PCB Glossary

ECL Emitter Coupled Logic
A type of unsaturated logic performed by emitter-coupled transistors. Higher speeds may be achieved with ECL than are obtainable with standard logic circuits. ECL is costly, power hungry, and difficult to use, but it is four times faster than TTL. [Graf]

Edge Clearance
The smallest distance from any conductors or components to the edge of the PCB.

Edge Connector
A connector on the circuit-board edge in the form of gold plated pads or lines of coated holes used to connect other circuit board or electronic device.

Electroless Copper
A thin layer of copper deposited on the plastic or metallic surface of a PCB from an autocatalytic plating solution (without the application of electrical current).

Electroless Deposition
The chemical coating of a conductive material onto a base material surface by reduction of metal ions in a chemical solution without using electrodes compared to electroplating.

Electronic Component
A part of the printed circuit board, such as resistor, capacitor, transistor, etc.

Electroplating
The electro deposition of an adherent metal coating on a conductive object. The object to be plated is placed in an electrolyte and connected to one terminal of a D.C. voltage source. The metal to be deposited is similarly immersed and connected to the other terminal.

Enclosures
The high-precision, close-tolerance housings which encase electronics products and assemblies. Typically constructed from various metals and plastics, enclosures are an integral part of electronics products and are critical for protection, environmental control, interconnection, compactness and multi-unit integration.

Environmental Stress Screening
Environmental Stress Screening is a process for the detection of early life defects in which components or assemblies are tested at the temperature and voltage extremes of their normal operating conditions for extended periods.

Epoxy
A family of thermosetting resins used in the packaging of semiconductor devices. Epoxies form a chemical bond to many metal surfaces.

Epoxy Smear
Epoxy resin which has been deposited on edges of copper in holes during drilling either as uniform coating or in scattered patches. It is undesirable because it can electrically isolate the conductive layers from the plated-through-hole interconnections.

ESR
Electro-statically applied Solder Resist.

Etchback
The controlled removal by a chemical process, to a specific depth, of nonmetallic materials from the sidewalls of holes in order to remove resin smear and to expose additional internal conductor surfaces.

Etching
The chemical, or chemical and electrolytic, removal of unwanted portions of conductive or resistive material.

Fab
Fabrication.

Fabrication drawing
A drawing used to aid the construction of a printed board. It shows all of the locations of the holes to be drilled, their sizes and tolerances, dimensions of the board edges, and notes on the materials and methods to be used. Called "fab drawing" for short. It relates the board edge to at least on hole location as a reference point so that the NC Drill file can be properly lined up.

Fiducial Mark
A printed board feature (or features) that is created in the same process as the conductive pattern and that provides a common measurable point for component mounting with respect to a land pattern or land patterns.

Fine Pitch
Fine pitch is more commonly referred to surface-mount components with a lead pitch of 25 mils or less.

Finger
A gold-plated terminal of a card-edge connector. Also see Gold Finger.

Flash
Flash is a densely packable, relatively inexpensive type of nonvolatile memory, which can be modified electrically, often while in a circuit. Flash architecture generally assumes that it will be read often but seldom written to.

Flex Circuit Assembly
Flex Circuit Assembly is an advanced process of attaching electrical components to a flexible circuit. Flex circuits are utilized in compact devices with mobile mechanical assemblies such as wireless devices and data storage systems.

Flip Chips
Flip Chips are structures that house circuits interconnected face down directly to the substrate with solder bumpers without leads, and are utilized to minimize printed circuit board surface area when compact packaging is required.

Flux
The material used to remove oxides from metal surfaces and enable wetting of the metal with solder.

Flying Probe
A type of bare board electrical test machine that uses probes on the ends of mechanical arms to locate and touch the pads on the board. The probes move quickly across the board verifying continuity of each net as well as resistance to adjacent nets.

Footprint
geometry of pads for soldering certain electronic component.

FR-1
A paper material with a phenolic resin binder. FR-1 has a TG of about 130C.

FR-2
A paper material that is similar to FR-2 - except that an epoxy resin is used instead of phenolic resin as a binder. Used mainly in Europe.

FR-3
The UL-designated rating for a laminate composed of glass and epoxy that meets a specific standard for flammability. FR-4 is the most common dielectric material used in the construction of PCBs.

Functional Test
The electrical testing of an assembled electronic device with simulated function generated by the test hardware and software.

