Glossary of Terms
Printed circuit boards are available with different features, elements and components which make their functionality unique. As a leading electronics contract manufacturer, we offer comprehensive PCB assembly services to various industrial sectors including Aerospace, Military, Medical, Defense, Telecommunication, Consumer Electronics, Renewable Energy and more. Get a quick understanding or reference on various PCB terms, buzz words, PCB glossary, tips, PCB design terminology, PCB assembly terms, guide and tools.
Active component - 1. A component which adds energy to the signal it passes. 2. A device that requires an external source of power to operate upon its input signal(s). 3. Any device that switches or amplifies by the application of low-level signals. Examples of active devices which fit one or more of the above definitions: transistors, rectifiers, diodes, amplifiers, oscillators, mechanical relays and almost all IC's (Contrast with passive component )
AlN ?Aluminum Nitride, a compound of aluminum with nitrogen.
AlN Substrate ?A substrate of aluminum nitride.
Alumina ?A ceramic used for insulators in electron tubes or substrates in thin-film circuits. It can withstand continuously high temperatures and has a low dielectric loss over a wide frequency range. Aluminum oxide (Al 2 O 3 )
Analog circuit ? A circuit in which the output varies as a continuous function of the input, as contrasted with digital circuit.
Anode - 1. The positive element such as the plate of a vacuum tube; the element to which the principal stream of electrons flows. 2. In a cathode-ray tube, the electrodes connected to a source of positive potential. These anodes are used to concentrate and accelerate the electron beam for focusing. (Graf)
Aperture - 1. An indexed shape with a specified x and y dimension, or line-type with a specified width, used as a basic element or object by a photo plotter in plotting geometric patterns on film. The index of the aperture is its Position (a number used in an aperture list to identify an aperture) or D code. 2. A small, thin, trapezoidal piece of plastic used to limit and shape a light source for plotting light patterns on film, and mounted in a mechanical disk called an "aperture wheel" which in turn is mounted on the lamp head of a vector photoplotter. An aperture is mostly opaque, but with a transparent portion that controls the size and shape of the light pattern. A vector photo plotter plots images from a CAD database on photographic film in a darkroom by drawing each line with a continuous lamp shined through an annular-ring aperture, and creating each shape (or pad) by flashing the lamp through a specially sized and shaped aperture. 3. A line of textual data in an aperture list describing the index names (D code and position), the shape, the usage (flash or draw) and the X and Y dimensions of an aperture. Some aperture lists leave out certain of those types of data. For example, laser photoplotters don't need to know whether an aperture is a flash or draw, so a modern-day aperture list might leave that datum out.
Aperture list - 1. An ASCII text data file which describes the size and shape of the apertures used by a photo plotter for any one photoplot. 2. A print-out of this file. 3. A binary version of this file. [Also called "aperture table."]
Aperture table ? Aperture list.
Aperture wheel - A component of a vector photoplotter, it is a metal disk having cut-outs with brackets and screw holes arranged near its rim for attaching apertures. Its center hole is attached to a motorized spindle on the lamp head of the photoplotter. When a D code denoting a particular position on the wheel is retreived from a Gerber file by the photoplotter, the wheel is caused to rotate so that the aperture in that position is placed between the lamp and the film.
In preparation for a photoplotting, the aperture wheel is set up by a technician who reads a printed aperture list , selects the correct aperture from a set of them stored in a box with compartments and, using a small screw driver, installs the aperture onto the position on the wheel which is called for on the list. This process is subject to human error and is one of the disadvantages of vector photoplotters as compared with laser photoplotters.
Artwork Artwork for printed circuit layout is photoplotted film (or merely the Gerber files used to drive the photoplotter), NC Drill file and documentation which are all used by a board house to manufacture a bare printed circuit board. See also Valuable Final Artwork.
ASCII - American Standard Code for Information Interchange. A text and control-code character set used in computers. Pronounced "ASS-key."
(Note: The following description is excerpted from "FOLDOC," Free Online Dictionary of Computing. The links in this definition point to FOLDOC, and will open in a new window.)
ASCII is the basis of character sets used in almost all present-day computers. US-ASCII uses only the lower seven bit s (character points 0 to 127) to convey some control codes , space, numbers, most basic punctuation, and unaccented letters a-z and A-Z. More modern coded character sets (e.g., Latin-1 , Unicode ) define extensions to ASCII for values above 127 for conveying special Latin characters (like accented characters, or German ess-tsett), characters from non-Latin writing systems (e.g., Cyrillic, or Han characters ), and such characters as distinct open- and close-quotation marks ("and"), ¾ and ®.
The complete ASCII character set known as "Latin-1", an extension to 256 characters of the US-ASCII 128-character set, has been provided online by Paul Lutus at Arachnoid.com.
Assembly - 1. The process of positioning and soldering components to a PCB. 2. Act or process of fitting together parts to make a whole.
Assembly drawing- A drawing depicting the locations of components, with their reference designators, on a printed circuit. Also called "component locator drawing."
Assembly house - A manufacturing facility for attaching and soldering components to a printed circuit.
ASTM - American Society of Testing and Materials.
ATE - Automatic Test Equipment. (See also DUT.)
AWG - American Wire Gauge. A PCB Layouter needs to know diameters of wire gauges to properly size E-pads. The American Wire Gauge, formerly known as the Brown and Sharpe (B + S) Gauge, originated in the wire drawing industry. The gauge is calculated so that the next largest diameter always has a cross-sectional area that is 26% greater. From this basic relationship, the following rules can be deduced.
Auto-router - automatic router, a computer program that routes a PC board layout (or a silicon chip layout) automatically.
Ball grid array- (Abbrev. BGA). A flip-chip type of package in which the internal die terminals form a grid-style array, and are in contact with solder balls ( solder bumps ), which carry the electrical connection to the outside of the package. The PCB footprint will have round landing pads to which the solder balls will be soldered when the package and PCB are heated in a reflow oven. Advantages of the ball grid array package are (1) that its size is compact and (2) its leads do not get damaged in handling (unlike the formed "gull-wing" leads of a QFP' ) and thus has a long shelf life. Disadvantages of the BGA are 1) they, or their solder joints, are subject to stress-related failure. For example, the intense vibration of rocket-powered space vehicles can pop them right off the PCB, 2) they can not be hand-soldered (they require a reflow oven), making first-article prototypes a bit more expensive to stuff, 3) except for the outer rows, the solder joints can not be visually inspected and 4) they are difficult to rework.
Base - The electrode of a transistor which controls the movements of electrons or holes by means of an electric field on it. It is the element which corresponds to the control grid of an electron tube.
Beam lead - A metal beam (flat metallic lead which extends from the edge of a chip much as wooden beams extend from a roof overhang) deposited directly onto the surface of the die as part of the wafer processing cycle in the fabrication of an integrated circuit. Upon separation of the individual die (normally by chemical etching instead of the conventional scribe-and-break technique), the cantilevered beam is left protruding from the edge of the chip and can be bonded directly to interconnecting pads on the circuit substrate without the need for individual wire interconnections. This method is an example of flip-chip bonding, contrasted with solder bump.
