GLOSSARY of Printed Circuits

Index to terms on this page:

daisy chain   DAP   database   datum dimension   Dcode  
D code   DDR SDRAM   decade   decal   Delta-I   DEN   designator  
destructive testing   device   Df   DFEMC   DFN   DFX   DIA   DICY   die   die attach paddle  
dielectric constant   die paddle  
differential signal  
differential signaling  
digital circuit   digital product model   diode   DIP   discrete   dissipation factor   displacement current   DNI   DNP   dogbone or dog bone   DOS   DOS-formatted   double-track   DPDT   DPMX   draw   DRC   drill bit wander   dropout voltage  
dry film solder mask   DSL   DSP   DTP  
dual in-line   DUT   DVD   DVD-R   DVD-R/RW drive   DVD+RW   DVD-RW   DVD+RW   DVI   DVT  

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 

1. noun  [PCB Components]   die attach paddle, q.v.
2. modifier  [Shipping]  Delivered at Appointed Place. Basically, shipped to your door or wherever you've agreed to receive a shipment.

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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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datum dimension —[Altium Designer 17 and earlier.] A dimension in which the first point selected is the zero datum and other points selected give the offset form the zero datum. Useful for getting many dimensions in an uncluttered manner. Works well to pick the PCB origin as the zero datum. Then the offsets are the x or y coordinates of the objects picked. In Altium Desiger 18.0 and later, Altium remaned this to Ordinate Dimension.

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Dcode — An alternate spelling of 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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DDR SDRAM — Double-Data-Rate Synchronous Dynamic Random Access Memory is a type of memory integrated circuit used in computers. It achieves greater bandwidth than the preceding single-data-rate SDRAM by transferring data on both the rising and falling edges of the clock signal (double pumped). This effectively nearly doubles the transfer rate without increasing the frequency of the front side bus. Thus a 100 MHz DDR system has an effective clock rate of 200 MHz when compared to equivalent SDR SDRAM, the “SDR” being a retrospective designation.

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decade — An order of magnitude in capacitance of decoupling capacitors. Example: 3 decades of decoupling capacitors would mean 3 orders of magnitude in capacitance; if the highest value would be 0.1 microfarad (uF), the other two values would be 0.01 uF and 0.001 uF (1 nanofarad).

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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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Delta-I — Also called "ground bounce," Delta-I noise is the voltage induced between the power conductors (e.g. the ground and the Vcc planes) when a circuit connected between them switches from one state to another.

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DEN — Materials and connection density (DEN)

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designator —

1. Reference designator.
2. Capitalized  [Altium Designer]  A field name (column heading) used in Altium Designer to mean either Pin Designator (aka pin number) or Reference Designator.

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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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Df — Dissipation factor, q.v.

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DFEMC —  noun  [PCB Design]  Design for Electromagnetic Compatibility (DFEMC)—Not officially part of the IPC-DFX standard (IPC-2231), these would be design steps or milestones that ensure that the manufactured PCBA is likely to pass FCC certification or other tests for EMC. (This last category was added by me, because I recognize the importance of Henry Ott's statement below:

In today's regulatory environment, electromagnetic compatibility (EMC) engineering plays an important roll in bringing electronic products to market. Often the functional performance of a product is not the primary problem in meeting product introduction schedules; passing the required EMC tests are.

[“Digital Circuit Radiation.” Electromagnetic Compatibility Engineering, by Henry W. Ott, John Wiley & Sons, 2009, pg. 464]

It is easy to improve EMC during the PCB design phase and very difficult to fix EMI problems that occur in manufactured PCBAs after they are built.

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DFN — Dual Flat No-lead

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DFX —  noun  [PCB Design]  Design For eXcellence. DFX is the creation of intermediate design steps or milestones during product development that ensure the resulting products are optimized for the targeted product values listed below. The X in DFX can also be thought of as a sort of variable, which can be replaced by the letters after "DF" in the categories below. The goal of DFX is manufactured products that are ideal or at least workable in terms of a balance of cost, functionality and salability. There are other categories of "Design For" not listed below, because they come earlier on in product development in the marketing research stage, thus are not PCB design outcomes. (E.g. DFE, Design For Environment, a program of the Environmental Protection Agency.)

DFX Categories
• Design for Supply Chain (DFSC)—Design steps or milestones that ensure material sourcing, supply, compliancy and lifecycle. Requirements are met during design stage.
• Design for Reliability (DFR)—Design steps or milestones that ensure reliability of a finished product or system.
• Design for Fabrication (DFF)—Design steps or milestones that ensure the producibility and cost effectiveness of the manufacture of the bare board.
• Design for Assembly (DFA)—Design steps or milestones that ensure the assembly of the PCB design and physical layout rules are met prior to prototype.
• Design for Manufacturability (DFM)—Design steps or milestones that ensure the manufacturability of a component or complete assembly to meet supplier’s capability.
• Design for Test (DFT)—Design steps or milestones that ensure testability by means of test probe access, coverage and schematics.
• Design for Electromagnetic Compatibility (DFEMC)—Not officially part of the IPC-DFX standard (IPC-2231), these would be design steps or milestones that ensure that the manufactured PCBA is likely to pass FCC certification or other tests for EMC.

