Printed Circuit Board (PCB) Glossary

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AOI - (Automated Optical Inspection)

Automatic laser/video inspection of traces and pads on the surface of inner-layer cores or outer-layer panels. The machine uses cam data to verify copper feature positioning, size and shape. Instrumental in locating "open" traces, missing features or "shorts".

AQL - (Acceptance Quality Level)

The maximum number of defectives likely to exist within a population (lot) that can be considered to be contractually tolerable; normally associated with statistically derived sampling plans.

AWG Equivalent

The American Wire Gauge (AWG) round-conductor number that is used to designate a flat conductor with an equal cross-sectional area.


A treatment that renders non-conductive material receptive to electroless deposition.

Active Components

Semiconductor devices, such as transistors and diodes, that can change its basic characteristics in an powered electrical circuit, such as amplifiers and rectifiers.

Additive Process

Deposition or addition of conductive material onto clad or unclad base material.


The surrounding environment coming into contact with the system or component in question.

Analog Circuit

An electrical circuit that provides a continuous quantitative output as a response from its input.


Text, notes, or other identification, constructed by a computer-aided system, intended to be inserted on a drawing, map or diagram.

Annular Ring

that portion of conductive material completely surrounding a hole.


An established clearance in the plane to accommodate a hole and its corresponding pad stack.


A group of elements or circuits (or circuit boards) arranged in rows and columns on a base material.


An accurately scaled configuration used to produce the artwork master or production master.

Artwork Master

The photographic film or glass plate that embodies the image of the PCB pattern, usually on a 1:1 scale.

Aspect Ratio

A ratio of the PCB board thickness to the diameter of the smallest hole.


A number of parts, subassemblies, or any combination thereof joined together.

Assembly File

A drawing describing the locations of components on a PCB.

Automated Test Equipment (ATE)

Equipment that automatically tests and analyzes functional parameters to evaluate performance of the tested electronic devices.

Axial Lead

Lead wire extending from a component or module body along its longitudinal axis.



An intermediate stage in the reaction of a thermosetting resin in which the material softens when heated and swells, but does not entirely fuse or dissolve, when it is in contact with certain liquids.

B-Stage Material

Sheet material impregnated with a resin cured to an intermediate stage (B-stage resin). PrePreg is the popular term.

B-Stage Resin

A thermosetting resin that is in an intermediate state of cure.


Bare Board Test.

Back Annotation

The process of extracting appropriate information from a completed printed board design and inserting it "back" into the corresponding schematic diagram.

Ball Grid Array (BGA)

A SMD package in which solder ball interconnects cover the bottom surface of the package.

Bare Board

An unassembled (unpopulated) printed circuit board.


The cylinder formed by plating through a drilled hole.

Base Copper

The thin copper foil portion of a copper-clad laminate for PCBs. It can be present on one or both sides of the board.

Base Copper Weight

see Copper Foil

Base Material

The insulating material upon which a conductive pattern may be formed. It may be rigid or flexible or both. It may be a dielectric or insulated metal sheet.

Base Material Thickness

The thickness of the base material excluding metal foil or material deposited on the surface.

Bed Of Nails Fixture

A test fixture consisting of a frame and a holder containing a field of spring-loaded pins that make electrical contact with a planar test object (i.e., a PCB).

Bill of materials (BOM)

A comprehensive listing of all subassemblies, components, and raw materials that go into a parent assembly, showing the quantity of each required to make the assembly.


A condition in which a plated hole discharges process materials of solutions from voids and crevices.

Blind Via

A conductive surface hole that connects an outer layer with an inner layer of a multi layer board without penetrating the entire board.


A localized swelling and separation between any of the layers of a laminated base material, or between base material or conductive foil. It is a form of delamination.

Board House

Board vendor. PCB Manufacturer.

Board Thickness

The overall thickness of the base material and all conductive material deposited thereon.

Bond Strength

The force per unit area required to separate two adjacent layers of a board by a force perpendicular to the board surface.


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.


The deviation from flatness of a board characterized by a roughly cylindrical or spherical curvature such that if the board is rectangular, its four corners are in the same plane.


The function of excising printed boards or printed board assemblies from their panel structure after all processing has been completed.

Built-In Self Test

An electrical testing method that allows the tested devices to test itself with specific added-on hardware.

Buried Via

A via hole that does not extend to the surface of a printed board.


A ridge left on the outside copper surface after drilling.


One or more conductors used for transmitting data signals or power.



The condition of a resin polymer when it is in a solid state with high molecular weight. Being insoluble and infusion.

C-Stage Resin

A resin in its final state of cure.


Computer Aided Design.


Computer Aided Manufacturing.

CAM Files

The data files used directly in the manufacture of printed wiring. The file types are: (1) Gerber files, which control a photo-plotter. (2) NC Drill file, which controls an NC Drill machine. (3) Fabrication drawings in Gerber, HPGL or any other electronic format. Hard copy prints may be available also. CAM files represent the final product of PCB design. These files are given to the board house which further refines and manipulates CAM in their processes, for example in step- and-repeat panelization


Computer Numerical Control. A system that utilizes a computer and software as the primary numerical control technique.


Coefficient of thermal expansion. The measure of the amount a material changes in any axis per degree of temperature change.


The property of a system of conductors and dielectrics which permits storage of electricity when potential difference exists between conductors.


Another name for a printed circuit board.


A chemical that is used to initiate the reaction or increase the speed of the reaction between a resin and a curing agent.

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.

Ceramic Ball Grid Array (CBGA)

A ball grid array package with a ceramic substrate.


A broken corner to eliminate an otherwise sharp edge. Chip: The individual circuit or component of a silicon wafer, the leadless form of an electronic component.

Check Plots

Pen plots, or plotted film, that are suitable for checking and for design approval by customers.

