C-stage The condition of a resin polymer when it is in the solid state, with high molecular weight, being insoluble and infusible.

CAD/CAM system Computer-aided design refers to the use of computers in formulating designs. Computer-aided manufacturing refers to the use of computers to translate the design into an actual product. CAD/CAM systems are usually modular, with hardware and software programs selected to user requirements. Typically, these systems include a computer and mass memory for information processing and storing, input terminals for design creation and observation, and output devices for converting stored information into drawings and reports. CAD/CAM systems are used in the electronics industry to perform all steps of artwork generation (from concept to actual production), specifically in the manufacturing of circuits.

camber The planar deflection of a flat cable or flexible laminate from a straight line or specified length. A flat cable or flexible laminate with camber is similar to the curve of an unbaked race track.

capacitance That property of a system of conductors and dielectrics that permits the storage of electricity when potential difference exists between the conductors.

capillary action The combination of force, adhesion, and cohesion that causes liquids such as a molten metal to flow between closely spaced solid surfaces against the force of gravity.

card guide A plastic or metal support for PCBs. It relieves the stress on connector contacts, makes insertion into and extraction from the connector easier, and eliminates the possibility of twisting the board.

carriers Holders for electric parts and devices that facilitate handling during processing, production, imprinting, or testing operations.

castellation A leadless termination used on LCCC packages for connection to the PCB.

catalyst A substance which accelerates the cure of a resin without being altered in the reaction.

Celsius A temperature reference related to Fahrenheit by °C = 5/9 × (°F − 32). Formally called centigrade.

center board support A mechanism employed in reflow ovens to prevent excessive PCB warpage during the reflow process. (See Figure 2 on following page.)

center-to-center spacing The nominal distance between the centers of adjacent features on any single layer of a PCB.

central component orientation A design concept in which the predominant components are centered in an area with the supporting components radiating outward. This method is applicable when there are one or more complex multi-lead components.

ceramic substrates These materials are used primarily because of their low loss qualities, long life characteristics, and ability to withstand high operating temperatures and heat shock. For general application, the aluminum oxide substrate (alumina) is preferred because of its availability, low cost, good thermal expansion coefficient to most inks. Beryllia substrates with a high thermal conductivity may be used in high power circuitry.

certification Verification that specified testing has been performed and required parameter values have been attained.

CFC Chlorinated fluorocarbon.

chamfer Angle on the leading edge of a printed wiring board that permits easier insertion of the board into the connector, or angle on the inside edge of the barrel entrance of a connector which permits easier insertion of the cable.

characteristic impedance The ratio of voltage to current in a propagating wave, i.e., the impedance which is offered to the wave at any point of the line. In printed wiring its value depends on the width of the conductor to ground plane(s), and the dielectric constant to the media between them.

checklist The specified criteria compiled for evaluation during an inspection.

chemical hole cleaning The chemical process for cleaning conductive surfaces exposed within a hole. See also etchback.

chip A single substrate on which all the active and passive circuit elements have been fabricated using one or all of the semiconductor techniques of diffusion, passivation, masking, photoresist, and epitaxial growth. A chip is not ready for use until packaged and provided with external connectors.

chip capacitors Discrete devices that introduce capacitance into an electronic circuit, made in tiny wedge or rectangular shapes.

chip carrier A high density integrated circuit packaging technique in which input and output terminals are around the perimeter of the device, instead of only on two sides, as in dual in-line packages.

chip component Refers to leadless ceramic or plastic discrete capacitors, resistors, and inductors.

chip resistors Chip resistors are small chips of ceramic. The ceramic chip is an inert substrate with the resistor on the surface. Their small size is their chief virtue but by no means their only virtue. Chip resistors have extremely low shunt or parasitic capacitance, no inductance, are stable, and generally low in cost.

chip scale package Active, multi-I/O package that is no larger than 125% of the size of the silicon integrated circuit chip.

chip testers Usually large, complex computer-based testers that test individual ICs, especially LSI and VLSI.

