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Printed Circuit Boards (PCB) Glossary

A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z  

A

Active Component: A component that depends on its external power source to activate its inputs. Examples of active devices include, silicon controlled rectifiers, transistors, valves, etc. Also, the active components can be referred to as ones that don’t include capacitor, resistor, and inductor.

Activating: This is a chemical treatment method employed to improve receptiveness of non-conductive laminates. Conductive material is deposited onto clad or unclad base material. This method is also known as seeding, catalyzing, and sensitizing.

Additive Process: As the name suggests, this process is employed in multi-layer boards for plating-through (non-conductive) holes to create vias.

AIN: AIN is aluminum nitride, which is a compound of nitrogen and aluminum.

AIN Substrate: This is an aluminum nitride substrate. 

Alumina: Alumina is a type of ceramic that is used as a substrate in thin film circuit or insulator in electron tubes. Alumina can withstand low dielectric loss over a wide range of frequencies, as well as extreme temperatures.

Ambient: It refers to a surrounding environment that comes in contact with the component or system under consideration.

Analog Circuit: In this circuit, the output signals vary as the continuous function of the input.

Annular Ring: Annular ring is a circular pad made from conductive material, which surrounds a hole.

Anode: Anode is a positive element in the plating tank. It is connected to the positive potential. Anodes are used to accelerate the movement of metal ions towards the panel of the circuit board being plated.

Anti-Solder Ball: It is a major technique employed during Surface Mount Technology (SMT) to limit the amount of tin that passes through the stencil.

Anti-Tarnish: This is a chemical process conducted post dip to reduce oxidation of copper circuits.

Any layer inner via Hole: Abbreviated as ALIVH, this technology is used for building multilayer PCB without a core. For PCBs using ALIVH, electrical connection is established between layers through soldering rather than vias or core board. This method is employed to produce BUM PCBs with inter connecting inner layers in extremely high density.

Aperture: This is an indexed shape with specific length and width dimensions. The index of the aperture is usually its D code. This is used as a basic element in plotting geometric elements on a film.

Aperture Wheel: A vector photoplotter metal disk component with screw holes and cutouts with brackets that are placed near rims for aperture attachment.

Aperture Information: The text file featuring the shape and size of each board element. It is also referred to as D: code list.

Aperture List/Aperture Table: This is an ASCII text data file comprising information regarding the apertures used by a photoplotter for any one photoplot. In short, this list comprises the size and shape of D codes.

Acceptance Quality Level (AQL): AQL is the maximum permissible, and tolerable level of defects in a lot. This is normally associated with statistically derived parts sampling. 

Array: Array refers to the group of circuits that are arranged in a certain pattern.

Array Up: These are individual PCBs available in the array configuration.

Array X Dimension: The extreme array measurement along the X axis, including borders or rails is termed as array X dimension. It is measured in inches.

Array Y Dimension: The extreme array measurement along the Y axis is termed as array Y dimension. This includes rails or borders, and is measured in inches.

Artwork: This refers to the photo plotted film in 1:1 pattern, and is used to create the Diazo production master.

Artwork Master: This is a photographic image of the PCB design on a film, which is used to build a printed circuit board.

AS9100: It is a quality management system that incorporates industry requirements, as well as ISO- 9001:2008 standards. This system is developed for defense, aviation, and aerospace industries.

ASCII: It stands for American Standard Code for Information Interchange. This is also referred to as “asskey”. These character sets are present in most of the modern day computers. US ASCII uses the lower seven bits to convey space, control codes, space numbers, punctuations, as well unaccented numbers a-z and A-Z. However, the newer codes use more bits in a RS 274x format for an object definition.

ASCII Text: It is a subset of US-ASCII. This unofficial subset features numbers, characters, punctuation, and unaccented letters A-Z and a-z. This subset contains no control codes.

Aspect Ratio: It is the ratio of the thickness of a smallest drilled hole diameter to the circuit board thickness.

Assembly: The process of soldering and positioning components on PCB, or the process of fitting components on a PCB to make it a whole is termed as assembly.

Assembly Drawing: This is a drawing, which provides location of components, as well as their designators on a printed circuit board.

Assembly House: It is a facility for manufacturing PCBs. Generally, assemblers and contract manufacturers use this term to promote their capabilities.

ASTM: This stands for American Society of Testing and Materials.

ATE: This refers to Automatic Test Equipment (Same as DUT). The ATE automatically tests and analyzes functional parameters to evaluate performance of electronic devices.

Automatic Component Placement: Automated equipment is used for component placement over a PCB. A high-speed component placement machine called chip shooter is used for placing smaller, and lower pin counts. However, complex components with high pin counts are placed by fine pitch machines.

Auto Router: It is an automatic router or a computer program that is used to automatically design or route the traces in a design.

AutoCAD: A computer-aided commercial software, which helps PCB designers to create precise 2D or 3D drawings. Generally, this software is used by silicon chip packaging, and RF designers.

Automatic Optical Inspection (AOI): This is basically video/laser inspection of pads and traces on the inner–layered cores. The machine uses camera to verify copper positioning, shape, and size. This method is used to locate open traces or missing shorts or features.

Automatic X-Ray Component/Pin Inspection: These inspection equipment use X-ray images to check under components or inside the joints to determine integrity of the soldering.

AWG: This stands for American Wire Gauge. A PCB designer needs to know wire gauge diameters to properly design E-pads. The AWG was previously referred to as the Brown and Sharpe (B+S) Gauge, and it was used in the wire designing industry. This gauge is always calculated such that the next large diameter possesses 26% large cross-sectional area.

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B

BareBoard: It is a finished printed circuit board with no mounted components. This is also known as BBT.

Back Drilling: The process of removing the unused via stubs by drilling a hone on one or both the sides of a PCB after plating. Back drilling is generally performed in high speed PCBs to reduce parasitic effects of the stubs of via.

Ball Grid Array (BGA): A chip package comprising internal die terminals that form an array in grid style. These terminals are in contact with solder bumps that carry the electrical connection outside the package. There are various advantages of BGA package, including its compact size, non-damaging leads, and a long shelf life.

Base: The transistor electrode that controls the holes or electron movements through an electric field. The base is always aligned to the control grid of the electron tube.

Base Copper: It is a thin portion of a copper foil lining a copper clad PCB laminate. This base copper can be present on a single or both sides of the PCB or inner layers.

Base Laminate: This is a base substrate on which the conductive pattern is designed. The base laminate material can be flexible or rigid.

Beam Lead: A metal beam that is deposited onto the die surface during the wafer processing cycle in the PCB assembly. When an individual die is separated, the cantilevered beam protrudes from the edge of the chip. This protrusion is used to bond the interconnecting pads on the circuit substrate and reduces the need for individual interconnections

Barrel: It is a cylinder formed by plating a drilled hole. Generally, walls of a drilled hole are plated to make a barrel.

Base Material: The type of insulating material on which the conductive pattern is formed is referred to as base material. This material can be flexible, rigid or a mixture of both. The base material can be an insulated metal sheet or a dielectric.

Base Material Thickness: It is the thickness of the base material excluding material on the surface or metal foil.

Bed of Nails: A text pattern comprising a holder and a frame. The holder features a field of spring loaded pins that make electrical contact with a test object.

Bevel: It is an angled edge of the PCB.

Bill of Materials (BOM): It is a list of components to be included during the printed circuit board assembly. The BOM for a PCB should include reference designators that are used for the components, as well as descriptions identifying each component. A BOM is used with an assembly drawing, or for ordering parts.

Blister: A separation and localized swelling that occurs between the layers of a laminated base material is called blister. This may also occur between a conductive foil and a base material. A blister is a form of delamination.

Blind Via: Blind via is a surface hole that is conductive, as well as connects an outer and an inner layer of a board. This term is used for multilayer PCBs.

Board: An alternate term for printed circuit board. Also, it is used for a CAD database representing the printed circuit board layout.

Board House: It is a term for printed circuit board vendor. Same as Assembly House.

Board Thickness: This is the overall thickness of the base material and the conductive material deposited on a surface. A PCB can be produced in any thickness. However, 0.8mm, 1.6mm, 2.4 and 3.2mm are the common ones.

Body: This is the portion of an electronic component that is exclusive of leads or pins.

Book: The Prepegflies in specified numbers, which are assembled on cores of inner layers while preparing for curing during a lamination process.

Bond Strength: This is defined as a force per unit area that is required to separate two layers that lie adjacent to each other on a printed circuit board. A perpendicular force is used for this separation.

Boundary Scan Test: These are edge connector test systems that use IEEE 1149 standards for describing test functionality that might be integrated in certain components.

Bow: Bow is a term for deviation from flatness of a board that is characterized by a spherical or cylindrical curvature.

Border Area: The external region of the base material that lies outside the end product that is being integrated within is referred to as border area.

Bottom SMD Pads: A number of Surface Mounted Device Pads at the bottom.

B: Stage: An intermediate stage in the PCB assembly, where a thermosetting resin liquefies on heating and swells up. However, it does not entirely dissolve or fuse due to the presence of certain liquids nearby.

B: Stage Material: It is a resin impregnated sheet material that is cured to an intermediate stage. It is commonly referred to as Prepeg.

B: Stage Resin: It is the thermosetting resin that is used during an intermediate curing state.

Buried via: This term is used for via that connects inner layers. Buried via cannot be seen from either sides of the board, and it doesn’t connect outer layers.

Build in Self-Test: This electric testing method is employed for tested devices that want to test their capabilities using an added hardware.

Buildtime: Every company has specified build time. Generally, it starts the following business day after receiving the order unless a hold occurs. 

Burr: It is a ridge that surrounds a hole on the outer copper surface. Generally, a burr is formed after drilling process.

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C

Cable: This is any sort of wire that has the capability to transfer heat or electricity.

CAD (Computer Aided Design): It is a system that allows PCB designers to design and see a PCB prototype on a screen or in the form of a printout. In other words, it is a system that allows PCB designers to create a PCB layout.

CAD CAM: This is a concatenation of the terms – CAM and CAD.

CAE (Computer Assisted Engineering): In PCB engineering, this term is used for various schematic software packages.

CAF (Conductive Anodic Filament) or (Conductive Anodic Filament Growth): This is an electrical short that occurs when a conductive filament grows in the laminate dielectric material between two conductors. This only occurs in adjacent conductors under the conditions like humidity, and DC electrical bias.

