Air Gap	The nonconductive air space between traces, pads, conductive matter, or any combination thereof.
Analog Circuit	A circuit comprised mostly of discrete components (resistors, capacitors, transistors), which produces data represented by physical variables such as voltage, resistance, etc.
Annular Ring	The width of the conductor surrounding a hole through a Printed Circuit Pad.
Aperture	Used in photo plotting. Defines the shapes and sizes of Gerber file entities.
Artwork - Taped	An accurately scaled configuration used to produce a Master Pattern. Generally prepared at an enlarged scale using various width tapes and special shapes to represent conductors.
Artwork - CAD	Computer generated accuracy in layout used to produce a Master Pattern. Generally prepared at 1:1 scale using various software packages with special libraries of shapes to represent conductors and components and various Surface Mount Arrays.
Assembly drawing	A drawing that shows all parts identified by their reference designator (C1, R1, U1, etc. like the silk-screened artwork), panel outline with datum and tooling hole positions. If auto-insertion is required, a list of X, Y coordinates of the parts may be helpful.
AWG	American Wire Gage. A method of specifying wire diameter. The higher the number, the smaller the diameter.
Axial Leads	Leads coming out of the ends and along the axis of a resistor, capacitor, or other axial part, rather than out the side.
"Bare" PCBs	Refers to the PCBs without any solder mask or legend on it.
Beveling	Refers to the 45-degree angle that makes finger contact edges smooth, thus enabling easier insertion by the consumer.
BGA	Ball Grid Array is a leadless SMD developed in recent years. Unlike traditional SMDs, this type of device does not have pin leads. Instead it contains solder balls at the bottom of the device. These solder balls melt and make contact to the pattern on boards during assembly.
BOM	Bill of Material. A component list with reference designators, part numbers, values, tolerance, description, and other information.
Break-away	A common PCB panel format with board units connected to a panel by number of tabs around the units. Units break-away from panel after assembly. Panel profiling of this format may be routed or punched.
Bridging	A condition that generally happens during the wave soldering operation where excess solder builds up and shorts out the adjacent conductors.
Bus	A Heavy trace or conductive metal strip on the Printed Circuit Board used to distribute voltage, grounds, etc., to smaller branch traces.
Bypass Capacitor	A capacitor used for providing a comparatively low impedance AC path around a circuit element.
CEM1 or CEM3	PCB material, both CEM-1 and CEM-3 are epoxy/fiberglass over a paper core, differing only in the type of paper used. These materials are less expensive and more punchable substitutes for FR-4. Not a military grade material.
Clearance	Separation between circuit entities. Generally refer to pad-pad, pad-trace, trace-trace, solder mask-pad, pad-drill, circuit-board edge, etc. These clearances are critical for board manufacturability and they should be set at a maximum when design allows.
Conformal Coat	A coating that is generally sprayed, dipped, or brushed on to provide the completed Printed Circuit Board protection from fungus, moisture and debris.
Copper pouring or copper hatch	CAD/CAM terms. Refers to filling of an enclosed area (generally defined by 0-width polygon lines) with a solid or hatch pattern to create a copper plane or a section of copper plane.
Copper thickness and copper plating	Cooper thickness usually specified in terms of number of oz/sq.ft (1/2 oz: 17.5um or 0.0007"/sq. ft; 1 oz: 35 um or 0.0014"/sq. ft, and etc.). The thickness of copper specified will be the final thickness of base material plus copper plating thickness. Generally base material comes with 1/4, 1/2, 1, and 2 oz, but finish copper thickness range from 1/2 to 4 or 5 oz.
Connector Tongue	A protrusion of the Printed Circuit Board edge that is manufactured to a configuration to mate with a receptacle that provides electrical and/or mechanical junction between the Printed Circuit Board and other circuitry.
Cut-and-clinch	Clinch is an operation where leads are bent at an angle after auto insertion to avoid component pop-up during wave-soldering.
Cut-outs	Removal of an internal area of the board.
Digital Circuit	A circuit comprised of mostly integrated circuits, which operates like a switch (i.e., it is either "ON" or "OFF").
