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Glossary of Terms
Underwriters Laboratories (UL) is a non-profit organization to perform product testing for manufacturers to meet stringent safety standards.
There are 3 strictly defined terms, namely Listing, Recognition and Classification.
The UL Listing is for a complete product. The famous UL logo with a circle bears the common symbol for most electrical products we purchased everyday.
Recognition is for electrical components and products not complete in themselves, but used in making a complete product or system. Printed Circuit boards comes under such category. A UL Recognized components lends itself more credibility when a finished complete systems is submitted to seeks approval for UL listing or classification.
UL Classification generally applies only to commercial or industrial productions what the UL tests for conformance with specific published standards or regulatory codes. A UL classified device bears no specific symbol.
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Annular Ring: That portion of conductive material completely surrounding a hole.
Array: A group of elements or circuits (or circuit boards) arranged in rows and columns on a base material.
Artwork: An accurately scaled configuration used to produce the artwork master or production master.
Assembly: A number of parts, subassemblies, or any combination thereof joined together.
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 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.
Burr:
A ridge left on the outside copper surface after drilling.
CAD: See Computer-Aided Design.
CAM: See Computer-Aided Manufacturing.
Circuit: The interconnection of a number of devices in one or more closed paths to perform a desired electrical or electronic function.
Circuitry Layer: A layer of a printed board containing conductors, including ground and voltage planes.
Component: An electronic device, typically a resistor, capacitor, inductor, or integrated circuit (IC), that is mounted to the circuit board and performs a specific electrical function.
Component Hole: A hole used for the attachment and electrical connection of a component termination, such as a pin or wire to the circuit board.
Component Side: The side of the circuit board on which most of the components will be located. Also called the “top side.”
Computer-Aided Design (CAD): A software program 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.
Deburring: Process of removing burrs after drilling.
Defect: Any nonconformance to specified requirements by a unit or product.
Definition: The fidelity of reproduction of pattern edges, especially in a printed circuit relative to the original master pattern.
Double-Sided Board: A printed board with a conductive pattern on both sides.
Drilling: The act of forming holes (vias) 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).
Electroplating: The electrodeposition 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.
Etching:
The chemical, or chemical and electrolytic, removal of unwanted portions
of conductive materials.
FR-1: A paper material with a phenolic resin binder. FR-1 has a Tg of about 130°C.
FR-2: A paper material with phenolic resin binder similar to FR-1 but with a Tg of about 105°C.
FR-3: 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.
FR-4: 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.
Gerber: A software format used by the photoplotter to describe the printed circuit board design.
Golden Board: See 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
HDI (High Density Interconnect): Ultra fine-geometry multi-layer PCB constructed with conductive microvia connections. These boards also usually include buried and/or blind vias and are made by sequential lamination.
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.
Imaging: 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.
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.
Laminate: 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.
Land: The portion of the conductive pattern on printed circuits designated for the mounting or attachment of components. Also called a pad.
Legend: 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 sprayed on using photographic imaging techniques to control deposition.
Line: See Conductor.
Lot: 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.
Mask: A material applied to enable selective etching, plating, or the application of solder to a PCB. Also called soldermask or resist.
Minor Defect: A defect that is not likely to result in the failure of a unit of 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
Nomenclature: Identification symbols applied to the board by means of screen printing, inkjetting, or laser processes. See Legend.
Outer-layer: The top and bottom sides of any type of circuit board.
Pad: See Land.
Panel: A rectangular sheet of base material or metal-clad material of predetermined size that is used for the processing of printed boards and, when required, one or more test coupons.
Pattern: The configuration of conductive and nonconductive materials on a panel or printed board. Also, the circuit configuration on related tools, drawing, and masters.
Photographic Image: An image in a photo mask or in an emulsion that is on a film or plate.
Photoplotting: 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.
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.
Plotting: The mechanical converting of X-Y positional information into a visual pattern such as artwork.
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.)
Reflow: The melting of electrodeposited tin/lead followed by solidification. The surface has the appearance and physical characteristics of being hot-dipped.
Registration: 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.
Resist: 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.
Rigid-flex: 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.
Router:
A machine that cuts away portions of the laminate to form the desired
shape and size of the printed board.
Scoring: 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.
SMOBC: See Soldermask Over Bare Copper
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.
Solder: 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 Leveling: The process by which the board is exposed to hot oil or hot air to remove any excess solder from holes and lands.
Soldermask: 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.
Step-and-Repeat: A method by which successive exposures to a single image are made to produce a multiple image production master.
Stripping: The process by which imaging material (resist) is chemically removed from a panel during fabrication.
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.
Top Side: See Component Side.
Trace:
A common term for conductor.
UL: 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).
UV Curing: Polymerizing, hardening, or cross linking a low molecular weight resinous material in a wet coating ink using ultra violet light as an energy source.
Via: A plated through-hole that is used as an interlayer connection but does not have component lead or other reinforcing material inserted in it.
Void: 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.
WIP: An acronym for work in progress.
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Source: Excerpts fromDan Beaulieu, 2003. Printed Circuit Board Basics.
UP Media Group Inc.: Atlanta, Georgia.