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GLOSSARY of Printed Circuits

by John Walt Childers, IPC-CID, Founder of Golden Gate Graphics

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Pronunciation Key

Golden Gate Graphics in an official Altium Service Bureau

Golden Gate Graphics is an official Altium Service Bureau

Terms that contain digits are alphabetized as if the numeric characters were spelled in English.

Terms with two or more words are alphabetized "dictionary style." They are alphabetized as though the spaces between the terms have been removed.
   If there are other characters in the term, such as a slash (/), these are treated the same as spaces and ignored for the purpose of alphabetizinig.


TOP       D

Index to terms on this page:

daisy chain   DAP   database   Dcode  
D code   decal  
destructive testing   device   DICY   die  
dielectric constant   die paddle  
differential signal  
differential signaling  
digital circuit   diode   DIP   DNI   DNP   DOS   DOS-formatted   double-track   draw   DRC  
dry film solder mask   DSP   DUT  



daisy chain — (DAY-zee CHAYN)  Pronunciation Key  noun  [Networking] A bus wiring scheme in which, for example, device A is wired to device B, device B is wired to device C, etc. The last device is normally wired to a resistor or terminator.
   All devices may receive identical signals or, in contrast to a simple bus, each device in the chain may modify one or more signals before passing them on. daisy_chain_Howe_Denis_FOLDOC
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DAP — (DAP)  Pronunciation Key  noun  [PCB Components] Die attach paddle. An exposed DAP (also called simply "EP" for "exposed paddle") provides a low thermal resistance between the die and the PCB to which the part is mounted and soldered. This allows rapid heat transfer from the die to the surrounding PCB copper traces, ground plane and air. Often this can be connected to ground and pierced with vias to more efficiently dissipate the heat straight into the ground plane.
On the PCB, vias should be placed in this exposed pad and connected to ground as an effective heat sink. Of course, if this die paddle is connected within the IC (integrated circuit) to some potential other than ground (rare), connect this pad and the vias to that potential instead of ground. If this die attached paddle is floating (not connected electrically to anything in the IC), the pad and the vias should be connected to ground. In PCB design layout of a DAP footprint, the solder paste artwork should not be one large rectangle: It should be several small rectangles. This prevents too large an amount of solder building up under the DAP and floating the package far enough off the PWB that some of the signal lands do not get solder, causing opens. See via and solder paste examples in Application Report - QFN/SON PCB Attachment, especially the topic "Solder Paste Screen Printing Process" and "Figure 11. Example Land Pattern and Exposed-Pad Stencil Design"
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database — A collection of interrelated data items stored together without unnecessary redundancy, to serve one or more applications.
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Dcode D code.
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D code — Draft code.  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.
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.

  1. D01 - Light on for next move.
  2. D02 - Light off for next move.
  3. 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.
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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.
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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.
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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.
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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]
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die — 1.  A chip. (Plural: dice)
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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]
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die paddle — (DAHY PAD-ə Pronunciation Key  noun  [PCB Components] (aka die attach paddle, or DAP) A thin plane of metal, within a packaged integrated circuit, to which a die is attached and which in turn is attached to a lead frame. Although adie paddle is internal to the IC package, it can be exposed on the bottom of the package in order to carry heat into the PCB, in which case a pad should be provided for soldering it to the PCB. If exposed, it typically carries no digital or analog signal but would usually be connected to ground. See also EP (Exposed Paddle).
On the PCB, vias should be placed in this exposed pad and connected to ground as an effective heat sink. Of course, if this die paddle is connected within the IC (integrated circuit) to some potential other than ground (rare), connect this pad and the vias to that potential instead of ground. If this die attached paddle is floating (not connected electrically to anything in the IC), the pad and the vias should be connected to ground. In PCB design layout of a DAP footprint, the solder paste artwork should not be one large rectangle: It should be several small rectangles. This prevents too large an amount of solder building up under the die paddle and floating the package far enough off the PWB that some of the signal lands do not get solder, causing opens. See via and solder paste examples in Application Report - QFN/SON PCB Attachment, especially the topic "Solder Paste Screen Printing Process" and "Figure 11. Example Land Pattern and Exposed-Pad Stencil Design"
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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]

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

Or see an alternative viewpoint: Differential Signaling Doesn't 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 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.
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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.
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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]

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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.
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DNI — Do Not Install. Same use as DNP, which means "Do Not Populate "
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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 component of that size and shape later for experimentation and debuggin.
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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.
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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.
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double-track
— Slang for fine line design with two traces between DIP pins.
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draw

  1. verb To plot a line on film by moving the film while shining a light through an aperture.  
  2. noun A line plotted thus.

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DRC — (DEE AR SEE)  Pronunciation Key  noun  [Computer Aided Design] Design Rule Checking or Design Rule Check.
Design rules are set up in the PCB layout CAD file and include constraints related to shorts, opens, clearance, etc. A DRC is run to check for violations. The PCB designer can run this check periodically as a batch process on the entire design. With advanced layout software such as Altium Designer, the DRC can be set to automatic or "online:"  A check is performed on-the-fly at any moment that the designer changes something and alerts him to any violation he may have just caused.
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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.
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DSP  — (DEE ES PEE) Pronunciation Key

  1. noun [Electronics] Digital Signal Processing
        
  2.  
  3. noun [Electronics] Digital Signal Processor. A microprocessor optimized for digital signal processing.
        

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DUT [Semi-conductor Manufacturing] 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 designed 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.
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Example Printed Boards

Click for Examples of PCBs designed by Golden Gate Graphics



References and Dictionaries

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.
You can buy the Modern Dictionary of Electronics new or used via the Internet.

Citation:
Graf, Rudolf F. Modern Dictionary of Electronics. Newnes, 1999.


The Random House Dictionary of the English Language, Unabridged, 2nd Edition

You need a big, comprehensive dictionary. Get this one. Despite being a big dictionary, The Random House has great definitions, quick to grasp.

Although out of print, as of 2020 you could still buy a great used copy online for $30 including shipping or possibly for much less. Two versions are available of the 2nd Edition, Unabridged:

I have no idea what the difference is for the deluxe edition, but there seem to be fewer copies of it available in 2020 than the regular edition. I'm sure they both have the same set of definitions. My copy has both ISBNs listed in the front matter, and it is the regular edition.

Citation:
Flexner, Stuart Berg, and Leonore Crary Hauck, editors. The Random House Dictionary of the English Language. Unabridged, 2nd Edition, Random House, 1987.

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