CAM (Computer Aided Manufacturing): The use of programs, computer systems, and procedures for establishing interactivity during various phases of manufacturing is termed as CAM. However, the decision making lies with the human operator or the computer that is used for data manipulation.

CAM Files: The term is applied to various data files that are used during the manufacture of printed wiring. The data file types are: Gerber files that are used for photoplotter controlling; NC drill file that is used to control an NC drill machine; and fabrication drawings in HPGL, Gerber, or any reliable electronic format. CAM files are basically the final product of the PCB. These files are provided to the manufacturer who manipulates and refines CAM in their processes.

Capacitance: This is the property of a system of dielectrics and conductors to store electricity, when potential difference exists between different conductors.

Carbon Mask: A type of liquid heat curing carbon paste that is added to the surface of the pad. This paste is conductive in nature. The carbon paste is composed of hardener, synthetic resin, and carbon toner. This mask is usually applied for key, jumper, etc.

Card: An alternative term for printed circuit board.

Card-edge Connector: It is a connector fabricated on the edge of the PCB. Generally, this connector is gold plated.

Catalyst: Catalyst is a chemical that helps initiate or increase the reaction time between a curing agent and a resin.

Ceramic Ball Array (CBGA): A ball grid array package made from ceramic.

Ceramic substrate printed board: The printed circuit board made from any of the three ceramic substrates: aluminum oxide (Al203), aluminum nitride (AIN), and BeO. This circuit board is known for its insulating performance, soft solderability, high thermal conductivity, and high adhesive strength.

Center to Center Spacing: This is a nominal distance between adjacent features on a single layer of a printed circuit board.

Chamfer: It is the process of cutting corners to eliminate a sharp edges.

Characteristic Impedance: This is a measurement of the inductance, resistance, conductance, and capacitance of a transmission line. The impedance is always expressed in the units of ohms. In the printed wiring, this value depends on the thickness and width of the conductor, the dielectric constant of the insulating media, and the distance between the ground plane(s) and conductor.

Chase: An aluminum frame that is used for screening inks on to the printed circuit board surface.

Check Plots: A plotted film or pen plots that are used for checking. Circles are used to represent pads, and rectangular outlines are used for thick traces. This technique is used for improving transparency between multiple layers.

Chip on Board (COB): It refers to a configuration, where a chip is attached to the printed circuit board directly using a solder or conductive adhesives.

Chip: An integrated circuit that is built on a substrate of semiconductor and then etched or cut from a silicon wafer. This is also referred to as die. A chip is incomplete and unusable until it is packaged and offered with external connections. This term is always used for a packaged semiconductor device.

Chip Scale Package: It is a chip package with total package size, which does not exceeds 20% of the size of the die. Eg: Micro BGA.

Circuit: This refers to a number of devices or elements that are interconnected to perform an electrical function in a desirable manner.

Circuit Board: This is a shortened version of PCB.

Circuitry Layer: It is the layer including conductors, including voltage and ground planes.

Clad: It is a copper object on the printed circuit board. Several times certain text items are to be used for a board to be “in clad”, which means text should be made from copper.

Clearances: A term that is used to describe the space from ground layer or power layer to through hole. The power layer and ground layer clearance is kept 0.025″ larger than the finish hole of the inner layers to prevent shorting. This allows for drilling, registration, and plating tolerances.

Clearance Hole: A hole in the conductor that is larger than a hole in the base material of a circuit board. This hole also lies coaxial to the hole in the base material.

CNC (Computer Numerical Control): The system that uses a software and a computer for a numerical control.

Coating: A thin layer of conductive, dielectric, or magnetic material that is deposited on surface of the substrate is termed as coatings.

Coefficient of Thermal Expansion (CTE):  It is the ratio of dimensional change of the object to the original dimension under the influence of temperature. CTE is always expressed in %/ºC or ppm/ºC.

Component: Any basic part used in the PCB.

Component Hole: A hole that is used for establishing an electrical connection of component terminations, including pins and wires on a PCB.

Component Side: This refers to the orientation of printed circuit board. The top layer should read in facing up.

Conductive Pattern: A design of the conductive material on a base material. It includes lands, conductors, vias, passive components and heat sinks.

Conductor Spacing: This is an easily viewable spacing between two adjacent edges of isolated patterns existing in isolated patterns of a conductor layer. The center to center spacing should not be taken into consideration.

Continuity: The continuous path or uninterrupted path for electrical current flow in an electrical circuit.

Conformal Coating: It is a protective and insulating coating that is applied on the completed circuit board. This coating conforms to the configuration of the coated object.

Connectivity: The integrated intelligence of the PCB CAD software that helps to maintain correct connections between component pins as defined in the schematic diagram.

Connector: A receptacle or a plug that can be easily attached or detached from its mate is termed as a connector. In a mechanical assembly, multiple connectors are used to join two or more conductors.

Connector Area: This is the area on the circuit board that is used for creating electrical connections.

Contact Angle: The angle between the two contact surfaces of the two objects when bonded is referred to as contact angle. This angle is usually determined by the chemical and physical properties of the two materials.

Copper Foil (Base Copper Weight): This is the coated copper layer on the board. This can be characterized by the thickness or weight of the coated copper. For example, 0.5, 1, and 2 ounces per square foot equals to 18, 35 and 70 um:thick copper layers.

Control Code: It is a character that is used during input or output to produce some special action. A control code is basically a non-printing character, and thus it doesn’t appear as a part of data.

Core Thickness: Core thickness is the thickness of the laminate without copper.

Corrosive Flux: A flux featuring corrosive chemicals that may initiate oxidation of tin or copper conductors. These corrosive chemicals may include amines, halides, organic and inorganic acids.

Cosmetic Defect:  It is a slight defect in the usual color of the board. This defect doesn’t affect a PCB’s functionality.

Countersinks/Counterbore Holes: This refers to the type of conical holes that are drilled on the PCB.

Cover Lay, Cover Coat: This refers to the application of outer layer (s) of insulating material over the conductive pattern on the printed circuit board surface.

Crosshatching: The large conductor area is broken by using a pattern of voids present in the conductive material. 

C- Stage: It is a condition where a resin polymer is completely cured, and in a cross-linked state. In this condition, a polymer will have high molecular weight.

Curing: The process of polymerizing an epoxy of thermosetting nature at a particular temperature and within specified time. This is an irreversible process.

Curing Time: It is the time required to complete epoxy curing. This time is measured on the basis of temperature at which the resin is being cured.

Cutlines: This is used by the PCB manufacturing for programming the router specifications. The cutlines represent the outer dimensions of a printed circuit board.

Current Carrying Capacity: it is the maximum current carrying capacity of the conductor under specific conditions without degradation of mechanical and electrical properties of the PCB.

Cutout: The grooves that are dug on the PCB are termed as cutouts.

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D

D Code: A datum within a Gerber file that acts as a photo plotter command. The D code takes the form of a number that is prefixed by letter “D20”.

Database: A collection of various interrelated or correlated data items that are stored together. A single database can be used to serve one or more applications.

Datum or Datum Reference: A pre-defined line, point or plane, which is used to locate the layer or pattern, during inspection or manufacturing process.

Deburring: This is a process of removing traces of copper material that are left behind around holes post drilling.

Defect: As the name suggests, this is any deviation from the normally accepted component or product characteristics. Also see major and minor defect.

Definition: The accuracy of edges of pattern in a printed circuit board. This accuracy is calculated relative to the master pattern.

Delamination: A separation between: different layers of the base material or between the conductive foil and laminate, or both. Generally, it refers to any planner separation on a printed circuit board.

Design Rule Checking or Design Rule Check: This refers to using a computer program to perform continuity checks of all conductor routings. This is done in accordance to the design rules.

Desmear: The removal of melted resin (epoxy resins) and debris from a hole wall is termed as desmear. Debris may be produced during the drilling process.

Destructive Testing: This is performed by sectioning a portion of a circuit panel. The sectioned portions are examined under the microscope. Generally, the destructive testing is conducted on coupons, rather than functional part of the PCB.

Develop: An operation or imaging operation where photo-resist is washed away or dissolved to create a copper board. This copper board consists of a photo-resist that allows pattern for plating or etching.

Dewetting: This condition occurs when molten solder starts receding from a coated surface, leaving behind irregular shaped globules on the solder. This can be easily recognized by thin covering of solder film coating the surface. However, the base is not exposed.

DFSM: Dry Film Solder Mask.

DICY: Dicyandiamide. This is the most popular cross-linking component used in the FR-4.

Die: An integrated circuit chip that is cut or diced out using a finished wafer.

Die Bonder: This is a placement machine that bonds IC chips to a board substrate.

Die Bonding: The term for attaching an IC chip to a substrate.

Dielectric Constant: It is the ratio of permittivity of material to vacuum. It is often referred to as relative permittivity.

Differential Signal: A signal transmission through two wires in opposite states. The signal data is defined as the polarity difference between the two wires.

Digitizing: A method of converting flat plane feature locations to a digital representation. The digital representation may involve x-y coordinates.

Dimensional Stability: It is a measure of dimensional change brought by factors such as humidity, temperature, chemical treatment, stress, or ageing. It is usually expressed as units/unit.

Dimensioned Hole: A hole on the printed circuit board, where determining the location of X-Y coordinate values is not coinciding with the stated grid.

Double-sided Board: A circuit board featuring conductive patterns on both sides is referred to as double-sided board.

Double-sided Laminate: It is a PCB laminate having tracks on both of its sides. The tracks are normally connected through PTH holes.

Double-sided Component Assembly: This refers to mounting on both the sides of the PCB. It refers SMD technology.

Drills: The solid carbide cutting tools with two helical flutes, as well as four faucet points. These tools are designed for removing chips present in abrasive materials.

Drill Tool Inspection: This is a text file containing drill tool number and corresponding size. However, quantity is also included in some reports. All drill sizes are interpreted as plated through finished sizes.

Drill File: This file comprises X:Y coordinates, which are viewable in any text editor.

Dry Film: The photo imagable material that is laminated on a copper panel. This material is exposed to 365nm UV light, which is directed through a negative photo tool. Exposed area is hardened by the UV light, whereas the non-exposed area is washed in a developer solution of 0.8% sodium carbonate.

Dry Film Resists: The photosensitive film is coated on the copper foil through various photographic methods. However, these films resist etching and electroplating process in the PCB manufacturing process.

Dry Film Solder Mask:  A solder mask film that is applied to the PCB using various photographic methods. This method can manage the higher resolution that is required for surface mount and fine line design.

