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Glossary of terms

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Term Definition
cache   A relatively small amount of intermediate computing memory that is faster, but more expensive, than main memory and where the most frequently used information is stored for fast access by a processor.
CAD (Computer-Aided Design)   A system where engineers create a design and see the proposed product in front of them on a graphics screen or in the form of a computer printout or plot. In electronics, the result would be a printed circuit layout. They may assist in performing all steps in artwork generation.
CAD/CAM   A concatenation of the terms CAD and CAM. CAD/CAM systems are computer-aided design/manufacturing methods that translate circuit designs into actual products.
CAE   (Computer-Aided Engineering or Computer Assisted Engineering). A software package used as an automated tool for circuit design and schematic generation.
CAF   (Conductive Anodic Filament). Metal migration between two conductors or the dendritic growth seen under Temperature, Humidity and Bias test.
CAM   (Computer-Aided Manufacturing). A system used to generate data for fabricating circuit boards and manufacturing finished assemblies. CAM files are data files used directly in the manufacture of printed wiring. Typically this data is manipulated by the fabricator to meet production requirements (for example for panelisation) and to ensure the intended result is achieved.
cap lamination  The original method to create multilayers. The layers are etched in pairs on a piece of laminate. The external or outerlayers (top[ and bottom side) are not etched before lamination. The layer pairs or pieces of laminate are then registered together on pins attached to lamination plates with prepreg separating each laminate. Following lamination the multilayer PCB is processed virtually the same as a a double sided PCB
capacitance   The property of a circuit element that permits it to store an electrical charge.
capacitor   A discrete device that stores an electrical charge on two conductors separated by a dielectric.
capillary action   The combination of force, adhesion and cohesion that prompts liquids, such as molten solder, to flow upward between closely spaced solid surfaces, e.g., lead (contact) and pad.
capture   Extract information automatically through the use of software, as opposed to hand-entering of data into a computer file.
card   Another name for a printed circuit board.
card-edge connector   A connector which is fabricated as an integral portion of a printed circuit board along part of its edge. Often employed to enable a daughter or add-on card to be plugged directly into another much larger printed board, the motherboard or back-plane. See finger.
carriers   Holding devices for PCBs and other parts to facilitate handling during component placement, soldering and other processing.
castellation   Metallised semicircular radial features on the edges of LCCCs that interconnect conducting surfaces. Castellations typically are found on all four edges of a leadless chip carrier. Each lies within the termination area for direct attachment to the land patterns.
catalyst   A chemical that is used to initiate the reaction or increase the speed of the reaction between a resin and a curing agent.
cathode   An electrode through which electric current flows out of a polarized electrical device. The direction of electric current is, by convention, opposite to the direction of electron flow. Therefore the electrons flow into the polarized electrical device and out of, for example, the connected electrical circuit.
CBGA  (Ceramic Ball Grid Array a.k.a. Column BGA). Less common than the standard ball grid array, which uses balls of eutectic solder, CBGAs contacts are columns of a high-melting solder. When reflowed in contact with eutectic solder on the substrate, only a small portion of the column melts into the joint, so that the package is held off the substrate. The resultsing separation gives a degree of flexibility which allows for differences in CTE between the ceramic body of the CBGA and the FR4 board.
cell   A tiny area within the memory array that actually stores the bit in the form of an electrical charge.
center to center spacing   The nominal distance between the centers of adjacent features on any single layer of a printed board, e.g.; gold fingers and surface mounts.
centroid   A point whose coordinates are the average of an associated parts dimensions (central point).