BGA - Ball Grid Array.
Board - printed circuit board. Also, a CAD database which represents the layout of a printed circuit.
Board house ?Board vendor. A manufacturer of printed circuit boards.
Body ?The portion of an electronic component exclusive of its pins or leads.
BOM [pronounced "bomb"]?Bill of Materials. A list of components to be included on an assembly such as a printed circuit board. For a PCB the BOM must include reference designators for the components used and descriptions which uniquely identify each component. A BOM is used for ordering parts and, along with an assembly drawing, directing which parts go where when the board is stuffed.
C4 - Controlled Collapsed Chip Connect. A type of flip-chip technology which is used in Intel's Pentium III™ and in Motorola's PowerPC 603™ and PowerPC 604™ RISC Microprocessors.
CAD - Computer Aided Design. A system where engineers create a design and see the proposed product in front of them on a graphics screen or in the form of a computer printout or plot. In electronics, the result would be a printed circuit layout.
CADCAM - Simply a concatenation of the two terms CAD and CAM.
CAE - Computer Assisted Engineering. In electronics work, CAE refers to schematic software packages.
CAF - Conductive Anodic Filamentation (or Conductive Anodic Filament growth) - An electrical short which occurs in PCBs when a conductive filament forms in the laminate dielectric material between two adjacent conductors under an electrical bias. CAF is a potentially dangerous source of electrical failure in the PCB. As PCB Layouts have increased in density, with hole-to-hole spacings reduced to 25 mils or less, CAF has become an everyday concern. [adapted from Erik J. Bergum, "CAF Resistance of NON- DICY FR-4," PC FAB , 9/2002]
CAM - Computer Aided Manufacturing. See CAM files below.
CAM files - CAM means Computer Aided Manufacturing. These are the data files used directly in the manufacture of printed wiring. . The types of CAM files are 1) Gerber file, which controls a photoplotter, 2) NC Drill file, which controls an NC Drill machine and 3) fab and assembly drawings in soft form (pen-plotter files). CAM files represent the valuable final product of PCB Layout. They are handed off to the board house which further refines and manipulates CAM data in their processes, for example in step- and-repeat penalization. Some PCB Layout software companies refer to all plotter or printer files as CAM files , although some of the plots may be check plots which are not used in manufacture.
Capture - 1. To draw (schematics) with CAE software in such a way that data, especially connectivity, can be extracted electronically. The extracted data would minimally be a netlist and preferably also a BOM. The more useful the data that is included in the schematic, the more useful will be the BOM and netlist extracted from it will be.
2. Extract data from a CAE schematic. E.g. " Capture a netlist."
3. The process of creating a CAE drawing containing intelligent data. E.G. "Schematic capture."
Card - another name for a printed circuit board.
Card-edge connector - A connector which is fabricated as an integral portion of a printed circuit board along part of its edge. Often employed to enable a daughter or add-on card to be plugged directly into another much larger printed board, the motherboard or backplane. See finger.
Capture - Extract information automatically through the use of software, as opposed to hand-entering of data into a computer file.
Cathode- 1. In an electron tube the electrode through which a primary source of electrons enters the interelectrode space. 2. General name for any negative electrode. 3. When a semiconductor diode is biased in the forward direction, that terminal of the diode which is negative with respect to the other terminal. 4. In electrolytic plating, the work piece being plated. (Graf)
CBGA - Ceramic Ball Grid Array.
CEM - A NEMA grade of industrial laminate having a substrate of woven glass surfaces over a cellulose paper core and a resin binder of epoxy. It has good electrical and mechanical properties, somewhat surpassed by those of FR-4.
Check Plots - Pen plots that are suitable for checking only. Pads are represented as circles and thick traces as rectangular outlines instead of filled-in artwork. This technique is used to enhance transparency of multiple layers.
Chip - 1. An integrated circuit manufactured on a semiconductor substrate and then cut or etched away from the silicon wafer. (Also called a die.) A chip is not ready for use until packaged and provided with external connections. 2. Commonly used to mean a packaged semiconductor device.
Chip-on-board - Abbreviated COB. In this technology integrated circuits, small portions of silicon wafers, are glued and wire-bonded directly to printed circuit boards instead of first being packaged. The electronics for many mass-produced toys are embedded by this system, which can be identified by the black glob of plastic sitting on the board. Underneath that glob (technical term: glob top), is a chip with fine wires bonded to both it and the landing pads on the board.
Chip Scale Package - A chip package in which the total package size is no more than 20% greater than the size of the die within. Eg: Micro BGA.
CIM - Computer Integrated Manufacturing. Used by an assembly house, this software inputs assembly data from a PCB CAM/CAD package, such as Gerber and BOM, as input and, using a pre-defined factory modeling system, outputs routing of components to machine programming points and assembly and inspection documentation. In higher end systems, CIM can integrate multiple factories with customers and suppliers.
Clad - A copper object on a printed circuit board. Specifying certain text items for a board to be "in clad" means that the text should be made of copper, not silkscreen.
Collector - 1. An electrode in a transistor that collects electrons or holes. 2. In certain electron tubes, an electrode to which electrons or ions flow after they have completed their function.
Component - Any of the basic parts used in building electronic equipment, such as a resistor, capacitor, DIP or connector, etc.
Component Library - A representation of components as decals, stored in a computer data file which can be accessed by a PCB CAD program.
Connection -One leg of a net. Also called a "pin pair" (PADS) and "from-to" (Protel).
Connectivity - The intelligence inherent in PCB CAD software which maintains the correct connections between pins of components as defined by the schematic.
Connector - A plug or receptacle which can be easily joined to or separated from its mate. Multiple-contact connectors join two or more conductors with others in one mechanical assembly.
Control Code - A non-printing character which is input or output to cause some special action rather than to appear as part of the data. Control codes are generated by holding down the Ctrl key on your computer keyboard while pressing one of the letter keys (e.g. (CTRL-G). Sometimes called "control characters."
Coupon - See test coupon.
CSP - Chip Scale Package or Chip Scale Packaging.
D code - Draft code. 1. A datum in a Gerber file which acts as a command to a photoplotter. A D code in a Gerber file takes the form of a number prefixed by the letter D, e.g. "D20". However, in some aperture lists the D is dropped. In aperture lists of Cadstar, the column heading "Position" actually refers to D code, and the D prefix is dropped. 2. D codes have multiple purposes. The first is to control the state of the light being on or off. Valid codes for light state are D01, D02, and D03.
D01 - Light on for next move.
D02 - Light off for next move.
D03 - Flash (Light On, Light Off) after move (effect is limited to block in which appears, i.e. non-modal). You can also think of a D03 as D02, D01, D02 series of commands linked together.
D codes with values of 10 or greater represent the aperture's position on the list or wheel. It is very important to understand that there is no universal "D10" or "D30". Unlike the D01 , D02, and D03 counterparts which have a fixed meaning ( draw, move, flash), D10 and higher values have aperture shapes and dimensions assigned to them by each individual user. Hence, one job's D10 could be a 10 mil Round, when another job's D10 could be a 45 mil Square.