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E

ECL: ECL stands for Emitter Coupled Logic, which uses a differential transmitter (transistor-based) to combine and amplify digital signals. This logic is complicated to use, expensive, yet is much faster than the Transistor-Transistor Logic (TTL).

Edge Bevel: Edge bevel is a chamfering operation done on the edge connectors to make them beveled. This makes the connectors easy to install, and improves their wear resistance.

Edge Clearance: Edge clearance refers to the smallest distance measured between any components or conductors, and the edge of the printed circuit board.

Edge Connector: Edge connector refers to the edge of a PCB. It has holes, which are used to connect another device or circuit board to the PCB.

Edge Dip Solderability Test: This is a method to test the solderability of a PCB. In this method, specimen is dipped into molten solder and withdrawn. This is done at a predetermined rate. Edge dip solderability testing can be done for all electronic components, as well as to substrates that carry metalized tracks.

Edge-Board Connector: As the name suggests, edge-board connectors are used to make consistent interconnection between the external wiring and the edge board contacts that are present on the edges of a PCB.

Electro-deposition: When electrical current is applied through a plating solution, it forms a deposition of conductive material, which is referred to as electro-deposition.

Electronic Component: An electronic component is a part of an electronic circuit. It can be an op-amp, a diode, capacitor, resistor, or logic gates.

Electroless Copper: A copper layer is deposited on a surface of a printed circuit board (PCB). Autocatalytic plating solution is used for the purpose. This layer so formed is referred to as Electroless copper.

Electrode Deposition: It refers to the deposition a conductive material from a plating solution, when an electrical current is applied to it.

Electroless Deposition: This process involves deposition of a metal or conductive material without using electric current.

Electroplating: Electroplating is the process in which electro-deposition of metal coating takes place on a conductive object. The object that is to be plated is inserted in an electrolytic solution. One terminal of a direct current (DC) voltage source is connected to it. The other terminal of the voltage source is connected to the metal to be deposited, which is also immersed in the solution.

Electrical Object: A PCB or a schematic file consists of a graphical object, which is referred to as an electrical object. Electrical connections like a wire or component pin can be made to this object.

Electrical Test: It is either a 1 sided or 2 sided testing performed mainly for the purpose of checking for any shorts or open circuit. It is recommended by experts that all surface-mount boards and multilayer boards should undergo electrical testing.

E-pad: E-pad is also referred to as an Engineering-pad. It is a surface mount pad present on a PCB. This pad is used for soldering wire to the PCB. Typically, a silkscreen is used to label E-pads.

EMC: EMC stands for Electromagnetic Compatibility. (1) EMC is the capability of an electronic equipment to operate well under intended electromagnetic environment, without getting degraded. (2) Electromagnetic Compatibility is the ability of an equipment to deliver a decent performance in the electromagnetic environment without interfering with other devices. 

Emitter: Emitter is one of the terminals of a transistor. It is an electrode, which causes flow of electrons and holes from it to the region between the electrodes of the transistor.

EMP: EMP refers to Electromagnetic Pulse, which is a result of detonation of nuclear weapons. It is also sometimes referred to as transient electromagnetic disturbance.

End-to-End Design: End-to-end design is a version of CAD/CAM/CAE in which the inputs and outputs are integrated with the software packages used. Thus, it does not require any manual intervention (except menu selection or a few keystrokes), and allows the design to flow smoothly from one step to the other. As far as Printed Circuit Board (PCB) design is concerned, the end-to-end design is the electronic schematic/PCB layout interface.

ENIG: ENIG stands for Electroless Nickel Immersion Gold. It is a type of finishing method of PCB. This method makes use of auto-catalytic properties of electroless nickel, which helps gold to attach itself uniformly with nickel.

Entrapment: Entrapment is the process of admitting and trapping of flux, air, and/or fumes. Contamination and plating are the two main reasons causing entrapment.

Entry Material: Entry material is a thin layer of either an aluminum foil or a composite material. It is generally placed on the surface of the circuit board for the purpose of improving the drill accuracy and avoid dents or burrs during the process.

Epoxy: Epoxy is the family of thermosetting resins. It plays a vital role in the formation of chemical bond with several metal surfaces.

Epoxy Smear: Epoxy resin, which is also referred to as resin smear, is a deposition on the edges or surface of the conductive inner layer pattern. This deposition is caused during the process of drilling.

ESR: ESR refers to Electro-statically applied Solder resist.

Etch: It is the process of removing the copper metal chemically, in order to get a required circuit pattern.

Etch Factor: The etch factor is the ratio of depth of etch or thickness of the conductor to the amount of undercut or lateral etch.

Etchback: Etchback is the process in which the resin smear is removed from the sidewalls of holes and additional internal conductor surfaces are exposed. This is done by carrying out a chemical process of non-metallic materials to a specific depth of the holes.

Etching: Etching is the process in which the unwanted portions of a resistive or conductive material are removed with the help of a chemical and an electrolyte.

Excellon: Excellon format is an ASCII (American Standard Code for Information Interchange) format, which is used in the NC drill file. This format is widely used today to drive NC drill machines.

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F

Fab: Fab is the shortened word for fabrication.

Fabrication Drawing: It is the detailed drawing, which plays a vital role in the construction of printed circuit board (PCB). A fabrication drawing consists of all the details including the locations and sizes of the holes to be drilled, along with their tolerances. The drawing also describes the types of materials and methods that are to be used, as well as the dimensions of the board edges. This drawing is also referred to as fab drawing.

Fast Turnaround: The quick response rate in which the circuit boards are made and dispatched within days, and do not take several weeks to get shipped.

FC: FC is the short-form for flex circuit, flexible circuitry, or flexible circuit.

Fiducial Mark: Fiducial mark is a feature on a PCB, which defines a common measurable point for mounting components a land pattern or patterns. This mark is created in the same process as conductive pattern.

Files Eagle: This is a viewer, which enables previewing of production files. Eagle previews the production files as they are interpreted by the plotting software. It allows you to output Excellon and Gerber files from Eagle.brd file.

Files Gerber: This is the standard format for files that are used to create necessary artwork for the purpose of circuit board imaging.

Files Ivex: It is a viewer, which helps preview production files. With the help of Ivex, you can preview the production files as they are interpreted by the plotting software. It allows you to output Excellon and Gerber files from Ivex.brd file.          

Files Protel: This is a viewer, which enables previewing of production files. Protel previews the production files as they are interpreted by the plotting software. It allows you to output Excellon and Gerber files from Protel file.

File Submission: Missing and extra files always extend the PCB fabrication work. Hence, many manufacturers request their customers to send file layers, and a drill file. For example, when placing an order for a 4-layer board with one side silkscreen, and a soldermask, a PCB manufacturer will request to send in 7 layers, and a drill file. Missing of any file layer will add to the delay. Also, presence of extra files with information that conflict with that of the order form will add to the delay. This information can be anything from readme, print, or old tool file. 

Film Artwork: Film artwork is a positive or negative part of a film, which consists of a circuit, nomenclature pattern, or solder mask.

Fine Line Design: Fine line design is a PCB design, which allows two to three traces between neighboring pins of a DIP (Dual In-line Package).

Fine Pitch: Fine pitch refers to chip packages, which have their lead pitches less than 0.050". The lead pitches vary from a minimum of 0.020” (0.5 mm) to 0.031” (0.8 mm).

Finger: Finger refers to a terminal of a card-edge connector. This terminal is gold-plated. It is also referred to as gold finger.

Finished Copper: Finished copper refers to the weight of the base and electroplated copper, which is measured per square foot of the material.

First Article: To make sure that the manufacturer manufactures a product that meets all the design requirements, a sample part or assembly is manufactured prior to beginning the production. This sample part is known as the first article.

Fixture: A fixture is a device, which allows interfacing a PCB with a spring-contact probe test pattern.

Flash: Flash is a small image in a film, which is created according to the command in a Gerber file. The most commonly used size of flash is ½ inch, but the maximum size may vary from one photo plotting shop to another.

Flat: Flat, which is also referred to as a panel, is a standard sized sheet of laminate material. This sheet is processed into one or more circuit boards.

Flex Circuit: A flex circuit, which is also referred to as a flexible circuit, is a printed circuit that is made from thin, and flexible material.

Flexible Circuitry: Flexible circuitry consists of an array of conductors that are bonded to a thin, and flexible dielectric. Its major advantages include circuit simplification, increased reliability, reduction in size and weight, and a greater range of operating temperature.

Flexible Printed Circuit: Flexible Printed Circuit or FPC is a flex circuit. It is also referred to as FC.

Flux: Flux is a material used to remove oxides from the surfaces that are to be joined with the help of welding or soldering. This material helps promote the fusion of surfaces.

Flip-Chip: Flip-chip is a mounting approach, which involves inverting (flipping) and connecting a chip (die) directly to the substrate instead of using the traditional wire bonding technique. Solder bump and beam lead are some examples of this kind of flip-chip mounting.

Flying Probe: A flying probe is an electrical test machine, which is used to touch and locate the pads on the board. This is done with the help of probes on the ends of the mechanical arms. These probes move across the board to verify the continuity of each net. The probes also verify the resistance to the adjacent nets.

Footprint: Footprint is the space or the pattern on a board, which is taken up by a component.

FPC: Refer to Flexible Printed Circuit, or flex circuit.

FPPY: FPPY stands for First Pass Panel Yield. It is defined as the number of good panels after deducting the defective ones.

FR-1: This is a Flame Retardant (FR) industrial laminate. FR- 1 is a low-grade version of FR-2.

FR-2: FR-2 is a National Electrical Manufacturers Association (NEMA) grade of industrial laminate. The laminate has a paper substrate and a resin binder of phenolic. This flame-retardant laminate is apt for PCBs and is more economical as compared to woven glass fabrics like FR-4.

FR-3: FR-3 is a paper material, which is similar to FR-2. The only difference between the two is that FR-3 uses epoxy resin as a binder.

FR-4: FR-4 is a NEMA grade of industrial laminate. This flame retardant laminate has a substrate of woven-glass fabric and epoxy resin binder. It is one of the most used dielectric material for PCB construction in the USA. At below-microwave frequencies, the dielectric constant of FR-4 between 4.4 and 5.2. The dielectric constant gradually drops, as the frequency exceeds 1GHz.

FR-6: FR-6 is a fire-retardant industrial laminate having glass-and-polyester substrate material. This laminate is cost-effective, and is mainly used in automobile electronics.

