity of adhesives filled with metallic particles is very much less (typically in the range 1–10% at best) than the metal from which it is formulated, despite conta …

J-lead
A lead configuration typically used on plastic chip carrier packages which have leads that are bent underneath the package body. A side view of the formed lead resembles the shape of the letter ‘J`

jackscrews
A means of controlling the plugging together of connectors and locking them in place. Rotation of the screws jacks the connectors together or apart. This is particularly useful for connectors having a large number of contacts and therefore a high insertion and withdrawal force.

JIT = Just-In-Time
Minimizing inventory by supplying material and components directly to the manufacturing line just before incorporating them into the product.

jumper
A component or wire that forms a discrete electrical connection between conductive areas on the external surface of a circuit board. Some jumpers are added during normal assembly, through-hole components using formed wire, and surface mount assemblies using zero-ohm chip resistors. Others are pluggable components.

junction temperature
The operating temperature of the active element of a circuit component.

keep-out area
A region of a circuit board where specific items such as components, conductors and holes cannot be placed during layout. The restriction may be as a result of electrical constraints (such as clearance for high voltage), mechanical constraints (such as requirement to fit boards close to each other), or process reasons (where clearance is needed fo …

keying
A mechanical method of preventing incorrect interconnection of mating components (such as connectors).

KGD = Known Good Die
Most semiconductor die are tested at wafer stage, using probes. Unfortunately, these tests are rarely at full operating frequency, or cover the whole range of possible fault modes. As a result, when probe-tested chips are assembled into a package, there is usually some drop-out. The problem with multi-chip modules and other COB applications is tha …

Known Good Board
See gold board.

laminate
A lamina is a ‘thin plate or scale`; a laminate is a composite built by laminating a number of (usually thin) layers of material. A PCB is a laminate both because it combines a number of layers of copper and insulator and because the base material is itself a laminate of epoxide resin and glass fibre. See copper-clad dielectric material.

lamination
The process of fabricating a circuit board by using heat and pressure to glue together a number of interconnection layers to form a single multilayer assembly.

land
A portion of a conductive pattern usually, but not exclusively, used for the connection and/or attachment of a component termination (usually by soldering), or as a contact point for a test probe. Also referred to as ‘pad`.

land pattern
The conductive pattern on a board which is intended for the attachment and electrical connection of a compatible surface mount device. Preferred term for footprint.

landfill (sites)
: Licensed facilities where waste is permanently deposited for disposal.

landfill tax
: A tax that applies to active and inert waste, disposed at a licensed landfill. The aim of the tax is to send a tough signal to waste managers to switch to less environmentally damaging alternatives to disposal.

landspreading
: Recovering waste by spreading onto land principally for agricultural benefit or ecological improvement. Sewage sludge and wastes from, for example, the food, brewing and paper pulp industries can be used for this purpose.

laser photoplotter
(also ‘laser plotter`) A photoplotter which simulates a vector photoplotter by using software to create a raster image of the individual objects in a CAD database, then plotting the image as a series of lines of dots at very fine resolution. A laser photoplotter is capable of more accurate and consistent plots than a vector photoplotter.

latching
A means of holding together a pair of mated connectors such that they will not walk apart under vibration or other physical forces. This usually only applies to board-to-cable or cable-to-cable connectors.

layout
Document or electronic equivalent that shows the physical size and location of electronic and mechanical components on a circuit board, and the routing of conductors that electrically interconnect the components. Information is provided in sufficient detail to allow the preparation of documentation and artwork for fabrication, assembly and test of …

layout grid
A lattice of orthogonal lines spaced in standard increments (typically 25 or 50 mils). Components, plated and non-plated holes, surface mount land patterns, and other features are usually located at the intersection of these grid lines during the layout of a circuit board.

layout rules
Rules established, based on the design type and performance requirements, that determine component placement, conductor routing, layer stack-up, etc.

leaching
Generally leaching is the dissolution of elements from a surface into the surrounding fluid medium. For the soldering community, the term applies to the action of liquid solder dissolving metals such as silver from surfaces. A particular case where leaching has been observed is the chip ceramic capacitor, whose inner terminals are typically of sil …

lead
(pronounced ‘leed`) One of the set of solid, formed conductors or wires that extend from a component and provide a mechanical and electrical connection. See pin.

lead forming
The process of bending component leads so that they may be inserted into holes or surface-mounted on a circuit board.

lead pitch
The distance between successive centres of the leads of a component package. The smaller the lead pitch, the smaller is the package area for a given pin count.

legend (marking)
A format of letters, numbers, symbols, and/or patterns on the printed board that are primarily used to identify component locations and orientation for convenience in assembly and replacement operations. Also referred to as ‘nomenclature`, ‘screen print` or silk screen`.

library
A structured catalogue of related items (such as schematic symbols or component part descriptions) that contains all the information about the items that is needed for their use in a design.

Life Cycle Analysis (Assessment)
: LCA is a systematic technique for identifying and evaluating the potential environmental benefits and impacts (use of resources; human health; ecological consequences) associated with a product or function throughout its entire life from extraction of raw materials to its eventual disposal and assimilation into the environment. LCA helps to place …

lifted pad
A pad or land that has partially separated from its base material.