Activating - A treatment that renders nonconductive material receptive to electroless deposition. Non-preferred synonyms: Seeding, Catalyzing and Sensitizing.
Active Component - A component that adds energy to the signal as it passes
Analog Circuit - A circuit in which the output varies as a continuous function of the input, as contrasted with digital circuit.
Annular Ring - The conductive foil and plating surrounding a hole.
Aramid - An organic fiber vs. mineral fiber material, like E glass
Array - Same as subpanel
Artwork - Photoplotted film (or the Gerber files used to drive the photoplotter), NC Drill file, and documentation used to manufacture a printed circuit board
Artwork Master - An accurately scaled (usually 1:1) pattern, which is used to produce the production master.
Aspect Ratio - The ratio of the circuit board thickness to the smallest hole diameter.
Assembly - The process of positioning and soldering components to a printed circuit board
B-Stage Material - Sheet material impregnated with a resin, cured to an intermediate stage (B-stage resins). Prepreg is the preferred term.
B-Stage Resin - A resin in an intermediate stage of a thermosetting reaction. The material softens when heated and swells when in contact with certain liquids, but it may not entirely fuse or dissolve.
Backplanes and Panels - Interconnection panels in which printed circuits, panels, or integrated circuit packages, can be plugged or mounted into or onto.
Back-Up Material - A material placed on the bottom of a laminate stack in which the drill terminates its drilling stroke.
Ball Grid Array (BGA) - Ball Grid Array (BGA) High-density interconnect package attached to the printed circuit board with a solder ball grid
Barrel - The cylinder formed by plating through a drilled hole.
Base Laminate - The substrate material upon which the conductive pattern could be formed. The base material may be rigid or flexible.
Base Material - The insulating material upon which the printed wiring pattern may be formed. "Bed-of-Nails" Technique: A method of testing printed circuit boards that employs a test fixture, mounting an array of contact pins configured so as to engage plated-through holes on the board.
Bismaleimide Triazine (BT) - Material type
Blister - A localized swelling and separating between any of the layers of a laminated base material, or between base material and conductive foil. It is a form of delamination.
Blow Hole - A void caused by out gassing.
Bond Strength - The force per unit area required to separate two adjacent layers of a board by a force perpendicular to the board surface. See: Peel Strength.
Blue Print - See fabrication drawing.
Breakdown Voltage - The voltage at which an insulator or dielectric ruptures, or at which ionization and conduction take place in the form of a gas or vapor.
Bridging Electrical - The formation of a conductive path between two insulated conductors such as adjacent foil traces on a circuit board.
C-Stage - The condition of a resin polymer when it is in the solid state, with high molecular weight, being insoluble and infusible.
CAD - See Computer Aided Design
CAM - See Computer Aided Manufacturing.
Card-edge Connector - See finger.
Center-to-Center Spacing - The nominal distance between the centers of adjacent features or traces on any layer of a printed circuit board.
Chamfer - A corner which has been machined to eliminate an otherwise sharp edge.
Characteristic Impedance - The ratio of voltage to current in a propagating wave: i.e., the impedance which is offered to this wave at any point of the line. The characteristic impedance is expressed in ohms. In printed wiring its value depends on the width and thickness of the conductor, the distance from the conductor to the ground plane(s), and the dielectric constant of the insulating media.
Check Plots - Film generated solely for checking the printed circuit board design. It is not used in the manufacturing of the board
Circumferential Separation - The crack in the plating extending around the entire circumference of a plated through hole.
Chip-on-Board (COB) - Integrated circuits glued and wire-bonded directly to a printed circuit board
Clad or Cladding - A relatively thin layer or sheet of metal foil that is bonded to a laminate core to form the base material for printed circuits.
Clearance Hole - A hole in the conductive pattern, larger than, but concentric with, a hole in the printed board base material.
Coefficient or Expansion, Thermal - The fractional change in dimension of a material for a unit change in temperature.
Component - Any of the basic parts used in building electronic equipment, such as capacitors, resistors, etc.
Component Hole - A hole used for the attachment and electrical connection of component terminations, including pins and wires, to the printed circuit board.