Functional Test: Functional testing is the standard test program, which is executed in order to simulate the functions of an electronic device. This confirms the proper functionality of the device.

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G

G10: G10 is a laminate, which consists of a woven epoxy-glass cloth infused in epoxy resin under heat and pressure. This laminate finds its use in thin circuits, for example watches. G10 does not have the anti-flammability properties like FR-4.

GC-Prevue: GC-Prevue is a Gerber viewer made by GraphiCode. It is also referred to as a CAM file viewer and printer. It helps store NC drill and Gerber files in a .GWK extension file. This makes GC-Prevue very valuable, when it comes to sharing electronic data. It is a freeware, and anyone can download it. This viewer can be used to import Gerber files in logical sequence, and display them in perfect register. Labels can also be added to the filenames. This helps describe the use and position of Gerber files in the stackup. This process of adding labels is also termed as annotating. After annotating, these files are viewed with the help of GC-Prevue, and the necessary data is saved. The resulting .GWK file is then passed on for further examination. GC-Prevue not only views and prints the files, but also helps measure size of the objects, as well as their relative distance from each other. Unlike other Gerber viewers, GC-Prevue helps set-up and save Gerber data in one single file. Other Gerber viewers require one file to set-up the Gerber files, and then requires an upgrade for saving these files.

Gerber File: Gerber file is named after Gerber Scientific Co., who invented the vector photoplotter. Gerber file is a data file, which is used to control a photoplotter.

GI: GI refers to the woven glass fiber laminate, which is impregnated with polyamide resin.

GIL Grade MC3D: GIL Grade MC3D is a composite laminate, which consists of woven-glass surface sheets on either sides of glass paper core. This laminate has low and stable dissipation and dielectric factor. It shows exceptional electrical properties.

Glass Transition Temperature: Glass transition temperature, is the temperature at which the amorphous polymer changes its form from a brittle and hard condition to a soft, rubbery or viscous one. During this transition of temperature, a number of physical properties, such as brittleness, coefficient of thermal expansion, hardness, and specific heat experience noteworthy changes. This temperature is denoted by Tg.

Glob Top: Glob top is used for protecting the chip and wire bonds on a chip-on-board, and packaged IC. It is a blob made from plastic material, which is non-conductive, and is generally black in color. The material used in the glob top has a low coefficient of thermal expansion, which protects the wire bonds from ripping loose in case of changes in ambient temperatures.

Glue Deposit: This occurs when glue is placed automatically at the center of a component. Glue deposit acts as a bonding agent between the circuit board and the component, thus providing an additional structural integrity.

Gold Finger:  Refer to finger. 

Gold Plated: It is the process in which a thin layer of gold is deposited on the surface of other metal, such as silver, or copper. This is done by electrochemical plating process.

Golden Board: Golden board is an assembly, or a board, which is free from any defects. It is also referred to as Known Good Board.

Grid: A grid is a network of two sets of parallel lines, which are equidistant. These lines form an orthogonal network. A grid is mainly used to locate points on a Printed Circuit Board (PCB).

Ground: Ground, which is also referred to as earth, is a common reference point for heat sink, shielding, and electric current return.

Ground Plane: Ground plane is a conductor layer that provides a common reference for heat sinking, shielding, as well as electrical circuit returns.

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H

Haloing: Haloing refers to a fracturing delimitation that is induced mechanically on or below the surface of base material. Haloing is either shown by a light area around the holes, or other machine areas. It can also be exhibited by both light, as well as machine areas.

Hard Board: A hard board refers to a rigid circuit board.

Hard Copy: Hard copy is the plotted or printed form of a computer data file or an electronic document.

HASL: HASL, which stands for Hot Air Solder Leveling, is a type of finish used on PCBs. In this process, the PCB is inserted into the molten solder bath. This covers all the exposed copper surfaces with solder.

HDI: HDI refers to High Density Interconnect. It is an extremely fine-geometry multi-layer PCB, which is built using conductive microvia connections. Generally, these boards are made by sequential lamination technique. HDI consists of buried and/or blind vias.

Header: The part of a connector assemble, which is mounted on a PCB is termed as a header.

Heavy copper PCB: Heavy copper PCBs are those circuit boards having more than 4 oz of copper.

Hermetic: Hermetic refers to the process of sealing an object airtight.

Hole: In a semiconductor, hole is the term, which is used to define the absence of an electron. Other than the positive charge that it carries, a hole has all the electrical properties as that of an electron.

Hole Breakout: The condition in which a hole is not surrounded by land completely, is termed as hole breakout.

Hole Density: Hole density refers to the number of holes present in a unit area of a PCB.

Hole Pattern: Holes on a printed circuit board are arranged in a pattern with respect to a reference point. This arrangement of holes is referred to as hole pattern.

Hole Void: It is the void present in the metallic deposit of a plated-through hole, which exposes the base material.

HPGL: HPGL stands for Hewlett-Packard Graphics Language. It is a text-based data structure of pen-plot files. These pen-plot files are very essential is driving the Hewlett-Packard pen plotters.

Hybrid: Any circuit, which is made from the combination of discrete component, monolithic IC, thick film, and thin film, is termed as a hybrid circuit.

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I

Imaging: When electronic data is transferred to the photo-plotter, it uses a light to transfer negative image circuitry pattern onto the panel. This process is called Imaging.

Immersion Plating: It is a type of surface coating in which a thin metal coating is applied on the surface of another base metal, by partial displacement of the base metal.

Impedance: The resistance offered by an electrical network consisting of inductance reaction, resistance, and capacitance, to the flow of current is referred to as impedance. The impedance of a circuit is measured in Ohms.

Immersion Coating:

  1. This is an electroless copper coating performed during the through-hole plating.
  2. The electroless deposition of nickel, tin, or silver and gold to holes and pads for creating a solderable finish. Immersion coating might also be applied on tracks for specific reasons.

Inclusions: The entrapment of foreign particles, metallic or non-metallic, inside any insulating material or conductive layer of a printed circuit board is called as inclusions.

In-Circuit Test: In-circuit test refers to the electrical test performed on individual components in the printed circuit board (PCB) assembly, rather than testing the whole circuit. 

Integrated Circuit: Integrated circuit, which is also referred to as an IC, is a miniaturized electronic circuit, which consists of both active, as well as passive components.

Inner Layers: Inner layers refer to the layers of metal foil or laminate that are pressed on the inside of a multilayer circuit board.

Inkjetting: Inkjetting is the process in which well-defined ink dots are dispersed on a printed circuit board. This is done with the help of an equipment, which uses heat for liquefying the solid ink pellet. After the ink has turned into liquid form, it is dropped on the printed surface, with the help of a nozzle. The ink dries quickly.

Insulation Resistance: Insulation resistance refers to the electrical resistance that is offered by an insulating material under specific conditions. This resistance is determined between a pair of grounding devices, contacts, or conductors in different combinations.

Inspection Overlay: Inspection overlay is a negative or positive transparency. It is generally used as an inspection aid, and is made from the production master.

Inspection Guidelines: Inspection guidelines are a set of procedures or rules set by IPC, which is the final American authority on how to design and manufacture PCBs. All circuit boards should meet the IPC Class 2 guidelines.

Internal Power and Ground Layers: Internal power or ground layers refer to the solid copper plains of a multi-layer board, which either carry power or are ground.

Interconnect Stress Test: Interconnect stress test is a system, which is specially designed to measure the ability of the total interconnect to survive both mechanical, as well as thermal strains. This test is carried out from the as manufactured state to that state, in which the product reaches the point of interconnect failure.

Interstitial Via Hole: An interstitial via hole refers to an embedded through-hole, which has a connection of two or more than two layer of conductor in a multilayer printed circuit board.

IPC: IPC is the Institute for Interconnecting and Packaging Electronic Circuits. It is the final American authority, which defines how to design and manufacture printed circuit board.

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J

Jump Scoring: Jump scoring in printed circuit boards allows the score line to jump over the panel border, resulting in a stronger assembly panel.

Jumper Wire: A jumper wire refers to an electrical connection, which is formed between two points on a printed circuit board. This connection is formed by a wire after the proposed conductive pattern is created.

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K

Kerf: It allows extra space for any hardware to be attached to the board. This happens due to the widening of the rout path on the blueprint.

Keying Slot: Keying slot refers to a slot present in a PCB. This slot is responsible for polarizing the printed circuit board. Thus, it only allows the PCB to be plugged into its mating receptacle. The pins can be properly aligned. This polarization prevents incorrect plugging, which can happen due to reversing or if the pin is plugged in other receptacle.

Known Good Board: The type of circuit board or assembly, which is confirmed to be defect-free. This type of board is also known as golden board.

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L

Laminate: Laminate is a basically a composite material, which is formed by attaching and bonding two or more layers of either same or different materials.

Lamination: Lamination is the process of creating a laminate. This process is carried out under heat and pressure condition.

Laminate Thickness: Laminate thickness means the thickness of metal-clad base, which can either be single-sided or double-sided. This thickness is measured before any subsequent processing.

Laminate Void: The cross-sectional area should normally contain epoxy resin. If it is not present in the cross-sectional area, then it is referred to as laminate void.

Laminating Presses: Laminating presses are multilayer equipment used for manufacturing multilayer boards. These equipment apply heat and pressure to laminate and pre-preg to get the desired output.

Leakage Current: Leakage current is caused due to a non-perfect capacitor. Current leaks generally occur when an insulator present between the conductors of a dielectric is not a perfect non-conducting material. This leads to the energy discharge or loss of energy of a capacitor.

Land: Land, which is also referred to as a pad, is the portion on a printed circuit board, with conductive pattern. This portion is specially designated for attaching or mounting electronic components.

Landless Hole: Landless hole, which is also referred to as padless plated hole, is a plated through hole, which does not have land(s).

Laser Photo Plotter: It is a photo plotter equipment, which uses laser. It uses a software to stimulate a vector photo-plotter, and produces a raster image of individual objects in the CAD database. An image is then plotted as a series of lines of dots by the photo-plotter. It has a very fine resolution. A laser photo-plotter is better than a vector plotter in terms of consistent plotting and accuracy.

Lay Up: Lay up is the process of assembling the already treated copper foils and pre-pregs for the purpose of pressing.

Layers: The indication of the different sides of a printed circuit board is given by the layers. On-board text, which consists of part number, company name, and logo is oriented right-reading on the top layer. This helps users determine in no time whether the files have been correctly imported or not. Thus, by taking this simple step, it can save a considerable amount of potential hold up and time-consuming hold notice.

