GLOSSARY of Printed Circuits

Index to terms on this page:

Valuable Final Artwork  
Van Allen Belt   vcc   vdd  
vector photoplotter   vee   VESA   vet   vett   via   via fill   VLSI   Voltage drop   voltage rail   VOS   VQFN   VQFP   VRM   vss   VSSOP   VSWR  

Valuable Final Artwork — A term used in " Streamlined_PCB_Design :"   Artwork for electronic circuits which have been laid out and documented in forms perfectly suited to the photo-imaging and numeric-controlled tooling processes of printed circuit manufacture. It is termed "final" because it has been thoroughly checked for errors and any corrected as needed and is now ready for manufacture without further work by the PCB designer. It is valuable because it could be exchanged with a customer for money or other support. Abbr. VFA.

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Van Allen Belt — The Van Allen radiation belt is a torus of energetic charged particles around Earth, trapped by Earth's magnetic field. Wikipedia - Van Allen radiation belt


The magnetosphere includes two doughnut-shaped radiation belts, or zones, centred on the Equator that are occupied by appreciable numbers of energetic protons and electrons trapped in the outermost reaches of the atmosphere. No real gap exists between the two zones; they actually merge gradually, with the flux of charged particles showing two regions of maximum density. The inner belt extends from roughly 1,000 to 5,000 km (600 to 3,000 miles) above the terrestrial surface and the outer belt from some 15,000 to 25,000 km (9,300 to 15,500 miles). The belts were named in honour of James A. Van Allen, the American physicist who discovered them in 1958. Source: Britannica.com - Magnetosphere.

The belt's radiation includes free protons, trapped from solar, which cause SEU's, thus damaging silicon-based electronics components. Also found in the Van Allen belt are free neutrons (from cosmic radiation), which tend to pass right through the silicon chips without interaction, but can be very hard on astronauts. One would not orbit a data-transmission satellite nor attempt to establish a space station within the Van Allen belt. Source: Bela Szabo, electrical engineer.

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vcc or VCC or Vcc — A name for a power net meaning "voltage collector," usually +5V for TTL circuits.

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vdd or VDD or Vdd — A name for a power net meaning "voltage drain," usually implying a more positive voltage.

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vector photoplotter — (also "vector plotter", or "Gerber photoplotter" after Gerber Scientific Co., which built the first vector photoplotters for commercial use)  It plots images from a CAD database on photographic film in a darkroom by drawing each line with a continuous lamp shined through an annular-ring aperture, and creating each shape (or pad) by flashing the lamp through a specially sized and shaped aperture. The "apertures" are thin trapezoidal pieces of plastic which are mostly opaque, but with a transparent portion that controls the size and shape of the light pattern passing through it. The apertures are mounted on an " aperture wheel " which can hold up to 24 apertures (or 70 on certain models). The lamp and aperture wheel are fixed, and the table holding the film is moved in x and y dimensions (on small photoplotters), or vice versa (on very large photoplotters). A numeric datum sent to the control circuit of the photoplotter is either a D code or an X and/or Y dimension in inches, to the nearest thousandth. If it is a D code equal to D10 or above, the message tells the wheel to rotate the corresponding aperture location into position in front of the lamp. .  Gerber photoplotters, if set up by an experienced craftsman, are well-suited for printed circuit artwork generation. Compare with laser photoplotter , which is faster, more accurate and has largely replaced the vector photoplotter.

There are still vector photoplotters in use. Some manufacturers take advantage of the large bed size of the largest Gerber photoplotters, roughly the size of a full-sized billiards table. This enables the production of very large photoplots. An example is Buckbee-Mears, which makes large antenna boards, and the USGS (United States Geological Survey) which has used them in map-making.

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vee or VEE or Vee — A name for a power net meaning "voltage emitter," usually -5V for ECL circuits.