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.


A number of electrical elements and devices that have been interconnected to perform a desired electrical function.

Circuitry Layer

A layer of a printed board containing conductors, including ground and voltage planes.

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 that is larger than, and coaxial with a hole in the base material of a printed board.


A thin layer of material, conductive, magnetic or dielectric, deposited on a substance surface.

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.


Any of the basic parts used in building electronic equipment, such as a resister, capacitor, DIP or connector, etc.

Component Hole

A hole used for the attachment and electrical connection of a component termination, including pin or wire to the circuit board.

Component Lead

The solid wire or formed conductor that extends from a component to serve as a mechanical or electrical connector, or both. (See also "Component Pin.")

Component Side

The side of the circuit board on which most of the components are mounted.

Computer Aided Design (CAD)

The interactive use of computer systems, programs, and procedures in the design process wherein, the decision-making activity rests with the human operator and a computer provides the data manipulation function.

Computer Aided Manufacturing (CAM)

The interactive use of computer systems, programs, and procedures in various phases of a manufacturing process wherein, the decision-making activity rests with the human operator and a computer provides the data manipulation functions.

Conductive Pattern

The configuration pattern or design of the conductive material on a base material. (This includes conductors, lands, vias, heat sinks and passive components when those are integral parts of the printed board manufacturing process.


A thin conductive area on a PCB surface or internal layer usually composed of lands (to which component leads are connected) and paths (traces).

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 coatings.

Conductor Width

The observable width of a conductor trace at any point chosen at random on a printed board as viewed from directly above.

Conformal Coating

An insulating protective coating which conforms to the configuration of the object coated and is applied on the completed board assembly.

Conformance Test Coupon Set

A complement of test coupons which are comprised of various coupon types, each of which is designed for a specific test or tests, but which were all made in the same manufacturing lot.


One leg of a net.


A plug or receptacle, which can be easily joined to or be separated from its mate. Multiple-contact connectors join two or more conductors with others in one mechanical assembly.

Connector Area

The portion of the circuit board that is used for providing electrical connections.

Contact Angle (Wetting Angle)

The angle between the contact surfaces of two objects when bonding. The contact angle is determined by the physical and chemical properties of these two materials.


An uninterrupted path for the flow of electrical current in a circuit.

Continuity Test

Resistance test to insure all the required points have electrical continuity.

Controlled Impedance

The matching of substrate material properties with trace dimensions and locations to create specific electric impedance as seen by a signal on the trace.

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 Island (Layer)

A portion of a single plane layer that is physically separated from the rest of the circuitry, intended to perform a shielding or copper distribution function, and may be electronically connected in order to provide a circuit return path. Several methods of plane generation exist that can generate copper islands.

Copper Weight

The mass of copper per unit area for a foil, typically expressed in ounces per square foot or micrometers.

Core Thickness

The thickness of the laminate base without copper.

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.

Coverlayer (Flexible Circuit)

The layer of insulating material that is applied totally or partially over a conductive pattern on the outer surfaces of a printed board. (Also referred to as "coverlay")

Crazing (Base Material)

An internal condition that occurs in reinforced laminate base material whereby glass fibers are separated from the resin at the weave intersections. (This condition manifests itself in the form of connected white spots or crosses that are below the surface of the base material.) It is usually related to mechanically-induced stress. (See "Measling.")

Creepage Distance

The shortest path between two conductors, which includes traces, terminals and structures, measured along the surface of the insulation.


The breaking up of large conductive area by the use of a pattern of voids in the conductive material.


The undesirable interference caused by the coupling of energy between signal paths.


The irreversible process of polymerizing a thermosetting epoxy in a temperature-time profile.

Curing Time

The time needed to complete curing of an epoxy at a certain temperature.

Current Carrying Capacity

The maximum electrical current that can be carried continuously by a conductor, under specified conditions, without causing objectable degradation of electrical and mechanical properties of the product.



Dry Film Solder Mask.


Dual in-line package with two rows of leads from the base in standard spacing between the leads and row. DIP is a through-hole mounting package.


Design rule check.


A collection of interrelated data items stored together without unnecessary redundancy, to serve one or more applications.

Date Code

Marking of products to indicate their date of manufacture. ACI standard is WWYY(weekweekyearyear)


The theoretically-exact point, axis or plane that is the origin from which the location of geometric characteristics of features of a part are established.

Datum Reference

A defined point, line or plane that is used to locate a pattern or layer for manufacturing purposes, inspection purposes, or both.


Process of removing burrs after PCB drilling.


The absorbing of noise pulses in power supply lines, that was generated by switching logic devices, so as to prevent the lines from disturbing other logic devices in the same power-supply circuit.


Any nonconformance to specified requirements by a unit or product.


The fidelity of reproduction of pattern edges, especially in a printed circuit relative to the original master pattern.

Dendritic Growth

Metallic filaments that grow between conductors in the presence of condensed moisture and an electric bias. (See also "Whiskers.")

Design Rule

Guidelines that determine automatic conductor routing behavior with respect to specified design parameters.

Design Rule Checking

The use of a computer program to perform continuity verification of all conductor routing in accordance with appropriate design rules.


The removal of friction-melted resin and drilling debris from a hole wall.


A condition that results when molten solder coats a surface and then recedes to leave irregularly-shaped mounds of solder that are separated by areas that are covered with a thin film of solder and with the basis metal not exposed.


Integrated circuit chip as diced or cut from a finished wafer.

Die Bonder

The placement machine bonding IC chips onto a chip-on-board substrate.

Die Bonding

The attachment of an IC chip to a substrate.