Discrete Component	A component that has been fabricated prior to its installation (i.e., resistors, capacitors, diodes and transistors).
D-Code	Used in photoplotting. D-Code assignment or aperture lists are used in defining shapes and sizes of Gerber file entities.
Drill file	An NC file containing tool and coordinate information for drilling. Common format accepted are: EIA or Excellon in either binary or ASCII text file.
DXF format	Data exchange Format, commonly use in mechanical CAD systems.
Electrical test	Electrical test or bare board test refer to PCB short/open test.
Electro-less gold plating	A gold plating process as a substitution of regular Tin/Lead plating. This type of plating applies a layer of thin gold (a fraction of micro-inches) to the entire circuit.
ERC	Electrical Rule Check verifies design violation against pre-set parameters such as In/Out matching in schematic capture, or spacing rules in CAD/CAM systems.
Fabrication drawing	A drawing required for manufacturing. For circuit board fabrication, also referred to as drill drawing. A fabrication drawing should include: board outline and cut-outs with datum and proper dimensions; sizes and locations of all tooling holes, mounting holes and slots; drill pattern and symbols; a drill table with tool assignment and hole specs such as size/qty/tolerance/plating; material and finish specifications; part number and drawing number (if applicable) with revision; for multi-layer the layer stack; for finger contact the beveling specs.; finally, any notes needed to clarify requirements.
Feed-Thru (VIA)	A plated through hole in a Printed Circuit Board that is used to provide electrical connection between a trace on one side of the Printed Circuit Board to a trace on the other side. Since it is not used to mount component leads, it is generally a small hole and pad diameter.
Fiducial mark	Fiducial marks are dots etched on board panel usually required by SMD assembly (provide viewing targets for camera to locate correct position).
Flow Soldering	Also called wave soldering. A method of soldering Printed Circuit Boards by moving them over a flowing wave of molten solder in a solder bath.
Flux	A preserve agent for soldering. Old types of flux require cleaning process after soldering. There is no-cleaning-flux available now and it is safe for both circuitry and environment.
FR4	General-purpose epoxy/fiberglass woven fabric PCB base material. FR-4 is similar to G-10, but fire retardant. FR-4 is sometimes referred to as G10FR.
Functional Test	A test to verify a product's behavior after components are mounted on board. The test is performed according to a customer's specification and parameters provided.
G-10	General-purpose epoxy/fiberglass woven fabric PCB material. Most vendors do not stock this material; instead, they use high-grade material like FR-4 as a substitution if you specify G-10.
Gen-CAM	A CAD/CAM data exchange format developed by IPC.
Gerber File	A widely accepted file format for photo plotting and is input to generate many formats of testing program and component placement program. There are two variants in Gerber file format: 274-D and 274-X (also called the extended Gerber or Gerber-X, with embedded aperture shape and sizes). PCB FAB EXPRESS accepts Gerber 274-X format only.
Glass Epoxy	A material used to fabricate Printed Circuit Boards. The base material (fiberglass) is impregnated with epoxy filler which then must have copper laminated to its outer surface to form the material required to manufacture Printed Circuit Boards.
Gold/Nickel plating	Generally required for contact fingers. Common specifications for this plating are: 0.00002" gold over 0.00015" nickel.
Grid	A two-dimensional network consisting of a set of equally spaced parallel lines superimposed upon another set of equally spaced parallel lines so that the lines of one set are perpendicular to the lines of the other.
Ground Plane	A condition where all unused areas (areas not consumed by traces or pads) of the Printed Circuit Board are left unetched and tied to the ground circuit throughout the board.
GX/GI	Teflon resin over woven fiberglass PCB material. Used for circuits requiring very low dielectric constants.
HAL	Hot Air Leveling, uses in conjunction with SMOBC (solder mask over bare copper), plates solder on component pads only (instead of Tin-plated traces and pad surface). Boards made to H.A.L have two advantages. First is the elimination of wrinkle effect on board surface after wave soldering (specially large copper presents). The second advantage is its ability to handle SMD assembly.