CFC  (Chlorinated fluorocarbon). Causes depletion of ozone layer and scheduled for restricted use by the Environmental Protection Agency. CFCs are used in air conditioning, foam insulation and solvents.
chamfer   To bevel or round an otherwise sharp or blunt edge. (Also see ‘ bevel’)
chassis   The supporting frame or structure that houses printed circuit assemblies.
check plots   Pen plots that are suitable only for checking. Pads are represented as circles and thick traces as rectangular outlines instead of filled-in artwork. This technique is used to enhance the transparency of multiple layers.
chemical stability   The ability of the characteristics of a material to remain unchanged by aging or variations in the environment.
chip carrier   A low profile surface-mount component package, usually square, whose conductor chip cavity or mounting area is a large fraction of the package size and whose external connections are usually on all four sides of the package. It may be leaded or leadless.
chip component   Generic term for any two-terminal leadless box-shaped surface mount passive device, such as a resistor or capacitor. Also known as ‘discretes.’
chip on film (COF)   An assembly method for bonding integrated circuit chips and other components onto a flexible printed circuit
chip package   A carrier in which an IC chip is mounted. The package interconnects the chip to the outside world and is sealed to provide environmental protection for the chip.
chip scale packaging   A method of using integrated circuits (chips) without encapsulating them in epoxy, thereby utilizing less space on the circuit board.
chip-on-Board (COB)   A configuration in which a chip is directly attached to a printed circuit board or substrate by solder or conductive adhesives.
circuit (circuitry)   The interconnection of a number of electrical elements and/or devices to perform a desired electrical function.
circuit coupling   The creation of a false signal in a circuit by a signal in another circuit. This is usually caused by radiated energy between adjacent conductors on the same or different layers.
circuit density   The proportion of circuit elements and interconnections required for performing an electrical function to the allotted area of a circuit board.
circuit fault   Incorrect performance of a circuit resulting in a specific error. In digital circuitry this could manifest itself as a logic error. During functional testing, artificial faults are sometimes injected into a circuit to verify the tester’s ability to identify them correctly.
circuit filter   Protective circuitry designed to prevent transmission of unwanted current or voltage deviations during operation.
circuit frequency   Usually pertains to the operating speed of a circuit and is a function of the types of components used, the dielectric properties of the circuit board( and the physical characteristics of the circuit conductors (dimensions/shape).
circuit net   See net.
circuit symbol   Used in a schematic diagram as a graphic representation of a specific type of electronic device.
clad   A copper object on a printed circuit board. Specifying certain text items for a board to be ‘in clad’ means that the text should be made of copper, not silkscreen.
cladding   A thin layer of metal foil bonded to a substrate to form the conductive PCB pattern.
clamshell fixture   An in-circuit test fixture that permits simultaneous probing of both sides of a board or assembly. The top probe section is hinged to allow board insertion.
cleanroom   The super-clean environment in which semiconductors are manufactured. The lower the rating (e.g. Class 100), the cleaner the facility. These rooms typically have hundreds of thousands of particles less per cubic metre than the normal environment.
clearance hole   A hole in the conductive pattern that is larger than, and coaxial with a hole in the base material of a printed board.
clinched lead   A component lead passed through a hole in the printed circuit board, that has been formed to prevent the component from falling out during soldering.
clinching   The process of forming or bending a component lead following its insertion through a hole in a circuit board. The main purpose is to secure the part mechanically during the soldering process.
clock speed   The switching frequency of the clock circuit in digital logic. It is principally determined by the rise/fall time required for the digital devices used in a circuit to change logic state (from 0 to 1 or vice versa).
closed bottom contact   The back of the contact is closed to prevent solder ingress, usually this applies to PCB and solder tail contacts.
closed entry socket   The entry for the mating plug contact is such as to prevent damage to the socket contact on insertion.
CMOS   (Complementary Metal Oxide Semiconductor). A MOS device containing both N-channel and P-channel MOS active elements. One of two basic processes (MOS and bipolar) used to fabricate integrated circuits.
CNC   (Computer Numerical Control). A system that utilizes a computer and software as the primary numerical control technique.