Dielectric Constant

A property of insulating materials which allows us to compare their ability to support or propagate an electric field. The dielectric constant of a material is in relation to a complete vacuum, which has a dielectric constant of 1.00. The dielectric constant of a material must be known to make signal impedance calculations.

Dielectric Strength


The converting of feature locations on a flat plane to a digital representation in X-Y coordinates.

Dimensional Stability

A measure of the dimensional change of a material that is caused by factors such as temperature changes, humidity changes, chemical treatment, and stress exposure.

Dimensioned Hole

A hole in a printed board whose location is determined by physical dimensions or coordinate values that do not necessarily coincide with the stated grid.

Discrete Component

A separate part of a printed board assembly that performs a circuit function, such as resistors, capacitors, diodes, etc.

Double-Sided Assembly

PCB assembly with components on both sides of the substrate.

Double-Sided Board

A printed board with a conductive pattern on both sides.

Dry-Film Resists

Coating material specifically designed for use in the manufacture of printed circuit boards and chemically machined parts. They are suitable for all photomechanical operations and are resistant to various electroplating and etching processes.

Dry-Film Solder Mask

Coating material (dry-film resist) applied to the printed circuit board via a lamination process to protect the board from solder or plating.



Electro-statically applied Solder Resist.

Edge Clearance

The smallest distance from any conductors or components to the edge of the PCB.

Edge Connector

A connector on the circuit-board edge in the form of gold plated pads or lines of coated holes used to connect other circuit board or electronic device.

Electro Less Deposition

The deposition of conductive material from an autocatalytic plating solution without the application of electrical current.

Electrod Eposition

The deposition of a conductive material from a plating solution by the application of electrical current.

Electroless Copper

A thin layer of copper deposited on the plastic or metallic surface of a PCB from an autocatalytic plating solution (without the application of electrical current).

Electroless Deposition

The chemical coating of a conductive material onto a base material surface by reduction of metal ions in a chemical solution without using electrodes compared to electroplating.

Electromagnetic Interference (EMI)

Unwanted electromagnetic energy that may couple into electrical circuits and adversely affect their performance.


The electro deposition of an adherent 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.

Electrostatic Discharge (ESD)

The rapid spontaneous transfer of electrostatic charge, induced by a high electrostatic field.

Embedded Component

A discrete component that is fabricated as an integral part of a printed board.

Embedded Passive

A sheet of resistive, capacitive or inductive material which is laminated onto a dielectric, and either etched or lased away to define individual resistors, capacitors or inductors.


A family of thermosetting resins used in the packaging of semiconductor devices. Epoxies form a chemical bond to many metal surfaces.

Epoxy Glass Substrate

A two-part epoxy resin reinforced with glass fiber to form an insulating material used to separate conductive layers and provide stability and strength.

Epoxy Smear

Epoxy resin which has been deposited on edges of copper in holes during drilling either as uniform coating or in scattered patches. It is undesirable because it can electrically isolate the conductive layers from the plated-through-hole interconnections.

Etch Factor

The ratio of the depth of etch to the amount of lateral etch, i.e., the ratio of conductor thickness to the amount of undercut.

Etch Resist

An organic or metal plated material used to protect the conductive pattern image from the etching chemistry. The organic material may be photosensitive.


The controlled removal of all components of the base material by a chemical process acting on the sidewalls of plated-through holes to expose additional internal conductor areas.


The chemical, or chemical and electrolytic, removal of unwanted portions of conductive materials.

Eutectic (Solder)

A mixture of substances (in fixed proportions) that melts and solidifies at a single temperature that is lower than the melting points of the separate constituents or of any other mixture of them. Eutectic solder composed of 63%Tin and 37%Lead melts/solidifies at 183 degrees Centigrade without going through a pasty (partially solid) phase.



A paper material with a phenolic resin binder. FR-1 has a TG of about 130°C.


A paper material with phenolic resin binder similar to FR-1 - but with a TG of about 105°C.


A paper material that is similar to FR-2 - except that an epoxy resin is used instead of phenolic resin as a binder. Used mainly in Europe.


Flame Retardant laminate made from woven glass fiber material impregnated with epoxy resin.



Fabrication Allowance

A dimensional value added to a printed board feature or feature location intended to assure that manufacturing variations can maintain certain physical or performance characteristics of the end product.

Fabrication Drawing

A drawing used to aid the construction of a printed circuit board. It shows all of the locations of the holes to be drilled, their sizes and tolerances, dimensions of the board edges, and notes on the materials and methods to be used. Called "fab Drawing" for short. It relates the board edge to at least one hole location as a reference point so that the NC Drill file can be properly aligned.

Fiducial Mark

A printed board feature (or features) that is created in the same process as the conductive pattern and that provides a common measurable point for component mounting with respect to a land pattern or land patterns.


A gold-plated terminal of a card-edge connector. Also see Gold Finger.

First Article

A sample part or assembly manufactured prior to the start of production for the purpose of assuring that the manufacturer is capable of producing a product that will meet specified requirements.

Flexible Printed Board

A printed board using a flexible base material only. May be partially provided with electrically non- functional stiffeners and/or coverlayer.

Flow Soldering

A wave, drag or dip soldering process where the product is brought into contact with molten solder in order to attach electronic components to the interconnecting surface.


The material used to remove oxides from metal surfaces and enable wetting of the metal with solder.

Flying Probe

A type of bare board electrical test machine that uses probes on the ends of mechanical arms to locate and touch the pads on the board. The probes move quickly across the board verifying continuity of each net as well as resistance to adjacent nets.


The physical area of a component that touches the surface of a circuit board. (For example, if you pressed a component into wet sand and then removed it, the size of the depression area would be the component's footprint. However, the term footprint is also used by many in the electronics industry to mean the size of the circuit board land pattern, which can be a significantly larger area for soldering purposes) See "Land Pattern"

Functional Test

The electrical testing of an assembled electronic device with simulated function generated by the test hardware and software.



