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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

Formerly known as

GLOSSARY of Printed Circuit Design and Manufacturing

This glossary has key terminology in use in PCB design and manufacturing, with a smattering of electronics. The definitions were chosen so that their context would likely apply to reading material encountered by a PCB designer. Therefore, many of these terms will have other meanings not given here. See recommended dictionaries below.

This collection of terms came about as I, a PCB designer, ran across words and acronyms in my field for which meanings were hard to find. As I tracked them down, I made them part of this glossary. If you are a PCB designer, then this glossary could be a good place to start when you find a need to look up the meanings of words related to printed circuits or electronics.

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Index to terms on this page:

ECL   EDA   EDB   EDID   EEE   EEPROM   EFD   EFF   EFI   E field   EIAJ   EIC   E/L  
electrical object   Electrical Reliability Test   electromagnetic induction   electromotive force   embedded   EMC   EM field   EMI   emitter   EMP   EMS   ENIG   end-to-end design   EP   E-pad   ERC   ERP   ERT   ESL   ESR   ET   etch   etch resist   eutectic alloy   eutectic solder   EVM   EVT   exposed paddle   Excellon  

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

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EDA — Electronic Design Automation, a type of software for producing PCB designs. It is the same thing as electrical CAD.

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EDB — Electronic Database

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EDID — Extended Display Identification Data

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EEE — Electric and Electronic Equipment (directive)

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EEPROM — Electrically erasable programmable read-only memory.

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EFD — Embedded Flash Drive (SandDisk: "iNAND is an Embedded Flash Drive (EFD) designed for mobile handsets and consumer electronic devices. iNAND is a hybrid device combining an embedded thin flash controller and standard MLC (Multi-Level Cell) NAND flash memory"

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EFF [Rights] Electronic Frontier Foundation. A nonprofit organization established to protect public access to online resources, including freedom of expression and right to privacy. EFF is concerned with the impact of computers on society and the ethical, legal, and social issues resulting from the information revolution. See also DMCA.

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EFI Computer Systems Administration Extensible Firmware Interface, a firmware interface specification, predecessor of Unified Extensible Firmware Interface (UEFI)

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E field — Electrical field

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EIAJ — Electronic Industries Association of Japan was one of two Japanese electronics trade organizations that were merged into the Japan Electronics and Information Technology Industries Association (JEITA).

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EIC — Equivalent IC

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E/L — External Layer, any layer of a PCB on the outside of the stackup (either the top or bottom layer) or both of the external layers as a group.

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electrical object — () [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.

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Electrical Reliability Test — After the PCB has been coated and cured (if necessary), a technician performs a battery of electrical tests on the different areas of the PCB to ensure functionality.

The main tests that are performed are circuit continuity and isolation tests. The circuit continuity test checks for any disconnections in the PCB, known as “opens.” On the other hand, the circuit isolation test checks the isolation values of the PCB’s various parts to check if there are any shorts. While the electrical tests mainly exist to ensure functionality, they also work as a test of how well the initial PCB design stood up to the manufacturing process.

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electromagnetic induction — Electromagnetic or magnetic induction is the production of an electromotive force (q.v.) across an electrical conductor in a changing magnetic field.
This is very useful in inductors, transformers, electric motors and generators. But in PCB design, it would be undesirable for two traces to be in such close proximity over a long distance that the fields generated by their signals couple inductively. This disrupts each of the signals.

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electromotive force — In electromagnetism and electronics, electromotive force (emf, measured in Volts) is the electrical action produced by a non-electrical source. Devices provide an emf by converting other forms of energy into electrical energy, such as batteries (which convert chemical energy) or generators (which convert mechanical energy).

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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.

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EMC — electromagnetic compatibility.  

  1. Electromagnetic compatibility is the branch of electrical engineering concerned with the unintentional generation, propagation and reception of electromagnetic energy which may cause unwanted effects such as electromagnetic interference (EMI)
  2. The ability of electronic equipment to operate without degradation in an intended electromagnetic environment
  3. 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 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.
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EM field — Electromagnetic field.