COB (Chip-On-Board)   Generic term for any component assembly technology in which an unpackaged silicon die is mounted directly on the substrate, instead of first being packaged. Connections from die to the pads on the board can be made by wire bonding, tape automated bonding (TAB), or flip-chip bonding. For commercial use the die is protected by a plastic ‘glob top’, usually black in colour.
Coefficient of Thermal Expansion   (CTE). The ratio of dimensional change of an object to the original dimension when temperature changes, expressed in %/ºC or ppm/ºC.
cohesive characteristics   See adhesive characteristics.
cold (solder) joint   A solder connection exhibiting poor wetting and of greyish, porous appearance due to insufficient heat or excessive impurities in the solder. The condition can be caused by applying insufficient heat to the joint, inadequately cleaning the surfaces prior to soldering, insufficiently heating the part being soldered, improper tinning of the soldering iron tip, or poor heat control.
compliant press-fit terminations   Contacts in a connector where the tails are formed to have a compliant section. This section deforms as the tail is pressed down into the plated through hole of the printed circuit board. The inherent spring force in the compliant section retains contact during the life of the equipment without the need for a soldering operation.
component   A separate part of a printed board assembly which performs a circuit function. Active devices, such as resistors, capacitors, or semiconductors, have distinct electrical characteristics that perform specific functions in a circuit and with terminals which may be inserted into or mounted on, a printing wiring board to form a printed wiring assembly. connector
component hole   A hole used for attachment and electrical connection of component terminations, including pins and wires (‘leads’), to the printed board.
component lead   See lead.
component lead extension   The distance a through-hole component lead extends beyond the surface of a circuit board after soldering.
component library   A representation of components as decals, stored in a computer data file which can be accessed by a PCB CAD program.
component metallisation   see component termination.
component mounting orientation   The direction in which the components on a printed board or other assembly are lined up, with respect to one another, to the solder wave, and to the board.
component side   The primary side of a printed board upon which the major of component parts are mounted. Where size allows, the component side may be printed with the ‘legend’. (Also see ‘ topside’)
component termination   This term can refer to a lead, but is more commonly a description applied to the interface between the body of the component and the board in a leadless device. Termination materials need to adhere to the component, forming a reliable connection, and be wettable by (but not soluble in) the solder used for attachment to the board. Typically, for a chip component, this termination will be made of several layers, with a ‘solder barrier’ (a material insoluble in solder) underlying a (usually thinner) layer of something highly solderable.
condensation soldering   A general term referring to a method of heating where an assembly is submerged into a hot, relatively oxygen-free, vapour. The vapour condenses on the relatively cool surface of the assembly, transferring its latent heat of vaporization to the parts being soldered. Also known as vapour phase soldering.
conduction   The ability of electrons to flow through a conductor. It is the reciprocal of resistance. Conduction is also a heat transfer mechanism in solid materials, involving transfer of kinetic energy within its molecular structure.
conductive adhesive   see anisotropic conductive adhesive and isotropic conductive adhesive.
conductive foil   A thin sheet of metal (usually copper) that covers one or both sides of the base laminate and is intended for forming the conductive pattern on a printed circuit board. (Also referred to as ‘cladding’ or ‘foil’)
conductive ink   The paste used on thick film materials to form the circuit pattern, usually containing metal, metal oxide and solvent.
conductor   A current-carrying interconnection path. A single conductive path in a conductive pattern. Also known as a ‘trace’.
conductor layer   The total conductor pattern formed on one side of a single layer of laminate material.
conductor pattern   The configuration or design of the conductive material on one side of a single layer of base material.
conductor separation   Permanent separation of the printed wiring conductive foil from the base laminate. (Also see ‘ delamination’)
conductor side   The side of a printed board containing the conductors. Commonly referred to as the ‘solder side’ when opposite through-hole components. (Also see ‘bottom side’)
conductor spacing   The observable distance between adjacent edges (not center to center spacing) of isolated patterns in a conductor layer.