There are two distinct ways to number an aperture list. The traditional 24 aperture system started with D10 - D19, jumping suddenly to D70 - D71, then back to D20 - D29, ending with D72 -D73. This is still a common format for output for CAD packages, and is still mandatory for old 24 aperture Gerber vector Photoplotters.
It is now common to start with D10, then increase numerically in steps of 1 (D10, D11, etc.) continuing up to D70 and beyond, rarely beyond 1000 individual apertures. From Advanced Microcomputer Systems CAE Glossary
Database - A collection of interrelated data items stored together without unnecessary redundancy, to serve one or more applications.
Decal -A graphic software representation of a component, so named because hand tape-up of printed circuit boards employed the use of pull-off and paste decals to represent components. Also called a part, footprint or package . On a manufactured board the body of a footprint is an epoxy-ink outline.
Destructive Testing - Sectioning a portion of printed circuit panel and examining the sections with a microscope. This is performed on coupons, not the funtional part of the PCB.
Device -Any type of electrical component on a PC board. It will have functions and properties unique to its type. In a schematic (and the extracted BOM), it will be labeled with a value or device number. There are two main classes of devices, passive and active.
DICY -Dicyandiamide, the most common cross-linking agent used in FR-4. [Erik J. Bergum, "CAF Resistance of NON- DICY FR-4," PC FAB , 9/2002]
Die -A chip. (Plural: dice)
Dielectric Constant -The ratio of the capacitance of a capacitor with the given dielectric to the capacitance of a capacitor having air for its dielectric but otherwise identical. (Graf)
Differential Signaling -A method of signal transmission through two wires which always have opposite states. The signal data is the polarity difference between the wires: Whenever either is high, the other is low. Neither wire is grounded. [Graf]
Regarding this alternative view: At Golden Gate Graphics we follow the advice of Douglas Brooks, not Lee W. Richey. Does that mean Ritchey is wrong? No. We adopt this policy of applying differential impedance design rules to our PCB layouts which have differential signaling, because it is the more conservative approach and is more likely to please our customers. It might also mean the boards manufactured to employ differential impedance control with testing via coupons and TDR will be more expensive. If the customer does not want this expense, that is their choice. If our layouts have incorporated differential impedance design rules, they will still work as well as a layout done without that control.
Digital Circuit -A circuit which operates like a switch (it is either "on" or "off"), and can make logical decisions. It is used in computers or similar decision making equipment.
Diode - 1. A device, as a two-element electron tube or a semiconductor, through which current can pass freely in only one direction. (Random House) 2. A semiconductor device with two terminals and a single junction, exhibiting varying conduction properties depending on the polarity of the applied voltage.(Graf)
DIP - Abbreviation for Dual In-line Package. A type of housing for integrated circuits. The standard form is a molded plastic container of varying lengths and 0.3 inch wide (although there are other standard widths), with two rows of through-hole pins spaced 0.1 inch between centers of adjacent pins.
DNI - Do Not Install. Same use as DNP, which means "Do Not Populate"
DNP - Do Not Populate. This acronym is often used on schematics to show that a component shown in the cirucit diagram is not actually placed and soldered on the finished printed circuit board during initial assembly. The footprint will be on the board, but no component will be there. This can allow an option for adding a componet of that size and shape later for experimentation and debugging.
DOS - Disk Operating System. A program that controls the computer's transfer of data to and from a hard or floppy disk. Personal computers that are IBM-compatible run DOS rather than other early varieties of operating systems.
DOS-formatted - (Of magnetic data storage media, such as floppy disks.) Prepared for storage of data in such a way that DOS transfer can occur.
Double-track - Slang for fine line design with two traces between DIP pins.
Draw - 1. v. To plot a line on film by moving the film while shining a light through an aperture. 2. n. A line plotted thus.
Dry film solder mask - A solder mask film applied to a printed board with photographic methods. This method can manage the higher resolution required for fine line design and surface mount. It is more expensive than liquid photoimageable solder mask.
DUT - Device Under Test. A DUT board (probe card) is used in automated testing of integrated circuits. It is part of the interface between the chip and a test head, which in turn attaches to computerized test equipment. The specific test equipment used will determine the value of the controlled impedance required for the chip tester boards. For more on DUT boards, click here. Depending on which system it is made for, one type of DUT board is used in testing individual integrated circuits in a silicon wafer before they are cut free and packaged, and another type is used for testing packaged IC's.
E-pad - "Engineering-pad." A plated-through hole or surface mount pad on a PCB placed on the board for the purpose of attaching a wire by soldering. These are usually labeled with silkscreen. E-pads are used to facilitate proto-typing, or simply because wires are used for interconnections instead of headers or terminal blocks.
ECL - Emitter Coupled Logic. A type of unsaturated logic performed by emitter-coupled transistors. Higher speeds may be achieved with ECL than are obtainable with standard logic circuits. ECL is costly, power hungry, and difficult to use, but it is four times faster than TTL.
Electrical Object - [Protel] A graphical object (in a PCB or schematic database) to which an electrical connection can be made, such as a component pin or a wire.
Embedded - (Of a micro-processor(s), or system controlled by such) Dedicated to doing one job or supporting one device and built into the product.
EMC - electromagnetic compatibility. (1) The ability of electronic equipment to operate without degradation in an intended electromagnetic environment (2) The ability of equipment to operate in its electromagnetic environment without creating interference with other devices. [From the National Instruments, Developer Zone, Measurement Encyclopedia ] At circuit board level, one could substitue the term circuit for equipment in the above definitions. Eg."If the ground returns are common, they can be connected at a single point near the external ground connection, which is good EMC practice." -- Jon Berrie, Technical Marketing Specialist Hot-Stage, Zuken .
EMP - Electromagnetic pulse. A reaction of large magnitude resulting from the detonation of nuclear weapons. (Graf)
End-to-end design - a version of CADCAM CAE in which the software packages used and their inputs and outputs are integrated with each other and allow design to flow smoothly with no manual intervention necessary (other than a few keystrokes or menu selections) to get from one step to the other. Flow can occur in both directions. In the field of PCB Layout, end-to-end design sometimes refers to only the electronic schematic/pcb layout interface, but this is a narrow view of the potentialities of the concept. For example, end-to-end systems can also implement electronic circuit simulation, parts procurement and beyond. For an introduction to the overall design flow of an electronics project, see the PCB Layouter definition and follow the link to the plain English description for a printed circuit board makers
Excellon - NC Drill file format. An ASCII format used in a file which drives an NC Drill machine. The earliest NC Drill machines were made by Excellon Automation Company. The format is in broad use, although the company has been sold.
Fab - Short for fabrication.
Fabrication Drawing - A drawing used to aid the construction of a printed board. It shows all of the locations of the holes to be drilled, their sizes and tolerances, dimensions of the board edges, and notes on the materials and methods to be used. Called "fab drawing" for short. It relates the board edge to at least on hole location as a reference point so that the NC Drill file can be properly lined up.
FC - Flexible Circuit, flexible circuitry, flexcircuit or flex circuit.