G10
A laminate consisting of woven epoxy-glass cloth impregnated with epoxy resin under pressure and heat. G10 lacks the anti-flammability properties of FR-4. Used mainly for thin circuits such as in watches.

Gerber File
Data file used to control a photo plotter.

GI
The woven glass fiber laminate impregnated with polyimide resin.

Gold Finger
The gold-plated terminal of a card-edge connector. Also see Finger.

Golden Board
See Known Good Board.

Ground
A common reference point for electrical circuits returns, shielding or heat sinking.

Ground Plane
A conductive plane as a common ground reference in a multilayer board for current returns of the circuit elements and shielding.

HASL C (Hot Air Solder Leveling)
A method of coating exposed copper with solder by inserting a panel into a bath of molten solder then passing the panel rapidly past jets of hot air.

HDI - (High Density Interconnect)
Ultra fine-geometry multi-layer PCB constructed with conductive micro-via connections. These boards also usually include buried and/or blind vias and are made by sequential lamination.

HDI
High Density Interconnect.

Header
The portion of a connector assembly which is mounted on a printed circuit.

Hermetic
Airtight sealing of an object.

Hole Breakout
A condition in which a hole is not completely surrounded by the land.

Hole Density
The number of holes per unit area on a PCB.

Hole Pattern
The arrangement of all holes in a printed board with respect to a reference point.

IC
Integrated Circuit.

Imaging
The process of transferring electronic data to the photo-plotter, which in turn uses light to transfer a negative image circuitry pattern onto the panel or film.

Immersion Plating
The chemical deposition of a thin metallic coating over certain basis metals that is achieved by a partial displacement of the basis metal.

Impedance
The resistance to the flow of current, represented by an electrical network of combined resistance, capacitance and inductance reaction, in a conductor as seen by an AC source of varying time voltage. The unit of measure is ohms.

In-Circuit Test
Electrical test of individual component or part of the circuit in a PCB assembly instead of testing the whole circuit.

In-Circuit Test
Electrical test of individual component or part of the circuit in a PCB assembly instead of testing the whole circuit.

Inclusions
Foreign particles, metallic or nonmetallic, that may be entrapped in an insulating material, conductive layer, plating, base material, or solder connection.

Inkjetting
The dispersal of well-defined ink "dots" onto a PCB. Inkjet equipment uses heat to liquefy a solid ink pellet and change the ink into a liquid, which is then dropped via a nozzle onto the printed surface, where it quickly dries.

Inner-Layers
The internal layers of laminate and metal foil within a multi-layer board.

In-Situ Dynamic Thermal Cycling Stress Testing
In-Situ Dynamic Thermal Cycling Stress Testing is an electronics testing method of exposing products from high to low temperature extremes for several cycles, which identities potential early product failures.

Insulation Resistance
The electrical resistance of an insulating material that is determined under specific conditions between any pair of contacts, conductors, or grounding devices in various combinations.

Integrated Circuits (IC)
single, integrated components containing a large number of discreet components, such as transistors and other semiconductor devices, as well as the layering which interconnect all of the semiconductor devices.

Interconnect
specialized, high-precision optical and electrical cable and harness assemblies and connectors utilized in the interconnection of electrical components and assemblies. Various interconnect technologies include single-mode and multi-mode cyber optics, coaxial, ribbon cable, shielded and tight pair, tight twisted pairs, patch cords and molded cables.

Interconnect Stress Test
The IST system is designed to quantify the ability of the total interconnect to withstand the thermal and mechanical strains, from the as manufactured state, until the products reaches the point of interconnect failure.

Interstitial Via Hole
An embedded through-hole with connection of two or more conductor layers in a Multilayer PCB.

IPC
The Institute for Interconnecting and Packaging Electronic Circuits, the final American authority on how to design and manufacture printed wiring. In 1999, IPC changed its name from Institute of Interconnecting and Packaging Electronic Circuits to IPC. The new name is accompanied with an identity statement, Association Connecting Electronics Industries.

Jump-Scoring
Similar to v-scoring, this is a process that is used when a printed circuit board is pannelized. It allows for a score line to jump over most of the panel border, leaving the border largely intact, and as a result, stronger and more rigid, resulting in a stiffer and stronger assembly panel.

KGB C (Known Good Board)
A board or assembly that is verified to be free of defects. Also known as a Golden Board.

Laminate
A product made by bonding together two or more layers of materials.

Laminate Thickness
Thickness of the metal-clad base material, single- or double-sided, prior to any subsequent processing.