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VESA — Video Electronics Standards Association

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vet — verb   [Qualifications]  To examine thoroughly. In the context of PCB Design and Schematic Capture, this means two pairs of eyes, manual netlist checking and visual examination of Gerber files (if not photoplotted film) with a Gerber viewer.

When a circuit designer (electrical engineer) vets a schematic he should be looking over it carefully for obvious errors, doing a final comparison of the symbols in the schematic with the spec sheets for pin outs and pin functions, checking the spec sheets for sample circuits that match his use (looking for missing associated components) and manual checking of a hard copy of the netlist against a hard copy of the schematic (highlighting as he goes, nodes on both that have been checked).

When a PCB designer vets a design, he uses automatic checking where he can. Any of the vetting not done by the engineer should be done by himself, if he is permitted. (It is far better for the circuit designer to vet the schematic, because he has the most knowledge of its inner workings.)

In design work, vetting is rarely done to this level of thoroughness, the excuse being "time to market" constraints or just "not enough time," commonly leading to more time spent debugging after the board is manufactured, more prototype spins and market opportunities missed.

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vett — mis-spelling of vet.(q.v.) Verb. To examine thoroughly.

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via — Feed-through. A plated-through hole in a PCB used to route a trace vertically in the board, that is, from one layer to another.
  [Derivation: Via is an acronym—vertical interconnect access.
Citation:
Haviv, Dror. Signal Integrity Journal RSS, Signal Integrity Journal, 24 Dec. 2020, "How to Stop Your Differential Vias from Leaking."]

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via fill — a plug for a via that prevents solder from running down into the PTH hole. Vias that are in component pads should be filled and this has become very common with chip scale packages such as DFN and QFN. These and other packages have an exposed solder pad under the body for ground and heat sinking. Better heat sinking is achieved if vias are placed in the exposed pad. Via fill material can be mildly conductive, as is CB100 from Dupont, or non-conductive as is PP-2795 made by Lackwerke Peters GmbH + Co KG. It is preferable to fill only the vias that are in pads and these particular vias can be called out in the CAM files by giving them a slightly different PTH finished hole size than similar-sized vias that are not to be filled.

Another via fill option is conductive ink plugs, as offered through EDINS bare board manufacturing representatives in South Korea. Where applicable, this is a very cost-effective technique as compared with other via fill material.

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VLSI — Very Large Scale Integration.

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Voltage drop — is the intentional loss in output voltage from a device as it drives a load. Employing droop in a voltage regulation circuit increases the headroom for load transients.

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voltage rail — Aka power supply rail

A DC voltage in a power supply. A computer's power supply converts AC power into several DC voltages (typically plus and minus 3.3v, 5v and 12v), each of which is known as a rail. The term comes from the power lines on motherboards. Power must be available throughout a motherboard; hence, voltage lines tend to run in long strips like railroad tracks. PCmag Encyclopedia - rail

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VOS — Output-voltage sense pin (Texas Instruments)

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VQFN — Very-thin (0.9mm maximum height) Quad Flat No-lead package.

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VQFP — Very thin Quad Flat Pack.

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VRM — voltage regulator model

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vss or VSS or Vss — A name for a power net meaning "voltage source," usually implying a more negative voltage and often equivalent to Ground or GND.

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VSSOP — Very-thin Shrink Small Outline package. Compare with TSSOP. Similar to TSSOP, but with component height less than 1 mm and pitch of 0.5mm, although I have seen some VSSOP packages with 1.1 mm height and pitch of 0.65 mm. This is a good case for a dimensional descriptive footprint name, which I and IPC came up with independently. I have swiched over to the IPC naming convention because it is just as good as the system I developed, but I augment the IPC name with a prefix showing the common acronym without the hyphen. IPC example of VSSOP: SOP50P310x90-8N. My example: VSSOP8_SOP50P310x90-8N

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VSWR — Voltage Standing Wave Ratio. Standard name for the standing-wave voltage ratio.

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