> ## EDA Terms and Definitions

> Annular ring

> A circular strip of conductive material that remains after a hole has been drilled through the pad of a printed circuit board.

> Anti-copper

> An area within a fill zone in which copper cannot be placed.

> Aperture

> An opening, similar to the aperture of a camera, that is used for photo-plotting. Apertures are available in various sizes and shapes.

> Aperture list

> A text file containing the dimensions for each of the apertures used to photo-plot PCB artwork.

> Clusters

> Components that are grouped according to their interrelationships and placed in close proximity on the board. This keeps the connections on the PCB short so that the board is easier to work with.

> Component

> An element or a part of a PCB.

> Component density

> The quantity of components on a unit area of a PCB.

> Component hole

> A hole in the printed circuit board that corresponds to a pin or wire of a component. This hole serves the dual function of attaching the component to the board and establishing the electrical connection between the pin or wire and the remainder of the board circuitry.

> Component library

> A computer data file that contains the footprint patterns for a number of components.

> Component side

> The uppermost or top layer of a board on which most components are placed.

> Component silkscreen

> The silkscreen markings of the printed circuit board that appear on the component side. The silkscreen is applied over the solder mask.

> Component solder mask

> The colored, usually translucent, coating applied to the board over the etched copper. It protects the selected areas from the soldering process.

> Connection

> An unrouted, partially routed, or completely routed path between two pads. In a net with n pads, there are exactly n–1 connections.

> Copper pour

> A method by which a copper zone is filled with a specified pattern, with objects that cross the zone or lie within the zone being avoided.

> Copper zone

> An area on a board designed to be covered by a layer of copper when manufactured. Also known as a "metal zone".

> Cross hatching

> The breaking up of large conductive areas by the use of a pattern of lines and spaces in the conductive material.

> Datum

> A specific location (a point) that serves as a reference to locate a PCB pattern or layer for manufacture.

> Density

> On a PCB, the degree to which components are packed on the board. Generally, the density is given as the number of square inches per equivalent, i.e., a lower number indicates a more dense board.

> Discrete components

> Components with three or fewer electrical connections (for example, resistors or capacitors).

> Electrical check

> The process of checking the PCB to ensure that the connections they are on match those specified in the net list.

> Fill zone

> A zone that defines an area to be filled with copper.

> Fine pitch

> A class of surface-mount components that is characterized by pins measuring 0.025 inches or less from pad center to pad center.

> Footprint

> The physical description of a component. It consists of three elements: padstacks, representing the pads of the component; obstacles, representing among other things, the physical outline of the component, silkscreens, keepouts/keepins, and assembly drawing data; and text documenting the footprint information (for example, the component name). You may want each project to have its own footprint library containing all the footprints used in that project.

> Ground plane

> A large area on the PCB, usually an entire layer, that provides a common ground connection for all component ground pins and other ground connections.

> Heatsink

> A mechanical device made of a high thermal conductivity material that dissipates heat generated by a component or assembly.

> Heuristics

> A method of routing that consists of repeated attempts to apply very simple routing patterns to unrouted connections in order to complete the routing quickly and cleanly. Typically, heuristics are used for memory and short point-to-point routing.

> Hole

> The area where board material must be removed by drilling or milling.

> Isolation

> The clearance around a pad, track, zone, or via that defines the nearest approach allowed by conductors of another signal set.

> Jumper wire

> A discrete electrical component or wire used to make electrical connections between points that have no copper etch due to board density or some other factor.

> Keepout

> An area fill within which no routing is allowed.

> Land

> The copper pad needed for a surface mount pin.

> Layer

> One in a series of planes in a PCB design on which tracks are arranged to connect components. Vias connect tracks and zones between layers.

> Manual routing

> Individual connections, in the form of traces, vertices, arcs, and so on, which are entered manually into the PCB design.

> Mounting hole

> A hole used for the mechanical support of a PCB or for the mechanical attachment of components to a PCB.

> Multi-layer board

> A PCB that has multiple layers, separated by dielectric material, with connectivity between layers established by vias or through-holes. This term usually refers to a board with more than two layers.

> Net

> A logical construct (circuit) that originates in a schematic and is transferred to a board to describe required electrical connections. The connections may be completed by using vias, tracks, or zones.

> Net list

> List of names of symbols or parts and their connection points which are logically connected in each net of a circuit. A net list can be extracted electronically on a computer from a properly prepared schematic.

> Obstacle

> An outline representing an object on the board. It must be taken into account during routing, placement, or copper pour.

> Pad

> On a PCB, a copper shape on one or more layers (there may be a hole and an isolation surrounding the copper) used for connecting a component pin to the PCB. The pad indicates where pins of a component are placed.

> Padstack

> A numbered list of pad descriptions. Each description contains a pad definition, including layer, style, drill diameter, size, offset, and solder mask guard width.

> PCB - Printed Circuit Board

> A PCB is a board made up of components affixed to a common surface and connected by copper tracks.

> Pin

> The portion of a component to which an electrical connection can be made.

> Ratsnest

> A number of unrouted straight-line connections between two or more pads that represent the electrical connections in the netlist. The ratsnest serves as a reminder that the pads must be connected, and that, currently, there is no track on the board to make that connection.

> Reference designator

> A character string denoting the type of component and a number that is specific to that component.

> Routing

> Placing conductive interconnects between components on a PCB layout. The process of turning nets into tracks.

> Schematic

> A graphical description of an electrical circuit.

> Segment

> The partial track that exists between two adjacent vertices or between a vertex and a pin. Sometimes the track between two pins is also called a segment, although connection is usually the more appropriate term here.

> Signal

> An electrical impulse of a predetermined voltage, current, polarity, and pulse width.

> Silkscreen

> Text or outlines (in ink) on the solder mask, on the top, and sometimes on the bottom of board modules. A silkscreen is used for component and identification placement on a PCB and usually includes component outlines, reference designators, polarity indicators, pin one markings, part numbers, the company name, and copyright info.

> SMT - Surface Mount Technology

> PCB technology whereby the leads on the chips and components are soldered onto the surface of the board rather than inserted into it. The use of SMT results in smaller and faster printed circuit boards.

> Solder mask

> A negative plot of pads with a guard band around the pads. Also, a lacquer applied to prevent solder from adhering to unwanted areas on the PCB.

> Solder paste

> A pattern that serves as a template for solder paste application when the board is manufactured.

> Solder side

> The PCB surface opposite the one on which most components are mounted (component side). Also, the bottom layer of the board.

> Test point

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

> Through-hole via

> A via that connects the surface layers on a PCB.

> Trace (Track)

> The copper trails (electrical connection between two or more points) on the PCB and the onscreen representation of that copper.

> Venting patterns

> Patterns etched in the board that allow gases formed during fabrication to escape.

> Vertex

> A logical point at which a track is ended and restarted. A vertex is located at each change of direction on the track.

> Via (feed-through hole)

> A hole connecting layers of a PCB. A through-hole via connects the surface layers of a board. On multilayer boards, a via not reaching a surface layer on one side is called a blind via, and a via not reaching a surface layer on either side, thus being externally invisible, is called a buried via.

> Viastack

> A numbered list of via descriptions. Each description contains a via definition, including layer, style, drill diameter, size, offset, and solder mask guard width.

> Via stringer

> The copper etch that exists between a SMT pad and a corresponding fanout via.

> Zero-length connection

> An unrouted connection between layers where the end points in the connection have the same X- and Y- coordinates.

> Zone

> An area on a PCB layer designated as copper or anti-copper. Copper zones may have net names, while anti-copper zones may not.

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