Laminate Void
An absence of epoxy resin in any cross-sectional area which should normally contain epoxy resin.

Lamination
The process manufacturing a laminate using pressure and heat.

Land
The portion of the conductive pattern on printed circuits designated for the mounting or attachment of components. Also called a pad.

Laser Direct Imaging
Laser Direct Imaging is a process that allows increasing board density through the use of increasingly small and accurate laser technology.

Laser Photo-Plotter
A plotter that uses a laser, which simulates a vector photo-plotter by using software to create a raster image of the individual objects in a CAD database, then plots the image as a series of lines of dots at a very fine resolution. A laser photo-plotter is capable of more accurate and consistent plots than a vector plotter.

Lead
A terminal on a component.

Leakage Current
A small amount of current that flows across a dielectric area between two adjacent conductors.
Legend
Printed letters or symbols on the board, such as part numbers and product number or logos.

Line
A thin conductive area on a PCB surface or internal layer usually composed of lands (to which component leads are connected) and paths (traces). Also known as a "conductor".

LPI
Liquid Photo-Imageable solder mask that uses photographic imaging to control a thinner mask deposition than the dry film solder mask.

Mask
A material applied to enable selective etching, plating, or the application of solder to a PCB.

Measling
Discrete white spots or crosses below the surface of the base laminate that reflect a separation of fibers in the glass cloth at the weave intersection.

Metal Foil
The plane of conductive material of a printed board from which circuits are formed. Metal foil is generally copper and is provided in sheets or rolls.

MIC
Monolithic Integrated Circuit

Micro Ball Grid Array
A method of mounting an integrated circuit or other component to a higher layer-count printed circuit board with an array of extremely small solder balls (or columns) at each contact, allowing for greater component density.

Microsectioning
The preparation of a specimen of a material, or materials, that is to be used in metallographic examination. This usually consists of cutting out a cross-section followed by encapsulation, polishing, etching, and staining.

Microvia
Usually defined as a conductive hole with a diameter of 0.005" or less that connects layers of a multi-layer PCB. Often used to refer to any small geometry connection holes created by laser drilling.

Mil
One thousandth of an inch.

Minimum Conductor Space
The smallest distance between any two adjacent conductors, such as traces, in a PCB.

Minimum Conductor Width
The smallest width of any conductors, such as traces, on a PCB.

Minor Defect
A defect that is not likely to result in the failure of a unit or product or that does not reduce its usability for its intended purpose.

Mounting Hole
A hole that is used for the mechanical support of a printed board or for the mechanical attachment of components to a printed board.

MTF
Multi-layer Thin Film

Multichip Module Laminates
A type of printed circuit board design that allows for the placement of multiple integrated circuits or other components in a limited surface area.

Multilayer PCB
Circuit boards consisting three or more layers of printed circuits separated by laminate layers and bonded together with internal and external interconnections.

Multimeter
A portable test instrument which can be used to measure voltage, current, and resistance.

NC Drill C (Numeric Control drill machine)
A machine used to drill the holes in a printed board at exact locations, which are specified in a data file.

Negative
A reverse-image copy of a positive, useful for checking revisions of a PCB and is often used for representing inner layer planes. When a negative image is used for an inner-layer it would typically have clearances (solid circles) and thermals (segmented donuts) that either isolate holes from the plane or make thermally relieved connections respectively.

NEMA
National Electrical Manufacturers Association

Net
A collection of terminals all of which are, or must be, connected electrically. Also known as signal.

Netlist
List of parts and their connection points which are connected in each net of a circuit.

New Product Introduction (NPI)
New Product Introduction (NPI) is an early product life-cycle process service to assist OEMs in achieving cost-effective, quick-to-market and quick-to-volume production. The NPI process includes technology selection, design and development engineering services, test and material strategies, design for manufacturability and prototyping.

Node
A pin or lead to which at least two components are connected through condcutors.

Nomenclature
Identification symbols applied to the board by means of screen printing, inkjetting, or laser processes. SeeLegend.

NPTH
Non-plated trough-hole.

Open
Open circuit. An unwanted break in the continuity of an electrical circuit which prevents current from flowing.

Outer-Layer
The top and bottom sides of any type of circuit board.

Pad
The portion of a conductive pattern for connection and attachment of electronic components on the PCB. Also called Land.

Panel
A rectangular sheet of base material or metal-clad material of predetermined size that is used for the processing of printed boards and, when required, one or more test coupons.