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EMI — ElectroMagnetic Interference.

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emitter — An electrode on a transistor from which a flow of electrons or holes enters the region between the electrodes. [Random House]
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EMP — Electromagnetic pulse. A reaction of large magnitude resulting from the detonation of a nuclear weapon. [Graf, Rudolf F. Modern Dictionary of Electronics. Newnes, 1999]
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  1. [PCB Manufacturing] Electronic Manufacturing Services or Electronic Manufacturing Solutions (EMS) is a term used for companies that design, manufacture, test, distribute, and provide return/repair services for electronic components and assemblies for original equipment manufacturers (OEMs).
  2. [Electrical Engineering] ElectroMagnetic Spectrum.

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ENIG — (EE-nig)  Pronunciation Key  noun  [PCB Manufacturing]  Electroless Nickel Immersion Gold. A printed circuit finish composed of a 3-5 micro-inches [0.08-0.13 microns] of gold plated electrolessly over 100-150 micro-inches [2.54-3.81 microns] of nickel, which has been plated electrolessly over the copper. The gold prevents the nickel from tarnishing.

ENIG is preferred over HASL (Hot Air Solder Level) for fine pitch SMT, because HASL leaves solder bumps. ENIG is also a great finish for lead-free solder assembly. In many board houses, this finish is actually cheaper than lead-free HASL. foil— A sheet of copper of various thicknesses used as an electrical layer in the construction of a PCB stack-up.

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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 design, 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 designer definition and follow the link to the plain English description for a printed circuit board designer
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EP — (EE-PEE)   Pronunciation Key  noun  [PCB Components] Exposed Paddle, q.v. (Aka "exposed DAP" or "external paddle."

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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.

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ERC — (Altium) Electrical Rules Check

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ERP — Enterprise Resource Planning. Enterprise resource planning Software (ERP) is business management software (typically a suite of integrated applications) that a company can use to collect, store, manage and interpret data from many business activities, including:

  • Product planning, cost
  • Manufacturing or service delivery
  • Marketing and sales
  • Inventory management
  • Shipping and payment

ERP provides an integrated view of core business processes, often in real-time, using common databases maintained by a database management system. ERP systems track business resources (cash, raw materials, production capacity) and the status of business commitments: orders, purchase orders, and payroll. The applications that make up the system share data across the various departments [1] ERP facilitates information flow between all business functions, and manages connections to outside stakeholders.

Enterprise system software is a multi-billion dollar industry that produces components that support a variety of business functions. IT investments have become the largest category of capital expenditure in United States-based businesses over the past decade. Though early ERP systems focused on large enterprises, smaller enterprises increasingly use ERP systems.

The ERP system is considered a vital organizational tool because it integrates varied organizational systems and facilitates error-free transactions and production. However, ERP system development is different from traditional systems development. ERP systems run on a variety of computer hardware and network configurations, typically using a database as an information repository.

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  1. Electrical Resistance Thermometer, aka thermistor
  2. Electrical Reliability Test (q.v.)

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ESL — Equibalent Series inductance. (The L stands for inductance.)

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ESR — Equivalent Series Resistance, a property of a capacitor or other part which does not function as a resistor, but adds a resistance component to characteristic impedance.

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ET — Electrical Test. (aka ERT, Electrical Reliability Test, q.v.).

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etch PCB manufacturing etch--verb to wear away the surface of (a metal, glass, etc.) by chemical action. To etch copper in PCB manufacturing, the echant used is a base (not an acid) typically containing ammonia and either ammonium chloride or ammonium sulfate.

See also etch resist.

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etch resist PCB manufacturingaka photo resist.

Etch resist is a mostly tin mixture that is applied in a thin coat to the copper laminate. Once the two sides of the laminate have been cleaned, the photo resist is applied. This is most often done with a roll laminator.

Photo of Roll Laminator
Figure 1. A Roll Laminator Used to Apply Photoresist

(Photo Roll_Laminator.png at ) Article by Kella Knack.