Fine line design - Printed circuit layout permitting two (rarely three) traces between adjacent DIP pins. It entails the use of a either dry film solder mask or liquid photoimageable solder mask (LPI), both of which are more accurate than wet solder mask.
Fine Pitch - Refers to chip packages with lead pitches below 0.050". The largest pitch in this class of parts is 0.8mm, or about 0.031". Lead pitches as small as 0.5mm (0.020") are used.
Finger - A gold-plated terminal of a card-edge connector. [Derived from its shape.]
Flash - 1. v. To turn a vector photoplotter lamp on for a brief but precise duration and then off, during which time the relative positions of the lamp and film remain fixed. This exposes the film with the image of a small object (the size and shape of which is controlled by the transparent portion of an aperture). 2. n. A small image on film created in such wise or as directed by a command in a Gerber file.) The maximum size (x or y dimension)for a flash varies from one photoplotting shop to another, but is commonly ½ inch.
Flex Circuit - Flexible circuit, or flexcircuit; a printed circuit made of thin, flexible material. For more information, see flexible circuitry below.
Flexcircuit - See flex circuit above.
Flexible Circuitry - An array of conductors bonded to a thin, flexible dielectric. It has the unique property of being a three-dimensional circuit that can be shaped in multiplanar configurations, rigidized in specific areas, and molded to backer boards for specific applications. As an interconnect, the main advantages of flex over traditional cabling are greater reliability, size and weight reduction, elimination of mechanical connectors, elimination of wiring errors, increased impedance control and signal quality, circuit simplification, greater operating temperature range, and higher circuit density. In many applications, lower cost is another advantage of using flexible circuits. From Comparison of Printed Flexible Circuitry and Traditional Cabling , an article By JACK LEXIN - vice president for marketing and sales at L.E. Flex Circuits , Carlsbad, Calif. appearing in interConnection Technology , December 1992 .
Flexible Printed Circuit - Flex circuit . Abbreviated FPC or FC.
Flip-chip- A mounting approach in which the chip (die) is inverted and connected directly to the substrate rather than using the more common wire bonding technique. Examples of this kind of flip-chip mounting are beam lead and solder bump.
First Article - A sample part or assembly manufactured prior to the start of production for the purpose of ensuring that the manufacturer is capable of manufacturing a product which will meet the requirements. (Graf)
Footprint - 1. The pattern and space on a board taken up by a component. 2. Decal.
FPC - Flexible Printed Circuit, or flex circuit.
FR-1 - A low-grade version of FR-2.
FR-2 - A NEMA grade of Flame-Retardant industrial laminate having a substrate of paper and a resin binder of phenolic. It is suitable for printed circuit board laminate and cheaper than the woven glass fabrics such as FR-4.
FR-4 - A NEMA grade of Flame-Retardent industrial laminate having a substrate of woven-glass fabric and resin binder of epoxy. FR-4 is the most common dielectric material used in the construction of PCBs in the USA. Its dielectric constant is from 4.4 to 5.2 at below-microwave frequencies. As frequency climbs over 1 GHz, the dielectric constant of FR-4 gradually drops.
FR-6 - Fire-Retardant glass-and-polyester substrate material for electronic circuits. Inexpensive; popular for automobile electronics. [Stammtisch Beau Fleuve Acronyms http://www.plexoft.com/SBF/F05.html#FR-4]
A comparison of many types of PCB laminates can be found at the ILNorplex (Industrial Laminates Norplex) Laminate Selector chart.
GC-Prevue - A CAM file viewer and printer made by Graphicode . The freeware version can store Gerber and NC Drill files within a database (.GWK extension), which makes it extremely useful for sharing electronic data: Because it is free, anyone can download and use it for importing Gerber files in a logical sequence, displaying them in perfect register, annotating (adding labels to the filenames to describe their use and position in the stackup) and viewing them, saving all that and then passing the resulting .GWK file on to another for examination. Besides merely looking at the files or printing them, GC-Prevue has features for measuring objects' size and relative distance from each other. To my (John Childers') knowledge, GC-Prevue is the only free Gerber viewer that sets-up and saves Gerber data in a database file. Other free Gerber viewers require one to set up the Gerber files each time and won't allow saving the set-ups unless one buys an upgrade. (From the viewpoint of a printed circuit makers serving engineers or customers, this inability to save set-ups makes the competing free Gerber viewers completely useless for sharing Gerber data.)
Gerber - see Gerber file.
Glob Top - A blob of non-conductive plastic, often black in color, which protects the chip and wire bonds on a packaged IC and also on a chip on board. This specialized plastic has a low coefficient of thermal expansion so that ambient temperature changes will not rip loose the wire bonds it is made to protect. In high-volume chip on board production, these are deposited by automated machinery and are round. In prototype work, they are deposited by hand and can be custom-shaped; however, in designing for manufacturability, one assumes a prototype product will "take- off" and ultimately have high market demand, and so lays out chip on board to accommodate a round glob top with adequate tolerance for machine-driven "slop-over".
Hard Copy - A printed or plotted form of an electronic document (computer data file).
Header - The portion of a connector assembly which is mounted on a printed circuit.
Hole - In a semiconductor, the term used to describe the absence of an electron; has the same electrical properties as an electron except that it carries a positive charge. (Graf)
HPGL - Hewlett-Packard Graphics Language, a text-based data structure of pen-plot files which are used to drive Hewlett-Packard pen plotters. Although Hewlett-Packard no longer makes pen plotters, the large-format dot matrix printers which replaced them can also be driven by HPGL.
IC - Integrated Circuit.
IPC -The Institute for Interconnecting and Packaging Electronic Circuits, the final American authority on how to design and manufacture printed wiring. In 1999, IPC changed its name from Institute of Interconnecting and Packaging Electronic Circuits to IPC. The new name is accompanied with an identity statement, Association Connecting Electronics Industries.
J, K , L
Laser Photoplotter - (also "laser plotter") A photo plotter which simulates a vector photoplotter by using software to create a raster image of the individual objects in a CAD database, then plotting the image as a series of lines of dots at very fine resolution. A laser photop lotter is capable of more accurate and consistent plots than a vector photoplotter.
LGA - 1. Land Grid Array. 2. Leadless Grid Array.
Lead (pronounced "leed") - A terminal on a component.
Liquid photoimageable solder mask (LPI) - A mask sprayed on using photographic imaging techniques to control deposition. It is the most accurate method of mask application and results in a thinner mask than dry film solder mask. It is often preferred for dense SMT.
LPI- stands for Liquid PhotoImageable. Refers to liquid photoimageable solder mask.
Manhattan Algorithm - An algorithm to determine a cross street for an avenue address in Midtown Manhattan New York City, or for the length of a trip from one address in Manhattan to another. If you know the building addresses for where you are and where you want to go in Manhattan, you can call a cab company and find out what it will cost you. An algorithm is used to get the answer, because in Manhattan the street and avenue numbers do not necessarily correspond intuitively to the building numbers. To see an example of the Manhattan algorithm as an intersection locator, go to http://www.ny.com/locator/. What does this have to do with PCB Layout? The Manhattan algorithm has many variations and uses in various branches of mathematics, including the mathematics of auto-routers. See also Manhattan length.
