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Glossary of terms

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Term Definition
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.
laminate thickness   Thickness of the metal-clad base material, single- or double-sided, prior to any subsequent processing.
laminate void   An absence of epoxy resin in any cross-sectional area that should normally contain epoxy resin.
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 direct imaging (LDI)   An image plotter that uses a laser, which simulates a vector photo-plotter by using software to create a raster image of the individual objects in a CAD database, then plots the image onto the photosensitized material as a series of lines of dots at a very fine resolution.
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 a PCA.
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.
LCCC (LCC)  Leadless (Ceramic) Chip Carrier A ceramic, hermetically-sealed integrated circuit package commonly used for military applications. Instead of leads, the package has metallised areas ‘castellations’ on four sides for interconnecting to the substrate.
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 silver alloys held together with a matrix of glasses. Solder can leach the silver to such an extent that electrical connection is no longer made. Solutions to the problem include both using silver alloys with platinum and palladium to reduce the solution rate, and providing a ‘nickel barrier’ plating on top of the original metallising. For most purposes, this barrier layer is supplied already solder plated.
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 configuration   The shape into which component leads are formed. The most common surface mount lead configurations are gull-wing and J-lead.
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.
leakage current   A small amount of current that flows across a dielectric area between two adjacent conductors.
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’.
LFD   Landfill Directive
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.
licensed site/waste management facility   A waste disposal or recovery facility licensed under the Environmental Protection Act.
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 the assessment of the environmental costs and benefits of these various options, and the development of appropriate and practical waste management policies, on a sound and objective basis.
lifted pad   A pad or land that has partially separated from its base material.
line certification   Assurance that a production line sequence is under management and will produce reliable PCBs in compliance with requirements.
liquidus   When heated, most alloys change gradually from being totally solid to being totally liquid over an extended temperature range. The liquidus is the temperature at which the alloy is totally liquid. Note that in the case of eutectic materials, there is no such pasty range See solidus and pasty range.
lithography   The transfer of a pattern or image from one medium to another, as from a mask to a wafer.
loads   Digital devices attached to a net that will have their logic levels changed by a driver on that net.
location pegs/hold-downs/strain reliefs   Features moulded into connector housings which position the connector accurately onto the PCB, hold it down during soldering and act as a strain relief on the solder joints when plugging and unplugging mating connectors. This is particularly relevant to surface mount and 90° mounted connectors. Hold-down features can also be formed into the tails of contacts.
logic families   A group of device types that share the same basic operating characteristics and parameters when processing digital signals (TTL, ECL, etc.).
lot and date code   Items manufactured in a group using the same materials and processes are given the same, unique lot code. Items manufactured or completed on the same date are given the same date code.
low insertion force   Refers to contacts, which, due to their design and function, require very little force to plug together. Used mainly in miniature and high pin count connectors.
LPI   (liquid photoimageable solder mask). A mask sprayed on using photographic imaging techniques to control deposition. It is the most accurate method of mask application and results in a thinner mask than dry film solder mask. It is often preferred for dense SMT.