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Glossary of terms

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Term Definition
G10   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.
gas-tight joint   The joint between male and female contacts, or a termination to a cable, which excludes air. This results in the connector maintaining good electrical continuity even under severe industrial atmospheric conditions.
Gb   for gigabyte (not gb or GB)
geometric dimensioning   A method that defines the location and associated tolerances of a mechanical feature in terms of its allowable position with relation to its theoretical (true) position.
Gerber data (Gerber file)   Named after Gerber Scientific Co., who made the original vector photoplotter. A data format that converts physical feature information (location, shape etc.) into data used to control a numerically controlled photoplotter that produces printed circuit artwork.
GI   The woven glass fiber laminate impregnated with polyimide resin.
glass decomposition temperature   (Td). Pronounced “T sub d”.
glass transition temperature   (Tg). Pronounced “T sub g”. The temperature at which a polymer changes from a hard and relatively brittle condition to a viscous or rubber condition. This transition generally occurs over a relatively narrow temperature range. Although there is no phase transition, in this temperature region many physical properties (such as hardness, brittleness, thermal expansion and specific heat) undergo significant and rapid changes. Glass transition temperature is also used as a shorthand way of indicating the temperature at which the mechanical and electrical properties of a laminate begin to degrade
glob top   A blob of non-conductive plastic, often black in colour, which protects the chip and wire bonds on some kinds of packages, particularly Chip-On-Board constructions. This specialized plastic has a low coefficient of thermal expansion so that ambient temperature changes will not rip loose the wire bonds it is designed to protect.
gold finger   A portion of a conductive pattern (usually gold plated) on or near any edge of a printed board that is intended for mating with an edge board connector. Also see printed contact.
gold plate removal   Thick gold plating is sometimes applied to leads as a protective measure, usually as a throwback to earlier Military Specification requirements. Unfortunately, tin and gold can form a brittle intermetallic interface, which will eventually cause the joint to fail – in fact, it is not unknown for gold-plated wires apparently firmly fixed in a solid joint to be able to pulled straight out of the joint! In order to get round this problem, the gold plating is usually stripped before assembly by a process of double dipping to ensure no possible build-up of gold
gold(en) board   A raw PCB, component or assembly already tested as functional to spec and used, via comparisons, to test similar units. Also referred to as a ‘known good board’.
granular solder   Solder appearance with a coarse, large grain structure, lacking in metallic lustre. Usually due to unclean conditions of the joining members, contaminated solder, or excessively high temperature of the molten solder. (Similar to cold solder)
grid origin   See datum intersection (origin).
gridless (shape-based) router   The type of CAD autorouting program that has the flexibility to find paths for conductors based on the shape of surrounding geometric features (such as conductor widths and spacings), instead of being restricted to a predefined grid.
ground   A common reference point for electrical circuits returns, shielding or heat sinking.
ground plane   A conductor layer that covers all or a large portion of a board (with suitable clearances around through-holes and vias), and which is used as a common reference point for circuit returns, shielding or heat sinks. The similar power plane distributes power to circuitry on the board. Both ground and power planes may also be used as an electromagnetic shield and as a reference plane for high-frequency (stripline) circuitry.
Grounding   As used by the connector industry, sending current flow to earth in the case of a short circuit.
gull-wing   A lead configuration typically used on small outline packages where the leads extend horizontally out of the package for a short distance, then drop to the pad level, then extend horizontally again away from the component to make attachment surfaces that rest on the pads. An end view of the package resembles a gull in flight.