GLOSSARY of Printed Circuits

Index to terms on this page:

backdoor  
ball grid array  
ball pitch   ball-pitch   balun   bandwidth   bare   bare board   base   BD  
beam lead   Benzotriazole  
best-in-class   BFR   BGA   bias  
bifilar windings   BIOS   bisphenols   blame   blind via   blue wire   BLVDS   BNC   board  
board house   body   BOM   boss   branches   BQFP   BSC   BSDL   BT   BT resin  
buck converter   build   BUM   buried via   bus   bus width  

backdoor — [Networking]  A backdoor is a malware type that negates normal authentication procedures to access a system. As a result, remote access is granted to resources within an application, such as databases and file servers, giving perpetrators the ability to remotely issue system commands and update malware.

Backdoor installation is achieved by taking advantage of vulnerable components in a web application. Once installed, detection is difficult as files tend to be highly obfuscated.
Citation at imperva: What is a backdoor

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ball grid array — () (Abbrev. BGA).   A flip-chip type of package in which the internal die terminals form a grid-style array, and are in contact with solder balls ( solder bumps ), which carry the electrical connection to the outside of the package. The PCB footprint will have round landing pads to which the solder balls will be soldered when the package and PCB are heated in a reflow oven. Advantages of the ball grid array package are (1) that its size is compact and (2) its leads do not get damaged in handling (unlike the formed "gull-wing" leads of a QFP) and thus the BGA package has a long shelf life. Disadvantages of the BGA are 1) they, or their solder joints, are subject to stress-related failure. For example, the intense vibration of rocket-powered space vehicles can pop them right off the PCB, 2) they can not be hand-soldered (they require a reflow oven), making first-article prototypes a bit more expensive to stuff, 3) except for the outer rows, the solder joints can not be visually inspected and 4) they are difficult to rework.

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ball pitch — (BAHL-pich)   Pronunciation Key  noun  [PCB Components] The distance between the centers of adjacent balls in a row or column of a BGA (Ball Grid Array). This will usually be a constant quantity throughout the BGA. (If only this were always, not just usually, the case.)
Ball pitch will be stated in any generic description of a BGA that has leads of consistent pitch. (Eg: a 1-mm BGA256 means a Ball Grid Array with 256 balls arranged in a quadrangular pattern with a pitch of 1 millimeter.) Ball pitch is fixed by the component manufacuturer and greatly affects the breakout and routing strategy.

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ball-pitch — Alternate spelling of ball pitch.

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balun — (BAY-lən)  Pronunciation Key  Electrical engineering An acronym for BALanced to UNbalanced. A device used for matching an unbalanced coaxial transmission line to a balanced two-wire system. One implementation of this can be a trace in a printed circuit board that acts as an inductor.

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bandwidth — is the highest sine wave frequency component that is significant in a signal. Because of the vagueness of the term “significant,” unless detailed qualifiers are added, the concept of bandwidth is only approximate.
Bandwidth is a figure of merit of a signal to give us a rough feel for the highest sine wave frequency component that might be in the signal. This would help guide us to identify the bandwidth of a measurement instrument needed to measure it, or the bandwidth of an interconnect needed to transport it. [Eric Bogatin - EDN November 19, 2013]

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bare — Not populated with components, naked (of a PCB).

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bare board — A finished printed circuit board which hasn't yet been stuffed, the final product of a board house.

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base — The electrode of a transistor which controls the movements of electrons or holes by means of an electric field on it. It is the element which corresponds to the control grid of an electron tube.

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BD — Boundary Devices

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beam lead — ()A metal beam (flat metallic lead which extends from the edge of a chip much as wooden beams extend from a roof overhang) deposited directly onto the surface of the die as part of the wafer processing cycle in the fabrication of an integrated circuit. Upon separation of the individual die (normally by chemical etching instead of the conventional scribe-and-break technique), the cantilevered beam is left protruding from the edge of the chip and can be bonded directly to interconnecting pads on the circuit substrate without the need for individual wire interconnections. This method is an example of flip-chip bonding, contrasted with solder bump.   [Graf, Rudolf F. Modern Dictionary of Electronics. Newnes, 1999]
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Benzotriazole — a monomolecular organic nitrogen-chemistry coating used as an Organic Solder Preservative (OSP).