Layer Sequence: As the name suggests, layer sequence is used to determine the sequence in which layers are required to be arranged to get a desired stack-up. It is very much helpful to CAD, and helps determine the type of the layer.

Layer-to-Layer Spacing: In a multilayer printed circuit board, the thickness of a dielectric material between conductive circuitry or adjacent layers is termed as layer-to-layer spacing.

Liquid Resist: The fabrication of circuits makes use of liquid form of photoresist, which is referred to as liquid resist.

Legend: Legend refers to a format of symbols or printed letters on a printed circuit board, for example, logos, part numbers, or product numbers.

LGA: LGA stands for land grid array. It is the surface mount packaging technology, which is used for Integrated Circuits (ICs) that have the pins on socket (if a socket is used) rather than the IC. One can electrically connect the land grid array to a printed circuit board either by soldering to the board directly or by the use of a socket.

Lot: Lot refers to the quantity of several printed circuit boards that have similar or common design.

Lot Code: Lot code is useful for some customers. Therefore, the lot code of a manufacturer is placed on the circuit boards. This helps for the purpose of future tracking. The location, or details such as whether the layer is to be in copper, mask opening, or silkscreen is represented and specified in a drawing.

LPI: LPI refers to the ink, which is used to control deposition. This ink is developed with the help of photographic imaging techniques. LPI is considered to be one of the most precise techniques for applying mask. This technique delivers mask that is thinner compared to that of a dry film solder. Therefore, LPI is mostly a preferred choice for dense surface mount technology. It can be used for applications like spray or curtain coat.

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M

Major Defect: A defect that may result in failure of the circuit or significantly reduce its usability is referred to as major defect.

Mask: This is a material applied on the printed circuit board to enable plating, etching or application of the solder.

Master Aperture List: An aperture list that can be used for two or more PCBs is called the master aperture list for that set of PCB.

Measling: A condition found in the base laminate in the form of crosses or white spots. Generally, it is found below the base laminate, and shows the fiber separation in the glass cloth.

Metal Electrical Face (MELF): A surface mounted discrete part, that is cylindrical, or barrel shaped anode. The barrel ends are metal capped. The barrel is laid on its side, the metal pads are laid on landing pads, and the part is soldered. The most common sizes are MLL41 and MLL34, which are MELF versions of DO – 35 and DO – 41 respectively.

Met Lab: Metallurgy laboratory. 1) It refers to processes of inspecting the board quality characteristics through micro sections. 2) The term is used as an alternative to micro sections.

Metal Foil: These are thin rolls or sheets of conductors, which are used to build a printed circuit board. Generally, copper is used as a metal foil.

Micro Ball Grid Array: Also, known as micro BGA. This is a fine pitch ball grid array. Generally, the fine pitch for BGA is less than or equal to 0.5mm. The MGA is very dense, and it is manufactured using controlled-depth laser-drilled blind microvia-in-pad technology.

Micro Circuits: These are very fine lines 2 mil or less, and small micro vias 3 mil or less.

Micro Sectioning: It a process of preparing a specimen for examination under the microscope. A specimen is cut into a cross section, followed by polishing, encapsulation, staining, etching, etc.

Microvia: It is used to connect two adjacent layers that are less than 6 Mil in diameter. Microvia may be formed through plasma etching, laser ablation, or photo processing.

Mil: One thousand of an inch 0.001″ (0.0254mm). This is an abbreviation of milli inch.

Minimum Annular Ring: This is the minimum width of the metal at the narrowest point, between the outer circumference of the land and the circumference of the hole. This measurement is created on the drilled hole on internal layers of the circuit board with multiple layers. Also, it is made on the edge of the plating found on the outer layers of double-sided printed circuit boards, and multilayer circuit boards.

Minimum Electrical Spacing/Minimum Conductor Spacing: It is the minimum distance between conductors that are lying adjacent to each other. This distance helps prevent corona, dielectric breakdown, or both, between the semiconductors of any given altitude and voltage.

Minimum Traces and Spacing: Traces or Tracks are the wires on a printed circuit board. Spaces are the distance between the pads or the distance between the traces, and distance between a trace and a pad. The order form selection is made on the basis of width of the smallest trace (wire, line, and track) or space between pads or traces.

Minimum Conductor Width: It is the smallest width of any conductor including traces on a printed circuit board.

Minor Defect: This defect is not likely to affect the usability of the component or unit for the purpose intended. It may be kind of departure from the established standards with no significant effect on the bearing or the effective operation of the circuit.

Misregistration: A term symbolizing lack of conformity between successively produced patterns or features.

Molded Carrier Ring (MCR): It is a fine-pitch chip package, which is known for protecting and supporting the leads. The leads are left straight; the lead ends are embedded in a plastic strip, which is termed as Molded Carrier Ring. The MCR is cut off before an assembly, and leads are formed. In this way, delicate leads are protected from damage, just before the assembly.

Monolithic Integrated Circuit: The term is abbreviated as MIC. This is a variant of printed circuit board, which is created within a substrate of semiconductor, with one of the circuit elements formed within a substrate. The term is also used for a complete circuit board that is fabricated as an assembly of circuit elements in a small structure. This circuit cannot be divided without destroying its electronic function.   

Mounting Hole: A hole used for mechanically supporting a printed circuit board or attaching components to the printed circuit board is termed as mounting hole.

Multilayer Circuit Board: A term for printed circuit board comprising of several layers of insulating materials or conductive patterns that are bonded together in multiple layers.

Multimeter: It is a test instrument that is used to measure current, voltage, and resistance. This instrument is portable in nature.

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N

Nail Heading: This is a flared connection of copper formed on an interconnect layer of the multilayered circuit board. Nail heading is brought by poor drilling.

NC Drill: A Numerical Control (NC) drill machine, which is used to drill holes at identified locations on a PCB following an NC drill file.

NC Drill File: This is a text file that guides an NC drill machine to drill holes.

Negative:

  • A reverse image copy of a positive checking revision of a PCB. This copy represents planes on the inner layer. A negative image used for an inner-layer will have thermals (segmented donuts) and clearances (solid circles) that make connections. These connections are thermally relieved. Also, there are chances that thermals and clearances may isolate holes from the plane.When the negative image of the current version is superimposed over a positive image copy of an earlier version, all areas will appear solid black. The areas where changes have been made will appear clear.
  • It is a PCB image that represents copper as clear areas, and void areas (where material is absent) as black areas. This is typical of solder mask and ground planes.

Net: It is a collection of terminals, which must be electrically connected. The synonym of this term is signal.

Netlist: It is a list of names of parts, or symbols, as well as their connection points that are connected logically in a net of a circuit. The Netlist can be captured from schematic drawing files of electrical CAE application.

Node: A lead or pin to which at least two or more components are connected is referred to as a node. These components are connected using conductors.

Nomenclature: The identification symbols that are applied to the circuit board by inkjetting, screen printing, or laser processes.

Nonfunctional Land: It is the land featuring internal or external layers, which are not connected to the conductive pattern on layer.

Non-plated Through Hole (NPTH): A drill drawing is used to identify NPTH in a PCB design. Most design packages calculate the amount of clearance around a NPTH and plated hole differently. This is because the non-plated holes may end up with less allowance, while passing through power planes and solid copper ground.

Notation: Notation is a PCB diagram that indicates location and orientation of components.

Notch: Also known as a slot, this is seen on the external layers of a circuit board. Generally, notches are seen in mechanical layers that are used for routing.

Number of Holes: As the name suggests, it refers to the total number of holes in a circuit board. There is no limit on the quantity of holes on the circuit board, and it doesn’t influence pricing.

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O

One Ounce Foil: It is the weight of 1 square foot of copper foil. (1 Oz= 0.00134 inches, ½ Oz = 0.0007 inches, etc.).

Open Circuit: It is an unwanted break in an electric circuit’s continuity that hampers the continuous current flow through the circuit.

OSP:  OSP refers to Organic Solder Preservative, and is also known as Organic Surface Protection. It is a lead-free procedure that helps PCB manufacturers meet the requirements of RoHS compliance.

Outer Layer: The top and bottom layer of any circuit board.

Outgassing: Emission or deaeration of gas from a printed circuit board, when it is exposed to vacuum or soldering operation.

Overhang: This is an increase of the conductor width. Overhang is generally brought by plating build-up or undercutting during the etching process.

Oxide: A chemical treatment that is performed to the inner layers of the PCB prior to lamination. This treatment is performed to increase clad copper roughness, and to improve its laminated bond strength.

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P

Package:

  • A printed circuit board component or a decal.
  • A PCB component that contains a chip, and acts to create a convenient mechanism to protect the chip on the shelf, or after attachment to a PCB. With leads soldered to a circuit board, a package may serve as an electrical conduction interface between the board, and the chip.

Pad: The conductive pattern portions on circuit boards that are designated for attaching or mounting components.

Pad Annulus: This refers to the width of the metal ring around a hole in the pad.

Panel: A rectangular sheet of metal-clad material or base material of a particular size, which is used for processing printed circuit boards. Also, a panel for printing one or more test coupons. This is mostly an epoxy-copper laminate known as FR-4. The most common panel size is 12ʺ by 18ʺ, of which 11ʺ by 17ʺ is used for printed circuitry.

Panelize:

  • An act of laying one or more identical printed circuits on a panel. All individual printed circuits placed on a panel should maintain a 0.3ʺ margin. However, some board houses permit or create less separation.
  • An act of laying multiple printed circuits or modules into a sub-panel, which can be easily assembled as a unit. The modules can be separated post-assembly into separate printed circuits.

Part: It is used in various contexts:

  • A component
  • A decal in a PWB database or drawing
  • A schematic symbol

Part Number: The number or name associated with your circuit board for your convenience.

Pattern: This refers to the configuration of conductors and non-conductive materials on a panel of a circuit board. It is also the circuit configuration on drawing, related tools, and masters.

Pattern Plating: The selective plating performed on conductor pattern.

PCB Array: These are the boards that are supplied in a pallet form. These are sometimes referred to as “stepped out”, “panelized”, “palletized”, “rout and retain”.

PCB Database:  It comprises of all essential PCB design data. It is generally stored on a one or more files on a computer.