HPGL format	HPGL is a pen-plot format file generated from almost all CAD systems.
Impedance control	Impedance control refers to a dual process of designing and manufacturing of high speed circuit boards. As the frequency of a circuit goes up to a certain point (a few hundred Mega Hz), circuit traces will act as transmission lines and require impedance matching. With circuit of this type, trace characteristics are the function of its geometry and have to be calculated with other parameters such as material dielectric constant, board thickness and type of transmission lines; then proper trace width can be determined. Manufacturing of this circuit type requires tight control of circuit trace width.
In-circuit test	A test to verify components' behavior after they have been mounted on a board.
IPC-A-600	An industrial grade quality standard for acceptance of PCBs.
IPC-D-356	A CAD/CAM data exchange format developed by IPC. Accepted by some CAM systems for use of photoplotting, electrical testing and other CAM functions.
Land	Land (same as pad), often referred as SMD Lands. SMD lands in most cases are suggested by component manufacturers and generally have standard codes such as 1206, SOT-23, SOIC14, etc. Consult component manufacturers or refer to IPC docs: ANSI/IPC-SM-782 for more information.
Legend	Text added to the finished boards using ink. See Silk-Screen.
Library	A collection of part information including symbol, foot-print, pad-stack and other cross reference information. Used in CAD/CAM EDA tools.
LPI	Liquid Photo-Imageable solder mask, as compared to traditional screen wet mask, has an advantage due to its precision. LPI generally has tighter registration tolerance
Manufacturability	A term defining the ability of a board design to meet manufacturing requirements.
Mask	See "solder mask".
Master Pattern	An accurately scaled pattern, which is used to produce the Printed Circuit within the accuracy specified in the Master Drawing.
MIL-P-55110C	A military grade quality standard for acceptance of PCBs.
MIL-STD-275E	A military grade quality standard for design layout of PCBs
Mils	The units used in describing trace width, line space, via size etc. One mil equals one-thousandth of an inch (1 Mil = 0.001 inch)
Minimum line space	smallest air gap between copper features.
Multi-layer PCB	PCB layers are referred to as number of sides of copper foil used. A PCB with one side of copper foil is called single-sided, with two sides of foil is called double-sided. PCBs with more than 2 sides of copper are defined as multi-layered, generally 4 layers, 6 layers and up.
Mother Board	Also called the Back Plane, or Matrix Board. A relatively large Printed Circuit Board on which modules, connectors, subassemblies or other Printed Circuit Boards are mounted and interconnections made by means of traces on the board.
Net-list	An ASCII list describes logical connections between component pins. Generated from schematic capture systems for transferring logical connections to layout systems. Other net-lists are generated from CAD/CAM systems for board test and in-circuit test purposes.
Non-plated-through	A type of hole on a circuit board generally used as mounting holes for the board. The wall of these holes/slots are not plated thus no connection between layers.
Pad	Pad refers to copper contact for component lead, common shapes accepted are round, square, rectangular, ob-round, and heat-relieved.
Padstack	In CAD layout EDA systems, padstack is a collection of pad shape and size information
Plating	A uniform coating of conductive material upon the base metal of the Printed Circuit Board.
Plated Holes (Plated Through Holes)	Holes with plating in them to conduct electricity, as opposed to Non-Plated through holes which do not have plating in them. Plated holes are used to connect traces across the different layers in the PCB.
Panelization	A general term in CAM editing used to prepare data in panel format. PC-103 or PC-104: A common type of solder mask, which has a shiny lighter finish than SR-1000. Generally available colors are green, blue, red, white and black.
Photoplotting or photoplot	Photoplotting is an electronic optical process to scan rasterized image data on films. Sometimes referred to as laser plotting. A photoplot is a film generated by a photoplotter, or referred to as artwork required for PCB fabrication.
Plated-through	A type of hole on a circuit board generally used to mount components and to create vias. The wall of these holes/slots is plated forming a circuit between layers.
Push-back	A PCB panel format with board units punched out from the panel then reset back into the same location by second operation.
Radial Lead	A lead extending out the side of a component, rather than from the end. Reference designator: Component ID used in schematic and PCB design, such as C1, C2, R1, R2, etc.
