Monday, March 16, 2009

PCB Glossary : A to C

Check out The printed circuit board industry is full of specific terminology and acronyms. To assist you in designing and ordering your circuit board, we’ve put together the following list of common terms:

Annular Ring:
That portion of conductive material completely surrounding a hole.

Aperture Information:
This is a text file describing the size and shape of each element on the board. These are also known as D-code lists. These lists are not necessary if your files are saved as Extended Gerber with embedded Apertures (RS274X).

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 that embodies the image of the PCB pattern, usually on a 1:1 scale.

Aspect Ratio:
A ratio of the PCB thickness to the diameter of the smallest hole.

Automated Optical Inspection (AOI):
Visual inspection of the circuit boards using a machine scanner to assess workmanship quality.

Automatic Test Equipment (ATE):
Equipment that automatically analyzes functional or static parameters in order to evaluate performance.

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, and on inner layers.

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).

An angled edge of a printed board.

Blind Via:
A conductive surface hole that connects an outer layer with an inner layer of a multi-layer 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.

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

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.

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.

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

See Computer-Aided Design.

See Computer-Aided Manufacturing.

A broken corner to eliminate an otherwise sharp edge.

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.

A room in which the concentration or airborne particles is controlled to specified limits.

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.

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.

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