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BFR — buffer

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BGA — See Ball Grid Array.

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bias — (BAHY əs)  Pronunciation Key  noun   [PCB Layout] Routing layer bias. A widely used definition of bias is “A particular tendency or inclination.” (From Random House Dictionary of the English Language, def 2). In PCB layout, bias refers to routing layer bias. On any given layer of a mulitlayer PCB, the bias is the tendency of a route to be parallel to one of the axes (x or y) or oblique (45 degree angle).

Obviously, it is the PCB designer (layout person) who controls the routing layer bias within the PCB file. If he is routing manually, he makes sure that the route he is adding trends in the direction of his choosing which is the same direction of the majority of other routes on that layer. With autorouting, the bias for each layer is set by design rule prior to routing.

If manually routing, the PCB designer can easily keep track of routing layer bias by re-naming his layers to include the bias. Altium Designer allows one to do this. Example 4-layer stack-up with renaming of layers:
Lay1 Ysig-&-PWR
Lay2 NegGND
Lay3 NegGND
Lay4 Xsig-&-PWR

If you think of your computer screen as a map, you could consider that the top is north, bottom south and so on. Oblique biases can be simply named by use of NE or SE in the name. “NE” (North East) would be added to layer names where the routes trend from lower left to upper right (or upper right to lower left, no difference here). “SE” (South East) added to a layer name would designate it as having routes that will trend from upper left to lower right. If you used the name “NW,” that would be the same as “SE.”

Routing layer bias is used to prevent wires from shorting as they go from a starting point to an ending point on the PCB. A route is routed in one direction, passed through a via to another layer, and then continued in a different direction. It is this basic technique that permits many criss-crossing connections to be routed in a PCB without shorting.

On layers that have both signals and poured copper, adhering to routing layer bias keeps the poured copper from being isolated. In other words, on such layers, don't route in an anti-bias (wrong way) direction. On a multi-layerd board with many signal and ground plane layers, but with only one signal layer between any two adjacent ground planes, routing layer bias can be safely disregarded in order to reduce via count.

On multi-layer boards with two signal layers between any pair of ground planes, routing layer bias is important to maintain so that signals on adjacent layers cross at right angles to each other, thus avoiding cross-talk. An X-bias would be adjacent to a y-bias layer. A NE-bias layer would be adjacent to a SE-bias layer.

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bifilar windings — windings made practically noninductive by winding two wires carrying current in opposite directions together, side by side, as one wire. In a bifalar winding of a transformer, two colors of enamel coating can be used for the pairs of wires, one having a darker color than its mating wire. (source) BI- (twice,two) + L fil(um) (thread, string) + -AR (adjective-forming suffix)

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BIOS —  [Computer Systems Administration]  Basic Input Output System. This is an older, legacy software used for starting up a personal computer. It is part of the computer's embedded software (aka firmware) and is located on the motherboard’s controller chip. The BIOS connects the hardware components of the computer with the operating system. It loads the bootloader, which is what boots the OS and initializes the system.

When a system is turned on, the BIOS performs a Power-On Self Test (POST) process which checks for possible hardware issues. If there is an error, the system displays an error message or emits cryptic beeps to let you know what is wrong. Upon completing an initial check, the bootloader will be loaded from MBR. Thus it is the very first software to run when a legacy personal computer is started.

For more info see BIOS article at The Windows Club.

Note that BIOS is not the only software that can start a computer. See the topic BIOS vs UEFI excerpted from The Windows Club at this glossary's entry UEFI.

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bisphenols —  [PCB Fabrication]  A group of organic chemical compounds with two hydroxyphenyl functionalities. Bisphenol is a common name; the letter following refers to one of the reactants. Bisphenol A (aka BPA) is the most popular representative of this group, often simply called "bisphenol."

Bisphenol A primarily serves as a basic building block for the production of polymer plastics and coatings, mainly polycarbonate and epoxy resins.

Epoxy resins are used in making the ink used on PCBs to apply a legend. They are also one of the main ingredients in many PCB dielectrics. The PCB dielectric most commonly used in America uses an epoxy resin with woven fiberglass and is designated FR-4. (Another category of resins used in PCB dielectrics is polyimides.)