PCB –Design Software Tools: As the name suggests, these are various software driven tools that enable a PCB designer to conduct a schematic, design a layout, routing, and perform optimizations. There are various PCB design software and tools available for purchase. Here is a very short list of those: ExpressPCB, EAGLE, PROTEL, CADSTAR, ORCAD, CIRCUIT MAKER, P-CAD 2000, PCB ELEGANCE, EDWIN, VISUALPC, BPECS32, AUTOENGINEER, EXPERT PCB, CIRCAD, LAYOUT, CIRCUIT LAYOUT, MCCAD, DREAM CAD, E-CAD, POWERPCB, PCB ASSISTANT, PCB DESIGNER,QCAD, QUICK ROUTE, TARGET 3001, WIN CIRCUIT 98, BOARD EDITOR, PCB, VUTRAX, CIRCUIT CREATOR, PADSPCB, DESIGN WORKS, OSMOND PPC, LAY01, SCORE, GElectronic, PRO-Board, PRO-Net , CSIEDA, VISUALPCB, WINBOARD, ULTIBOARD, EASY PC, RANGER, PROTEUS, EPD -Electronics Packaging Designer , AutoTrax Eda, Sprint Layout, CADINT, KICAD, Merlin PCB Designer, FREE-PCB, TinyCAD, WINQCAD, Pulsonix, DIPTRACE.

PCB Design Service Bureau: A company that offers PCB design service. The word bureau is French term for desk, or office. Also, this service is performed from an office at a desk. Many times, such bureaus are also referred to as PCB design shops.

PCB Prototype: A printed circuit board that is manufactured for testing purposes. In many cases, prototypes are manufactured for a specific application. The prototyping also includes all various aspects of a production. Hence, it helps streamline the product development, and production process, while helping reduce costs.

PCB Fabrication Process: The process of PCB fabrication can be simplified as: Copper laminate>>Drill board > Cu deposition>> Photolithography >> Tin lead plate or finishing >> Etch >>Hot air level >> Solder mask >> E-testing >> Routing/scouring>> Product inspection >> Final cleaning >> Packaging. Most manufacturers follow the same process, but there may be slight variations across various organizations.

PCMICA: This stands for Personal Computer Memory Card International Association

PEC: Printed Electronic Component.

Phenolic PCB: This laminate material is comparatively cheaper than fiber glass material.

Photographic Image: This is an image in an emulsion or in a photo mask that is on the plate or film.

Photo Print: A process of creating a circuit pattern image by hardening a polymeric, photosensitive material. A ray of light is made to pass through photographic film, which helps harden a photosensitive material.

Photo Plotting: In this process, an image is generated by directing a light beam over a light-sensitive material.

Photo-Resist:  A material that is sensitive to portions of the spectrum of light. A light sensitive material is applied to the PCB panel under production, and is exposed to develop the pattern from the photoplot. The remaining copper, which remains uncovered by the resist is etched away, and the copper pattern needed for the board remains behind. 

Phototool: This is printed by the photo plotter to be used for creating a copper pattern. This is also used for making patterns for silkscreen and soldermask.

Plasma Etching: This process is performed for removal of copper from the PCB panel, whenever special RF materials are used. These RF materials cannot be processed through standard etching procedures.

Plated Hole: This refers to a hole that is drilled on a circuit board, and has completed a plating process. The plated holes conduct electricity, as opposed to non-plated holes. The plated holes are used to connect traces over different layers of a PCB.

Printed Circuit Board: Abbreviated as PCB. Alternatively, known as Printed Wiring Board (PWB). It is a base of insulating material with a pattern of conducting material lying over them. This circuit board starts conducting electricity, when components are soldered to it.

Pre-Peg: Check B-stage.

Probe Test: A metal load with spring loading, which is used for making an electrical contact between test equipment, and the unit under test.

Push-back: A PCB panel whose board units are punched out, and then reset to their original positions through a second operation.

Pulse Plating: This is a method of plating using pulses.

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Q

QFP: QFP refers to Quad Flat Pack, which is rectangular, or square in shape. It is a fine-pitch SMT (Surface Mount Technology) package having gull-wing shaped leads on its four sides. Generally, the lead pitch of a QFP is either 0.65 mm or 0.8 mm, in spite of the variations in this theme with small lead pitches. The pitches of these variants are as follows:

  • Thin QFP (TQFP):  0.8mm
  • Plastic QFP (PQFP): 0.65mm (0.026")
  • Small QFP (SQFP): 0.5mm (0.020")

These packages can have their lead counts varying from 44 leads to 240 leads, or sometimes even more. Though these are descriptive terms, they do not have any industry-wide standards for sizes. To have a detailed understanding of a particular manufacturer’s part, a printed circuit designer requires a specification sheet of the part. For example, a short description such as PQFP-160, is not sufficient for describing the lead pitch and mechanical size of the part.

Quantity: Quantity is basically used to produce the data in the Price Matrix price table.

Quick Turn: Quick turn refers to fast turnaround provided by a PCB manufacturer. It is defined as fulfilling a request in a less amount of time.

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R

Rats Nest: A rats nest or ratsnest is a bunch of straight lines between pins, forming a crisscross pattern on the board. As the name suggests, it forms a confusing mess, which is similar to a rat’s nest. It helps suggest potential paths for routing between a set of connected connectors. Rats nest graphically represents the connectivity of a Printed Circuit Board (PCB) Computer Aided Design (CAD) database.

Readme File: Readme file is a text file, which provides information required for manufacturing an order. It is typically included in a zip file. It is always advisable to include the email addresses and phones numbers of engineers or designers. This helps accelerate the problem solving process at the manufacturing stage.

Reference Designator: A reference designator, which is abbreviated as Ref Des, is the name given to a component. It helps identify the component on a printed circuit board. Reference designator typically starts with a letter, and is followed by a numeric value. It consists of one or two letters, which designate the class of the component. These designators are generally placed close to the respective component. It is made sure that a reference designator does not go under the component. It should be visible, after the component is mounted on the PCB. Most of the times, reference designators appear as yellow or white epoxy ink (also called as silkscreen) on a PCB.

Reference Dimension: These are the dimensions that are only provided for informational purpose. Mostly reference dimensions are provided without tolerances, and are not responsible for governing the manufacturing operations.

Reflow: Reflow is the process in which an electrodeposited tin/lead is melted, and then solidified. The resultant surface has its physical characteristics and appearance similar to that of a hot-dipped one.

Reflow Oven: Reflow oven is a device through which boards are passed. These ovens have solder paste deposits.

Reflow Soldering: Reflow soldering is the process in which two coated metal layers are melted, joined, and solidified by applying heat to pre-deposited solder paste and the surface.

Registration: Registration is a standard term, which is used to ensure whether the plotted circuit board is following the design, as well as layout position of components.

Residue: Residue is an unwanted substance that remains on a substrate, even after the completion of a process step.

Resin Smear:  Refer to epoxy smear.

Resin-Starved Area: Resin-starved area refers to a localized area on a PCB, which lacks a sufficient amount of resin. This area is mostly identified by exposed fibers, dry spots, low gloss, etc.

Resist: During the manufacturing or testing process, some areas of a pattern might get affected by the action of solder, plating, or etchant. To protect these areas from getting affected, a coating material, which is referred to as a resist, is used.

Resistivity: Resistivity refers to the capability or property of a material to resist the flow of electrical current through it.

Reverse Image: Reverse image is the resist pattern that is present on a printed circuit board, which allows the exposure of conductive areas. This helps in plating.

Revision: Revision refers to updating the data, when the same drawing has an updated version.When the data is updated, it avoids any possible confusion at the time of manufacturing a board to required specifications. Revision number should be always included along with the drawing.

Rework: Rework, which is also termed as reprocessing, is the process of making articles adhere to the specifications.

RF: RF is the short-form used for Radio Frequency.

RF and Wireless Design: Radio frequency or wireless design refers to the circuit design operating in a range of electromagnetic frequencies, which is above the radio range, and below visible light. This operating range varies between 30 KHz and 300 GHz, and all the broadcast transmissions taking place between AM radio and satellites fall into this range.

Rigid-Flex: Rigid-flex is the construction of a built-in connection on multi-layer flex circuits. Rigid-flex PCBs are a combination of rigid and flexible board technology in an application.

Rise Time: After the change has started, a certain amount of time is required for an output voltage of a digital circuit to go from a low voltage level (0) to a high voltage level (1). The technology used in a circuit determines the rise time. The rise time of gallium arsenide components is approximately 100 picoseconds, which is almost 30 to 50 times faster than some CMOS components.

Robber: Robber refers to an exposed area, which is joined to a rack that is used in the electroplating process. A robber is mainly used to get more uniform current density on the parts that are plated.

RoHS: RoHS stands for Restriction of Hazardous Substances. It is a directive laid down in different parts of the world, which puts a restriction on the use of hazardous substances in electronic and electrical equipment.

RoHS Compliant PCB: The circuit boards that adhere to the RoHS directives are referred to as RoHS compliant PCBs.

Route or Track: Route, which is also sometimes referred to as a track, is wiring or a layout of electrical connections on a PCB.

Router: Router is a machine, which is used to cut the unwanted portions of a board to get it into a desired shape and size.

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S

Saturation:

  1. Saturation is the state of a transistor at which increase in the base current has no effect on, or does not increase the collector current any further. 
  2. The operating condition of a circuit, where any change or increase in the input signal has no effect on the output is termed as saturation. 
  3. Saturation is the operating condition or state reached, when a transistor is driven hard enough to make it biased in the forward direction. When a transistor under the saturation condition is used in a switching application, the charge stored in the base region stops the transistor from turning off quickly.
  4. It is the condition or state at which, for a given applied voltage, a semiconductor device conducts most heavily. Saturation, in most of the devices also refers to the state at which the normal amplification mechanisms become inoperative or “swamped”.

Schematic: Schematic or a schematic diagram is a representation of the elements of a system, with the help of graphic symbols, functions, and electrical connections of a particular circuit arrangement.

Scoring: Scoring refers to a technique in which grooves are made on the opposite sides of a panel. These grooves are machined to a depth that allows separation of each individual board from the panel one the component assembly is done.

Screen: A screen refers to a cloth material, which is coated with a design that decides the location and flow of coatings forced through its openings. The cloth material is either polyester or stainless steel, which makes it suitable for circuit boards.

Screen Printing: Screen printing is a process in which an image is transferred to a surface. This is done by forcing proper media through a stencil screen with the help of a squeegee.

Selective Plate: Selective plate is a process of plating a specific area on a PCB with a different metal. The process of creating a selective plate consists of imaging, exposing, and plating the selected area.