Component Side - That side of the printed circuit board on which most of the components will be mounted.
Computer Aided Design (CAD) - A system where engineers use a graphics screen or plot to create and view a design. In printed circuit board design, CAD files are submitted to the manufacturer. See Computer Aided Manufacturing
Computer Aided Manufacturing (CAM) - A system where manufacturers use CAD data files to drive areas of the printed circuit board manufacturing process. Types of files include Gerber files, drill files, netlists, and fab drawings
Conductive Anodic Filamentation (CAF) - An electrical short created when a conductive filament forms in the dielectric material between two adjacent conductors.
Conductive Pattern - The configuration of design of the conductive material on the base laminate. Includes conductors, lands, and through connections
Conductor Spacing - The distance between adjacent edges, (not centerline to centerline), of conductors on a single layer of a printed board.
Conductor Base Width - The conductor width at the plane of the surface of the base material. See also: conductor width.
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 printed circuit board.
Connector - A plug or receptacle that can be easily joined with or separated from its mate.
Contaminant - An impurity or foreign substance whose presence on printed wiring assemblies could electrolytically, chemically, or galvanically corrode the system.
Coordinate Tolerancing - A method of tolerancing hole locations in which the tolerance is applied directly to linear and angular dimensions, usually forming a rectangular area of allowable variation. See also: Positional Limitation Tolerancing and True Position Tolerancing.
Copper Foil - A cathode-quality electrolytic copper used as a conductor for printed circuits. It is made in a number of weights (thicknesses): the traditional weights are 1 and 2 ounces per square foot (0.0014" and 0.0028" thick).
Core Material - The fully cured inner-layer segments, with circuiting on one or both sides, which form the multilayer circuit.
Cosmetic Defect - Cosmetic Defect A defect, such as a slight change in its usual color, which does not affect functionality of the circuit board.
Coupon - One of the patterns of the quality conformance test circuitry area. See: Test Coupon.
Crazing - A condition existing in the base material in the form of connected white spots or "crosses" on or below the surface of the base material, reflecting the separation of the fibers in the glass cloth and connecting weave in intersections
Current-Carrying Capacity - The maximum current which can be carried continuously, under specified conditions, by a conductor without causing degradation of electrical or mechanical properties of the printed circuit board
CAT Testing Conductor Analysis Technology - Conductor Analysis Technology is a method of benchmarking one company's capabilities against other companies through an IPC established database. Capabilities such as line width/space, hole wall quality, impedance, and registration can be assessed at certain technology levels (e.g. layer count, blind/buried vias). Results are measured by an outside source on product manufactured to capture specific market technologies
CTE Coefficient of Thermal Expansion - The tendency of a material to expand as it is heated. It is the characteristic thermo-mechanical properties of a material that dictate the amount of movement. CTE is usually reported in ppm/degree C in both the x-y (in plane,) and the z (out of plane, like a through hole) dimension. Material will move at one rate below it's Tg and at a greater rate after it passes the Tg.
Datum Reference - A defined point, line, or plane used to locate the pattern or layer for manufacturing, inspection, or for both purposes.
Deburring - Process of removing a burr after board drilling. Deburring operations fall into two categories; producing a clean, sharp edge when removing heavy burrs; and reducing the edge of the holes to prevent build-up in plating
Defect - Any deviation from the normally accepted characteristics of a product or component. See also: Major Defect and Minor Defect.
Delamination - A separation between any of the layers of a base material or between the laminate and the conductive foil, or both.
Dewetting - A condition which occurs when molten solder has coated a surface and then recedes, leaving irregularly shaped globules of solder separated by areas covered with a thin solder film; base metal is not exposed.
Dicyandiamide (DICY) - A common cross-linking agent used in FR-4
Dielectric - An insulating medium which occupies the region between two conductors.
Dielectric Constant Dk - The property of a dielectric which determines the electrostatic energy stored (capacitance) per unit volume for a unit potential gradient. Also called permittivity. It really is a relative term reflecting the ratio of the speed of a signal in free space to the speed of the signal in a material via capacitance
Dielectric Strength - The voltage that an insulating material can withstand before breakdown occurs, usually expressed as a voltage gradient (such as volts per mil.).