End-user applications of BPA-based polycarbonate plastic are hard plastic items, such as compact discs, computers, home appliances, spectacles, safety glasses, optical lenses, re-useable water bottles, food containers, tableware, dental sealants, the lining of canned foods and drinks, medical devices, safety helmets, construction materials and high performance paints and coatings to withstand extreme conditions.

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blame — [Apache Subversion] (Of a text file) See who changed which line and when.

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blind via —  noun [PCB Fabrication]  Blind means closed at one end. Of a via, drilled or ablated from the outside of the finished board to an inner termination layer.

This can be accomplished by drilling all the way through a lamination or stack-up of laminatons (layers) and then adding such drilled lamination(s)to other laminations to construct a PCB.

The effect of blind vias is that traces on nearby layers can run below any via without causing a short and thus higher density of circuitry results.

In the case of laser-ablated vias, only two adjacent layers (one lamination plus copper on both sides, thus two layers) can be intersected because of the low aspect ratio of ablated vias. In the case of drilled vias, several layers can be intersected. Additional layers are added after drilling to one side to result in those vias becoming blind. source:

From Jerry Arreola, PCB Design and Engineering Service Manager, Pal-Pilot Date: October 28, 2016
A set of blind Laser-drilled microvias can be added to the outside of a fully laminated PCB, drilling down from the top layer to the 2nd layer without need for sequestial lamination. The dielectric has to be less than 3 mil thick (actual example 2.95 mil [74 microns]). The laser bit size is 5 mil [127 micron]. The via pad and ball pad are 10 mil [254 micron]. In the fab drawing, there must be a top to layer 2 drill table for laser-drilled microvias separate from the through-hole drill table. A note in the fab drawing describing this would read: Microvias. Layer 1 to Layer 2, laser drilled, 5 mil bit in 10 mil pad. Solid copper fill laser holes (Via-in-Pad).

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blue wire —

1. A small guage wire used in rework of a PCA, and which is usually insulated with blue plastic. Typically 30 guage for fine pitch surface mount PCA's.
2. Blue wire — slang for goofs that show up on an assembled electronic circuit, because they are typically corrected using blue wire. One of the intentions of a PCB designer is that there are no "blue wires" on his designs, especially none caused by him.

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BLVDS — Bus Low-Voltage Differential Signaling [acronymfinder.com]

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BNC — Bayonet Neill Concelman. The BNC (Bayonet Neill Concelman) connector is a miniature quick connect/disconnect radio frequency connector used for coaxial cable. It features two bayonet lugs on the female connector; mating is fully achieved with a quarter turn of the coupling nut. (Read more at Wikipedia BNC connector)

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board — printed circuit board. Also, a CAD file which represents the layout of a printed circuit.

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board house — Board vendor. A manufacturer of printed circuit boards. Aka fabricator.

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body — The portion of an electronic component exclusive of its pins or leads.

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BOM — (BAHM)   Pronunciation Key  Bill of Materials. A list of components to be included on an assembly such as a printed circuit board. For a PCB the BOM must include reference designators for the components used and descriptions which uniquely identify each component. A BOM is used for ordering parts and, along with an assembly drawing , directing which parts go where when the board is stuffed.
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boss — A protrusion, inside an enclosure, of any shape, but often cylindrical, which serves to fix in position an object inside the enclosure. The boss butts-up against the object when the entire unit is fully assembled. Some examples of objects that might make contact with a boss are a PCB, a battery or battery holder or another part of the enclosure, such as a lid.

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branches — [Apache Subversion] Divergent copies of development lines. Free Version Control with Subversion by Red-Bean.com. From GitHub github branching --plain English: Branching is the way to work on different versions of a repository at one time. By default your repository has one branch named master which is considered to be the definitive branch. We use branches to experiment and make edits before committing them to master.
When you create a branch off the master branch, you're making a copy, or snapshot, of master as it was at that point in time. If someone else made changes to the master branch while you were working on your branch, you could pull in those updates.
When you work with a version control system, you must consider how to set up a branch structure. You can create a branch by mirroring the source code file. Then you can change the branch without affecting the source.
This is a must-see for conceptual understanding: Microsoft - Branch strategically

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BQFP — Bumpered Quad Flat Pack. A bumpered quad flat pack is one that has extensions at the four corners to protect the leads against mechanical damage before the unit is soldered. See picture at https://en.wikipedia.org/wiki/Quad_Flat_Package
Example image is at: Cyrix Cx486SLC in bumpered quad flat package (BQFP)

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BSC — Basic Spacing between Centers. Used on mechanical drawings to indicate that a dimension is center to center. This is a theoretical true position dimension and has no tolerance.