Shadowing: Shadowing is the condition reached during etchback. In this condition, the dielectric material, which is in contact with the foil is not removed completely, though satisfactory etchback is achieved elsewhere.

Short: Short is also referred to as a short circuit. It is an abnormal connection in which the resistance between the two points of a circuit is extremely low. This results in an excess current between these two points, which is capable of damaging the circuit. This abnormal connection can occur in a printed wiring CAD database, when conductors from different nets come closer than the minimum space, which is allowed. This minimum space is decided by the design rules that are being used.

Short Run: Short run in manufacturing of PCBs refers to the requirement in which only one to tens of printed circuit board panels are required to fulfill the order instead of hundreds of them. The short run can be determined on the basis of the size of printed circuit board to be made, and the size of manufacturing facility.

Silkscreen: Silkscreen, which is also sometimes referred to as silkscreen legend, can be defined in two ways as follows:

  1. Silkscreen is generally used on the component side. It is basically used to identify manufacturer marks, company logos, test points, warning symbols, components, and the part number of PCB and PCBA. It gets its name from the method or type of printing i.e. screen printing. The silkscreen layer is just ink, which is non-conductive. This layer is placed on the traces of a PCB, without any interference.
  1. Silkscreen is a Gerber file, which helps control the photo plotting of this legend.

Signal Layer: The layers where the conductive traces can be laid out, are referred to as signal layers.

Single-Sided Board: Single-sided boards are circuit boards, which have conductors only on one side. These circuit boards do not have plated-through holes.

Single Track: Single track refers to a PCB design, which has only one route between adjacent DIP pins.

Size X & Y: The dimensions of a printed circuit board are in inches or metric. Maximum X & Y configuration is 108″. This means that if the width (X) of a PCB is 14″, then it can have a maximum length (Y) of 7.71″.

Skip Plate: Skip plate is the area in plating, where metal is not present.

SMOBC: SMOBC stands for Solder Mask Over Bare Copper. It is a method, which is used to fabricate a printed circuit board. SMOBC results in final metallization being copper with no protective metal beneath. In this process, the non-coated areas, are coated using solder resist. Also, the component terminal areas are exposed in this process. This helps eliminate the tin lead that is present under the mask.

SMD: SMD stands for Surface Mount Device. An electronic device, which is made using the Surface Mount Technology (SMT), is termed as SMD.

SMT: Surface Mount Technology (SMT) is a method used for making electronic circuits. In this method, the components are directly mounted on Printed Circuit boards (PCBs). This method is also sometimes referred to as surface mount. In this technology, the components are soldered on the board without making use of holes. This technology is mainly used for creating printed wiring. The result of this technology is higher component density. Besides this, SMT allows smaller printed wiring boards.

Small Outline Integrated Circuit (SOIC): SOIC is a type of surface mounted integrated circuit, which has its pin-out layout similar to that of DIP (Dual-Inline-Package) circuits.

Silicon Wafer: Silicon wafer is a thin disk of silicon consisting of a set of integrated circuits before they are being cut free and packaged. The wafer resembles a music CD, and diffracts the reflected light into rainbow patterns. On observing closely, individual ICs can be seen, which form a uniform patchwork. These ICs are generally square- or rectangular-shaped.

Soft Copy: Soft copy is an electronic form of a document. It can either be stored on a storage media, or can be a data file that is saved in computer memory.

Solder: Solder is an alloy, which is melted to seal or join metals having high melting points. Solder itself as a low melting point.

Solder Balls: Solder balls, which are also referred to as solder bumps are round balls that are bonded to the contact area of a transistor. These balls or bumps are used for connecting conductors with the help of face-down bonding techniques.

Solder Bridging: Solder bridge is an unwanted connection of two conductors. This occurs when a solder blob of solder connects the conductors, and forms a conductive path.

Solder Bumps: Solder bumps refer to round-shaped solder balls that are bonded to component pads. These are mainly used in face-down bonding method.

Solder Coat: Solder coat refers to a layer of solder directly applied to a conductive pattern from a molten solder bath.

Solder Leveling: Solder leveling is a process of removing extra and unwanted solder from holes and lands of a circuit board. This is done by exposing the board to hot air or hot oil.

Solderability Testing: It is the testing method, which determines the ability of a metal to be wetted by solder.

Solder Mask: It is a technique in which everything present on a circuit board is plastic coated except for fiducial marks, the contacts to be soldered, and the gold-platted terminals of any card-edge connectors.

Solder Mask Color: Solder mask can be of different colors, which include blue, red, white, etc.

Solder Paste: It is a paste, which is applied on a PCB or its panel. Solder paste provides a stable placement and soldering of surface mount components.

Solder Paste Stencils: Solder paste stencils are mainly used to make sure that only the right amount of solder paste is applied. This helps realize the finest electrical connections.

Solder Plate: It is a tin/lead alloy, which is plate in a pattern that defines finished features or circuits.

Solder Resists: Solder resists are coatings, which are used to insulate those portions of a circuit patterns that do not require solder.

Solder Wick: Solder wick is a band, which is typically used to remove molten solder from a solder joint or just desoldering. It can also be used to removing the molten solder from solder bridge.

Space Transformer (ST): A space transformer is one of the major components of high-density probe cards, which provides high routing density, pitch reduction, and localized mid-frequency decoupling.

SPC: SPC refers to Statistical Process Control. It is a process of data collection, which monitors the stability and functions of a circuit.

Sputtering: Sputtering is a deposition process, in which a surface (generally referred to as a target) is immersed in an inert gas plasma. Ionized molecules are then bombarded on this target to release surface atoms. Sputtering is based on the target material’s disintegration by ion bombardment.

Squeegee: Squeegee is a tool used to force the ink or resist through the mesh. It is mainly used in silk screening.

SQFP: SQFP, which stands for Shrink Quad Flat Package or Small Quad Flat Package is one of the variants of a QFP. See QFP.

Stacked Vias: As the name suggests, stacked vias are micro vias in High-Density Interconnect (HDI) PCB. These vias are stacked upon each other

Starvation Resin: As the name implies, starvation resin is the deficiency of resin in base material. This deficiency occurs after lamination, as a result of dry spots, low gloss, or weave texture.

Step–and–Repeat: Step-and-repeat is a process of exposing a single image successively for producing a multiple-image production master. This process is used in CNC programs.

Streamlined PCB Design: Streamlined PCB design, which is also referred to as streamlined design or SLPD, is basically a set of policies that help guide the designing of PCBs. The main purpose of deriving these policies is to simplify PCB design and eliminate errors systematically.

Strip: It is the process of removing plated metal or developed photo resist.

Stuff: Stuff refers to the process of attaching and soldering different components to a printed wiring board.

Sub-Panel: Sub-panel is a group of printed circuits, which are also referred to as modules that are arrayed in a panel. A sub-panel is handled by both the assembly house, as well as the board house as if it were a single printed wiring board. Typically, a sub-panel is prepared at the board house. Most of the material separating individual modules are routed, and thus leaving small tabs. These tabs are strong enough to allow the assembly of a sub-panel as a unit. On the other hand, these tabs are also weak enough to enable easy final separation of assembled modules.

Substrate: A substrate is either an active material, which is monolithic compatible, or a passive material, which is thin film and hybrid. It is used as a supporting material for attaching parts of an integrated circuit.

Subtractive Process: Subtractive process is exactly opposite to the additive process. A subtractive process is a process in manufacturing of a printed circuit, wherein an already existing metallic coating is subtracted for building a product.

Surface Finish: Surface finish refers to the type of finish that is required by a customer for a printed circuit board. Regular boards can have surface finishes, such as gold plating, immersion silver, OSP (Organic Solderability Preservative), immersion gold, and HASL (Hot Air Solder Leveling).

Surface ft.: Surface feet refers to the total surface area of a given work piece in feet.

Surface Mount Pitch: The pitch of the surface mount refers to the dimensions from the center to the center of surface mount pads. These dimensions are measured in inches. There are three pitch values as follows:

  • Standard pitch: >0.025"
  • Fine pitch: 0.011"-0.025"
  • Ultra-fine pitch: <0.011"

As the pitch of a board gets fine, the costs of test fixture and processing increase.

Symbol: A symbol is a simplified design, which is used to represent certain part in a schematic circuit diagram.

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T

TAB: TAB stands for Tape Automated Bonding. It is a process in which bare Integrated Circuits (ICs) are placed on PCBs by attaching them to fine conductors in a polyimide or polyamide film.

Tab Plate: Tab plate refers to selective plating on edge connectors, typically nickel/gold.

Tab Routing (with & without perforation holes): Tab routing is one of the most widely used approach for PCB panelizing, which is done with or without perforation holes. Non-rectangular boards can be produced with the help of tab routing. It is the optimal way of setting up parts that are relative to the tooling process.

Temperature Coefficient (TC): When temperature changes, electrical parameters, such as capacitance or resistance undergo change. The ratio of the quantity change of these parameters is termed as temperature coefficient (TC). It is expressed in ppm/°C or %/°C.

T/d: The temperature at which a circuit loses 5% of its volume because of outgassing, is termed as temperature of destruction.

Tented Via: It refers to a via having a dry film solder mask, which covers both the plated-thru holes, as well as the pads, is termed as tented via. This helps insulate via from foreign objects, which in turn protects it from accidental shocks.

Tenting: Tenting refers to covering holes of a printed circuit board, along with the surrounding conductive pattern with the help of dry film resist.

Terminal: A terminal is a point of connection, where two or more conductors in a circuit are connected. Generally, one among the two conductors is lead of a component or an electrical contact.

Terminal Block: Terminal block is a type of header. Wires are directly attached to this header without using a connector plug. Terminal blocks have holes through which each wire is inserted and anchored with the help of a screw.

Testing: Testing refers to a method, which makes sure whether assemblies, sub-assemblies, and/or a finished product adhere to a set of parameters and functional specifications. There are different types of testing, such as environmental, reliability, in-circuit, and functional testing.

Test Board: As the name suggests, a test board is a printed board used to determine the acceptability of a group of boards that are or will be produced by the similar fabrication process.

Test Coupon: A test coupon refers to a PCB, which is used to ensure the good quality of a Printed Wiring Board (PWB). These coupons are fabricated on the same panel as that of PWBs. Generally, these coupons are fabricated at the edges.

Test Fixture: Test fixture refers to the device that acts as an interface between the unit under test and the test equipment.