Pattern
The configuration of conductive and nonconductive materials on a panel or printed board. Also, the circuit configuration on related tools, drawing, and masters.

PCB
Printed Circuit Board. Also called Printed Wiring Board (PWB).

PEC
Printed Electronic Component.

Photo Plotter
Device used to generate photographically by plotting objects onto film for use in manufacturing printed wiring.

Photo Resist
A material that is sensitive to portions of the light spectrum and that, when properly exposed can mask portions of a base metal with a high degree of integrity.

Phototool
A transparent film that contains the circuit pattern, which is represented by a series of lines of dots at a high resolution.

Pick-and-Place:
A manufacturing operation of assembly process in which components are selected and placed onto specific locations according to the assembly file of the circuit.

Pin
A terminal on a component, whether SMT or through-hole. Also called a lead.

Pin-Through-Hole (PTH)
Pin-Through-Hole (PTH) is an older method of fusing relatively low-density electrical components to one side of a printed circuit board substrate, utilizing pin-through-hole connections.

Pitch
The center-to-center spacing between conductors, such as pads and pins, on a PCB.

Plasma
A highly-ionized gas containing an approximately equal number of positive ions and negative electrons. Thus, as a whole it is electrically neutral, though conductive and affected by magnetic fields.

Plated-Through Hole
A hole in a PWB with metal plating added after it is drilled. Its purpose is to serve either as a contact point for a through-hole component or as a via.

PI
Polyimide. (Also Pi)

Pitch
The center-to-center spacing between conductors, such as pads and pins, on a PCB.

Plasma
A highly-ionized gas containing an approximately equal number of positive ions and negative electrons. Thus, as a whole it is electrically neutral, though conductive and affected by magnetic fields.

Plastic Leaded Chip Carrier (PLCC)
A component package with J-leads.

Plastic Leaded Chip Carrier
An SMT chip package that is rectangular or square- shaped with leads on all four sides. The leads are spaced at 0.050 inches, so this package is not considered fine-pitch.

Plated-Through Hole
A hole in a PWB with metal plating added after it is drilled. Its purpose is to serve either as a contact point for a through-hole component or as a via.

Plating Resist
Material deposited as a covering film on an area to prevent plating on this area.

Plotting
The mechanical converting of X-Y positional information into a visual pattern such as artwork.

Positive
A developed image of photo-plotted file, where the areas selectively exposed by the photo plotter appear black and unexposed areas are clear. For outer-layers, color will indicate copper. Positive inner-layers will have clear areas to indicate copper.

Prepreg
A sheet of material that has been impregnated with a resin cured to an intermediate stage. I.E. B-stage resin.

Printed Circuit Board (PCB)
Printed Circuit Board (PCB) is a board made from an insulating, non-conductive material that has conductive metal tracks (electronic interconnects) called traces on it. Integrated circuits and components are soldered to the board, and the metal traces between terminals connect the various devices and components. Multilayer circuit boards consist of multiple laminated layers of electrically integrated substrate, each with unique circuit traces.

Probe Test
A spring-loaded metal device used to make electrical contact between test equipment and the unit under test.

Product Assurance
Product Assurance guarantees that the product is built according to specifications and meets all standards and regulations.

Prototyping
Prototyping is an element of new product introduction, which involves building initial quantities, in short production runs, of an electronic product for testing, as well as for design validation and manufacturability refinement. The prototyping process involves nearly all aspects of a product prior to volume production and can significantly streamline the design and product development process, while substantially reducing costs.

PTH (plated-through Hole)
A plated hole used as a conducting interconnection between different layers or sides of a PCB either used as connection for through-hole component or as a via.

Pulse Plating
A method of plating that uses pulses instead of a direct current.

reference designator (abbrv. "ref des")
The name of a component on a printed circuit by convention beginning with one or two letters followed by a numeric value. The letter designates the class of component; eg. "Q" is commonly used as a prefix for transistors. Reference designators appear as usually white or yellow epoxy ink (the "silkscreen") on a circuit board. They are placed close to their respective components but not underneath them, so that they are visible on the assembled board. By contrast, on an assembly drawing a reference designator is often placed within the boundaries of a footprint --a very useful technique for eliminating ambiguity on a crowded board where reference designators in the silkscreeen may be near more than one component.

Reference Dimension
A dimension without a tolerance that is used only for informational purposes that does not govern inspection or other manufacturing operations.