Manhattan length - The length of the two sides of a right triangle as a distance between two points, as opposed to the hypotenuse.. (Derived from the Manhattan algorithm for determining the length of a taxicab trip following streets and avenues on the island of Manhattan, NY.) Routing of traces in orthagonal patterns in a PCB Layout, or in a semiconductor chip, follows the same pattern as streets and avenues in a city. The minimum distance between two component leads, or two nodes on a chip, when routing on 90 degrees is the Manhattan length.
Advanced PCB auto-routers permit specification of maximum length of classes of nets as a percentage of Manhattan length . For example, one could specify clocks as 120% and random nets as 160% of Manhattan length . (This percentage, expressed as a ratio, becomes the "Manhattan coefficient", ie. a Manhattan coefficient of 1.2 means the routed length is 120% of the Manhatten length .) Specifying such limits on the auto-router prevents long and circuitous routes.
Master Aperture List - 1. An aperture list which is used for every PCB Layouted by a PCB Layout service bureau or department. If a new layout requires one or more new apertures, they are added to the list, either at the end or in some previously unused positions set aside for that purpose. The previously used aperture positions are never edited to change their parameters. Thus the updated list can still be used as a master for any previous PCB's made. This type of master aperture list became possible only with the advent of laser photoplotters, which can have upwards of 1000 positions if need be. 2. Any aperture list which is used with two or more PCB's would be called the master aperture list for that set of PCB's.
MCR - Molded Carrier Ring. A type of fine-pitch chip package named for the method of supporting and protecting the leads. The leads are left straight; the ends of the leads are embedded in a strip of plastic, which is the Molded Carrier Ring. Just before assembly (placing on a PCB for soldering), the MCR is cut off and the leads are formed. In this way, the delicate leads are protected against damage in handling until just before assembly.
MELF- Metal ELectrical Face - A surface mount discrete part, usually a diode, that is barrel shaped, or cylindrical. The ends of the "barrel" are capped with metal, the "metal electrical face." The "barrel" is laid on its side, the metal ends upon landing pads, and the part is soldered that way. The two most common sizes are MLL34 and MLL41, which are roughly MELF versions of a DO-35 and DO-41 respectively.
MIC- Monolithic Integrated Circuit.
Micro Ball Grid Array - A fine pitch ball grid array. Fine pitch for BGAs is anything less than 1.27 mm [50 mil ] (some say 1.00 mm [39 mil]). SMTnet terms and definitions SMT in Line terms and definitions.
Micro BGA - micro Ball Grid Array.
Mil- One thousandth of an inch (0.0254 mm). [From abbreviation of mil li-inch, which means one-thousandth of an inch.]
MLC - Multi-Layer Ceramic
Monolithic - 1. Existing as one large, undifferentiated whole. 2. (of an integrated circuit or its elements) built upon or formed within a single slice of silicon substrate.
Monolithic Integrated Circuit- 1. Abbreviated MIC. An integrated circuit formed upon or within a semiconductor substrate with at least one of the circuit elements formed within the substrate. 2. A complete electronic circuit fabricated as an inseparable assembly of circuit elements in a single small structure. It cannot be divided without permanently destroying its intended electronic function. [Graf]
MTF- Multi-layer Thin Film.
Multimeter- A portable test instrument which can be used to measure voltage, current, and resistance.
NC Drill- Numeric Controlled (computer controlled) drill machine. A machine used to drill the holes in a printed board at exact locations, which are specified in a data file. Also known as "CNC drill."
NC Drill File- A text file which tells an NC drill where to drill its holes.
Negative - 1. n . A reverse-image contact copy of a positive, useful for checking revisions of a PCB. If the negative of the current version is superimposed over a positive of an earlier version, all areas will be solid black except where changes have been made. 2. adj . (Of a PCB image) Representing copper (or other material) as clear areas and absence of material as black areas. Typical of power and ground planes and solder mask.
Net - A collection of terminals all of which are, or must be, connected to each other electrically. Also known as a signal.
Netlist- List of names of symbols or parts and their connection points which are logically connected in each net of a circuit. A netlist can be "captured" (extracted electronically on a computer) from a properly prepared CAE schematic.
Node- A pin or lead which will have at least one wire connected to it. In a netlist, a node is described by a component reference desginator together with a pin number.
Open- Open circuit. An unwanted break in the continuity of an electrical circuit which prevents current from flowing.
Package- 1) Decal or printed wiring board component. 2) A type of PCB component which contains a chip and acts to make a convenient mechanism for protecting the chip while on the shelf and after attachment to a PCB. With its leads soldered to a printed circuit board, a package serves as the electrical conduction interface between the chip and the board. An example is a DIP.
Panel - material (most commonly an glass/epoxy-copper laminate known as core) sized for fabrication of printed circuit boards. Panels come in many, many sizes, the most common being 12" by 18" and 18" by 24". Subtract 1/2" to 1" margins (check with your board house) from the panel size to arrive at the space available for printed circuitry.
Panelize - 1. To lay up more than one (usually identical)printed circuits on a pans. Individual printed circuits on a panel need a margin between them of 0.3". Some board houses permit less separation. 2. Lay up multiple printed circuits (called modules) into a sub-panel so that the sub-panel can be assembled as a unit. The modules can then be separated after assembly into discrete printed circuits.
Part - 1. Component. 2. A decal in a PWB database or drawing. 3. A symbol in a schematic.
Passive Component A device which does not add energy to the signal it passes. Examples: resistor, capacitor, inductor. (Contrast with active component.
PC board - Printed Circuit board.
PCB - Printed Circuit Board.
PCB database- All of the data fundamental to a PCB Layout , stored as one or more files on a computer.
PCB Layout - 1. The creation of artwork for the manufacture of bare PCBs . 2. The artwork so created. 3. A computer database used to generate such artwork as data files (CAM files). Also called PCB layout.
PCB Layouter- One who creates the artwork for printed circuit boards. For you recruiters out there who are asked to find one, and for anyone else interested, here is a plain English description for a Printed Circuit Board makers . Hint: It is not the same as an electrical engineer.
PCB Layout service bureau- A business engaged in PCB Layout as a service for others, especially electrical engineers. The word bureau is French for desk, or office, and this service is indeed performed from an office while sitting at a desk. Also called PCB Layout shop.
PCB layout- PCB Layout.
PCMCIA An acronym which means: "People Can't Memorize Computer Industry Acronyms." Wait a minute. That's WRONG! Click here to find out its true meaning: Personal Computer Memory Card International Association
Photoplotter - Device used to generate artwork photographically by plotting objects (as opposed to copying an entire image at once as with a camera) onto film for use in manufacturing printed wiring.
Pin 1. A terminal on a through-hole component. [Derived from its physical shape on through-hole components, which predated SMT.] Also called lead. 2. In the term "pin count," pin refers to a terminal on any component, whether through-hole or SMT.
