GLOSSARY of Printed Circuits

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Index to terms on this page:

TAB   tab terminal    tact switch   tactile switch   tag   TAR   TDFN   TDR   TDSON   teardrop   TEC   Telnet   tented via   terminal   terminal block  
test coupon   TGZ   thermal pad   thin film   TH Pad  
through-hole   THT   thru-hole   TI  
tin-silver-copper   TO-   ToF   tombstoning  
top view   topology   TortoiseSVN   TQFP   trace   trace pitch   track   transducer   transmission line   transponder   tranzorb   Trillium   trunk   TSDSON   TSSOP   TTL   TVS   TVSOP   TYP  

TAB — Tape Automated Bonding.

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tab terminal — (aka "quick disconnect" or "blade connector." or "AMP FASTON terminal.") These are widely used in electronic and electrical equipment, and compatible terminals are manufactured by many different vendors.

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tact switch — (slang) Tactile switch.

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tactile switch — A push-button switch with a very low actuation force that is momentary (terminals are normally open and are closed only while the button is being pushed). The actuation force is low enough that merely touching the button (actuator) with ones finger will close the terminals.

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tag — [Apache Subversion] Named, stable snapshot of a particular line of development. [svn-book as PDF and online]

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TAR — (Tape ARchive) file, that is a standard format in the Unix/Linux world.

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TDFN — Thin Dual Flat No-lead.

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TDR — Time Domain Reflectometer, a device which a board house can use for measuring characteristic impedance of a conductor on a printed board, thus insuring an accurate build for controlled impedance.

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TDSON — Thin Dual Small Outline Non-leaded, a near chip-scale package (Infinion.com).

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teardrop — The addition of conductive material at the interface between the conductor and the land. Also know as "Filleting." [IPC-T-50M]

Extra copper added to a trace and pad (or land) where the trace intersects the pad. The word derives from the resulting shape.

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TEC — noun   ThermoElectric Cooler, a type of active heat sink used on CSP's. Also called Peltier thermoelectric cooler, it depends for its function on the Peltier effect .

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Telnet — [Networking]  Telnet is a remote access protocol that can be used to control devices over the internet. It is a notoriously weak service that can easily be backdoored. Hackers have long exploited the service in Distributed denial of service attacks (DDoS) and other botnet-related attacks.
Citation from threatpost: Bad actor scanned Internet for devices open to the Telnet port

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tented via — a via with dry film solder mask completely covering both its pad and its plated-thru hole. This completely insulates the via from foreign objects, thus protecting against accidental shorts, but it also renders the via unusable as a test point. Sometimes vias are tented on the top side of the board and left uncovered on the bottom side to permit probing from that side only with a test fixture.

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terminal — A point of connection for two or more conductors in an electrical circuit; one of the conductors is usually an electrical contact, lead or electrode of a component.

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terminal block — A type of header to which wires are attached directly instead of by means of a connector plug. Each wire is inserted in a hole in the terminal block , and then anchored by means of a screw.

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test coupon — An area of patterns and holes located on the same fabrication panel as the actual PCB, but separate from the electrical circuits and outside the board outline(s). It is designed to reflect the technology used on the PCB, such as smallest plated-through hole size, any blind or buried vias, etc. It is cut away from the panel and can be embedded in a clear plastic to prepare it for destructive testing.

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TGZ — Tar File Gzipped

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thermal pad — A heat-transfering plane of metal within a packaged integrated circuit to which a die is attached. Although a thermal pad 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 land 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.

For information on PCB design of footprints with thermal pads, see in this glossary exposed paddle.

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thin film — A film of conductive or insulating material, usually deposited by sputtering or evaporation, that may be made in a pattern to form electronic components and conductors on a substrate or used as insulation between successive layers of components.   [Graf, Rudolf F. Modern Dictionary of Electronics. Newnes, 1999]

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TH Pad — Through-hole pad.

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through-hole — (Of a component, also spelled "thru-hole"). Having pins designed to be inserted into holes and soldered to pads on a printed board. Contrast with surface mount.

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THT —

1. Through-Hole Technology. Electronic components mounted on a circuit board by passing their leads through holes in the board and usually soldering them in place.
2. A Through-Hole (Technology) Component

thru-hole — Same as through-hole.

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TI — Texas Instruments, an IC manufacturer.

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tin-silver-copper — Aka SAC (SnAgCu). A lead-free (Pb-free) alloy commonly used for electronic solder. The tin-silver-copper alloy has been the prevailing alloy system used to replace tin-lead because it is near eutectic, with adequate thermal fatigue properties, strength, and wettability.[1] Lead-free solder is gaining much attention as the environmental effects of lead in industrial products is recognized, and as a result of Europe's RoHS legislation to remove lead and other hazardous materials from electronics. Japanese electronics companies have also looked at Pb-free solder for its industrial advantages.

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TO- — Transistor Outline package, a JEDEC acronym. Eg., TO-92 is an acronym for JEDEC Transistor Outline Package, Case Style 92.

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ToF — Time of Flight, relating to reflected signals. ST Microelectronics makes a ToF sensor.

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tombstoning — [PCB assembly]  "A surface mount passive component, like a resistor or a capacitor, that partially lifts from a pad on one end. As your component stands on end like it’s rising from the dead, it ends up looking like a tombstone in the graveyard of what is now a defunct PCB design with an open circuit."
Citation:
Sattel, Sam. “What Is PCB Tombstoning?: Eagle: Blog.” Eagle Blog, Autodesk, 2 Feb. 2021, www.autodesk.com/products/eagle/blog/what-is-pcb-tombstoning/.

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top view — [PCB assembly and PCB design] Of a component: This is the viewpoint of looking down on the part from the side of the board from which it is inserted or placed.