configuration control   A method for ensuring that a specific version of data and drawings defines the correct requirements and physical description of the intended version of a PCA, and that the actual hardware conforms in all respects to the data and drawings.
conformal coating   An insulating protective coating applied to the completed board assembly, which conforms to the configuration of the objects coated and provides a barrier against deleterious effects of their environment.
connectivity   The intelligence inherent in PCB CAD software which maintains the correct connections between pins of components as defined by the schematic.
connector   A device that provides a mechanically pluggable interface for electrical terminations. A plug or receptacle which can be easily joined to or separated from its mate. Multiple-contact connectors join two or more conductors with others in one mechanical assembly.
connector mating/un-mating force   The total force required to plug and unplug connectors, made up of the sum of the individual contact forces plus any friction due to housing misalignment.
consignment   A type of outsourcing in which the OEM customer provides "kits" which include all materials required for the building their products and the EMS subcontractor provides only assembly equipment and labor. The opposite of "turnkey", where the EMS provider controls most or all elements of material acquisition and supply chain management.
contact angle   The angle of wetting between the solder fillet and termination or land pattern. A contact angle is measured by constructing a line tangential to the solder fillet that passes through a point of origin located at the plane of intersection between the solder fillet and termination or land pattern. Contact angles of less than 90° (positive wetting angles) are acceptable. Contact angles greater that 90° (negative wetting angles) are unacceptable.
contact bounce   Movement causing an open-circuit between a male and female connector contact or in a relay. This can occur due to vibration conditions during service, or during the plugging together operation of a connector.
contact carrying capacity   The maximum current a mating pair of contacts, or all contacts in a connector or relay simultaneously, can pass without causing degradation due to overheating and thermal stress. This is usually specified at room temperature and at maximum operating temperature, with a de-rating curve in between.
contact rating   The maximum and minimum voltage, current and power that a contact pair can be guaranteed to operate with under specified environmental conditions.
contact resistance   The resistance in the conductive path between two touching surfaces. It relates primarily to resistance across mating connector contacts.
contact retention   The specified force at which contacts will start to receive damage or pull out of a connector housing.
contact size   Defines the maximum wire size that can be used with a contact in a cable connector. This determines the contact diameter and current rating.
contaminant   An impurity or foreign substance whose presence on an assembly could electrolytically, chemically, or galvanically corrode the system.
continuity   An uninterrupted path for the flow of electrical current in a circuit.
continuity test   A test for the presence of current flow between two or more interconnected points.
controlled impedance   The matching of substrate material properties with trace dimensions and locations in an effort to create specific electric impedance for a signal moving along a trace.
convection   The mechanism for transfer of heat from a solid surface (such as a component) to a surrounding fluid (usually air). Natural convection is heat transfer to ‘still’ air; forced convection involves heat transfer to air that is moved by artificial means such as a fan.
convection/IR   A solder reflow oven for SMD interconnect that combines convection and infrared (IR) radiation heating.
conveyor   A PCB transporting system for moving assemblies to various processes. An edge conveyor supports the boards at opposite sides; a mesh conveyor fully supports the board. On reflow ovens, a secondary mesh conveyor is often located below the edge mechanism to catch fallen components.
coplanarity   The leads of a package should be ‘coplanar with’ the PWB, that is, there should be no gap between the leads and a flat board. If they are not, the non-coplanarity problem can result in open-circuit joints. The term coplanarity is however usually (somewhat incorrectly) used to refer to the maximum distance between the surface and the highest pin when the package rests on a perfectly flat surface. A typical specification for coplanarity is not greater than 0.1mm.
copper foil (base copper weight)   Coated copper layer on the board. It can either be characterized by weight or thickness of the coated copper layer. For instance, 0.5, 1 and 2 ounces per square foot are equivalent to 18, 35 and 70 um-thick copper layers.