Digital Circuit - A circuit in which the output is non-continuous (typically "on" or "off") and can make logical decisions, as contrasted with analog circuit
Digitizing - Any method of reducing feature locations on a flat plan to digital representation in X-Y coordinates
Dimensional Stablity - A measure of dimensional change caused by factors such as temperature, humidity, chemical treatment, age, or stress; usually expressed as units/unit.
Dimensioned Hole - A hole in a printed circuit board where the means of determining location is by coordinate values not necessarily coinciding with the stated grid.
Dissipation Factor Df - The tangent of the loss angle of the insulating material. Also called the loss tangent or approximate power factor. It is a factor used to express the tendency of insulators or dielectrics to absorb some of the energy in an AC signal or looking at it another way, as the power loss of a signal in the laminate substrate only
Dual In-Line Package (DIP) - A type of housing for integrated circuits.
Drill, Circuit Board - Solid, carbide cutting tools with four facet points and two helical flutes designed specifically for the fast removal of chips in extremely abrasive, glass-epoxy materials.
Drill Wander - The sum of accuracy and precision deviations from the targeted location of the hole.
Dry-Film Resists - Coating material in the form of laminated photosensitive sheets specifically designed for use in the manufacture of printed circuit boards and chemically machined parts. They are resistant to various electroplating and etching processes.
Edge-Board Connector - A connector designed specifically for making removable and reliable interconnection between the edge board contacts on the edge of a printed board and external wiring.
Edge Dip Solder Ability Test - A test performed by taking a specially-prepared specimen, fluxing it with a non-activated rosin flux, and then immersing it into a pot of molten solder at a predetermined rate of immersion for a pre-determined dwell time, and then withdrawing it at a pre-determined rate.
Edge Spacing - The distance of a pattern, components, or both, from the edges of the printed circuit board.
Electroless Deposition - The deposition of conductive material from an autocatalytic reduction of a metal ion on certain catalytic surfaces.
Electroless Plating - The controlled auto catalytic reduction of a metal ion on certain catalytic surfaces.
Electroplating - The electro-deposition of a metal coating on a conductive object. The object to be plated is placed in an electrolyte and connected to one terminal of a d-c voltage source. The metal to be deposited is similarly immersed and connected to the other terminal. Ions of the metal provide transfer to metal as they make up the current flow between the electrodes.
Emulsion Side - The side of the film or glass on which the photographic image is present.
Entry Material - A material placed on top of a laminate stack for drilling.
Etchback - The controlled removal of all components of base material by a chemical process on the sidewall of holes in order to expose additional internal conductor areas.
Etch Factor - The ratio of the depth (conductor thickness) to the amount of lateral etch (undercut).
Etching - The process of removing unwanted metallic substance (bonded to a base) via chemical, or chemical and electrolytic means.
Fab - Short for fabrication. Also used as a term for printed circuit board (as in "bare fab").
Fabrication - 1. The manufacturing of a printed circuit board.
2. Point in the printed circuit board manufacturing process where the boards are routed from the panel.
Fabrication Drawing - A drawing that gives the printed circuit board manufacturer pertinent information regarding the board design. Often includes dimensions, tolerances, and notes on the materials and methods to be used. Also called a blueprint.
Finger - A gold plated terminal of a card-edge connector.
Fixture - A device that enables interfacing a printed circuit board with a spring-contact probe test pattern. It contains either an abdicated head or an interface for interchangeable test heads and a means of keying the product to be tested.
Flexural Strength - The strength of a material subjected to bending. It is expressed as the tensile stress of the outermost fibers of a bent test sample at the instant of failure.
Flux - A substance used to promote or facilitate fusion, such as a material used to remove oxides from surfaces to be joined by soldering or welding.
Foil - A thin sheet of metal, usually copper or aluminum, used as the conductor for printed circuits. The tinnier the foil, the lower the required etch time. Thinner foils also permit finer definition and spacing. See: Copper Foil.
Fused Coating - A metallic coating (usually tin or solder alloy) which has been melted and solidified, forming a metallurgical bond to the base material.