chip-and-wire A hybrid technology employing face-up-bonded chip devices exclusively interconnected to the substrate conventionally, i.e., by flying wires.

chip-on-board (COB) A hybrid technology exclusively employing face-up-bonded chip devices interconnected to the substrate conventionally, i.e., by flying wires. A generic term for mounting an unpackaged silicon die directly onto the PCB. Connections can be made by wire bonding, tape automated bonding (TAB), or flip-chip bonding.

chlorinated hydrocarbon An organic compound having hydrogen and chlorine atoms in its structure, such as methyl chloroform (1,1,1 trichloroethane) and used as a cleaner.

circuit The interconnection of a number of devices in one or more closed paths to perform a desired electrical or electronic function.

circuit card assembly (CCA) Term for a PWB after all electrical components have been attached. Also see printed circuit assembly and printed wiring assembly.

circuit density Number of circuits on a given area of a printed circuit board.

circuit mil area (CMA) A unit of area equal to the area of a circle whose diameter is one mil (0.001”). Used chiefly in specifying cross-sectional areas of conductors.

circuit tester A method to properly test production volume PCBs, such as by bed-of-nails, footprint, guided probe, internal trace, loaded board, bare board, or component testing.

circuit verifier An assembly that electrically stimulates an item being tested and monitors proper response. This includes shorts and opens testing, as well as functional diagnostic testing. Also called analyzer, test set, and tester.

clad or cladding A relatively thin layer or sheet of metal foil bonded to a laminate core to form the base material for printed circuits.

clamshell fixture An in-circuit test fixture designed to probe both sides of a PCB. The top probe plate is hinged to alloy the PCB to be inserted. Also referred to as a clamshell tester.

clean room A special manufacturing area where the air is filtered to remove dust particles and precautionary measures are used to keep contamination away from the unprotected circuit during processing.

clearance The space between the punch and walls of the die plate. This space has a direct relation to part or hole sizes.

clearance hole A hole in the conductive pattern larger than, but coaxial with, a hole in the PCB base material.

clinched leads Component leads that extend through the PCB and are formed to effect a spring action, metal-to-metal electrical contact with the conductive pattern prior to soldering.

clinching Process of crimping through-hole component leads underneath the printed circuit board to maintain the component in place.

close center probing Test points on a product that are located on centers closer than 0.050″.

cluster test An in-circuit test method in which a group of components are checked as a unit.

coatings Material used for a wide variety of purposes, such as moisture protection, bonding of windings into integral masses, improvement of electrical masses, improvement of electrical properties, protection against chemicals and mechanical abuse, appearance, etc. Some printed circuit coatings facilitate repairability by selectively stripping the coating with chemical solvents. Examples include various resins, varnishes, epoxies, lacquers, and phenolic materials.

coefficient of thermal expansion The fractional change in dimension of a material for a unit change in temperature. Expressed in parts per million per °C. Also known as CTE.

cohesion The force of attraction between like molecules.

cold cleaning An organic solvent cleaning process in which liquid contact accomplishes the solution and removal of residues after soldering.

cold short A brittle condition in metal at temperatures that are below the recrystallization temperature.

cold solder joint A solder connection exhibiting poor wetting and a grayish, porous appearance due to insufficient heat, inadequate cleaning prior to soldering, or excessive impurities in the solder solution.

color selectivity Preferential absorption of radiation caused by emitted energy in the visible band wavelength (.39–.79 microns).

combinational test Test procedure using both in-circuit and functional test methods.

component A part or combination of parts mounted together to perform a design function(s).

component density The quantity of components placed on a PCB per unit area.

component hole A hole used for the attachment and electrical connection of component terminations, including pins and wires, to the PCB.

component lead The solid or stranded wire or formed conductor that extends from a component and serves as a mechanical and/or electrical connection that is readily formable to a desired configuration.

component side The side of the PCB on which most of the components or the active components are mounted. See also primary side.

composite board A completely laminated, multi-layer PCB.

computer-guided probe A fault-isolation technique based solely on good circuit data. The probe algorithm acts as the master instruction to an operator to probe various IC pins on the unit under test until it derives the final diagnosis and diagnostics.

