Glossary

GLOSSARY of Printed Circuit Design and Manufacturingby John Walt Childers, CID, Founder ofGolden Gate Graphics

While the new glossary is being developed and tested, this legacy glossary is still in use.

A collection of words with their meanings. This glossary has key terminology in use in PCB design and manufacturing, with rudimentary electronics. The words have other meanings not given here. For those, consult an English language or electronics dictionary:Recommended dictionaries.

Do you needon-line definitionsfor another subject?

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.Examplesof active devices which fit one or more of the above definitions: transistors, rectifiers, diodes, amplifiers, oscillators, mechanical relays and almost allICs(Contrast withpassive component)

Aluminum Nitride, a compound of aluminum with nitrogen.

Asubstrateof aluminum nitride.

A ceramic used for insulators in electron tubes or substrates inthin-filmcircuits. It can withstand continuously high temperatures and has a low dielectric loss over a wide frequency range. Aluminum oxide (Al2O3)

A circuit in which the output varies as a continuous function of the input, as contrasted withdigital circuit.

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]

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 photoplotter in plotting geometric patterns on film. The index of theapertureis itsPosition(a number used in an aperture list to identify an aperture) orD 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 anaperture wheelwhich in turn is mounted on the lamp head of avector photoplotter. Anapertureis mostly opaque, but with a transparent portion that controls the size and shape of the light pattern. A vector photoplotter plots images from aCADdatabase on photographic film in a darkroom by drawing each line with a continuous lamp shined through an annular-ringaperture, and creating each shape (or pad) byflashingthe lamp through a specially sized and shapedaperture. 3. A line of textual data in anaperturelist describing the index names (D code and position), the shape, the usage (flash or draw) and the X and Y dimensions of anaperture. Some aperture lists leave out certain of those types of data. For example, laser photoplotters dont need to know whether an aperture is a flash or draw, so a modern-day aperture list might leave that datum out.

1. AnASCII textdata file which describes the size and shape of the apertures used by a photoplotter for any one photoplot. 2. A print-out of this file. 3. A binary version of this file. [Also called aperture table.]

A component of avector photoplotter, it is a metal disk having cut-outs with brackets and screw holes arranged near its rim for attachingapertures. Its center hole is attached to a motorized spindle on the lamp head of the photoplotter. When aD codedenoting a particular position on the wheel is retreived from aGerber fileby 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 printedaperture 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 withlaser photoplotters.

Artwork for printed circuit design 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 alsoValuable Final Artwork.

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 take you off this site unless you right-click on the link and select Open link in new tab .)

is the basis of character sets used in almost all present-day -ASCIIuses only the lower sevenbits (character points 0 to 127) to convey somecontrol codes, space, numbers, most basic punctuation, and unaccented letters a-z and A-Z. More modern coded character sets (e.g.,Latin-1Unicode) 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, orHan characters), and such characters as distinct open- and close-quotation marks ( and ), and .

Thecomplete ASCII character setknown as Latin-1, an extension to 256 characters of theUS-ASCII128-character set, has been provided online by Paul Lutus at .

A thoroughly unoffical subset ofUS-ASCIIwhich contains the space character, numbers, most basic punctuation, and unaccented letters a-z and A-Z, but lacks thecontrol codes.

1. The process of positioning and soldering components to aPCB. 2. Act or process of fitting together parts to make a whole. .

A drawing depicting the locations of components, with theirreference designators, on a printed circuit. Also called component locator drawing.

A manufacturing facility for attaching and soldering components to a printed circuit. Aka assembler and also CM, for contract manufacturer.

American Society of Testing and Materials.

Automatic Test Equipment. (See alsoDUT.) .

American Wire Gauge. A PCB Designer needs to know diameters of wire gauges to properly sizeE-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: (click here for an explanationof theASTMdata by Global Wire Group.)

automatic router, a computer program thatroutesa PC board design (or a silicon chip design) automatically.

(Abbrev. BGA).Aflip-chiptype of package in which the internaldieterminals 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. Thewill 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 theball grid arraypackage are (1) that its size is compact and (2) its leads do not get damaged in handling (unlike the formed gull-wing leads of aQFP) and thus has a long shelf life. Disadvantages of theBGAare 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 tostuff, 3) except for the outer rows, the solder joints can not be visually inspected and 4) they are difficult to rework.

The electrode of a transistor which controls the movements of electrons orholesby means of an electric field on it. It is the element which corresponds to the control grid of an electron tube.

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 thedieas 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 offlip-chipbonding, contrasted withsolder bump[Graf]

printed circuit board. Also, a CAD file which represents the layout of a printed circuit.