Glass Transition Temperature - The temperature at which amorphous polymer changes from hard and relatively brittle to a viscous or rubbery condition. When this transition occurs many physical properties undergo significant changes. Changes include hardness, brittleness, coefficient of thermal expansion and specific heat.
Grid - An orthogonal network of two sets of parallel lines for positioning features on a circuit board. Ground Plane: A conducting surface used as a common reference point for circuit returns, shielding, or heat sinking.
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, machined areas, or both.
Hole Breakout - A condition in which a hole is not completely surrounded by the land.
Hole Density - The quantity of holes in a printed circuit board per unit area.
Hole Pull Strength - The force, in pounds, necessary to rupture a plated-through hole or its surface terminal pads when loaded or pulled in the direction of the axis of the hole. The pull is usually applied to a wire soldered in the hole, and the rate of pull is given in inches per minute.
Hole Void - The void in the metallic deposit of a plated-through hole exposing the base material. Insulation Resistance: The electrical resistance of the insulating material (determined under specified conditions) as measured between any pair of contacts or conductors.
Insulation Resistance - The electrical resistance of the insulating material (determined under specified conditions) as measured between any pair of contacts or conductors.
Internal Layer - A conductive pattern, which is contained entirely within a multilayer, printed board.
Interstitial Via Hole - A plated-through hole connecting two or more conductor layers of a multilayer printed board but not extending fully through all of the layers of base material comprising the board.
IPC (Institute for Interconnection and Packaging Electronic Circuits) - A leading printed wiring industry association that develops and distributes standards, as well as other information of value to printed wiring designers, users, suppliers, and fabricators.
IR - Infrared heating for solder-reflow operation.
IST Testing Interconnect Stress Testing - IST tests and quantifies interconnect and PTH reliability and failure mechanisms. It is similar to other heating/cooling cycle test methods except that the test allows one to know when the sample tested fails and the type of failure that occurs. This allows one to quantify and baseline a process and/or product. The test consists of electrically heating to 150 °C in 3 minutes and of cooling to room temperature in 2 minutes a network of via and component holes. The resistance of the network is monitored through each cycle and the cycling is continued until the resistance increases by 10% indicating failure. At this point the failure site can be identified and cross sectioned and a graph of the resistance against cycles can be analyzed to identify the failure mode and point of occurrence.
Jumper Wire - An electrical connection formed by wire between two points on a printed board added after the intended conductive pattern is formed.
Keying Slot - A slot in a printed circuit board that polarizes it, thereby permitting it to be plugged into its mating receptacle with pins properly aligned, but preventing it from being reversed or plugged into any other receptacle.
Laminate - A product made by bonding together two or more layers of metal.
Laminate Void - Absence of laminate material in an area which normally contains laminate material.
Laminating Presses - Multilayer: Equipment that applies both pressure and heat to laminate and prepreg to make multilayer boards.
Lamination - The process of preparing a laminate; also, any layer in a laminate.
Land - A portion of a conductive pattern usually, but not exclusively, used for the connection and/or attachment of components. Also called Pad, Boss, Terminal area, Blivet, Tab, Spot, or Donut.
Landless Hole - A plated-through hole without a land(s).
Laser Photoplotter - A device that exposes photosensitive material, usually a solver halide or diazo material, subsequently used as the master for creating the circuit image in production. Also called Laser Photo generator or LPG
Layback - A geometric drill bit defect of the cutting edges.
Layer-to-Layer Spacing - The thickness of dielectric material between adjacent layers of conductive circuitry in a multilayer printed circuit board.
Lay-Up - The technique of registering and stacking layers of multilayer board materials (laminate and prepreg) in preparation for the laminating cycle.
Legend - A format of lettering or symbols on the printed circuit board; e.g., part number,component location and patterns.
Major Defect - A defect that could result in failure or significantly reduce the usability of the part for its intended purpose.
Mask - A materiel applied to enable selective etching, plating, or the application of solder to a printed circuit board.
Maximum, Plated-Through Hole Size - A hole size equal to the specified hole size before plating, plus the manufacturing tolerance, less twice the minimum plating thickness.