Reflow Soldering
Melting, joining and solidification of two coated metal layers by application of heat to the surface and predeposited solder paste.

Reflow
The melting of electrodeposited tin/lead followed by solidification. The surface has the appearance and physical characteristics of being hot-dipped.

Resin (Epoxy) Smear
Resin transferred from the base material onto the surface of the conductive pattern in the wall of a drilled hole.

Resist
Coating material used to mask or to protect selected areas of a pattern from the action of an etchant, solder, or plating.

RF (radio frequency) and wireless design
A circuit design that operates in a range of electromagnetic frequencies above the audio range and below visible light. All broadcast transmission, from AM radio to satellites, falls into this range, which is between 30KHz and 300GHz.

Rigid-Flex
A PCB construction combining flexible circuits and rigid multi layers usually to provide a built-in connection or to make a three dimensional form that includes components.

Routing (tracing)
The process of placing electronic connections (traces) between pads on the board.

Scanning Electron Microscopy
Scanning Electron Microscopy is a scanning method, which utilizes a microscope with 200 times magnification or greater.

Schematic
A diagram which shows, by means of graphic symbols, the electrical connections and functions of a specific circuit arrangement.

Scoring
A technique in which grooves are machined on opposite sides of a panel to a depth that permits individual boards to be separated from the panel after component assembly.

Screen Printing
A process for transferring an image from a patterned screen to a substrate through a paste forced by a squeegee of a screen printer.

Semiconductors
Semiconductors are materials whose properties fall between those of insulators and conductors, and is also the term used for all electronic components made from semiconductor material. Semiconductors, most commonly silicon and germanium, are the basic foundation of nearly all solid-state electronic devices.

Short
Short circuit. 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 used.

Signal layer
Layer of a board, in which traces can be placed. For a two-sided board two signal layers are available - the Top and the Bottom layers.

Silkscreen (Also called "silkscreen legend")
The decals and reference designators in epoxy ink on a printed wiring board, so called because of the method of applicationthe ink is "squeegeed" through a silk screen, the same technique used in the printing of T-shirts.

Single-Sided Board
A printed board with conductive pattern on one side only.

Small Outline Integrated Circuit (SOIC):
An integrated circuit with two parallel rows of pins in surface mount package.

Small-Outline J-lead (SOJ)
Small-Outline J-lead (SOJ) is a type of chip module, which utilizes inward extending J-shaped pins to attach chips to a printed circuit board surface.

SMD
Surface Mount Device.

SMOBC C(Solder Mask Over Bare Copper)
A method of fabricating a printed circuit board that results in final metallization being copper with no protective metal. The non-coated areas are coated by solder resist, exposing only the component terminal areas. This eliminates tin lead under the mask.

SMT
Surface Mount Technology.

Solder
An alloy that melts at relatively low temperatures and is used to join or seal metals with higher melting points. A metal alloy with a melting temperature below 427C (800F).

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.

Solder Bridging
Solder connecting, in most cases, misconnecting, two or more adjacent pads that come into contact to form a conductive path.

Solder bumps
solder balls.

Solder Coat
A layer of solder that is applied directly from a molten solder bath to a conductive pattern.

Solder Leveling
The process by which the board is exposed to hot oil or hot air to remove excess solder from holes and lands.

Solder Mask or Solder resist:
Coating to prevent solder to deposit on.

Solder Wick
A band of wire removes molten solder away from a solder joining or a solder bridge or just for desoldering.

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. .

SPC - Statistical Process Control
The collection of process data and creation of control charting is a tool used to monitor processes and to assure that they remain In Control or stable. Control charts help distinguish process variation due to assignable causes from those due to unassignable causes.

Static Random Access Memory (SRAM)
Static Random Access Memory (SRAM) is a type of non-volatile memory commonly used in caching, which is faster (and more expensive) than dram because it does not require refreshing.

Step-and-Repeat
The successive exposure of a single image on order to produce a multiple-image production master. Also used in CNC programs.

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

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.

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.]

Surface Mount Technology (SMT)
Surface Mount Technology (SMT) is the principal technology for the assembly of printed circuit boards by soldering electrical components directly to a board substrate that uses less space than the pin-through-hole method. SMT is a highly flexible technology that can be continually reconfigured to meet customer-specific product requirements. Each SMT assembly line is designed to have PCB screen printing, component placement and solder reflow capabilities.