condensation inert curing Adhesive curing method using condensation inert heating as the heat transfer medium.

condensation inert heating A general term referring to condensation heating where the part to be heated is submerged into a hot, relatively oxygen-free vapor. The part, being cooler than the vapor, causes the vapor to condense on the part transferring its latent heat of vaporization to the part. Also known as vapor phase.

condensation inert soldering Reflow soldering method using condensation inert heating as the heat transfer medium.

conduction Heat transfer that occurs within or between solids due to temperature gradients across the solids.

conductive adhesive An adhesive material that has metal powder added to increase electrical conductivity.

conductive epoxy An epoxy material (polymer resin) that has been made conductive by the addition of a metal powder, usually gold or silver.

conductive foil A thin sheet of metal that may cover one or both sides of the base material and intended to form a conductive pattern.

conductive ink In hybrid technology, the conductive paste used on thick film materials to form the printed conductor pattern. Usually contains metal, metal oxide, glass frit, and solvent.

conductive pattern The configuration or design of the conductive material on the base material. Includes conductors, lands, and through connections when these connections are an integral part of the manufacturing process, such as additive.

conductor A thin conductive area on a PCB or internal layer, usually composed of path and lands to which component leads are connected. Also called a trace.

conductor base spacing The conductor spacing at the plane of the surface of the base material.

conductor base width The conductor width at the plane of the surface of the base material.

conductor layer The total conductive pattern formed upon one side of a single layer of base material. See also physical layer.

conductor spacing The distance between adjacent edges (not centerline to centerline) of isolated conductive patterns in a conductor layer.

conductor thickness The thickness of the conductor including all metallic coating.

conductor to hole spacing The distance between the edge of a conductor and the edge of a supported or unsupported hole.

conductor width The observable width of the pertinent conductor at any point chosen at random on the PCB, normally viewed vertically above unless otherwise specified.

conformal coating A thin protective coating applied to a PCB assembly that conforms to the configuration of the assembly.

connector A device providing electrical connections/disconnections that consists of a mating plug and receptacle that interconnects PCBs with cables, racks, or chassis. Commonly used PC connectors are edge, two-piece, and hermaphroditic.

constraining core substrate A composite PCB consisting of epoxy-glass outer layers hound to a low thermal expansion core material. The core artificially constrains the expansion of the outer layers to match the expansion coefficient of ceramic chip carriers.

contact angle The angle of wetting between the solder fillet and the termination or land pattern. It is measured by constructing a line tangent 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. Also known as wetting angle.

contact spacing The distance between the centerlines of adjacent contact areas.

contamination Any foreign material such as dirt, oil, and epoxy glass on an SMC lead or pad or on a footprint pad that interferes with solderability.

continuity A continuous path for the flow of current in an electrical circuit.

continuity test A test procedure in which voltage is applied at two interconnected points to determine the presence or absence of current flow.

continuity testing A testing procedure wherein voltage is applied to two interconnected lands in order to observe the presence or absence of current flow. This process is repeated until all interconnections on the board have been tested.

controlled collapse chip connection (C4) A solder joint connecting a substrate and a flip-chip, where the surface tension forces of the molten solder supports the weight of the chip and controls the height of the joint.

convection Heat transfer that occurs at the interface of a solid and fluid or gas due to temperature differences.

convection, controlled Convection heat transfer in which the convective characteristics (such as flow, rate, velocity and temperature) are precisely controlled.

convection, enhanced Convection heat transfer that occurs by drawing or drafting the fluid or gas over the solid media.

convection, forced Convection heat transfer that occurs by forcing the fluid or gas over the solid media. Also known as convection dominant.

convection, free Convection heat transfer that occurs due to movement of air caused by density gradients near the solid surface.