Pin-out - Pin-number assignment, the relation between the logical inputs and outputs of an electronic device and their physical counterparts in the PCB package . pin-outs will involve pin numbers as a link between schematic and PCB Layout (both being computer generated files). In more complicated packages, they may also involve pin names. Even for devices with only two pins and no polarity, such as resistors, the netlist extracted from a schematic will have a pin 1 and pin 2 for each resistor, even though the schematic might not show a pin number label as such. (The visibility in the schematic of the pin numbers can be turned on or off at will, but the significance of the pin number assignment is still there in the schematic and subsequently, through the netlist extracted from it, the PCB database.) For CAD CAE electronics to work at all, the pin-outs for the PCB database must agree with the schematic.
PI - Polyimide. (Also Pi)
Plasma- A highly-ionized gas containing an approximately equal number of positive ions and negative electrons. Thus, as a whole it is electrically neutral, though conductive and affected by magnetic fields.
Plated-through Hole- A hole in a PWB with metal plating added after it is drilled. Its purpose it to serve either as a contact point for a through-hole component or as a via. In PCB vernacular and documentation, the spelling of the word through is sometimes shortened to thru.
Plastic Leaded Chip Carrier - An SMT chip package that is rectangular or square- shaped with leads on all four sides. The leads are spaced at 0.050 inches, so this package is not considered fine-pitch.
Populate - Install (place, attach and solder) components onto (a printed wiring board). (Slang) Also known as "stuff". This can refer to a single component, as in the acronym used in schematics "DNP", which means "Do Not Populate".
Pos - An abbreviation for Position used by GC-Prevue.
Position- A type of index for an aperture in an aperture list which is a number from 1 to the number of apertures in the aperture list. Position 1 is linked to D code D10, 2 is D11 and so on. Positions appear only in aperture lists, and never in a Gerber file. Cadstar aperture lists use the column heading Position to mean D code. Abbreviated "Pos" in GC-Prevue.
Positive noun A developed image of photoplotted film, where the areas selectively exposed by the photo plotter appear black, and unexposed areas are clear. Board houses work from positives, and a photo plotter produces positives, thus one set of positives is all the film that is needed to produce a printed wiring board. modifier (of a printed wiring image) Representing copper as black areas and absence of copper as clear areas. Typical of images of routed layers of a PWB.
PQFP Plastic Quad Flat Pack. See QFP.
Primitive- (Found in CAD software programs and documentation) 1. Some CAD software documentation (especially Altium makers) extends this term to mean any object in a CAD database--graphics, text or otherwise; so this could be a group of graphic objects if manipulated as a unit, eg. a PCB decal. It may also mean an indivisible graphic object, i.e. a graphical object which may have component parts, but which can not have those parts separated out as individual entities. It can also refere to a parameter or text string. Examples of this in PCB CAD: wire segment, route, pad or padstack, text string. 2. Any geometric shape such as a circle, polygon or square. 3. A function, operator, or type which is built into a programming language (or operating system), either for speed of execution or because it would be impossible to write it in the language. Primitives typically include the arithmetic and logical operations (plus, minus, and, or, etc.) and are implemented by a small number of machine language instructions.
Printed Circuit Board
A flat plate or base of insulating material containing a pattern of conducting material and components placed and soldered to it. It is an electrical circuit. It is a "printed wiring board" (PWB) that has been "stuffed".
The conducting material is commonly copper which has been coated with solder or plated with tin or tin-lead alloy. The usual insulating material is epoxy laminate. But there are many other kinds of materials used in more exotic technologies.
Single-sided boards, the most common style in mass-produced consumer electronic products, have all conductors on one side of the board. With two-sided boards, the conductors, or copper traces, can travel from one side of the board to the other through plated-thru holes called vias, or feed-throughs. In multilayer boards, the vias can connect to internal layers as well as either side.
- A PCB without the components, a "bare board" or a printed wiring board.
Probe card- DUT board.
PWA- Printed Wiring Assembly; same as PCB . A PWA is a bare board (PWB) that has been populated.
PWB - Printed Wiring Board; a "bare board"; an unstuffed PCB . It is flat plate or base of insulating material containing a pattern of conducting material. It is not an electrical circuit until components are placed and soldered to it.
QFP- Quad Flat Pack, a fine-pitch SMT package that is rectangular or square with gull-wing shaped leads on all four sides. The lead pitch of a QFP is typically either 0.8mm or 0.65mm, although there are variations on this theme with smaller lead pitches: TQFP also 0.8mm; PQFP tooled at either 0.65mm (0.026") or 0.025" and SQFP at 0.5mm (0.020"). Any of these packages can have a wide variety of lead counts from 44 leads on up to 240 or more. Although these terms are descriptive, there are no industry- wide standards for sizes. Any printed circuit makers will need a spec sheet for the particular manufacturer's part, as a brief descrition like "PQFP-160" is inadequate to define the mechanical size and lead pitch of the part.
Ratsnest -A bunch of straight lines (unrouted connections) between pins which represents graphically the connectivity of a PCB CAD database. [Derived from the pattern of the lines: as they crisscross the board, the lines form a seemingly haphazard and confusing mess similar to a rat 's nest.)
Reference Designator (abbrv. "ref des")?The name of a component on a printed circuit by convention beginning with one or two letters followed by a numeric value. The letter designates the class of component; eg. "Q" is commonly used as a prefix for transistors. Reference designators appear as usually white or yellow epoxy ink (the "silkscreen") on a circuit board. They are placed close to their respective components but not underneath them, so that they are visible on the assembled board. By contrast, on an assembly drawing a reference designator is often placed within the boundaries of a footprint --a very useful technique for eliminating ambiguity on a crowded board where reference designators in the silkscreeen may be near more than one component.
Register - In printed board manufacture, many terms are borrowed from the subject of printing. Register has the following specialized printing definition from Macmillan Dictionary for Students :
(noun) proper alignment of various plates, stones, or screens to assure clear and accurate reproduction, as of color. Examples: in register, off register.
In printed circuit layout, the makers gets his photoplot files in register before he views them with his Gerber file viewer. The board manufacturer produces film from the Gerber files and uses them in register with respect to the panels of material from which he will build the boards. He is going to want the pads on both sides and on internal layers to be in register before he drills holes in the panel.
Usage note: The term registration is often used in the printed circuit industry for this sense of the noun register . Register , already being a noun, doesn't need the suffix -tion added to it to make it a noun. You wouldn't say, "Count the money in the cash registration." This misuse of registration has become so common that it has entered the literature of PCB Layout and manufacturing. How illiterate we must sound to professional printers when we say "registration" when we mean "register!"
Registration - See register.
RF - Radio Frequency.
Rise Time - the time required for an output voltage of a digital cirucit to change from low voltage level (0) to high voltage leve (1), after the change has started. (For more defintions of the term, see Modern Dictionary of Electronics , by Rudolf F. Graf.) Very short rise times, not high clock speeds, are the primary cause of cross-talk in PCBs. Rise times are charactericstic of the technology being used in a circuit. Gallium Arsenide components can have rise times around 100-picoseconds (millionths of millionths of seconds), 30 to 50 times faster than some CMOS components.
Route - 1. n. A layout or wiring of a connection. 2. v. The action of creating such a wiring.