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DIA —  noun [Mechanical Engineering] - drawings  Diameter.

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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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die attach paddle — noun  [PCB Components]   Abbreviation: DAP. Also called "exposed paddle." A thin plane of metal, within a packaged integrated circuit, to which a die or chip. is attached. Although a die attach 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.

An exposed die attach 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 planes. See exposed paddle for in-depth PCB layout issues and examples, particulary as regards to solder paste design and use of thermal vias.

[Although sometimes called die attach "pad," it has been named "paddle" to describe its shape, which on dual packages is roughly similar to the broad end of a canoe paddle, and its size, which is much larger than a typical signal pad.]

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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, Rudolf F. Modern Dictionary of Electronics. Newnes, 1999]

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die paddle — (DAHY PAD-əl) Pronunciation Key  noun  [PCB Components] See die attach paddle.

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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
See via and solder paste examples in Texas Instruments' 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"
[Although sometimes called die attach "pad" instead of "paddle," it has been named "paddle" partly to distinguish it from "pad" (q.v.), which applies to a metallic portion of a PCB or IC package for transfering signal connections and attaching the package to the PCB. Also, the word "paddle," is adequate to describe its shape, which is roughly similar to the broad end of a canoe paddle, and its size, which is much larger than a typical pad.]

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, Rudolf F. Modern Dictionary of Electronics. Newnes, 1999]

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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digital product model — An accurate, detailed representation of a commodity to be offered for sale (InvestorWords definition of a product is "The end result of the manufacturing process, to be offered to the marketplace to satisfy a need or want."), existing before it actually materializes in the real world and mocked-up as information (with a human-friendly interface) in the form of electronic signals.

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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, Rudolf F. Modern Dictionary of Electronics. Newnes, 1999]

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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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discrete — noun (nickname for a discrete component) A component that performs only one function (in contrast with an integrated circuit) and has only two leads, such as a capacitor, resistor, inductor or diode. A definition for the common adjective discrete is “constituting a separate entity or part.” A transistor could be considered a discrete, but common usage in electronics reserves the term for two-terminal components.

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Dissipation factor — a measure of loss-rate of energy of an electrical oscillation. The lower the better. Abbr. DF or Df See Wikipedia https://en.wikipedia.org/wiki/Dissipation_factor

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displacement current — current caused by a fluctuating magnetic field. However it is not an electric current of moving charges in traces, but a time-varying electric field in the dielectric (the plastic and fiberglass material of the PC board).

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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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DNP —

1. "Do Not Populate" or "Do Not Place" (used in place of a value for a symbol on a schematic) and means "do not stuff, "unstuffed" or "not used."
2. (relating to thermal expansion) Distance from the Neutral Point. The neutral point of a BGA undergoing thermal expansion is typically its center. A corner of the package is a point of highest DNP, where the greatest strain occurs on solder joints exposed to fluctuating ambient temperatures. This is due to the difference in the coefficients of thermal expansion between the package and the PCB.

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dogbone or dog bone — a BGA pad, the short track from it to a via and the via. All of them together, the pad, track and via, resembles a dog bone.

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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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DPDT — Double-Pole, Double-Throw. "Double-pole" means that there are effectively two electrically isolated switches, but that they are ganged so that they can only be switched simultaneously. "Double-throw" means that the switch can be "thrown" into either of two positions that make an electrical connection. A position in which the switch can only be open -- i.e., an off position that one cannot tap in to, is not counted among the throws. A DPDT switch may have one, two, or three rest positions. A DPDT switch with one rest position is called a DPDT momentary. (The rest position may be open or it may be one of the throws.)

A DPDT switch would be appropriate for switching ordinary two-phase power between either of two alternative loads or for switching an appliance between either of two AC power supplies. (With three-phase power, the same applications would require triple-pole double-throw switches.) Another application of DPDT switches would be in selecting which of two alternative phones is connected to an ordinary (two active wires) phone line, or which of two phone lines is connected to a particular phone. If you were switching a single line among three phones, or a single phone among three lines, you would use a double-pole triple-throw switch. http://www.plexoft.com/SBF/D05.html#DPDT

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DPMX — IPC-DPMX aka IPC-2581 Digital Product Model eXchange. PCB designs can be output for manufacturing to to IPC-2581 format, rather than Gerber and drill files, fab and assembly drawings and also rather than ODB++.