There is a roll of photo resist for each side of the laminate. This resist is made up of two layers. One is the photo resist itself while the other is a carrier film that protects the resist during handling.

The circuit pattern is printed on the photoresist in a panel printer, which shines a strong UV light through photo-plotted film, protecting the desired pattern from the etchant. The resist prevents the etching solution from contacting the desired conductive patterns. Because the etchant does not affect the resist, it removes only the undesired copper.

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eutectic alloy — A combination of two or more metals that has a sharply defined melting point and no plastic range. [[Graf, Rudolf F. Modern Dictionary of Electronics. Newnes, 1999] ]

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eutectic solder — Solder that has the lowest possible melting point for its combination of elements. Eutectic tin-lead solder is composed of 63% tin and 37% lead. It melts at 361 °F (183 °C). Eutectic tin-silver solder has 96.5% tin with 3.5% silver, and melts at 430 °F (221 °C). [[Graf, Rudolf F. Modern Dictionary of Electronics. Newnes, 1999] ]

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EVM — Evaluation Module

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EVT Engineering Validation Test

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exposed paddle noun  [PCB Components] Abbreviation: EP. A thermal (heat transfering) pad. It is a thin plane of metal, within a packaged integrated circuit, to which a die or chip. is attached. Although an exposed paddle is internal to the IC package, it is exposed on the bottom of the package in order to carry heat into the PCB. Therefore, a pad should be provided for soldering it to the PCB. It typically carries no digital or analog signal but would usually be connected to ground so that heat could be efficiently transferred to the built-in heat sinks of ground planes in the PCB.

Exposed paddles are very common in no-lead components like DFNs and QFNs. Aka "exposed DAP," "external paddle," "die attach paddle," or "die paddle." Exposed paddles are also thermal pads.

An 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 planes.

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 Voltage potential other than ground (rare), connect this pad and the vias to that Voltage 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 the PCB design of a footprint with an exposed paddle, the solder paste artwork should not be one large rectangle—it should be several small rectangles. This configuration has acquired the slang term "window pane" or "window paning." The term applies to the pattern, whether in the CAD file, the artwork or the solder paste stencil.

QFN-33 0.5 mm pitch - Orange-Colored Solder Paste.png
Example of solder paste window paning under an exposed paddle from a 2D view of a QFN-33, 0.5 mm pitch - Orange-Colored Solder Paste. Red is copper. Solder paste on signal terminals should be the same width and length as the metal terminations of the package, as determined by the datasheet's maximum values.
Window paning prevents too large an amount of solder building up during reflow under the exposed paddle, which could float the package far enough off the PCB that some of the signal lands would not get solder, causing opens.

See via and solder paste design examples in this PDF download from 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."

Warning: The above design example from Texas Instruments is illustrative but if it were followed explicitly, it would result in solder mask dams (aka solder mask bridges or green oil bridges) of 3 mils [0.08 mm], which is less than 4 mils and is therefore not good DFA (Design For Assembly) practice. The example TI shows could be improved to eliminate possible solder bridging by using solder-mask-defined pads on the HDI QFN shown (pad pitch of 0.5 mm).

QFN33 0.5 mm pitch - Purple-Colored Solder Mask
Example of solder-mask- defined pads. QFN-33, 0.5 mm pitch - Purple-Colored Solder Mask. Red is copper. (32 signal lands + 1 EP = 33 lands total)
For details on how to design solder-mask-defined pads and implement solder mask dams of at least 4 mils in 0.5mm-pitch (or less) ICs, see the following article: Design For Assembly – Prevention of Solder Bridging in High Density Interconnect PCB Components

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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.

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Alphabetizing Method

Terms that begin with a symbol or a digit are placed in the SYMBOLS page. Terms that contain digits within them 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 (/), dash (-) or plus sign (+), these are treated the same as spaces and ignored for the purpose of alphabetizing.

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.

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 2022 you could still buy a great used copy online for $40 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.

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

Golden Gate Graphics in an official Altium Service Bureau
Golden Gate Graphics is an official Altium Service Bureau