SAC4 - Self-Aligned Controlled Collapse Chip Connect. A variation of C4 flip-chip technology. . PFEIFFER L, WEST KW, WONG YH ,Journal of the Electrochemical Society (JES) Volume 134, Number 11, November 1987.
Saturation - 1. The operating condition of a transistor when an increase in base current produces no further increase in collector current. 2. A circuit condition whereby an increase in the driving or input signal no longer produces a change in the output. 3. The condition when a transistor is driven so hard that it becomes biased in the forward direction. In a switching application, the charge stored in the base region prevents the transistor from turning off quickly under saturation conditions. 4. Generally, that state in which a semiconductor device is conducting most heavily for a given applied voltage. In many devices it is also a state in which the normal amplification mechanisms have become "swamped" and inoperative.
Schematic - A diagram which shows, by means of graphic symbols, the electrical connections, components and functions of an electrical system. The components are represented by agreed-upon symbols, and the conductors connecting them by lines. If two lines cross each other, a large dot represents a junction, whereas no dot represents no connection.
Short - Short circuit. 1. An abnormal connection of relatively low resistance between two points of a circuit. The result is excess (often damaging) current between these points. Such a connection is considered to have occurred in a printed wiring CAD database or artwork anytime conductors from different nets either touch or come closer than the minimum spacing allowed for the design rules being use.
Signal - 1. A net. 2. A net other than a power or ground net.
Silicon Wafer - a thin, iridescent, silvery disk of silicon which contains a set of integrated circuits, prior to their being cut free and packaged. A silicon wafer will diffract reflected light into rainbow patterns and, being a similar size, looks so much like a music CD that it could be mistaken for one (except that it has no label or hole in the middle). On closer inspection, one can see the individual (usually rectangular- or square-shaped) integrated circuits which form a uniform patchwork quite unlike the surface of a music CD. When cut or etched from the wafer these circuits are then called chips or dice.
Silkscreen - (Also called "silkscreen legend") 1. The decals and reference designators in epoxy ink on a printed wiring board, so called because of the method of application?the ink is "squeegeed" through a silk screen, the same technique used in the printing of T-shirts.
A silk mesh size commonly used is 6 mils. With this mesh size, the absolute minimum line width of any silkscreen legend artwork is 6 mils, which leaves a very faint line. 7 mils works better for a practical minimum line width.
Newer silkscreening methods allow for sikscreen draws of 5 mils, which come out very clear. A good reference designator size to use is 35 mils high with a 5 mil draw
2. A Gerber file controlling the photoplotting of this legend.
Single Track - PCB Layout with only one route between adjacent DIP pins.
SMD - 1. Surface Mount Device (SMT component). 2. Solder-Mask Defined
SMT - Surface Mount Technology.
Soft - Pertaining to or consisting of software.
Soft Copy - An electronic form of a document; a data file in computer memory or stored on storage media. When one is looking at a soft copy he is viewing the document as displayed on a computer monitor.
Software - Programs, data files, procedures, rules, and any associated documentation pertaining to the operation of a computer system or of a computer application.
Solder Balls - The round solder balls bonded to a transistor contact area and used to make connection to a conductor by face-down bonding techniques.
In IBM's ceramic BGA's, the solder used in solder balls has a higher melting point than that used in soldering the ball to the chip substrate and the BGA to a board. IBM uses 10/90 tin/lead for the solder ball and eutectic solder for the assembly. The high melt balls of the BGA do not melt during PCB assembly and thus create a pre-determined standoff height for the component.
PBGA packages use a eutectic solder ball which provides a collapsible joint similar to C4.
Solder Bumps - solder balls.
Solder Mask - A technique wherein everything on a circuit board is coated with a plastic except 1) the contacts to be soldered, 2) the gold-plated terminals of any card-edge connectors and 3)fiducial marks.
Space Transformer - Abbreviated ST. A major component of certain high-density probe cards. It provides pitch reduction, high routing density and localized mid-frequency decoupling. A major developer of ATE systems which use space transformers is Wentworth Labs.
Sputtering - A deposition process wherein a surface, or target, is immersed in an inert-gas plasma and is bombarded by ionized molecules that eject surface atoms. The process is based on the disintegration of the target material under ion bombardment. Atoms broken away from the target material by gas ions deposit on the part (substrate), forming a thin film.(Graf)
SQFP - Shrink Quad Flat Pack. See QFP.
ST - Space Transformer.
Stable Datum - a datum along which all other data align. From any confusion, order and sanity can emerge providing one merely selects a datum, assigns it importance or seniority and then begins to align other data against it.
The stable datum for any PCB layout could be stated this way: The schematic is the "Bible." In other word, the schematic says the circuit is this way, and the PCB Layout must follow that pattern perfectly.
Streamlined Design - See Streamlined PCB Layout.
Streamlined PCB Layout -Streamline? v. Cause to be quick and efficient. Streamlined design = accuracy plus speed. Streamlined PCB Layout, or SLPD, is a set of policies that guide John Childers' design of printed circuit boards. The policies have been derived with the aim of simplifying and systematically eliminating errors from PCB Layout.
Sub-panel - A group of printed circuits (called modules) arrayed in a panel and handled by both the board house and the assembly house as though it were a single printed wiring board. The sub-panel is usually prepared at the board house by routing most of the material separating individual modules, leaving small tabs. The tabs are strong enough so that the sub-panel can be assembled as a unit, and weak enough so that final separation of assembled modules is easily done.
Surface Mount - Surface mount technology. The technology of creating printed wiring wherein components are soldered to the board without using holes. The result is higher component density, allowing smaller PWB 's. Abbreviated SMT.
Symbol - A simplified design representing a part in a schematic circuit diagram.
TAB - Tape Automated Bonding.
Tented Via - a via with dry film solder mask completely covering both its pad and its plated-thru hole. This completely insulates the via from foreign objects, thus protecting against accidental shorts, but it also renders the via unusable as a test point. Sometimes vias are tented on the top side of the board and left uncovered on the bottom side to permit probing from that side only with a test fixture.
TDR - Time Domain Reflectometer, a device which a board house can use for measuring characteristic impedance of a conductor on a printed board, thus insuring an accurate build for controlled impedance.
Terminal - A point of connection for two or more conductors in an electrical circuit; one of the conductors is usually an electrical contact, lead or electrode of a component.
Terminal Block - a type of header to which wires are attached directly instead of by means of a connector plug. Each wire is inserted in a hole in the terminal block , and then anchored by means of a screw.
Test Coupon - An area of patterns and holes located on the same fabrication panel as the actual PCB, but separate from the electrical circuits and outside the board outline(s). It is made to reflect the technology used on the PCB, such as smallest plated-through hole size, any blind or buried vias, etc. It is cut away from the panel and can be embedded in a clear plastic to prepare it for destructive testing.
Thin Film - A film of conductive or insulating material, usually deposited by sputtering or evaporation, that may be made in a pattern to form electronic components and conductors on a substrate or used as insulation between successive layers of components. [Graf]
Through-hole - (Of a component, also spelled "thru-hole"). Having pins made to be inserted into holes and soldered to pads on a printed board. Contrast with surface mount.