A laminate consisting of woven epoxy-glass cloth impregnated with epoxy resin under pressure and heat. G10 lacks the anti-flammability properties of FR-4. Used mainly for thin circuits such as in watches.


The woven glass fiber laminate impregnated with polyimide resin.

Gerber File

'Data file used to control a photo-plotter. A type of data that consists of aperture selection and operation commands and dimensions in X- and Y- coordinates. Named after the Gerber Scientific Co., who made the original vector photo-plotter.'

Glass Transition Temperature (Tg)

The temperature at which the circuit board material changes from being in a hard and relatively stable condition to being in a viscous or rubbery condition.

Gold Finger

The gold-plated terminal of a card-edge connector. Also see Finger.


A common reference point for electrical circuits returns, shielding or heat sinking.

Ground Plane

A conductor layer, or portion thereof, that serves as a common reference for electrical circuit returns, shielding, or heat sinking.

Ground Plane Clearance

Removed portions of a ground plane that isolate it from a hole in the base material to which the plane is attached.

Gull Wing Leads

An SMT lead form. Leads extending horizontally from the component body centerline, bent downward immediately past the body and then bent outward just below the bottom of the body, thus forming the shape of a gull's wing (a type of bird).



Hot Air Solder Leveling. A method of coating exposed copper with solder by inserting a panel into a bath of molten solder then passing the panel rapidly past jets of hot air.

HDI (High Density Interconnect)

Ultra fine-geometry multi layer PCB constructed with conductive surface Microvia connections between layers. These boards also usually include buried and/or blind vias are made by sequential lamination.


A mechanical device that is made of high thermal conductivity and low specific heat material that dissipates heat generated by a component or assembly.

Heatsink Plane

A continuous sheet of metal on or in a printed board that functions to dissipate heat away from heat generating components.

Heel Fillet

The solder fillet formed in the land area behind the lead.


Airtight sealing of an object.

Hole Breakout

A condition in which a hole is partially surrounded by the land.

Hole Density

The number of holes per unit area on a PCB.

Hole Filling Process

A process of adding a conductive or non-conductive fill material to a plated through-hole, followed by adding an etch resist that covers the hole and its land. The process also includes etching away of the unwanted copper and subsequent stripping of the etch resist. (see also "via" definitions)

Hole Pattern

The arrangement of all holes in a printed board with respect to a reference point.

Hole Plugging Process

A process of plugging a plated through-hole with liquid solder mask material after the circuit configuration has been completed in order to prevent chemistry from entering the hole during the assembly process. (see also "via" definitions)

Hot Air (Solder) Leveling (HAL or HASL)

A physical deposition process using a solder bath into which the printed board is dipped into a molten solder bath and withdrawn across a set of hot air knives (forced hot air flow) used to remove excess solder.



The Institute for Interconnecting and Packaging Electronic Circuits. The final American authority on how to design and manufacture printed wiring.


The process of transferring electronic data to the photo-plotter, which in turn uses light to transfer a negative image circuitry pattern onto the panel or film.

Immersion Plating

The chemical deposition of a thin metallic coating over certain basis metals that is achieved by a partial displacement of the basis metal.


The resistance to the flow of current, represented by an electrical network of combined resistance, capacitance and inductance reaction, in a conductor as seen by an AC source of varying time voltage. The unit of measure is ohms.

In-Circuit Test

Electrical test of individual component or part of the circuit in a PCB assembly instead of testing the whole circuit.

In-Circuit Testing

The application of test signals directly to a device's input terminals and sensing the results directly from the device's output terminals.


Foreign particles, metallic or nonmetallic, that may be entrapped in an insulating material, conductive layer, plating, base material, or solder connection.


The dispersal of well-defined ink "dots" onto a PCB. Inkjet equipment uses heat to liquefy a solid ink pellet and change the ink into a liquid, which is then dropped via a nozzle onto the printed surface, where it quickly dries.


The internal layers of laminate and metal foil within a multi-layer board.

Insulation Resistance

The electrical resistance of an insulating material that is determined under specific conditions between any pair of contacts, conductors, or grounding devices in various combinations.

Interconnect Stress Test

The IST system is designed to quantify the ability of the total interconnect to withstand the thermal and mechanical strains, from the as manufactured state, until the products reaches the point of interconnect failure.

Interstitial Via Hole

An embedded through-hole with connection of two or more conductor layers in a multilayer PCB.

Intrusive Soldering

A process in which the solder paste for the through- hole components is applied using a stencil or syringe to accommodate through-hole components that are inserted and reflow-soldered together with the surface- mount components.



The preferred surface mount lead form used on PLCCs, so named because the lead departs the package body near its Z axis centerline, is formed down then rolled under the package. Leads so formed are shaped like the letter "J."


similar to v-scoring, this is a process that is used when a printed circuit board is pannelized. It allows for a score line to jump over most of the panel border, leaving the border largely intact, and as a result, stronger and more rigid, resulting in a stiffer and stronger assembly panel.



Known good board or assembly. Also known as a golden board.



Liquid Photo-Imageable Solder Mask. An ink that is developed off using photographic imaging techniques to control deposition. It is the most accurate method of mask application and results in a thinner mask than dry film solder mask. It is often preferred for dense SMT. Application can be spray, curtain coat or squeegee.

Laminate Thickness

Thickness of the metal-clad base material, single or double sided, prior to any subsequent processing.

Laminate Void

An absence of epoxy resin in any cross-sectional area which should normally contain epoxy resin.


The process manufacturing a laminate using pressure and heat.


The portion of the conductive pattern on printed circuits designated for the mounting or attachment of components. Also called Pad

Land Pattern

A combination of lands that is used for the mounting, interconnection and testing of a particular component.