Test Point: As the name implies, test point is a point in a circuit at which different functional parameters are tested.

TG: TG stands for the glass transition temperature. It is the point at which the resin contained in the solid base laminate starts exhibiting soft, plastic-like symptoms. This phenomenon occurs at rising temperatures, and is expressed in degrees Celsius (°C).

Thermal Pad: A thermal pad is a special type of pad, which allows easy conduction of heat towards the heat sink. Typically, a thermal pad is made from paraffin, and helps conduct the heat away from electronic components, thus preventing any damage.

Thief: Thief is a common term used for cathode, which is placed on a board. Thief regulates the current density, which goes through the circuit.

Thin Core: Thin core is basically a thin laminate, which has its thickness less than 0.005 inches.

Thin Film: Thin film refers to film of insulating or conductive material, which is deposited by evaporation or sputtering, which may be made in a pattern. It can either be used to form an insulation layer between successive layers of components, or to form electronic components and conductors on a substrate.

Through-Hole: Through-hole, which is also spelled as thru-hole, is a mounting technique. In this technique, pins are designed to be inserted into holes. These pins are then soldered to pads on a printed circuit board.

Tooling: Tooling is defined as processes and/or costs involved in setting up to manufacture a printed circuit boards’ run for the first time.

Tooling Holes: Tooling holes refer to the holes that are drilled in a printed circuit board, which is used for manufacturing hold-down.

Top side: Top side is that side of a PCB, where components are mounted.

TQFP: TQFP stands for Thin Quad Flat Pack. It is similar to a QFP, excluding low-profile, that is, thinner.

Trace: The segment of a route is termed as trace.

Trace width Calculator: Trace width calculator is a JavaScript web calculator, which is used to determine the trace width of PCB connectors for a given circuit. It is done with the help of the formulas from IPC-2221 (formerly IPC-D-275).

Track: Please see the definition for Trace.

Traveler: A traveler is a formula for manufacturing a circuit board. A traveler identifies each order, and travels from start to finish with each order. Instructions for each step in a process are given by a traveler. Information regarding the history and traceability is also provided by the traveler.

Trillium: The name of a company, which makes ATE and DUT systems.

TTL: TTL stands for Transistor-Transistor Logic. It is the most largely used semiconductor logic, which is also referred to as multiple-emitter transistor logic. The basic logic element of this logic is multiple-emitter transistor. This logic has medium power dissipation and high speed.

Turnkey: Turnkey refers to a type of outsourcing method. This method turns over to the subcontractor for all aspects of manufacturing, which include testing, material acquisition, and assembly. The opposite of turnkey method is consignment, in which all the required materials are provided by the outsourcing company, while the assembly equipment and labor is provided by the subcontractor.

Twist: Twist refers to a defect in the lamination process. This defect causes twisted or uneven arc on the plane printed circuit board.

Two-Sided Board: A two-sided board is the same as double-sided board. Please see the definition for double-sided board.

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U

UL: UL is the short form for Underwriter’s Laboratories, Inc. The corporation works for establishing safety standards on different components and equipment. It is supported by some underwriters, and provides inspection, testing, validation, certification, auditing, and advising related to safety.

Unclad: Unclad is a cured epoxy glass, which does not have any copper layer or layers.
 
Underwriters Symbol: The underwriter’s symbol is basically a logo or symbol, which indicates that a product has been recognized by the Underwriters Laboratory (UL).

Unsaturated Logic: Unsaturated logic is the condition in which transistors operate outside their saturation region. This helps make switching faster. Emitter-coupled logic is one such example of an unsaturated logic.

Unstuffed: Unstuffed is a slang term used in PCB manufacturing, which is not much populated.

US-ASCII: US-ASCII is the 7-bit version of the American Standard Code for Information Interchange (ASCII). It uses character codes 0-127. This version is the basis for the 8-bit versions, such as MacASCII, Latin-1, as well as larger coded character set like Unicode.

UV Cure/UV Curing: UV curing is the process of exposing a material to ultra violet light for the purpose of cross inking, or polymerizing and hardening it.

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V

Valuable Final Artwork: Valuable Final Artwork is a term referred in context of “Streamlined PCB design”.  The artwork is perfectly suited for activities like numeric control tooling for printed circuit manufacture and photo imaging in the circuit boards. These boards are thoroughly checked for errors and flaws before being dispatched for manufacture. It can be exchanged with any customer for money or any other support, hence it is termed as Valuable. 

Vapor Phase: It is a process, where a vaporized solvent is used for heating the solder. The solder is generally heated beyond its melting point to create a durable component-to-board solder joint.

VCC/Vin: The input voltage coming from any external source. The input voltage may come from wall transformers, mains, power outlets, dedicated power supplies, batteries, and solar panels. VCC is related to GND.

VDD or Vdd or vdd: A term used for voltage drain. VDD usually implies a positive voltage.

VEE or Vee or vee: It is also known as Emitter supply of the VEE is usually -5V for ECL circuits. The VEE is associated with the collector and emitter sides of any bipolar transistor like NPN.

Vector Photoplotter: Also known as Gerber photoplotter, this equipment plots a CAD database on a film in a darkroom by drawing a line through a lamp light that is shined through a ring aperture (more precisely an annual ring aperture). The apertures are pieces of thin plastic that are trapezoidal shaped, but featuring a thin transparent portion that controls the shape and size of the light pattern. These apertures are mounted on an aperture wheel. At a time, an aperture wheel can hold 24 apertures. Gerber photoplotters are ideal for printed circuit board artwork creation. Today, large sized vector photoplotters are used for producing large photoplots.

Via or VIA: VIA, also known as vertical interconnect access, are the plated-through holes in the printed circuit boards. These holes are used to make electrical connections between different layers on any printed circuit board.

Via Filling: A process of filling vias to close them. Generally, non-conductive paste is used for the purpose. Via filling is performed on PCBs where large amount of drills are made by vacuum lifter during the fixation. Also, this process helps prevent the runoff of solder. Via filling is basically used on inner layers, where buried vias are found. 

VLSI: VLSI stands for Very Large Scale Integration. It is the process of creating integrated circuits where thousands of transistors are combined to form a single chip. It is the successor to large-scale integration (LSI), medium-scale integration (MSI) and small-scale integration (SSI) technologies.

Void: These are the empty spaces on the circuit board, where there are no electronic components or substances present.

VQFP: VQFP stands for Very Thin Quad Flat Pack.

VQTFP: Very Thin Quad Flat Package.

vss or VSS or Vss: It stands for Collector supply voltage. VSS usually implies negative voltage and it is equivalent to GND (ground).

V-Scoring: The edges of the circuit board is “scored” in order to break it apart after the assembly. V-scoring allows the creation of two beveled scoring lines along the perimeter of the board. This allows easy breaking of board afterwards. This method is well-suited for medium to large volume production of panels that require straight cutting. V-scoring requires no space between the units.

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W

Warping: This refers to the finished board warp and a twist. All printed circuit boards have warps due to manufacturing. The warp ratio increases, if materials used contain a high level of moisture. Hence, mentioning warping tolerance is very important.

Wave-soldering: A soldering process which involves soldering, pre-heating, and cleaning.

Weave Exposure: This is a surface condition, where unbroken fibers of a woven glass cloth are not completely covered by a resin. Weave exposure is used in reference to a base material.

Weave Texture: A surface condition in which a weave pattern of a glass cloth becomes clearly visible. However, unbroken fibers of the woven cloth are covered with resin.

Wedge Voids: These are basically layer separation defects in a drilled hole. Wedge voids are also sites that retain chemicals.

Wet Solder Mask: A wet epoxy ink is applied on copper traces of a circuit board through a silk screen. A wet solder mask generally has a resolution of a single track design. This means it is not suited for fine-line designs.

WEEE Directive: WEEE Directive is the EU directive 2002/96/EC, which aims to curb increasing amount of electronic waste. WEEE is an abbreviation of Waste of Electrical and Electronic Equipment.

Whisker: A needle-shaped and slender metallic growth on a circuit board.

Wicking:  In this process, copper salts are migrated into the glass fibers of an insulating material of a plated hole

WIP: WIP stands for Work in Progress. It is generally used as folder name’s extension or directory where data is stored temporarily denoting the current work in progress.

Wire: Wire is a strand of metallic conductor in the form of a thin flexible thread or rod. When referring to a printed circuit board, a wire can be a route or track.

Wire Bonding: A method of attaching a very fine wire to semiconductor components, to interconnect them. These wires are made from aluminum, which contains 1% silicon. The wires measure 1-2 mm in diameter.

Wire Bondable Gold: This is a soft gold. This coating is softer than most other gold finishes, which means it can be bonded easily for stronger connections. The finish comprises 99% pure gold (24 carat) with typical thickness ranging from 30-50 micro inches of gold.

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X

X: X axis refers to the principal horizontal or left-to-right direction axis in a two-dimensional system of co-ordinates.

X-Ray: During the PCB manufacturing, X-ray is used for analyzing BGA components, as well as multilayer circuit boards.

X-Outs: This term is used when an array of PCBs found on a single board fails final inspection or electrical test. The PCBs are “X’ed” out using a marker to indicate that they should not be used. Many times, customers specify percentage of X-outs allowed in an array, whereas others may not tolerate X-outs in an array. This point should be specified while quoting the PCBs because additional costs may be incurred.

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Y

Y Axis: Y axis refers to any principal vertical or bottom-to-top direction axis in a two-dimensional system of co-ordinates.

Young’s Modulus: This is amount of force applied by an object, when it expands or contracts as a result of change in temperature.

Yield: In PCB manufacturing, the yield rate refers to the usable PCBs from a production panel.

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Z

Z Axis: It refers to an axis, which lies perpendicular to the plane formed by X and Y reference. Z axis usually represents the board’s thickness.

Zero Defects Sampling: A statistical sampling method, where a given sample is inspected for defects. If any defects are found, the entire sample is rejected. It is a statistics based attribute sampling plan (C = O).

Zero Width: This is an outline shape with “O” thickness line width. The most common example is using a polygon to draw shapes or copper fill to define the drawing limit of an entity.

Zip File: A compressed file that includes all design files that are needed for printed circuit board manufacturing. For example, the files required for a two layer circuit board may include Gerber files for the top and bottom copper, top and bottom soldermask, and top silkscreen. There will be a fabrication drawing and the NC drill file too. Generally, all the pre-mentioned files have a big file size. Thus, manufacturers require their customers to send them zip files. 

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