Registration	The alignment of a pad on one side of the Printed Circuit Board (or layers of a multilayer board) to its mating pad on the opposite side.
Route and Retain	Internal routing such that PCBs remain intact on the panel for easy assembly. Later these boards are "snapped apart".
Routing	In a PCB CAD layout application, routing refers to making manual/automatic-wiring connections to logical nodes in a net. In PCB fabrication, routing refers to board edges profiling by running an NC program.
Scoring	see V-scoring
Sequencing	An assembly term referring to arrangement of axial/radial components in their order of insertion sequence, and to prepare a new tape/reel by a sequencer.
Silk-screen	A legend printing, or the legend of circuit boards, generally white lettering. Also known as Legend or Nomenclature.
Solder mask (soldermask)	A non-conductive surface screened or laminated on the PCB to protect the circuit from oxidation, and shorts during wave-soldering. Common solder mask types are: SR-1000, PC-103/4, LPI.
Solder paste	Form of solder to be printed on SMD pads by using a stencil in assembly.
Space	See Air gap.
SMOBC	Solder Mask Over Bare Copper, used in conjunction with HAL (hot air leveling), denotes solder mask applied to bare copper (instead of to Tin-plated surface). Boards made using SMOBC have two advantages. First, the elimination of wrinkle effects on board surface after wave-soldering (especially large copper areas); the second advantage is the board's ability to handle SMD assembly.
SMT pitch	distance between same points on adjacent SMD pads.
Span	Refers to the center-to-center lead spacing of axial and radial components.
SR-1000	A common type of solder mask, with a darker mat finish than PC-103/4. Generally available colors are green, blue, red, white and black.
Stencil	Stencil is a cooper foil screen with SMD pads etched openings used for solder paste printing in assembly.
Step/repeat	A general term in phototooling referring to an image unit, which is stepped and repeated into multiple image units.
Testability	This term defines the ability of meeting electrical requirements.
Thermal relief or heat relief	A thermal relief or heat relief is a type of circuit pad used at a location where there is a component pin or fan-out via that connects to a copper plane. The purpose of using a thermal relief pad is to provide a connection while dissipating heat through the big copper plane.
Through hole	A type of hole on a circuit board generally used for component pins and vias. The wall of these holes/slots are plated creating a circuit between layers where required.
Tin-lead/reflow	The most commonly used solder plating process in the PCB industry. The process applies 0.0004"(min.) to 0.0008"(max.) of Sn/Pb on all conductive areas. However, Tin-lead plating may not be a suitable a process if you have SMD on the board.
Tooling Hole	Also called Fabrication Hole, Pilot Hole, or Manufacturing Hole.
UL	Underwriters Laboratories, a recognized agent to test and approve electronic processes for meeting the standards set by the organization. Most PCB vendors are UL approved, but not many of them will print a UL logo on your boards. Instead, vendors print their granted code that meets the type of process used, with 94 V-0 or 94 V-1 if boards meet these fire resistance ratings.
V-scoring (Scoring)	A board profiling process that involves cutting straight lines from both sides of board. This profiling method is more time efficient than a traditional routing process, suitable for medium to large volume production with panels requiring only straight line cuts. With this process, no space is needed between units.
Via	Interconnection between circuit layers. Common type of via connects traces on all layers, blind via or buried via are connected to defined layers only.
Warping	Warping generally refers to finished board warp and twist. All boards may have a certain degree of warp as a result of manufacturing, especially if materials contain a high volume of moisture. Therefore you should specify your warping tolerance.
Wave-soldering	A machine soldering process involving pre-heat, fluxing, soldering, and cleaning. Most commonly used solder composition is 63%Sn/ 37%Pb.
Wet mask	General type of solder mask applied by screen. Usually refers to types of solder mask like SR-1000 and PC-103/4. LPI is NOT a type of wet mask.
Zero width	Zero width represents an outline shape drawn by "0" thickness line width. The most commonly used definition is the polygon to draw copper fill, or shapes defining the drawing limit of an entity.