Laser Photo-Plotter

A plotter that uses a laser, which simulates a vector photo-plotter by using software to create a raster image of the individual objects in a CAD database, then plots the image as a series of lines of dots at a very fine resolution. A laser photo-plotter is capable of more accurate and consistent plots than a vector plotter.

Layer-to-Layer Registration

The process of aligning circuit features (lands) on individual layers of a printed board through the use of tooling image location features (fiducials) or tooling holes.

Layer-to-Layer Spacing

The thickness of dielectric material between adjacent layers of conductive patterns in a printed board.


A length of insulated or uninsulated metallic conductor that is used for electrical interconnections. A terminal on a component.

Lead Free Solder

An alloy that does not contain more than 0.1% lead (Pb) by weight as its constituent and is used for joining components to substrates or for coating surfaces.

Leakage Current

A small amount of current that flows across a dielectric area between two adjacent conductors.

Least Material Condition (LMC)

The condition in which a feature of size contains the least amount of material within the stated limits of size.


A format of lettering or symbols on the printed circuit board; e.g., part number, serial number, component locations and patterns.


A thin conductive area on a PCB surface or internal layer usually composed of lands (to which component leads are connected) and paths (traces). Also known as a "conductor".

Local Fiducial

A fiducial mark (or marks) used to locate the position of a land pattern for an individual component on a printed board. (See "Fiducial Mark")

Lot Size

A collection of units produced in one continuous, uninterrupted fabrication run.


Major Defect

A defect that is likely to result in failure of a unit or product by materially reducing its usability for its intended purpose.


A material applied to enable selective etching, plating, or the application of solder to a PCB.

Mass Lamination

The simultaneous lamination of a number of pre-etched, multiple-image, C-staged resin panels or sheets that are sandwiched between layers of B-staged resin and copper foil.


Discrete white spots or crosses below the surface of the base laminate that reflect a separation of fibers in the glass cloth at the weave intersection.


The preparation of a specimen of a material, or materials, that is to be used in metallographic examination. This usually consists of cutting out a cross-section followed by encapsulation, polishing, etching, and staining.


A transmission line (see Transmission Line) structure that consists of a signal conductor that runs parallel to and is separated from a much wider reference plane.


Usually defined as a conductive hole with a diameter of 0.006 in or less that connects layers of a multilayer PCB. Often used to refer to any small geometry connecting hole the creation of which is beyond the tradition practical drilling capabilities.


One thousandth of an inch.

Minimum Annular Ring

The minimum width of metal(s) at the narrowest point between the edge of a hole and the outer edge of a circumscribing land. (This determination is made to the drilled hole on internal layers of multilayer printed boards and to the edge of the plating on external layers of multilayer and double-sided printed board.)

Minimum Conductor Space

The smallest distance between any two adjacent conductors, such as traces, in a PCB.

Minimum Conductor Width

The smallest width of any conductors, such as traces, on a PCB.

Minimum Electrical Spacing

The minimum allowable distance between adjacent conductors, or between conductors and non-common conductors such as mounting hardware, ground, etc., at a given voltage and altitude, that is sufficient to prevent dielectric breakdown, corona, or both, from occurring between the conductors.

Minor Defect

A defect that is not likely to result in the failure of a unit or product or that does not reduce its usability for its intended purpose.

Mounting Hole

A hole that is used for the mechanical support of a printed board or for the mechanical attachment of components to a printed board.


NC Drill

Numeric Control drill machine used to drill holes at exact locations of a PCB specified in NC Drill File.


Non-plated trough-hole.


A reverse-image copy of a positive, useful for checking revisions of a PCB and is often used for representing inner layer planes. When a negative image is used for an inner-layer it would typically have clearances (solid circles) and thermals (segmented donuts) that either isolate holes from the plane or make thermally relieved connections respectively.


A collection of terminals all of which are, or must be, connected electrically. Also known as signal.


A pin or lead to which at least two components are connected through condcutors.


Identification symbols applied to the board by means of screen printing, inkjetting, or laser processes. SeeLegend.


The design target dimension for a physical characteristic of a product or a feature to which a tolerance may be applied that establishes the limits of variation from the target that are acceptable.

Nonfunctional Land

A land that is not connected electrically to the conductive pattern on its layer.


Open - Open circuit.

An unwanted break in the continuity of an electrical circuit which prevents current from flowing.

Organic Solderability Preservative (OSP)

An organic compound that reacts selectively with copper surfaces forming a thin, uniform film that prevents copper oxidation and maintains solderability after extended printed board storage.


The top and bottom sides of any type of circuit board.


PCB - Printed Circuit Board.

Also called Printed Wiring Board (PWB).


Personal Computer Memory Card International Association.


Printed Electronic Component.

PTH (plated-through Hole)

A plated hole used as a conducting interconnection between different layers or sides of a PCB either used as connection for through-hole component or as a via.


The portion of the conductive pattern on printed circuits designated for the mounting or attachment of components. Also called land.

Pallet (Printed Board)

The printed board image or images plus the additional contiguous deliverable material from the panel. This may include tabs, fiducials, tooling holes, etc.


The configuration of conductive and nonconductive materials on a panel or printed board. Also, the circuit configuration on related tools, drawings and masters.

Pattern Plating

The selective plating of a conductive pattern.

Photo Plotter

Device used to generate photographically by plotting objects onto film for use in manufacturing printed wiring.

Photo Print

The process of forming a circuit pattern image by hardening a photosensitive polymeric material by passing light through a photographic film.

Photo Resist

A material that is sensitive to portions of the light spectrum and that, when properly exposed can mask portions of a base metal with a high degree of integrity.

Photographic Image

An image in a photo mask or in an emulsion that is on a film or plate.


