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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       S

Index to terms on this page:

SAC4   saturation   schematic   short   signal  
silicon wafer   silkscreen  
single track   SLPD   SMD   SMT   soft  
soft copy   software  
solder balls  
solder bumps  
solder coat  
solder mask  
space transformer   sputtering   SQFP   ST  
stable datum   stack-up  
STEP model   Streamlined Design  
Streamlined PCB Design   stuff   sub-panel   substrate  
surface mount   symbol  



SAC4 — Self-Aligned Controlled Collapse Chip Connect. A variation of C4 flip-chip technology. . PFEIFFER L, WEST KW, WONG YH ,Journal of the Electrochemical Society (JES) Volume 134, Number 11, November 1987.

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saturation

  1. The operating condition of a transistor when an increase in base current produces no further increase in collector current.  
  2. A circuit condition whereby an increase in the driving or input signal no longer produces a change in the output.  
  3. The condition when a transistor is driven so hard that it becomes biased in the forward direction. In a switching application, the charge stored in the base region prevents the transistor from turning off quickly under saturation conditions.  
  4. Generally, that state in which a semiconductor device is conducting most heavily for a given applied voltage. In many devices it is also a state in which the normal amplification mechanisms have become "swamped" and inoperative.  

[Graf]

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schematic — A diagram which shows, by means of graphic symbols, the electrical connections, components and functions of an electrical system. The components are represented by agreed-upon symbols, and the conductors connecting them by lines. If two lines cross each other, a large dot represents a junction, whereas no dot represents no connection.

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short — Short circuit. 1. An abnormal connection of relatively low resistance between two points of a circuit. The result is excess (often damaging) current between these points. Such a connection is considered to have occurred in a printed wiring CAD database or artwork anytime conductors from different nets either touch or come closer than the minimum spacing allowed for the design rules being use.

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signal

  1. A net.
  2. A net other than a power or ground net.


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silicon wafer — a thin, iridescent, silvery disk of silicon which contains a set of integrated circuits, prior to their being cut free and packaged. A silicon wafer will diffract reflected light into rainbow patterns and, being a similar size, looks so much like a music CD that it could be mistaken for one (except that it has no label or hole in the middle). On closer inspection, one can see the individual (usually rectangular- or square-shaped) integrated circuits which form a uniform patchwork quite unlike the surface of a music CD. When cut or etched from the wafer these circuits are then called chips or dice.

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silkscreen — (Also called "silkscreen legend")

  1. The decals and reference designators in epoxy ink on a printed wiring board , so called because of the method of application—the ink is "squeegeed" through a silk screen, the same technique used in the printing of T-shirts.
    A silk mesh size commonly used is 6 mils. With this mesh size, the absolute minimum line width of any silkscreen legend artwork is 6 mils, which leaves a very faint line. 7 mils works better for a practical minimum line width.
    Newer silkscreening methods allow for sikscreen draws of 5 mils, which come out very clear. A good reference designator size to use is 35 mils high with a 5 mil draw
  2. A Gerber file controlling the photoplotting of this legend.


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single track — PCB design with only one route between adjacent DIP pins.

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SMD

  1. Surface Mount Device (SMT component).  
  2. Solder-Mask Defined


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SMT — Surface Mount Technology.

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soft — Pertaining to or consisting of software.

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soft copy — An electronic form of a document; a data file in computer memory or stored on storage media. When one is looking at a soft copy he is viewing the document as displayed on a computer monitor.

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software — Programs, data files, procedures, rules, and any associated documentation pertaining to the operation of a computer system or of a computer application.

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solder balls — The round solder balls bonded to a transistor contact area and used to make connection to a conductor by face-down bonding techniques.

In IBM's ceramic BGA's, the solder used in solder balls has a higher melting point than that used in soldering the ball to the chip substrate and the BGA to a board. IBM uses 10/90 tin/lead for the solder ball and eutectic solder for the assembly. The high melt balls of the BGA do not melt during PCB assembly and thus create a pre-determined standoff height for the component.
PBGA packages use a eutectic solder ball which provides a collapsible joint similar to C4.
[Source:   IBM Ceramic Ball Grid Array Surface Mount Assembly and Rework ]

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solder bumps — solder balls.

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solder coat — A layer of solder that is applied directly from a molten solder bath to a PWB during manufacture, after the application of solder mask. This coats the terminals (copper pads) to be soldered during assembly with solder, providing a non-oxidizing protective layer.
   The most widely-used method of applying solder coat is hot air solder leveling (HASL)..

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solder mask — A technique wherein everything on a circuit board is coated with a plastic except 1) the contacts to be soldered, 2) the gold-plated terminals of any card-edge connectors and 3)fiducial marks.

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space transformer — Abbreviated ST. A major component of certain high-density probe cards. It provides pitch reduction, high routing density and localized mid-frequency decoupling.  A major developer of ATE systems which use space transformers is Wentworth Labs.

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sputtering — A deposition process wherein a surface, or target, is immersed in an inert-gas plasma and is bombarded by ionized molecules that eject surface atoms. The process is based on the disintegration of the target material under ion bombardment. Atoms broken away from the target material by gas ions deposit on the part (substrate), forming a thin film.   [Graf]

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SQFP — Shrink Quad Flat Pack. See QFP.

