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GLOSSARY of Printed Circuits

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

   SYMBOLS    A    B    C    D    E    F    G    H    I    J    K    L    M    N    O    P    Q    R    S    T    U    V    W    X    Y    Z   

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.

TOP       U

Index to terms on this page:

U   UAV   UBGA   UDF   UEFI   uF   UL  
Ultra-Fine Pitch Technology   ULVDS  
unsaturated logic   unstuffed   US-ASCII  

U — Stands for micro, as in mirco-electronic or micro-processor. U is used for its resemblance to the Greek lower-case letter mu, μ, a symbol for micro. Because micro-processors are integrated circuits, U is used as the alpha character prefix in a reference designator which gives a name to an integrated circuit component in a schematic or on a PCB (Eg. U8). "IC" is also used for this, depending on the electronic circuit designer's personal preference (Eg. IC8).

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UAV — Unmanned Airial Vehicle. The UAV is an acronym for Unmanned Aerial Vehicle, which is an aircraft with no pilot on board. UAVs can be remote controlled aircraft (e.g. flown by a pilot at a ground control station) or can fly autonomously based on pre-programmed flight plans or more complex dynamic automation systems. The UAV.

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UBGA — Ultra FBGA, that is Ultra Fine-line Ball Grid Area. UBGA is used by Altera to designate BGAs with a ball pitch of 0.8mm.

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UDF — (Universal Disc Format). This format is only supported by Windows Me and later versions and should be selected when creating video DVDs. The DVD Forum's DVD-VR format uses UDF 2.00 for DVD-R, DVD-RW and DVD-RAM. Philips' DVD+VR format uses UDF 1.02 with an ISO 9660 bridge for DVD+R and DVD+RW.

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UEFI —  [Computer Systems Administration]  Unified Extensible Firmware Interface. BIOS (firmware) and UEFI (software) are two interfaces for computers to start the operating system and peripherals .

BIOS vs UEFI excepted from The Windows Club. "UEFI vs BIOS: What Is the Difference between BIOS and UEFI?" The Windows Club, The Windows Club, 10 Dec. 2021,

While they are both used for starting the computer, they are NOT the same. BIOS is firmware that uses the Master Boot Record (MBR) to save information about the hard drive data while UEFI is software that uses the GUID Partition Table (GPT) .

UEFI was originally developed in 2007 as a standard for modern interfaces. This platform supports a wide variety of modern hardware platforms. This is the newer and more advanced firmware interface that aims to correct the technical shortcomings of BIOS. Similar to BIOS, it also serves as a bridge, connecting a computer's operating system to its firmware. UEFI comes with a number of features and advantages that cannot be obtained through the legacy BIOS. This technology will eventually replace the BIOS entirely.

In UEFI, the .efi file (not a firmware file such as BIOS uses) stores all startup information, and it is located on the EFI System Partition on the hard drive. You’ll find the bootloader on the same partition. The most important thing to note here is that UEFI bypasses the BIOS Power On Self Test (POST) so that the operating system can boot directly. Unlike BIOS, it does not have restrictions on size, so more components can be initialized simultaneously.

BIOS only works in 16 bits and therefore it cannot address more than 1MB of space. As a consequence, it can only initialize one device at a time and the booting might take longer.

In contrast, UEFI operates in 64-bit mode, meaning it has higher addressable memory and thus it makes the booting process faster. Furthermore, UEFI supports networking, so you can troubleshoot remotely even without installing an operating system. As a result, most motherboard manufacturers find it to be a much better choice in most cases. For this reason, it has gained popularity recently.

The next difference between the two programs is that BIOS stores bootloader data in the Master Boot Record (MBR). The MBR is located in the first sector of the disk, so it can be easily corrupted, which would make the operating system unresponsive.

UEFI, on the other hand, makes use of the GUID Partition Table, which performs cyclic redundancy checks to identify any corruption issue. Thus, it creates a more robust boot environment that can be easily recovered. It is capable of supporting more than four primary partitions.

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uF — microfarad. One millionth of a Farad. (For Farad, see a good dictionary of electronics such as [Graf, Rudolf F. Modern Dictionary of Electronics. Newnes, 1999] .)

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UL — Underwriter's Laboratories, Inc., a corporation supported by some underwriters for the purpose of establishing safety standards on types of equipment or components.

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Ultra-Fine Pitch Technology — A surface-mount assembly technology with component terminations on centers less than or equal to 0.40 mm [15.7 mil].

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ULVDS — Ultra Low Voltage Differential Signaling

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unsaturated logic — A form of logic containing transistors operated outside the region of saturation , which makes for very fast switching.  An example is emitter-coupled logic ( ECL ).  (For other definitions and examples see [Graf, Rudolf F. Modern Dictionary of Electronics. Newnes, 1999].

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unstuffed Slang [PCB Manufacturing] Not populated.

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US-ASCII — The 7-bit (using character codes 0-127) version of ASCII, which preceded (and is the basis for) 8-bit versions such as Latin-1, MacASCII and later, even larger coded character sets such as Unicode.

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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