A photographic process whereby an image is generated by a controlled light beam that directly exposes a light-sensitive material.


A transparent film that contains the circuit pattern, which is represented by a series of lines of dots at a high resolution.


A manufacturing operation of assembly process in which components are selected and placed onto specific locations according to the assembly file of the circuit.


A terminal on a component, whether SMT or through-hole. Also called a lead.


The center-to-center spacing between conductors, such as pads and pins, on a PCB.

Plastic QUAD Flat Pack (PQFP)

A surface mount family of integrated circuit packages, bounded on all four sides by bumpers, with leads exiting from all four sides of the package and formed into a "gullwing" lead format.


The chemical or electrochemical deposited metal on a surface.

Plating Resist

Material deposited as a covering film on an area to prevent plating on this area.

Plating Void

The area of absence of specific metal from a specific cross-sectional area.


The mechanical converting of X-Y positional information into a visual pattern such as artwork.


A developed image of photo-plotted file, where the areas selectively exposed by the photo plotter appear black and unexposed areas are clear. For outer-layers, color will indicate copper. Positive inner-layers will have clear areas to indicate copper.


Sheet material (e.g., glass fabric) impregnated with a resin cured to an intermediate stage (B-stage resin).


A sheet of material that has been impregnated with a resin cured to an intermediate stage, i.e., B-staged resin.

Pressfit Contact

An electrical contact that can be pressed into a hole in an insulator or printed board with or without plated- through holes.

Printed Board (PB)

The general term for completely processed printed circuit and printed wiring configurations. (This includes single-sided, double-sided and multilayer boards with rigid, flexible, and rigid-flex base materials.)

Printed Circuit

A conductive pattern that comprises printed components, printed wiring, or a combination thereof, all formed in a predetermined design and intended to be attached to a common base. (In addition, this is a generic term used to describe a printed board produced by any of a number of techniques).

Printed Circuit Board (PCB)

A flat plate or base of insulating material containing a pattern of conducting material. It becomes an electrical circuit when components are attached and soldered to it. The conducting material is commonly copper which has been coated with solder or plated with tin-lead alloy. The usual insulating material is epoxy laminate but there are many other kinds of materials used in more exotic technologies. Single sided boards have all conductors on one side of the board. With two-sided boards, the conductors, or copper traces, can travel from one side of the board to the other through plated-thru holes called vias, or feed throughs. In multilayer boards, the vias can connect to internal layers as well as either side.

Printed Wiring Board

A part manufactured from rigid base material upon which completely processed printed wiring has been formed.

Probe Point

The predetermined location on a printed board where electrical contact can be made to exposed circuitry for electrical diagnostic purposes.

Probe Test

A spring-loaded metal device used to make electrical contact between test equipment and the unit under test.

Propagation Delay

The time from output to input required for a signal to travel along a transmission line, or the time required for a logic device to receive an input stimulus, perform its function, and present a signal at its output.

Pulse Plating

A method of plating that uses pulses instead of a direct current.


Quad Flat Pack (QFP)

A generic rectangular component package, containing an electronic device, with leads on all four sides that are formed in a ''gullwing'' shape.

Quality Conformance Test Circuitry

A portion of a printed board panel that contains a complete set of test coupons that are used to determine the acceptability of the board(s) on the panel.


RF (radio frequency) and wireless design

A circuit design that operates in a range of electromagnetic frequencies above the audio range and below visible light. All broadcast transmission, from AM radio to satellites, falls into this range, which is between 30KHz and 300GHz.

Radial Lead Component

A component where the leads are located on the bottom, radially and parallel to the central axis.

Reference Designator

The name of components on a printed circuit by convention beginning with one or two letters followed by a numeric value. The letter designates the class of component; eg. "Q" is commonly used as a prefix for transistors. Reference designators appear as usually white or yellow epoxy ink (the "silkscreen") on a circuit board. They are placed close to their respective components but not underneath them. So that they are visible on the assembled board.

Reference Dimension

A dimension without a tolerance that is used only for informational purposes that does not govern inspection or other manufacturing operations.

Reflow Soldering

Melting, joining and solidification of two coated metal layers by application of heat to the surface and predeposited solder paste.

Reflow Temperature

The temperature range of a reflow soldering process during which the solder is in its liquidus phase.


The melting of an electrodeposited tin/lead followed by solidification. The surface has the appearance and physical characteristics of being hot-dipped.


The degree of conformity of the position of a pattern (or portion thereof), a hole, or other feature to its intended position on a product.


The probability that a component, device, or assembly will function properly for a definite period of time under the influence of specific environmental and operational conditions.

Resin (Epoxy) Smear

Resin transferred from the base material onto the surface of the conductive pattern in the wall of a drilled hole.


Coating material used to mask or to protect selected areas of a pattern from the action of an etchant, solder or plating.


A PCB construction combining flexible circuits and rigid multi layers usually to provide a built-in connection or to make a three dimensional form that includes components.

Rigid-Flex Printed Board

A printed board with both rigid and flexible base materials.

Rise Time (Transition Duration)

The time required for a logic-signal voltage to switch from 10 to 90 percent of the difference between logic states.


A layout or wiring of a connection. The action of creating such a wiring. The term is also used for the actual milling of a PCB.

Route (or Track)

A layout or wiring of an electrical connection.

Router Bit

A straight or shaped rotary cutting tool used in a power router to cut, trim or shape materials by rotary action.


A mechanical method that removes a portion of the material outlining a printed board, using a cutting bit, in order to facilitate ease of breakout (removal) from the manufacturing/assembly panel.



Surface mount device.


Solder mask Over Bare Copper


Solder Mask Over Bare Copper. Method of fabricating a printed circuit board that results in final metallization being copper with no protective metal. The non-coated areas are coated by solder resist, exposing only the component terminal areas. This eliminates tin lead under the mask.