Board vendor. A manufacturer of printed circuit boards. Aka fabricator.

The portion of an electronic component exclusive of its pins or leads.

[pronounced bomb]Bill of Materials. A list of components to be included on an assembly such as a printed circuit board. For a PCB theBOMmust includereference designatorsfor the components used and descriptions which uniquely identify each component. ABOMis used for ordering parts and, along with anassembly drawing, directing which parts go where when the board isstuffed.

Controlled Collapsed Chip Connect. A type offlip-chiptechnology which is used in Intels Pentium III and in Motorolas PowerPC 603 and PowerPC 604 RISC Microprocessors. Here is an Friday, February 07, 2003introduction to the C4CBGA interconnect technologyby Kromann, Gerke and Huang of Motorolas Advanced Packaging Technology Division.

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.

Simply a concatenation of the two termsCADandCAM.

Computer Assisted Engineering. In electronics work, CAE refers to schematic software packages.

Conductive Anodic Filamentation (or Conductive Anodic Filament growth) – An electrical short which occurs inPCBswhen a conductive filament forms in the laminate dielectric material between two adjacent conductors under an electrical bias.CAFis a potentially dangerous source of electrical failure in the PCB. As PCB designs have increased in density, with hole-to-hole spacings reduced to 25milsor less,CAFhas become an everyday concern. [adapted from Erik J. Bergum, CAF Resistance of NON-DICYFR-4,PC FAB, 9/2002]

Computer Aided Manufacturing. (SeeCAM files)

CAM means Computer Aided Manufacturing. These are the data files used directly in the manufacture of printed wiring. . The types ofCAM filesare 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 design. They are handed off to the board house which further refines and manipulates CAM data in their processes, for example in step- and-repeat panelization. Some PCB design software companies refer to all plotter or printer files asCAM files, although some of the plots may be check plots which are not used in manufacture.

v.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 anetlistand preferably also aBOM. 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.Capturea netlist.n.The process of creating a CAE drawing containing intelligent data. E.G. Schematic capture.

another name for a printed circuit board.

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. Seefinger.

Extract information automatically through the use of software, as opposed to hand-entering of data into a computer file.

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 workpiece being plated.[Graf]

ANEMAgrade 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 ofFR-4.

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.

1. An integrated circuit manufactured on a semiconductor substrate and then cut or etched away from thesilicon wafer. (Also called adie.) Achipis not ready for use until packaged and provided with external connections. 2. Commonly used to mean a packaged semiconductor device.

Abbreviated COB. In this technologyintegrated circuits, small portions of silicon wafers, are glued andwire-bondeddirectly to printed circuit boards instead of first being packaged. The electronics for many mass-produced toys areembeddedby 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.

A chip package in which the total package size is no more than 20% greater than the size of thediewithin. Eg: Micro-BGA.

The creation of the functional description and diagram (the schematic) of an electronic circuit. Done by an electrical engineer, this is NOT the same thing asprinted circuit design.

Computer Integrated ed by an assembly house, this software inputsassemblydata from a PCB CAM/CAD package, such asGerberandBOM, 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,CIMcan integrate multiple factories with customers and suppliers.

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, notsilkscreen.

1. An electrode in a transistor that collects electrons orholes. 2. In certain electron tubes, an electrode to which electrons or ions flow after they have completed their function.

Any of the basic parts used in building electronic equipment, such as a resistor, capacitor,DIPor connector, etc.

A representation of components as decals, stored in a computer data file which can be accessed by a PCB CAD program.

One leg of anet. Also called a pin pair (PADS) and from-to (Protel).

The intelligence inherent in PCB CAD software which maintains the correct connections between pins of components as defined by the schematic.

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.

A non-printing character which is input or output to cause some special action rather than to appear as part of the data.Control codesare 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.

Chip Scale Packageor Chip Scale Packaging.

Draft code. 1. A datum in aGerber filewhich acts as a command to aphotoplotter.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.

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 apertures 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 jobs D10 could be a 10 mil Round, when another jobs 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 Gerbervector 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.

A collection of interrelated data items stored together without unnecessary redundancy, to serve one or more applications.

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,footprintorpackage. On a manufactured board thebodyof afootprintis an epoxy-ink outline.

Sectioning a portion of printed circuit panel and examining the sections with a microscope. This is performed oncoupons, not the funtional part of the PCB.

Any type of electricalcomponenton a PC board. It will have functions and properties unique to its type. In aschematic(and the extractedBOM) , it will be labeled with a value ordevicenumber. There are two main classes of devices,passiveandactive. .