Thru-hole - Same as through-hole.
TQFP - Thin Quad Flat Pack. Essentially the same as a QFP except low-profile, that is, thinner.
Trace - Segment of a route.
Track - Trace.
TTL - Transistor-Transistor Logic. Also called multiple-emitter transistor logic. A widely used form of semiconductor logic. Its basic logic element is a multiple-emitter transistor. TTL is characterized by fairly high speed and medium power dissipation. (Graf)
UL - Underwriter's Laboratories, Inc., a corporation supported by some underwriters for the purpose of establishing safety standards on types of equipment or components.
Unstuffed - Slang - PCB Manufacturing Not populated.
US-ASCII - The 7-bit (using character codes 0-127) version of ASCII, which preceded (and is the basis for) 8-bit versions such as Latin-1, MacASCII and later, even larger coded character sets such as Unicode.
Valuable Final Artwork - A term used in " Streamlined_PCB_Design :" Artwork for electronic circuits which have been laid out and documented in forms perfectly suited to the photo-imaging and numeric-controlled tooling processes of printed circuit manufacture. It is termed "final" because it has been thoroughly checked for errors and any corrected as needed and is now ready for manufacture without further work by the PCB Layouter. It is valuable because it could be exchanged with a customer for money or other support. Abbr. VFA. (Based on "Valuable Final Product").
Valuable Final Product - Something that can be exchanged with other activities in return for support. The support usually adds up to food, clothing, shelter, money, tolerance and cooperation (goodwill).... A valuable final product (VFP) is valuable because it is potentially or factually exchangeable. The key word in this sense is EXCHANGEABLE. And exchangeability means outside, with something outside the person or activity. A valuable final product could as easily be named a VALUABLE EXCHANGEABLE PRODUCT. (L. Ron Hubbard, March 25, 1971, "Valuable Final Products.")
VDD or vdd or Vdd - A name for a power net meaning "voltage drain," usually implying a more positive voltage.
Vector Photoplotter - (also "vector plotter", or "Gerber photoplotter" after Gerber Scientific Co., which built the first vector photoplotters for commercial use) It plots images from a CAD database on photographic film in a darkroom by drawing each line with a continuous lamp shined through an annular-ring aperture, and creating each shape (or pad) by flashing the lamp through a specially sized and shaped aperture. The "apertures" are thin trapezoidal pieces of plastic which are mostly opaque, but with a transparent portion that controls the size and shape of the light pattern passing through it. The apertures are mounted on an "aperture wheel" which can hold up to 24 apertures (or 70 on certain models). The lamp and aperture wheel are fixed, and the table holding the film is moved in x and y dimensions (on small photoplotters), or vice versa (on very large photoplotters). A numeric datum sent to the control circuit of the photo plotter is either a D code or an X and/or Y dimension in inches, to the nearest thousandth. If it is a D code equal to D10 or above, the message tells the wheel to rotate the corresponding aperture location into position in front of the lamp. Gerber photoplotters, if set up by an experienced craftsman, are well-suited for printed circuit artwork generation. Compare with laser photoplotter, which is faster, more accurate and has largely replaced the vector photoplotter.
There are still vector photoplotters in use. Some manufacturers take advantage of the large bed size of the largest Gerber photoplotters, roughly the size of a full-sized billiards table. This enables the production of very large photoplots. An example is Buckbee-Mears, which makes large antenna boards, and the USGS (United States Geological Survey) which has used them in map-making.
Via -Feed-through. A plated-through hole in a PWB used to route a trace vertically in the board, that is, from one layer to another.
VLSI - Very Large Scale Integration.
VQFP - Very thin Quad Flat Pack.
VSS or vss or Vss - A name for a power net meaning "voltage source," usually implying a more negative voltage and often equivalent to Ground or GND.
Wafer - See silicon wafer.
WIP - Work In Progress. (Usage at Golden Gate Graphics: wip is used as the extension of the name of a folder or sub-directory which groups data in temporary storage locations for current "work in progress." Any folders beneath the .WIP folder in the directory structure would be named for the software, company and job in that order. Eg: pclayout.wip/Cadstar/AcmeInc/A2Dboard).
Wire Bonding - The method used to attach very fine wire to semiconductor components (dice) to interconnect these components with each other or with package leads. The wires might be 1 to 2 mils in diameter and made of aluminum containing 1% silicon.
X, Y, Z
Wet Solder Mask - Applied by means of distributing wet epoxy ink through a silk screen, a wet solder mask has a resolution suitable for single-track design, but is not accruate enough for fine-line design.
Wire Wrap Area - A portion of a board riddled with plated-through holes on a 100-mil grid. Its purpose is for accepting circuits which may be found necessary after a PWB has been manufactured, stuffed, tested and debugged.
About Endless "Word Chains" and Bad Dictionaries
I don't recommend bad dictionaries. A bad dictionary will define a term using words even more obscure or rarely used than the term being defined (using big words to define simple words). The user reads the definition, sees a word that he doesn't understand, looks up that word, sees another word that he doesn't understand, looks up that one and so on. This is a "word chain." A bad dictionary needlessly sends the user on endless word chains.
A good dictionary allows the user to quickly come to understanding of the term by using generally simpler words to define the term. One will still get onto word chains, but they won't be endless.
Macmillan Dictionary for Students
I recommend the Macmillan Dictionary for Students , William D. Halsey/ Editorial Director; Macmillan Publishing Company, New York and Collier Macmillan Publishers, London. The definitions are very good and the derivations use the full names of languages, rather than abbreviations. MacMillan Publishing Company, 866 Third Avenue, New York, NY 10022.
This dictionary can be purchased from eLearnAid.com or from Amazon.com and Barnes & Nobles Bookstores.
Webster's New World Dictionary for Young Adults
Young adult or grizzled and wizened PCB Layouter, you can make great use of this dictionary for quickly clearing up words you thought you knew but weren't quite sure of. Because it is a smaller vocabulary, it doesn't include less commonly used meanings, saving time in clearing up words. (When you look up a word, besides understanding the one definition you were looking for, you are reading and understanding the rest of the definitions, aren't you?) It does not include derivations, however, so you'll need a second dictionary ( MacMillan or the Webster's New World Collegiate for those. Prentice Hall General Reference, 15 Columbus Circle, New York, NY 10023.
The Random House Dictionary of the English Language, The Unabridged Edition
You need a big, comprehensive dictionary. Get this one. Despite being a big dictionary, The Random House has great definitions, quick to grasp. Random House. Inc., 201 E. 50th Street, New York, NY 10022.
Modern Dictionary of Electronics by Rudolf F. Graf
This is the best, most usable dictionary for electronics, because its definitions help you grasp the terms and therefore the subject. Lesser dictionaries define electronics terms with even more difficult technical jargon, leading one into endless " word chains ." Not this one. Published by Butterworth-Heinemann , 225 Wildwood Avenue, Woburn, MA 01801. (Formerly published by Howard W. Sams & Co., Inc.)
You can buy the Modern Dictionary of Electronics via the Internet.
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