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BSDL — Boundary Scan Description Language. (See JTAG in this glossary for an extremely brief explanation).

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BT —

1. Benzotriazole (also BTA).
2. BT resin
3. Bluetooth

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BT resin — bismaleimide-triazine co-polymer. BT resin is a dielectric material, a rigid substrate used in BGAs. In a flip chip, high temperature solder balls are attached directly to the silicon die. BT resin forms a layer between the flipped die and the solder balls on the bottom of the package.
Interconnection between the die and the solder ball lands is by filled plated-through vias which penetrate the BT resin. (An alternative to BT resin is polyimide tape, a flex based tape substrate.) Dielectric coefficinet = 3.9 to 4.9

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buck converter — a voltage regulator that outputs a lower voltage than the input.

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build —

1. verb  [PCB Design Slang]
(Of a footprint) Design or layout.
2. verb  [PCB Manufacturing]
fabricate and assemble.

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BUM — Build Up Manufacturing

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buried via — (BAIR-eed VEE-ə) Pronunciation Key  noun  [PCB Manufacturing]  Buried means hidden. A via drilled or ablated from an inner termination layer of the finished board to another inner termination layer.

This can only be accomplished by a layer add-on technique, such as in build-up manufacturing. The via hole is created and plated, and then addtional layers are added before the board is finished.

The effect of buried vias is that traces on nearby layers can run above and below any via without causing a short and thus higher density of circuitry results.

In the case of laser-ablated vias, only two adjacent layers can be intersected (one lamination plus copper on both sides, thus two layers) because of the low aspect ratio of ablated vias. In the case of drilled vias, several layers can be intersected. Additional layers are added after drilling to bury the vias.

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bus —

1. [Electronics] A group of conductors considered as a single entity which interconnects various parts of a system, e.g. data bus or address bus. [Graf def 9]

Various schemes have been invented to solve the problem of collisions: multiple stations trying to transmit at once, e.g. CSMA/CD, bus master.
The term is almost certainly derived from the electrical engineering term "bus bar" - a substantial, rigid power supply conductor to which several connections are made. This was once written "'bus bar" as it was a contraction of "omnibus bar" - a connection bar "for all", by analogy with the passenger omnibus - a conveyance "for all".
There are busses both within the CPU and connecting it to external memory and peripheral devices. The data bus, address bus and control signals, despite their names, really constitute a single bus since each is useless without the others.
The width of the data bus is usually specified in bits and is the number of parallel connectors. This and the clock rate determine the bus's data rate (the number of bytes per second which it can carry). This is one of the factors limiting a computer's performance. Most current microprocessors have 32-bit busses both internally and externally. 100 or 133 megahertz bus clock rates are common. The bus clock is typically slower than the processor clock.
Some processors have internal busses which are wider than their external busses (usually twice the width) since the width of the internal bus affects the speed of all operations and has less effect on the overall system cost than the width of the external bus.
Various bus designs have been used in the PC, including ISA, EISA, Micro Channel, VL-bus and PCI. Other peripheral busses are NuBus, TURBOchannel, VMEbus, MULTIBUS and STD bus.
https://foldoc.org/bus
2. [CAE] A group of nets that differ in name by a numbered suffix only.
3. [Networking] A set of electrical conductors (wires, PCB tracks or connections in an integrated circuit) connecting various "stations", which can be functional units in a computer or nodes in a network. A bus is a broadcast channel, meaning that each station receives every other station's transmissions and all stations have equal access to the bus.

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bit width —

1. the number of signals (conductors) in a bus (q.v.)
2. The number of signals (conductors) in any group of signals considered as a single entity that have a common purpose.

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