Dicyandiamide, the most common cross-linking agent used inFR-4. [Erik J. Bergum, CAF Resistance of NON- DICY FR-4,PC FAB, 9/2002]

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]

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]

For more information see the articles on this page:Douglas Brooks Articles on Differential Traces

Or see an alternative viewpoint:Differential Signaling Doesnt Require Differential Impedance Or, How to Design a Differential Signaling Circuit, by Lee W. Ritchey

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 ofapplying 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 viacouponsandTDRwill 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.

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.

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]

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 ofthrough-holepins spaced 0.1 inch between centers of adjacent pins.

Do Not Install. Same use as DNP, which means Do NotPopulate

Do NotPopulate. 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 debuggin.

Disk Operating System. A program that controls the computers 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.

(Of magnetic data storage media, such as floppy disks.) Prepared for storage of data in such a way that DOS transfer can occur.

Slang for fine line design with two traces betweenDIPpins.

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.

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.

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.

Depending on which system it is designed for, one type of DUT board is used in testing individual integrated circuits in asilicon waferbefore they are cut free and packaged, and another type is used for testing packagedICs.

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-padsare used to facilitate proto-typing, or simply because wires are used for interconnections instead ofheadersorterminal blocks.

Emitter Coupled Logic. A type ofunsaturated logicperformed by emitter-coupled transistors. Higher speeds may be achieved with ECL than are obtainable with standard logic circuits.ECLis costly, power hungry, and difficult to use, but it is four times faster thanTTL[Graf]

[Protel]A graphical object (in a PCB or schematic file) to which an electrical connection can be made, such as a component pin or a wire.

(Of a micro-processor(s), or system controlled by such) Dedicated to doing one job or supporting one device and built into the product.

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 , which unfortunately has gone off-line as of 2017] At circuit board level, one could substitue the termcircuitforequipmentin 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 goodEMCpractice. — Jon Berrie, Technical Marketing Specialist Hot-Stage,Zuken.

An electrode on a transistor from which a flow of electrons orholesenters the region between the electrodes.[Random House]

Electromagnetic pulse. A reaction of large magnitude resulting from the detonation of nuclear weapons.[Graf]

a version ofin 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 design,end-to-end designsometimes refers to only the electronic schematicpcb 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 thePCB designerdefinition and follow the link to the plain English description for a printed circuit board designer

NC Drill file format. An ASCII format used in a file which drives anNC Drillmachine. The earliest NC Drill machines were made by Excellon Automation Company. The format is in broad use, although the company has been sold.

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.

Flexible Circuit, flexible circuitry, flexcircuit orflex circuit.

Printed circuit design permitting two (rarely three) traces between adjacentDIPpins. 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.

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.

A gold-plated terminal of a card-edge connector. [Derived from its shape.]

1.v.To turn avector photoplotterlamp 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 anaperture). 2.n.A small image on film created in such wise or as directed by a command in aGerber file.) The maximum size (x or y dimension)for aflashvaries from one photoplotting shop to another, but is commonly inch.

Flexible circuit, or flexcircuit; a printed circuit made of thin, flexible material. For more information, seeflexible 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.

Flex circuit. Abbreviated FPC or FC.

A mounting approach in which thechipdie) is inverted and connected directly to the substrate rather than using the more commonwire bondingtechnique.Examplesof this kind of flip-chip mounting arebeam leadandsolder bump.

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]

Click here for an action definition of footprint.1. The pattern and space on a board taken up by a component. 2.Decal.

Flexible Printed Circuit, orflex circuit.

ANEMAgrade 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.

ANEMAgrade of Flame-Retardent industrial laminate having a substrate of woven-glass fabric and resin binder of epoxy.FR-4is the most common dielectric material used in the construction of PCBs in the USA. Itsdielectric constantis from 4.4 to 5.2 at below-microwave frequencies. As frequency climbs over 1 GHz, the dielectric constant ofFR-4gradually drops.

Fire-Retardant glass-and-polyester substrate material for electronic circuits. Inexpensive; popular for automobile electronics. [Stammtisch Beau Fleuve Acronyms

An article written in 2015 by Atar Mittal is worth study if you need to choose PCB materials for your electronics project. It includes a Laminate Selector Chart entitled PCB Material Properties and Recommended Application AreasHDI PCBs: Choosing The Right Material

A comparison of many brands of PCB laminates can be found at theStandard Printed Circuits Microwave Laminates Comparison Chart.

ACAMfile viewer and printer made byGraphicode. The freeware version can storeGerberandNC Drillfiles within a file (.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 perfectregister, 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