Mealing - A condition at the interface of the conformal coating and base material, in the form of discrete spots or patches, which reveals a separation of the conformal coating from the surface of the base material; usually due to thermally induced stress.
Measling - A condition existing in the base laminate in the form of discrete white spots "crosses" below the surface of the base laminate, reflecting a separation of fibers in the glass cloth at the weave intersection.
Microsectioning - The preparation of a specimen for the microscopic examination of the material to be examined, usually by cutting out a cross-section, followed by encapsulation, polishing, etching, staining, etc..
Mil - One-thousandth (0.001) of an inch.
Minimum Annular Ring - The minimum metal width, at the narrowest point, between the circumference of the hole and the outer circumference of the land. This measurement is made to the drilled hole on internal layers of multilayer printed circuit boards and to the edge of the plating on outside layers of multilayer boards and double-sided boards.
Minimum Electrical Spacing - The minimum allowable distance between adjacent conductors at any given voltage or altitude that is sufficient to prevent dielectric breakdown, corona or both.
Minimum Plated-Through Hole Size - A hole size equal to the specified hole size before plating, less the manufacturing tolerance, less twice the minimum plating thickness.
Minor Defect - A defect which is not likely to reduce the usability of the unit for its intended purpose. It may be a departure from established standards having no significant bearing on the effective use or operation of the unit.
Mixed Assembly - A printed wiring assembly that combines through-hole components and surface mounted components on the same board.
Mis-Registration - The lack of dimensional conformity between successively produced features of patterns.
Multilayer Printed Circuit Boards - Printed circuit boards consisting of three or more conducting circuit planes separated by insulating material and bonded together with internal and external connections to each level of the circuitry as required.
Nail Heading - The flared condition of copper on the inner conductor layers of a multilayer board caused by hole drilling.
Negative - An artwork master or production master in which the intended conductive pattern is transparent to light, and the areas to be free from conductive material are opaque.
Nonfunctional Land - A land on internal or external layers, not connected to the conductive pattern on its layer.
Outgassing - De-aeration or other gaseous emission from a printed circuit board when exposed to reduced pressure, heat, or both.
Overhang - Increase in printed circuit conductor width caused by plating build-up or by undercutting during etching.
Pad - The portion of the conductive pattern on printed circuits designated for the mounting or attachment of components. See: Land
Pads Only - A multilayer construction with all circuit traces on inner layers and component terminal area only on one surface of board. This adds two layers, but may avoid the need for subsequent solder resist, and usually inner layers are easier to form which may lead to higher overall yields.
Panel - The base material containing one or more circuit patterns that passes successively through the production sequence and from which printed circuit boards are extracted. See: Backplanes and Panels.
Panel Plating - The plating of the entire surface of a panel (including holes).
Pattern - The configuration of conductive and nonconductive materials on a panel or printed board. Also the circuit configuration on related tools, drawings and masters.
Pattern Platting - Selective plating of a conductive pattern.
Peel Strength - The force per unit width required to peel the conductor or foil from the base material.
PHOTOMASTER - An accurately scaled copy of the artwork master used in the photo-fabrication cycle to facilitate photo-processing steps.
Photoplotter - A high accuracy (+0.001" or better) flatbed plotter with a programmable, photo image projector assembly. It is most often used to produce actual size master patterns for printed circuit artwork directly on dimensionally-stable, high-contrast photographic film.
Pinhole - A minute hole through a layer or pattern.
Pit - A depression in the conductive layer that does not penetrate entirely through it.
Plated-Through Hole - A hole with the deposition of metal (usually copper) on its sides to provide electrical connections between conductive patterns at the levels of a printed circuit board.
Plating, Electroless - A method of metal deposition employing a chemical reducing agent present in the processing solution. The process is further characterized by the catalytic nature of the surface which enables the metal to be plated to any thickness.
Plating, Electrolytic - A method of metal deposition employing the work or cathode; the anode; the electrolyte, a solution containing dissolved salts of the metal to be plated; and a source of direct current. See: Electroplating.