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ST Space Transformer.

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stable datum — a datum along which all other data align. From any confusion, order and sanity can emerge providing one merely selects a datum, assigns it importance or seniority and then begins to align other data against it.

The stable datum for any PCB layout could be stated this way:  The schematic is the "Bible." In other words, the schematic says the circuit is this way, and the PCB design must follow that pattern perfectly.

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stack-up — The arrangement of layers of materials in the construction of a PCB. The individual layers can be of various thicknesses.
   Most commonly, rigid PCBs are 1/16 inch [1.5875 mm] thick in total. This is the thickness of "cards" you can add to your desktop computer. There is a tolerance on this overall 1/16th inch thickness of plus or minus 10%. Of course, PCBs can be thinner or thicker based on the end use for which they are intended.
   In the case of the computer card, if the card has a lot of electronic power, such as a gamer's video card, it will be physically large. But also, it will have more layers than a simple Wi-Fi card. Needing to remain 1/16th inch thick [62.5 mils or 1.5875 mm], the layers will be thinner. Especially the center layer.
   At the center layer of a PCB stack-up is a core (q.v.). The rest of the layers we can call "outer" layers. These are made thin. The best practice is to keep the outer dielectrics at 4 mils [102 microns] to 8 mils [204 microns] thickness. The use of thin outer layers has to do with electromagnetic compatibility (EMC).
   EMC side-note: Thin layers help in electromagnetic field containment when layers with signal wires are sandwiched between ground planes. The thin layers of dielectric between the conducting layers means the electromagnetic fields (EM fields) set up between the signals and ground plane will be small. The smaller the EM fields, the less noise is generated by electromagnetic interference (EMI). This is fundamental to improving EMC.
   The core at the center, being a slab of dielectric with layers of copper on top and bottom, provides the two inner-most layers of copper and enough dielectric thickness to make up the difference between the thickness of all the other materials and the 1/16th inch thickness of the card. This provides rigidity. If the core were too thin, the card would be flimsy and not fit snuggly into the motherboard connector. If the core were too thick, the card wouldn't fit at all. And all this might be more than you wanted to know about PCB stack-up. If you're a printed circuit designer, you already know all this. If not, I probably lost you a long time ago.
  
   Stack-up 10 layers in CAD 3D perspective showing thick center core
   Stack-up 10 layers in CAD 3D perspective showing thick center core and thin outer layers. Vertical dimension has been exaggerated for illustration.
  
   Stack-up 6 layers in CAD 3D perspective showing even thickec center core
   If the layers are reduced from 10 to 6, the center core must be thicker to maintain the overall thickness of 1/16th inch.

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STEP model — (STEP MAHD-dəl)  Pronunciation Key  noun  [Computer Aided Design] A 3D body in CAD. STEP stands for "Standard for the Exchange of Product model data."
Altium Designer 13 and 10 can import STEP models into footprints and PCBs. 3D engineering drawing software such as Solid Works can export STEP models. STEP model files may have the extension .STP or .STEP. Most connector manufacturers have been very helpful to PCB designers by providing STEP models of their parts.

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Streamlined Design — See Streamlined PCB Design

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Streamlined PCB Design (SLPD) — (The verb streamline means "Cause to be quick and efficient.") Streamlined design = accuracy plus speed. SLPD is a set of policies that can guide the design of printed circuit boards. The policies have been derived with the aim of simplifying PCB design and systematically eliminating errors from it. This should speed design and manufacturing.

Streamlined PCB Design is not a quick-and-dirty way for a PCB designer to make a fast buck. Some PCB designers who have learned some of its elements have complained that it is more work for them, not less.

It is important to get the viewpoint here: The system is streamlined with highest priority directed at the broad view of the overall electronics project and secondly from the narrower view of each step in the cycle of production. Therefore, part of a PCB designer's job in implementing SLPD is doing extra things in just such a way that help is provided to the downstream actions in the overall production cycle, especially board manufacture and assembly.

If one can eliminate whole categories of errors from creeping in, the overall cycle of production gets completed sooner with higher quality and reliability.  Design and production become quick, efficient, streamlined.

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stuff — () Slang Populate. Attach and solder components to (a printed wiring board ).

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sub-panel — A group of printed circuits (called modules) arrayed in a panel and handled by both the board house and the assembly house as though it were a single printed wiring board. The sub-panel is usually prepared at the board house by routing most of the material separating individual modules, leaving small tabs. The tabs are strong enough so that the sub-panel can be assembled as a unit, and weak enough so that final separation of assembled modules is easily done.

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substrate — The supporting material on or in which the parts of an integrated circuit are attached or made. The substrate may be passive (thin film , hybrid ) or active ( monolithic compatible). [For more information see Modern Dictionary of Electronics, by Rudolf F. Graf.]

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surface mount — Surface mount technology. The technology of creating printed wiring wherein components are soldered to the board without using holes. The result is higher component density, allowing smaller PWB 's. Abbreviated SMT.

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symbol — A simplified design representing a part in a schematic circuit diagram.

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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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