convention A definite formatting method used in electronic diagrams to present the clearest picture of the circuit function. Some common conventions are (1) circuit signal flow from left to right with inputs on the left and outputs on the right; (2) various function stages of the circuit in the same sequence as the signal flow; (3) voltage potentials with the highest voltage at the top of the sheet and the lowest at the bottom; and. (4) auxiliary circuits that are included, but are not a main part of the signal flow, such as oscillators and power supplies, on the lower half of the drawings.

conveyor, edge Conveying mechanism that supports the product by the edges.

conveyor, mesh Conveying mechanism that fully supports the product.

conveyor, secondary Conveying mechanism used beneath the edge conveyor. Used to catch fallen product in the reflow process.

cooldown The period in the reflow process, after peak temperature, during which the temperature falls to the point where the solder joints solidify or freeze.

coordinate tolerancing A method of tolerancing hole locations in which the tolerance is applied to linear and angular dimensions, usually forming a rectangular area of allowable variation.

coplanarity Measurement of the distance between the lowest and highest pin of a package when rested on a flat surface.

coplanarity error The maximum deviation of component leads away from perfect planarity. Determined by placing the package on a flat surface and measuring the worst-case lead height off the surface.

coplanarity test A measure of the distance between the lowest and highest pins of a device when rested on flat plane.

copper foil A cathode-quality electrolytic copper deposited as a thin, continuous sheet on rotating drums direct from refinery electrolytes. Used as a conductor for printed circuits, copper foil readily bonds to insulating substrates, accepts the printed resists, and etches out to make printed circuits. It is made in a number of weights (thicknesses). The traditional weights are 1 to 3 ounces per square foot (0.0014” to 0.0042” thick).

copper mirror test Test for corrosivity of flux to a thin copper film vacuum-deposited on a glass plate.

copper-clad invar A metallurgically bonded material, consisting of 36% nickel and 64% iron alloy, that is used in the fabrication of PCBs. It is normally employed to solve thermal expansion mismatch problems with surface-mounted devices and multi-layer boards.

corner mark The mark at the corners of the PCB artwork, the inside edges of which usually locate the borders and establish the contour of the board. Also called crop mark.

corrosion Slow destruction of materials by chemical agents and electrochemical reactions.

corrosive fluxes Fluxes consisting of inorganic acids and salts, generally required when the condition of the surface is not well-suited for rapid wetting by molten solder. Also called acid fluxes.

cosmetic defect A variation from the conventional appearance of an item, such as a slight change in its usual color.

cover layer, cover coat Outer layer(s) of insulating material applied over the conductive pattern on the surface of the PCB. Sometimes referred to as a “pads only” layer when a copper foil clad laminate is used.

cratering Wave soldering defect caused by minute quantities of gas originating in the base laminate and escaping through pin holes in the plating, thus blowing some of the molten solder out of the hole. This gives the board a faulty appearance, but an adequate joint usually remains.

crazing A condition that occurs internal to the laminated base material in which the glass fibers separate from the resin at the weave intersections. Crazing is visible as white spots or crosses below the base material surface and is usually a result of mechanically induced stress.

creep strength Resistance of a material to stretching and deformation.

crop mark The mark at the corners of the PCB artwork, the inside edges of which usually locate the borders and establish the contour of the board. Also called corner mark.

cross-sectional area of a conductor The sum of the cross-sectional areas of its component wires, that of each wire being measured perpendicular to its individual axis.

crosshatching The breaking of large conductive areas with a pattern of voids in the conductive material.

CTE Coefficient of thermal expansion.

cure To change the physical properties of a material by chemical reaction, by the action of heat and catalysts, alone or in combination, with or without pressure.

curing agent A chemical added to a thermosetting resin to stimulate curing. Also called hardener.

curing temperature The temperature at which a material is subjected to curing.

curing time In the molding of the thermosetting plastics, the amount of time it takes for the material to be properly cured.

current-carrying capacity The maximum current that can be carried continuously, under specified conditions, by a conductor without causing objectionable degradation of electrical or mechanical properties of the PCB.

cycle rate (1) A component placement term similar to the placement rate, except it measures the machine speed as it moves from the component pickup location to the board site location and back again without actually picking and placing components (a dry run). Also referred to as the test rate.