Plating Resists - Materials which, when deposited on conductive areas, prevent the plating of the covered areas. Resists are available both as screened-on materials and dry-film photopolymer resists.
Plating Void - The absence of a plating metal from a specified plating area.
Plotting - The mechanical inverting of X-Y positional information into a visual pattern, such as artwork.
Polymide Resins - High temperature thermoplastics used with glass to produce printed circuit laminates for multilayer and other circuit applications requiring high temperature performance.
Positional Limitation Tolerancing - Defines a zone within which the axis or center plane of a feature is permitted to vary from (theoretically exact) position.
Positive - An artwork master or production master in which the intended conductive pattern is opaque to light, and the areas intended to be free from conductive material are transparent.
Prepreg - Sheet material consisting of the base material impregnated with a synthetic resin,such as epoxy or polyimide, partially cured to the B-stage.
Preproduction Test Board - A test board (as detailed in IPC-ML-950), the purpose of which is to determine whether the contractor has the capability of producing the multilayer board satisfactorily, prior to the production of finished boards.
Press-Fit Contact - An electrical contact which can be pressed into a hole in an insulator, printed board (with or without plated-through holes), or a metal plate.
Press Platen - The flat heated surface of a lamination press used to transmit heat and pressure to lamination fixtures and into a lay-up.
Printed Wiring Layout - A sketch that depicts, the printed wiring substrate, the physical size and location of electronic and mechanical components, and the routing of conductors that interconnect the electronic parts in sufficient detail to allow preparation of documentation and artwork.
Production Master - A 1:1 scale pattern which is used to produce one or more printed boards (rigid or flexible) within the accuracy specified on the Master Drawing. See below.
(A)Single-Image Production Master: A production master used in the process of making a single printed circuit board.
(B)Multiple-Image Production Master: A production master used in the process on making two or more printed circuit boards simultaneously.
PTH (Plated-Through Hole) - Refers to the technology that uses the plated-through hole as its foundation
PPO Polyphenylene Oxide - Material type
PPE Polyphenylene Ether - Material type
PTFE Teflon - Material type
Reflowing - The melting of an electro-deposit followed by solidification. The surface has the appearance and physical characteristics of being hot-dipped.
Register Mark - A mark used to establish the relative position of one or more printed wiring patterns, or portions thereof, with respect to desired locations on the opposite side of the board.
Registration - The degree of conformity of the position of a pattern, or a portion thereof, with its intended position or with that of any other conductor layer of the board.
Resin Smear - Resin, normally caused by drilling, transferred from the base material onto the surface or edge of the conductive pattern. Sometimes called: Epoxy Smear.
Resin Starved Area - A region in a printed circuit board that has an insufficient amount of resin to wet out the reinforcement completely. Evidenced by low gloss, dry spots or exposed fibers.
Resist - Coating material used to mask or to protect selected areas of a pattern from the action of an etchant, solder, or plating. See: Dry-Film Resists, Plating Resists, and Solder Resists.
Reverse Image - The resist pattern on a printed circuit board enabling the exposure of conductive areas for subsequent plating
Screen Printing - A process for transferring an image to a surface by forcing suitable media through a stencil screen with a squeegee. Also called: Silk Screening.
SEC - Solvent Extraction Conductivity
Shadowing - A condition occurring during etchback in which the dielectric material, in intimate contact with the foil, is incompletely removed although acceptable etchback may have been achieved elsewhere.
Silk Screening - See: Screen Printing.
SIR - Surface Insulation Resistance
SMC (Surface Mounted Component) - Component with terminations designed for mounting flush to printed wiring board.
Solder Leveling - The process of dipping printed circuit boards into hot liquids, or exposing them to liquid waves to achieve fusion.
Solder Mask Coating - Non-preferred term for Resist.
Solder Resists - Coating which mask and insulate portions of a circuit pattern where solder is not desired.
Solder Ability Testing - The evaluation of a metal to determine its ability to be wetted by solder. Such evaluations include: the edge dip solderability test; the meniscus test; and the globule test.
Spindle Runout - The measure of the wobble present as the drilling machine spindle rotates 360 degrees.
