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Glossary of terms

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Term Definition
backplanes or backpanels  Complex, multi-layer printed circuit boards used to connect racks of other boards in an electronics rack or enclosure.
ball grid array  see BGA
bare board  An unassembled (unpopulated) printed board.
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.
barrel  The cylinder formed by plating the walls of a drilled hole.
base laminate   The insulating support material (most usually epoxy-glass) used in the fabrication of printed wiring boards. (Also see ‘substrate’)
base metal (or material)  A metal or material upon which coatings are deposited.
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).
BBT   Bare Board Test.
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.
Bellcore   The most common set of safety, spatial and environmental design guidelines applied to telecommunications equipment in the United States. The equipment design guidelines, are described in Telcordia documents: GR-63 NEBS™ Requirements: Physical Protection; GR-1089, Electromagnetic Compatibility and Electrical Safety - Generic Criteria for Network Telecommunications Equipment. The concept was first introduced by Bell Labs in the 1970s to simplify the design and deployment of telecommunications equipment in the Bell System. Telcordia, and its predecessor, Bellcore, has maintained the NEBS documents since the divestiture of the Bell System in 1984. NEBS requirements are utilized all over the world for a host of commercial, utility and defense applications. Still, the most frequent application of NEBS is to design and test equipment intended for use in Regional Bell Operating Company (RBOC) central offices.
bevel  A sloping surface or line. The angle on the leading edge of a printed circuit board (the gold finger) to provide easier insertion into a connector. (Also see ‘ chamfer’)
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, in conjunction with the assembly drawing(s), shows which parts are positioned where on the assembly.
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.
bleeding   A condition in which a plated hole discharges process materials of solutions from voids and crevices.
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 profiling   (also 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. When gold fingers are present the measurment is taken at the finger location.
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.
bond strength   The force required to separate a layer of material from the adjoining base. It is a measure of the structural effectiveness of adhesives, welds, solders, glues, or of the chemical bond formed between materials, when subjected to stress loading (shear, tension, or compression).
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.
book   A specified number of prepreg plies which are assembled along with inner-layer cores in preparation for curing in a lamination press.
border area   The region of a base material that is external to that of the end product being fabricated within it.
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.
BPEO   (Best Practicable Environmental Option). A procedure that takes into account the total impact of a process and the technical possibilities for dealing with it. BPEO establishes the waste management option, or mix of options, that provides the most benefits or the least damage to the environment as a whole, at acceptable cost, in the long-term as well as in the short-term.
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.
B-stage   A partially cured thermosetting adhesive used in multilayer boards. During lamination, the application of heat and pressure completes the curing process.
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 constructions, consists of reinforcing sheets impregnated with resin and cured to this intermediate stage.
BT resin   (Bismaleimide-Triazine ). Has become the preferred laminate material for many manufacturers because of its high Tg, low dielectric constant and good insulation properties.
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   Electrical connections between various integrated circuits and peripheral semiconductors.
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.
Business process management   (BPM). is a holistic management approach[1] focused on aligning all aspects of an organization with the wants and needs of clients. It promotes business effectiveness and efficiency while striving for innovation, flexibility, and integration with technology. BPM attempts to improve processes continuously. It can therefore be described as a "process optimization process." It is argued that BPM enables organizations to be more efficient, more effective and more capable of change than a functionally focused, traditional hierarchical management approach.
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.