copper weight   A measurement of the thickness of copper foil, in terms of its weight in ounces per square foot of surface area. 1-ounce copper is nominally 35µm (0.0014 in) thick, ½-ounce copper is 18µm (0.0007 in thick.
copper-clad dielectric material   The basic material used for fabricating a printed circuit board, consisting of a flat reinforced dielectric to which is bonded copper foil on one or both surfaces.
core   A supporting plane that is internal to a packaging and interconnecting structure. Multilayer circuit boards may contain unclad laminate cores, or special-purpose cores made of metal (aluminium, copper) to enhance heat dissipation or for other purposes.
core thickness   The thickness of the laminate base without copper.
corrosion   Gradual destruction of a metal or alloy due to chemical processes such as oxidation or the action of a chemical agent.
corrosive   A substance that causes corrosion; chemically reactive with ability to wear away gradually.
corrosive flux   A flux that contains corrosive chemicals such as halides, amines, inorganic or organic acids that can cause oxidation of copper or tin conductors.
cost-benefit (trade-off) study   The analysis of the cost of implementing each of an alternative (design/manufacturing/assembly/test) approach (or solution to a problem) versus the benefits of doing so.
covers (or hoods)   Used on cable connectors to protect and insulate the terminations.
CPU   (Central Processing Unit). The computer module in charge of retrieving, decoding, and executing instructions.
crazing   An internal condition existing in the laminate base material in the form of connected white spots or crosses on or below the surface of the base laminate, reflecting the separation of glass fibres from resin at the connecting weave intersections. Crazing is usually related to mechanically-induced stress. (Also see ‘ measling’)
critical signal paths   Conductors carrying signals that may be particularly sensitive to distortion by external signals, and require routing in specific locations on a board, or layout in a specific physical geometrical configuration.
cross-hatching   The breaking up of the large PWB conductor areas by the use of a pattern of voids.
crosstalk   See circuit coupling.
CSP (Chip-Scale Package)   The Chip-Scale Package exists in many forms, often employing BGA and flip-chip elements. Regardless of the construction, the aim is to create a high-density IC package only slightly larger than the chip. A number of definitions have been proposed, of which the most usual is that the package should be no more than 1.5 times the chip in area and no more than 1.2 times the chip in linear dimension. CTE is not a linear function of temperature, it being quite common for materials to expand and shrink differently at different temperatures. For example, water first shrinks and then expands as it cools, having a maximum density at around 4°C.
CTE   (Coefficient of Thermal Expansion). The rate at which a material changes dimension as its temperature is increased. Can refer to the linear dimensions or the volume of the material. Expressed as the fractional change in dimension divided by the change in temperature, most commonly as ppm/°C. Often referred to as thermal coefficient of expansion (TCE). CTE is not necessarily isotropic, that is, the same in all directions. Most metals are isotropic, but most laminate materials have a CTE in the Z axis (through the thickness of the laminate) which is different from that of the XY axis (in the same plane as the laminate). Stresses from the higher Z-axis expansion have a major impact on the reliability of through-hole metallisation.
CTI  (Comparative tracking index). It indicates the highest usable voltage for a laminate. It becomes important in application with high humidity, such as washing machines or cars. A higher index means a better protection. Similar is 'PTI' and 'KC'
curing agent   A chemical added to a resin to stimulate a final set or hardening.
current rating   The maximum allowable continuous current that can be passed through a component or a conductor without causing degradation of performance.
cuts   Modification of a circuit board by separating conductors on an external layer to break a circuit connection.
cyanate esters   Chemical substances generally based on a bisphenol or novolac derivative, in which the hydrogen atom of the phenolic OH group is substituted by a cyanide group. The resulting product with an -OCN group is named a cyanate esterconstraining core substrate A composite PCB consisting of epoxy-glass layers bound to a low thermal expansion core material, such as copper-invar-copper, graphite-epoxy and aramid fibre-epoxy. The core constrains the expansion of the outer layers to match the expansion coefficient of ceramic chip carriers.