Starvation, Resin - A deficiency of resin in base material apparent after lamination by the presence of weave texture, low gloss, or dry spots.
Storage Life - The period of time during which a liquid resin or adhesive can be stored and remain suitable for use. Also called: Shelf Life.
Step-and Repeat - A method by which successive exposures of a single image are made to produce a Multiple-Image Production Master.
Substrate - A material, on whose surface an adhesive substance is spread for bonding or coating.
Surface Leakage - The passage of current over the boundary surface of an insulator as distinguished from passage through its volume.
Tg Glass transition temperature - The temperature at which laminate mechanical properties change significantly. It is not the temperature in which the glass melts. When the Tg temperature is reached, the resin changes from its "glassy" state and causes changes in the laminate's properties
Terminal Area - A portion of a conductive pattern, usually but not exclusively, for the connection and/or attachment of components. Also known as: Pad.
A portion of a conductive pattern, usually but not exclusively, for the connection and/or attachment of components. Also known as: Pad. - A portion of a printed circuit board or panel containing printed circuit coupons, used to determine acceptability of such boards.
Tetra Functional - Describes an epoxy system for laminates that has four cross-linked bonds rather than two, and results in a higher glass transition temperature, or Tg: Glass transition temperature. The temperature at which laminate mechanical properties change significantly.
Thief - An auxiliary cathode placed to divert current to itself from portions of the work which would otherwise receive too high a current density.
Thin Foil - A metal sheet less than 0.0007 inches (1/2 oz) thick.
Thermoplastic - A bonding agent that bonds by melting and forming a mechanical bond in the substrate. It will reverse when the temperature reaches it melting point, but it provides the highest electrical performance.
Thermoset - A bonding agent that results in chemical bonds that cannot be reversed once set. e.g. FR4, Getek, Speedboard C.
Through Connection - An electrical connection between conductive patterns on opposite sides of an insulating base; e.g., plated-through hole or clinched jumper wire.
Through-Hole Technology - Traditional printed wiring fabrication where components are mounted in holes that pierce the board.
Tooling Holes - The term for holes placed on a printed circuit board or a panel, used for registration and hold-down purposes during the manufacturing process.
True Position - The theoretically exact location of a feature or hole established by basic dimension.
True Position Tolerancing - A method of Tolerancing hole locations. The tolerance is expressed as a radius or diameter of allowable variation from the "true position" center defined by a dimension or grid coordinate. See also: Coordinate Tolerancing and Positional Limitation Tolerancing.
Twist - The deformation of a rectangular sheet such that one of the corners is not in the plane containing the other three corners.
UV (Ultraviolet) Curing - Polymerizing, hardening, or cross linking a low molecular weight resinous material in a wet coating or ink, using ultraviolet light as an energy source.
Ultrasonic Cleaning Equipment - Equipment consisting of an ultrasonic generator and tank to hold cleaning liquid, using a transducer which converts electrical energy into mechanical energy, used for immersion cleaning. Automated and conveyorized cleaning systems exist.
Undercut - The reduction of the cross section of metal foil conduct caused by the etchant removing metal from under the edge of the resist.
Underwriters' Laboratory Symbol (UL) - A logotype authorized for placement on a product which has been recognized/accepted by Underwriters Laboratories, Inc.
Vapor Phase - The solder-reflow process that uses a vaporized solvent as the source for heating the solder beyond its melting point, creating the component-to-board solder joint.
Via Hole - A plated-through hole used as a through connection, but in which there is no intention to insert a component lead or other reinforcing material.
Void - The absence of substance in a localized region.
Warp - Non-preferred term for Bow.
Weave Exposure - A surface condition of base material in which the unbroken fibers of woven glass cloth are not completely covered by resin.
Weave Texture - A surface condition of base material in which a weave pattern of glass cloth is apparent although the unbroken fibers of the woven cloth are completely covered with resin.
Wetting - The information of a relatively uniform, smooth, unbroken and adherent film for solder to a base material.
Whisker - A slender acicular (needle-shaped) metallic growth on a printed circuit board.
Wicking - Migration of copper salts into the glass fibers of the insulating material.