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topology —

1. [Electrical Circuits] The topology of an electronic circuit is the form taken by the network of interconnections of the circuit components. Different specific values or ratings of the components are regarded as being the same topology. Topology is not concerned with the physical layout of components in a circuit, nor with their positions on a circuit diagram. It is only concerned with what connections exist between the components. There may be numerous physical layouts and circuit diagrams that all amount to the same topology.
   Wikipedia Topology (electrical circuits)
2. [Networking] Physical topology is the placement of the various components of a network, including device location and cable installation, while logical topology illustrates how data flows within a network, regardless of its physical design. Distances between nodes, physical interconnections, transmission rates, or signal types may differ between two networks, yet their topologies may be identical.

TortoiseSVN — A very user-friendly Apache Subversion client for Windows. (SVN stands for Subversion)

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TQFP — Thin Quad Flat Pack. Essentially the same as a QFP except low-profile, that is, thinner.
A thin quad flat pack (TQFP) provides the same benefits as the metric QFP, but is thinner. Regular QFPs are 2.0 to 3.8 mm thick depending on size. TQFP packages range from 32 pins with a 0.8 mm lead pitch, in a package 5 mm by 5 mm by 1 mm thick, to 256 pins, 28 mm square, 1.4 mm thick and a lead pitch of 0.4 mm.
Source: Charles Cohn, Charles A. Harper (ed) Failure-free integrated circuit packages, McGraw-Hill, 2005 ISBN 0-07-143484-4 at Amazon.com pages 22-28.

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trace — A segment of a route. Aka track, q.v.

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trace pitch — the distance between the center lines of two or more equal-width traces. This is an important quantity to a PCB designer who is routing a board on a specific grid and especially differential pairs. The trace pitch equals the trace width plus the air gap or spacing between the traces. If routing differential pairs with edge-coupled impedance control, the PCB designer can prevent downstream problems by using a trace pitch that fits on a convenient grid and gives leeway for the board house to re-calculate the edge-coupled impedance based on their material qualtities. The board house should be able to globally change the trace width (and thus spacing) without any re-routing and without introducing any spacing errors. The grid that works best for a 1mm-ball-pitch BGA is 0.1mm, with the trace pitch set at 0.2mm. The trace width can be anything less than or equal to 0.1mm that adds to the spacing to make 0.2mm. In calculating controlled edge-coupled impedance, keep the trace pitch constant, trying various trace widths and spacings that add up to this.

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track — Aka Trace.

1. [PCB Layout] A segment of a line, whether copper trace (printed wire) or silkscreen line.
2. [Altium Designer] Any line or trace in a PCB CAD file that does not curve is called in Altium Designer a track. Parameters can be width and layer and net (or No Net if not connected). In Altium Designer's PCB menus, to draw a track in silkscreen, make the "Top Overlay" layer active and use Place -> Line. For copper, make one of the copper layers active and use Place -> Track.

transducer — An electronic device that converts energy from one form to another. Common examples include microphones, loudspeakers, thermometers, position and pressure sensors, and antenna. Examples familiar to PCB designers include opto-isolators, LEDs and components that make use of the piezoelectric effect such as pressure sensors.

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transmission line — A signal-carrying circuit with controlled electrical and magnetic characteristics used to transmit high-frequency signals. "High frequency" can refer to electronic signals operating at or above 100MHz.

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transponder — A wireless communications, monitoring, or control device that picks up and automatically responds to an incoming signal. The term is a contraction of the words transmitter and responder. Transponders can be either passive or active.

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tranzorb — (slang) A circuit protection device, protecting the circuit from high voltage spikes, such as could be received by a lightning hit. A tranzorb consists of a varistor (variable resistor or voltage dependent resistor (VDR)) used as a transient voltage suppressor (TVS). A varistor has very high resistance at low voltage and very low resistance at high voltage, thus a tranzorb will allow a large current to flow through it when voltage is high and only very small leakage current to flow when voltage is low. To protect a circuit, the tranzorb can be placed electrically between the power supply and the ground, or across an input line and ground if the input is from a wire exposed to possible lightning hits. If lightning strikes the line, the voltage spike will be transmitted harmlessly to ground (one hopes).

Tranzorbs can be either polar (unidirectional) or bipolar (bidirectional.) The unipolar version is actually an "avalanche diode." But this is probably more than you wanted to know about tranzorbs. (If not see "varistor" at Wikipedia.)

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Trillium — A company that makes DUT or ATE systems.

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trunk — [Apache Subversion] The main line of development. [svn-book as PDF and online]

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TSDSON — Thin Shrinked Dual Small Outline Non-leaded, a near-chip-scale package (Infinion.com).

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TSSOP — Thin Shrink Small Outline Package, a dual in-line small outline package. Thin is a relative term and for the small outline packages commonly implies a package height of 1.2 mm or less. TSSOP's commonly have a lead pitch of 0.5 to 0.65mm. Example of IPC name: SOP65P640X120-8N Example of John Walt Childers' name: TSSOP8_SOP65p640x120-8n

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TTL — Transistor-Transistor Logic. Also called multiple-emitter transistor logic.  A widely used form of semiconductor logic. Its basic logic element is a multiple-emitter transistor. TTL is characterized by fairly high speed and medium power dissipation.   [Graf, Rudolf F. Modern Dictionary of Electronics. Newnes, 1999]

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TVS — Transient Voltage Suppressor. See tranzorb.

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TVSOP — Very Thin Small Outline Package. This is a Texas Instrument acronym. The pitch is 0.40mm.
TI Packaging terminology

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TYP — [Mechanical Engineering-drawings] Typical.

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