Surface Mount Technology. Defines the entire body of processes and components which create printed circuit board assemblies with lead less components.

SPC - Statistical Process Control.

The collection of process data and creation of control charting is a tool used to monitor processes and to assure that they remain In Control or stable. Control charts help distinguish process variation due to assignable causes from those due to unassignable causes.


A diagram which shows, by means of graphic symbols, the electrical connections and functions of a specific circuit arrangement.

Schematic Diagram

A drawing that shows, by means of graphic symbols, the electrical connections, components and functions of a specific circuit arrangement.


A technique in which grooves are machined on opposite sides of a panel to a depth that permits individual boards to be separated from the panel after component assembly.

Screen Printing

The transferring of an image to a surface by forcing a suitable media with a squeegee through an imaged-screen mesh.

Self Declaration

The manufacturer's view of its products and process capabilities in order to meet the customer's requirements, the requirements of a standard, and/or the applicable associated specification sheet(s).

Semi-Additive Process

An additive process wherein the entire thickness of electrically- isolated conductors is obtained by the combined use of electroless metal deposition and electroplating, etching, or both. (See also "Fully-Additive Process.")

Sequential Lamination

The process of manufacturing multilayer printed boards in which multiple double-sided printed boards with interconnecting holes between conductive patterns on both sides are laminated or combined, after which additional layers (usually single-sided) are attached to the partially completed board stack-up.


A physical barrier, usually electrically conductive, that reduces the interaction of electric or magnetic fields upon devices, circuits, or portions of circuits.

Short - Short circuit.

An abnormal connection of relatively low resistance between two points of a circuit. The result is excess (often damaging) current between these points. Such a connection is considered to have occurred in a printed wiring CAD database or artwork anytime conductors from different nets either touch or come closer than the minimum spacing allowed for the design rules being used

Short, Electrical

A fault that connects two or more points that should be electrically separated.

Silk Screen (Silk Legend)

Epoxy-ink Legend printed on PCB. The most common colors used are white and yellow.


The decals and reference designators in epoxy ink on a printed wiring board so called because of the method of application - the ink is "squeegeed" through a silk screen, the same technique used in the printed of T-shirts. Minimum line width at ACI for silkscreen is .008. Also called "silkscreen legend".

Single-Sided Board

A printed board with conductive pattern on one side only.

Skin Effect

The increase in resistance of a conductor at microwave frequencies that is caused by the tendency of electric current to concentrate at the conductor's surface.

Small Outline Integrated Circuit (SOIC)

An integrated circuit with two parallel rows of pins in surface mount package.

Small Outline Package (SOP)

A generic rectangular component package, whose chip cavity or mounting area occupies a major portion of the package area, with leads or metal pad surfaces on two opposing sides.


An alloy that melts at relatively low temperatures and is used to join or seal metals with higher melting points. A metal alloy with a melting temperature below 427°C (800°F).

Solder Ball

A small sphere of solder adhering to a laminate, resist, or conductor surface. (This generally occurs after wave solder or reflow soldering.)

Solder Bridging

Solder connecting, in most cases, misconnecting, two or more adjacent pads that come into contact to form a conductive path.

Solder Bumps

Round solder balls bonded to the pads of components used in face-down bonding techniques.

Solder Coat

A layer of solder that is applied directly from a molten solder bath to a conductive pattern.

Solder Connection

A metallurgical connection serving electrical/mechanical/thermal functions that employs solder for the joining of two or more metal surfaces.

Solder Fillet

Solder, with a normally concave surface, that is at the intersection of the metal surfaces of the solder connection.

Solder Mask

Non-preferred term for solder resist.

Solder Mask or Solder resist

Coating to prevent solder to deposit on.

Solder Paste

Finely divided particles of solder, with additives to promote wetting and to control viscosity, tackiness, slumping, drying rate, etc, that are suspended in a cream flux.

Solder Wick

A band of wire removes molten solder away from a solder joining or a solder bridge or just for desoldering.


The ability of a metal to be wetted by molten solder.

Stencil (Solder Paste/Adhesive)

A thin sheet of material containing openings to reflect a specific pattern, designed to transfer a paste-like material to a substrate for the purpose of component attachment.


The successive exposure of a single image on order to produce a multiple-image production master. Also used in CNC programs.

Stiffener Board

A material fastened to the surface of a printed board to increase its mechanical strength.

Stress Relief

The portion of a component lead or wire lead that is formed in such a way as to minimize mechanical stresses after the lead is terminated.


A transmission line structure that consists of a signal line that runs parallel to and is sandwiched between and separated by a dielectric from two reference planes.


Components are attached and soldered to a printed wiring board. Often done by an assembly house.


A group of printed circuits arrayed in a panel and handled by both the board house and the assembly house as though it were a single printed wiring board. The sub-panel is usually prepared at the board house by routing most of the material separating individual modules leaving small tabs.


A material on whose surface adhesive substance is spread for bonding or coating. Also, any material which provides a supporting surface for other materials used to support printed circuit patterns.

Subtractive Process

The fabricating of a conductive pattern by the selective removal of unwanted portions of a conductive foil.

Supported Hole

A hole in a printed board that has its inside surfaces plated or otherwise reinforced.

Surface Mount

Surface mount technology (SMT). Components are soldered to the board without using holes. The result is higher component density, allowing smaller PWB.

Surface Mounting Technology (SMT)

The electrical connection of components to the surface of a conductive pattern that does not utilize component holes.


Temperature Coefficient (TC)

The ratio of a quantity change of an electrical parameter, such as resistance or capacitance, of an electronic component to the original value when temperature changes, expressed in %/ºC or ppm/ºC.