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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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drill bit wander — This is the phenomenon of a drill bit bending and flexing while a hole is being drilled. It applies particularly to very small diameter bits. Drill bit wander causes the final hole location to potentially be different from its ideal theoretical location as specified in the NC drill file.

Through-hole pad diameters are designed large enough to accomodate drill bit wander. The extra size of the pad is monitored by the standards being enforced regarding breakout. Military standards require breakout to be tangential, which means the edge of the drill hole can't extend beyond the edge of the pad. This increases the cost of the PCB over one complying with commercial standards, which allow breakout of 50%.

Teardrops are added to traces where they enter a pad to help insure that the trace doesn't get cut in two by an out-of-position drill hole.

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dropout voltage — The input-output differential at which a regultor cirucuit ceases to regulate against further reductions in input voltage. [[Graf, Rudolf F. Modern Dictionary of Electronics. Newnes, 1999]]

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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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DSL — Digital Subscriber Line

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DSP  — (DEE ES PEE) Pronunciation Key

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

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DTP — diameter of true position. Assembly Tolerancing - Another part of the equation is the assembly variation. This variation represents the location of the component in relation to its true position as defined by the design. The term diameter of true position (DTP) is used to describe this variation and is a single number that can be used in any dimensional tolerance analysis. The location of components is described within the design data by the centroid of the component location in relationship to the point of origin of the assembly [IPC d_7251WD1]

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dual in-line — modifier  [PCB Components]   The configuration of two rows of leads on opposite sides of a component body. The term DIP, for dual in-line package, is reserved for through-hole components. A surface mount package can also be dual in-line and this description is often shortened to simply "dual" in order to distinguish these from DIPs.

In-line means that a lead on one side of the body will have a corresponding lead exactly opposite, in other words lined up. If the leads were not in line then the lead configuration would be called "staggered."

Standard IPC zero orientation is shown in the figure below. Note that conventional pin numbering begins with 1 as the upper left lead, continues down the left side and then up the opposite side in a more-or-less counter-clockwise sequence. Standardization of pin numbering is important for PCB designers and electrical engineers, because the pin numbering system is what ties the information in the schematic to the PCB layout and manufacture. If the pin numbering is wrong, the electronics simply won't work.

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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. 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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DVD — Digital Video Disk

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DVD-R — DVD-Recordable) A write-once (read only) DVD disk for both movies and data endorsed by the DVD Forum. DVD-Rs are often called "DVD Dash Rs" or "DVD Minus Rs" to distinguish them from the competing "Plus R" format (see DVD+R).
DVD-Rs are the DVD counterpart to CD-Rs and use the same dye-layer recording technology to "burn" the disc. Pioneer was the first to introduce DVD-R drives, which recorded 3.95GB. By 2000, the capacity was increased to the industry standard 4.7GB.
DVD-R for Authoring, DVD-R for General. In 2000, DVD-R was split into two types to deal with copy protection. The original DVD-R, which uses a 650 nm recording wavelength, was dubbed "DVD-R(a)" for Authoring. A different format with copy protection that records at 635 nm is called "DVD-R(g)quot; for General. Although DVD-R(a) and DVD-R(g) can read each other's format, they cannot write each other's format.
A Small Fortune in the Beginning. DVD-R machines (DVD burners) cost as much as $17,000 in their first incarnations back in 1997, but dropped to under $500 by 2002 and less than $100 two years later.
(See also UDF)

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DVD-R/RW drive — A DVD drive that reads and writes DVD-RW and DVD-R media. It also typically reads DVD+RW and DVD+R media. My Toshiba SD-R5002 6-in-1 DVD-R/RW Drive. # Record formats supported: DVD: DVD-R(General Ver. 2.0), DVD-RW Ver 1.1 and CD: CD-R, CD-RW (See also UDF)

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DVD+R/RW drive — A DVD drive that reads and writes DVD+R and DVD+RW media.It also typically reads DVD-RW and DVD-R media.

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DVD-RW — (DVD-Read Write) A rewritable (re-recordable) DVD disk for both movies and data from the DVD Forum. Also called "DVD Dash RW" and "DVD Minus RW," DVD-RW uses phase change recording. The media hold 4.7GB per side and can be rewritten 1,000 times.

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DVD+RW — (DVD+Read Write) A rewritable (re-recordable) DVD disk for both movies and data from the DVD+RW Alliance. DVD+RW media can be read on DVD-Video players and computer DVD-ROM drives. Using phase change technology, the first DVD+RW disks held 3GB per side, but were later increased to the industry standard 4.7GB. A double sided disk holds 9.4GB. DVD+RW supports both the CLV and CAV recording formats, the latter providing more uniform random access for interactive data applications.

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DVI — Digital Visual Interface

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DVT — Design Verification Testing [Lee Ritchey, Printed Circuits Handbook.]

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