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

Synchronous Dynamic Random Access Memory (SDRAM)
Synchronous Dynamic Random Access Memory (SDRAM) is a relatively new type of dram, which synchronizes itself with the CPUs bus and is capable of running at higher clock speeds than conventional memory.

System Design and Engineering
System Design and Engineering is a series of processes for taking an electrical product from customer-supplied requirements to volume production, with focuses on functionality, cost, size, manufacturability, scalability, compatibility, durability, safety and serviceability. The process includes hardware design, product architecture, circuit design and schematic capture, technology assessment and selection, component selection, parts sourcing and production quantity ordering, printed circuit board layout, mechanical design, software development, concurrent and sustaining engineering, sub-assembly integration and interconnection, enclosure and packaging design, functional and environmental compliance and prototyping, as well as programmable device software development and other services.

TAB
Tape Automated Bonding.

Tape Automated Bonding
Tape Automated Bonding is a specialized assembly-process technology, which involves the application of components onto a circuit board using temperature and pressure.

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.

Temperature Coefficient (TC)
The ratio of a quantity change of an electrical parameter, such as resistance or capacitance, of an electronic component to the original value when temperature changes, expressed in %/ºC or ppm/ºC.

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 topside of the board and left uncovered on the bottom side to permit probing from that side only with a text fixture.

Tenting
The covering of holes in a printed board and the surrounding conductive pattern with a dry film resist.

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

Test Coupon
A portion of a printed board or of a panel containing printed coupons used to determine the acceptability of such a board.

Test Fixture
A device that interfaces between test equipment and the unit under test.

Test Point
A specific point in a circuit board used for specific testing for functional adjustment or quality test in the circuit-based device.

Testing
A method for determining whether sub-assemblies, assemblies and/or a finished product conform to a set of parameter and functional specifications. Test types include: in-circuit, functional, system-level, reliability, environmental.

TG - (Glass transition temperature)
The point at which rising temperatures cause resin inside the solid base laminate to start to exhibit soft, plastic-like symptoms. This is expressed in degrees Celsius (C).

Thermal pad
Pad of a special form used when it is connected to copper pours. Thermal pads improve solderability of the joint, reducing the chance of a so called " cold solder joint "

Thief
An extra cathode placed as to divert to itself some of the current from portions of the board which otherwise would receive too high a current density.

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]

Three-Dimensional Laser Paste
Three-Dimensional Laser Paste is a volumetric inspection method that utilizes a microscope with lasers.

Through-hole
A drilled hole in the board, usually for mounting purposes.

Toolin, g Holes
The general term for holes placed on a PCB or a panel of PCBs for registration and hold-down purposes during the manufacturing process.

Trace (or Route,track)
A layout or wiring of an electrical connection.

Turnkey
A type of outsourcing method that turns over to the subcontractor all aspects of manufacturing including material acquisition, assembly and testing. Its opposite is consignment, where the outsourcing company provides all materials required for the products and the subcontractor provides only assembly equipment and labor.

Twist
A laminate defect in which deviation from planarity results in a twisted arc.

UL
Underwriters Laboratories. A popular safety standard for electrical devices supported by many underwriters.

UV Curing
Polymerizing, hardening, or cross linking a low molecular weight resinous material in a wet coating ink using ultra violet light as an energy source.

Via
A plated-through hole used for interconnection of conductors on different sides or layers of a PCB.

Void
The absence of any substances in a localized area.

Wave Soldering
A manufacturing operation in which solder joints are soldered simultaneously using a wave of molten solder.

Wet solder mask
Applied by means of distributing wet ep, oxy ink through a silk screen, a wet solder mask has a resolution suitable for single-track design, but is not accruate enough for fine-line design.

WIPWork In Progress
[Usage at Golden Gate Graphics: wip is used as the extension of the name of a folder or sub-directory which groups data in temporary storage locations for current "work in progress." Any folders beneath the .WIP folder in the directory structure would be named for the software, company and job in that order. Eg: pclayout.wip/Cadstar/AcmeInc/A2Dboard ]

wire
Besides its usual definition of a strand of conductor, wire on a printed board also means a route or track .

Wire bonding
The method used to attach very fine wire to semiconductor components (dice) to interconnect these components with each other or with package leads. The wires might be 1 to 2 mils in diameter and made of aluminum containing 1% silicon.

Wire wrap area
A portion of a board riddled with plated-through holes on a 100-mil grid. Its purpose is for accepting circuits which may be found necessary after a PWB has been manufactured, stuffed, tested and debugged.