Tented Via

A via with dry film solder mask completely covering both its pad and its plated-thru hole. This completely insulates the via from foreign objects, thus protecting against accidental shorts, but it also renders the via unusable as a test point. Sometimes vias are tented on the topside of the board and left uncovered on the bottom side to permit probing from that side only with a text fixture.


The covering of holes in a printed board and the surrounding conductive pattern with a dry film resist.


A point of connection for two or more conductors in an electrical circuit; one of the conductors is usually an electrical contact or lead of a component.

Test Board

A printed board that is deemed to be suitable for determining the acceptability of a group of boards that were. Or will be, produced with the same fabrication process.

Test Coupon

A portion of quality conformance test circuitry that is used for a specific test, or group of related tests, in order to determine the acceptability of a product.

Test Fixture

A device that interfaces between test equipment and the unit under test.

Test Point

A special point of access to an electrical circuit that is used for electrical testing purposes.


A method for determining whether sub-assemblies, assemblies and/or a finished product conform to a set of parameter and functional specifications. Test types include: in-circuit, functional, system-level, reliability, environmental.

Thermal Coefficient of Expansion (TCE)

See "Coefficient of Thermal Expansion (CTE)"

Thermal Conductivity

The property of a material that describes the rate at which heat will be conducted through a unit area of the material for a given driving force.

Thermal Mismatch

Difference in coefficients of thermal expansion of materials that are bonded together. (See also "Coefficient of Thermal Expansion (CTE).")

Thermal Relief

The crosshatching of a ground or voltage plane that minimizes blistering or warping during soldering operations.


An extra cathode placed as to divert to itself some of the current from portions of the board which otherwise would receive too high a current density.

Thin Small Outline Package (TSOP)

A package that has the same features as the SOP package except that its thickness is reduced to 0.8mm - 1.2mm [0.0315 in ? 0.0472 in].

Through-Hole (thru-hole)

Having pins designed to be inserted into holes and soldered to pads on a printed board.

Through-Hole Mounting

The electrical connection of components to a conductive pattern by the use of component holes.

Through-Hole Technology (THT)

The electrical connection of components to a conductive pattern by the use of component holes.

Time to Decomposition (Td)

The time it takes a base laminate material to lose an established percentage of weight at a given temperature using Thermogravimetric Analysis (TGA).


The application of molten solder to a basis metal in order to increase its solderability.


The total amount by which a specific dimension is permitted to vary.

Tooling Feature

A physical feature that is used exclusively to position a printed board or panel during a fabrication, assembly or testing process.


Segment of a conductor route or net.



Transmission Line

A structure for guiding or conducting electromagnetic energy from one point to another. A transmission line consists of two or more parallel conductors each separated by a dielectric. (See "Microstrip" and "Stripline")

True Position

The theoretically-exact location for a feature or hole that is established by basic dimensions.


A type of outsourcing method that turns over to the subcontractor all aspects of manufacturing including material acquisition, assembly and testing. Its opposite is consignment, where the outsourcing company provides all materials required for the products and the subcontractor provides only assembly equipment and labor.


A laminate defect in which deviation from planarity results in a twisted arc.


Underwriters Symbol

A logotype denoting that a product has been recognized (accepted) by Underwriters Laboratories Inc. (UL).

Unsupported Hole

A hole in a printed board that does not contain plating or other type of conductive reinforcement.



'A mechanical method that removes a portion of the material outlining the board, in order to facilitate ease of breakout (removal) from the manufacturing or assembly panel.'

Vapor-Phase Soldering

A reflow soldering method that is based on the exposure of the parts to be soldered to hot vapors of a liquid that has a boiling-point that is sufficiently high to melt the solder being used.


'Feed through. A plated-through hole in a PWB that is used as an interlayer connection, but in which there is no intention to insert a component lead or other reinforcing material.'

Via Planarization

'The process of removing metallization and/or organic materials associated with the surface of a via structure. It is most commonly employed in filled via fabrication.'

Via, Filled (Type V Via)

'A via with material applied into the via targeting a full penetration and encapsulation of the hole.'

Via, Filled and Capped (Type VII Via)

A Type V via with a secondary metallized coating covering the via. The metallization is on both sides.

Via, Filled and Covered (Type VI Via)

'A Type V via with a secondary covering of material (liquid or dry film solder mask) applied over the via. It may be applied from either one side or both sides.'

Via, Plugged (Type III Via)

A via with material applied allowing partial penetration into the via. It may be applied from either one side or both sides

Via, Plugged and Covered (Type IV Via)

A Type III via with a secondary covering of material applied over the via. The secondary covering may be applied from either one side or both sides.

Via, Tented (Type 1 Via)

A via with a mask material (typically dry film) applied bridging over the via wherein no additional materials are in the hole. It may be applied to one side or both.

Via, Tented and Covered (Type II Via)

A Type I via with a secondary covering of mask material applied over the tented via.

Voltage Plane

A conductor layer, or portion thereof, that serves as a common voltage source at other than ground potential for an electrical circuit, shielding, or heat sinking. (See also "Ground Plane" and "Signal Plane.")

Voltage Plane Clearance

Removed portions of a voltage plane that isolate it from a hole in the base material to which the plane is attached.


Wave Soldering

A process wherein assembled printed boards are brought in contact with a continuously flowing and circulating mass of solder.


Migration of copper salts into the glass fibers of the insulating material.



The horizontal or left-to-right direction in a two-dimensional system of coordinates. (This axis is perpendicular to the Y axis.) X-Out - A method of identifying a defective part.



The vertical or bottom-to-top direction in a two-dimensional system of coordinates.



The axis perpendicular to the plane formed by the X and Y datum reference. This axis usually represents the thickness of the boards.