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Annular Ring:

Select functional portion of conductive material completely surrounding a hole.

Aperture Information:

Common text file readable by any computer describing the size and shape of each element on the board. These are also known as D-code lists. Not necessary if project files are saved as Extended Gerber with embedded Apertures (RS274X).


PCB elements, groups of elements or circuits arranged in rows and columns on a base material.


Accurately scaled configuration used to produce the artwork master or production master.

Artwork Master:

Photographic negative or positive acetate film that embodies the image of the PCB pattern, commonly on a 1:1 scale.

Aspect Ratio:

The ratio of the PCB thickness to the diameter of the smallest hole.

Automated Optical Inspection (AOI):

Amplified visual inspection of production circuit boards using a machine scanner to assess workmanship quality.


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, and on inner layers.

Base Material:

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:

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

Bed-Of-Nails Fixture:

Common 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).


The angled edge of a printed board.

Blind Via:

Conductive surface hole that connects an outer layer with an inner layer of a multi-layer board.


Separation and localized swelling between any of the layers of a laminated base material, or between base material or conductive foil.

Bond Strength:

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


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

B-Stage Material:

Resin cured sheet material to an intermediate stage (B-stage resin). The popular term is “Prepreg”.

B-Stage Resin:

Thermosetting resin that is in an intermediate state of cure.

Buried Via:

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


Computer-Aided Design.


Computer-Aided Manufacturing.


The technique by which a broken corner is created to eliminate an otherwise sharp edge.


Functional interconnection of a number of devices in one or more closed paths to perform a desired electrical or electronic response.

Circuitry Layer:

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

Clean Room:

Specialized manufacturing room in which the concentration of airborne particles is controlled to specified limits.


Any electronic device, typically a resistor, capacitor, inductor, or integrated circuit (IC), that is mounted to the circuit board and performs a specific electrical response.

Component Hole:

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

Component Side:

side of the circuit board on which most of the components will be located.

Computer-Aided Design (CAD):

Common software programs with algorithms for drafting and modeling, providing a graphical representation of a printed board’s conductor layout and signal routes.

Computer-Aided Manufacturing (CAM):

The use of computers to analyze and transfer an electronic design (CAD) to the manufacturing floor.

Computer-Integrated Manufacturing (CIM):

Software that takes assembly data from a CAD or CAM package and, using a pre-defined factory modeling system, outputs routing of components to machine programming points and assembly and inspection documentation.


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.

Conformal Coating:

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

Connector Area:

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

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.

Core Thickness:

The thickness of the laminate base without copper.


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.


A separation between any of the layers of the base of laminate or between the laminate and the metal cladding originating from or extending to the edges of a hole or edge of board.

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 has coated a surface and then receded, leaving irregularly shaped mounds separated by areas covered with a thin solder film and with the base material not exposed.


An insulating medium that occupies the region between two conductors.

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.

Double-Sided Board:

A printed board with a conductive pattern on both sides.


The act of forming holes (via’s) in a substrate by mechanical or laser means.

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 Soldermask:

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

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).


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 direct current (DC) voltage source. The metal to be deposited is similarly immersed and connected to the other terminal.


A family of thermosetting resins. Epoxies form a chemical bond to many metal surfaces.

Epoxy Smear:

Epoxy resin that 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.


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.

Flying Probe:

A testing device that uses multiple moving pins to make contact with two spots on the electrical circuit and send a signal between them, a procedure that determines whether faults exist.


The UL-designated rating for a laminate composed of glass and epoxy that meets a specific standard for fire-retardance. FR-4 is the most common dielectric material used in the construction of PCBs.


A software format used by the photoplotter to describe the printed circuit board design.

Golden Board:

Known Good Board.

Ground Plane:

A conductor layer, or portion of a conductor layer, used as a common reference point for circuit returns, shielding, or heat sinking.

Hole Breakout:

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

Hole Pattern:

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

Hot Air Solder Leveling (HASL):

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.


The process by which panelization data are transferred to the photoplotter, which in turn uses light to transfer a negative image circuitry pattern onto the panel.


The total passive opposition offered to the flow of electric current. This term is generally used to describe high-frequency circuit boards.


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.

Known Good Board (KGB):

A board or assembly that is verified to be free of defects. Also known as a Golden Board.


The plastic material usually reinforced by glass or paper that supports the copper cladding from which circuit traces are created.

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 that should normally contain epoxy resin.


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


The process in which treated prepregs and copper foils are assembled for pressing.


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

Liquid Photoimageable Soldermask (LPI):

A mask using photographic imaging techniques to control deposition.




A quantity of circuit boards that share a common design.

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. Also called soldermask or resist.

Metal Foil:

The plane of conductive material of a printed board from which circuits are formed. Metal foil is generally copper and is provided in sheets or rolls.


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.

Minor Defect:

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

Multi-Layer Board:

Printed boards consisting of a number (four or more) of separate conducting circuit planes separated by insulating materials and bonded together into relatively thin homogeneous constructions with internal and external connections to each level of the circuitry as needed.


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


The and bottom sides of any type of circuit board.




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

Pattern Plating:

The selective plating of a conductive pattern.

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.

Photo Print:

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


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

Plated Through-Hole:

A hole with plating on its walls that makes an electrical connection between conductive layers, external layers, or both of a printed board.


A flat plate of metal within the lamination press in between which stacks are placed during pressing.

Plating Void:

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


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


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


The process by which a combination of heat and pressure are applied to a book, thereby producing fully cured laminated sheets.

Printed Board:

The general term for completely processed printed circuit or printed wiring configurations. It includes single, double-sided, and multi-layer boards, both rigid and flexible.

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 Wiring Board:

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


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

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. Also called soldermask or mask.


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


A machine that cuts away portions of the laminate to form the desired shape and size of the printed circuit board.


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:

A process for transferring an image to a surface by forcing suitable media through a stencil screen with a squeegee.

Single-Sided Board:

A printed board with conductive pattern on one side only.

Soldermask Over Bare Copper (SMOBC):

A 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 pads.

Surface Mount Technology (SMT):

Defines the entire body of processes and components that create printed circuit board assemblies with leadless components.


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).


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


A method by which successive exposures to a single image are made to produce a multiple image production master.


The process by which imaging material (resist) is chemically removed from a panel during fabrication.


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

Test Coupon:

A portion of a printed board or of a panel containing printed coupons used to determine the acceptability of such a board.


Glass transition temperature. The point at which rising temperatures cause the solid base laminate to start to exhibit soft, plastic-like symptoms. This is expressed in degrees Celsius (°C).

Tooling Holes:

The general term for holes placed on a PCB or a panel of PCBs for registration and hold-down purposes during the manufacturing process.


Component Side.


A common term for conductor.


The list of instructions describing the board, including any specific processing requirements. Also called a shop traveler, routing sheet, job order, or production order.


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


Underwriters Laboratories, Inc., an independent product safety testing and certification organization.

Underwriters Symbol:

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


A plated through-hole that is used as an interlayer connection but does not have component lead or other reinforcing material inserted in it.


The absence of any substances in a localized area.

Wave Soldering:

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

X Axis:

The horizontal or left-to-right direction in a two dimensional system or coordinates.

Y Axis:

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

Z Axis:

Perpendicular to the plane formed by the X and the Y datum reference.

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