How To Be A Circuit Board Designer - Definitions

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After reading this tutorial, you will have
a better understanding of these terms:

A | B | C | D | E | F | G | H | I | J | K | L | M
N | O | P | Q | R | S | T | U | V | W | X | Y | Z

Common acronyms are listed after the letter "Z"


The surrounding environment coming into contact with the system or component in question.
Text, notes, or other identification, constructed by a computer-aided system, intended to be inserted on a drawing, map or diagram.
Annular Ring (Annular Width)
That portion of conductive material completely surrounding a hole.
An established clearance in the plane to accommodate a hole and its corresponding pad stack.
A group of elements or circuits arranged in rows and columns on a base material. For circuit board designers, the word array is usually referring to how the individual circuit boards are arranged on the fabrication panel or in an assembly pallet
The data that describes all of the graphic images needed to fabricate a bare board (circuit patterns for each layer, solder mask patterns for both sides, and maybe include silkscreen patterns and paste screen patterns for SMT designs. More formally, "An accurately-scaled configuration that is used to produce the Artwork Master or Production Master."
Aspect Ratio
The ratio of the length or depth of a hole to its pre-plated diameter.
Asymmetric Stripline
A stripline signal conductor that is embedded, but not centered, between two planes
AWG Equivalent
The American Wire Gauge (AWG) round-conductor number that is used to designate a flat conductor with an equal cross-sectional area.
Axial Lead
Lead wire extending from a component or module body along its longitudinal axis.


Back Annotation
The process of extracting appropriate information from a completed printed board design and inserting it "back" into the corresponding schematic diagram.
Ball Grid Array (BGA)
A surface mount package wherein the bumps for terminations are formed in a grid on the bottom of a package.
Bare Board
An unassembled (unpopulated) printed board.
Base Material
The insulating material upon which a conductive pattern may be formed. (The base material may be rigid or flexible, or both. It may be a dielectric or insulated metal sheet.)
Bed-of-Nails Fixture
A test fixture consisting of a frame and a holder containing a field of spring-loaded pins that make electrical contact with a planar test object.
Bilateral Tolerance
A tolerance in which variation is permitted in both directions from the specified dimension.
Blind Via
A via extending only to one surface of a printed board.
Bow (Sheet, Panel, or Printed Board)
The deviation from flatness of a board characterized by a roughly cylindrical or spherical curvature such that, if the product is rectangular, its four corners are in the same plane. (See also "Twist.")
The function of excising printed boards or printed board assemblies from their panel structure after all processing has been completed.
Buried Via
A via that does not extend to the surface of a printed board.
One or more conductors used for transmitting data signals or power.


Coefficient of Thermal Expansion (CTE)
The linear dimensional change of a material per unit change in temperature. (See also "Thermal Expansion Mismatch.")
Component Hole
A hole that is used for the attachment and/or electrical connection of component terminations, including pins and wires, to a printed board.
Component Lead
The solid wire or formed conductor that extends from a component to serve as a mechanical or electrical connector, or both. (See also "Component Pin.")
Computer-Aided Design (CAD)
The interactive use of computer systems, programs, and procedures in the design process wherein, the decision-making activity rests with the human operator and a computer provides the data manipulation function.
Computer-Aided Manufacturing (CAM)
The interactive use of computer systems, programs, and procedures in various phases of a manufacturing process wherein, the decision-making activity rests with the human operator and a computer provides the data manipulation functions.
Conductor Spacing
The observable distance between adjacent edges (not center-to-center spacing) of isolated conductive patterns in a conductor layer.
Conductor Width
The observable width of a conductor trace at any point chosen at random on a printed board as viewed from directly above.
Conformal Coating
An insulating protective covering that conforms to the configuration of the objects coated (e.g. Printed Boards, Printed Board Assembly) providing a protective barrier against environmental conditions.
Conformance Test Coupon Set
A complement of test coupons which are comprised of various coupon types, each of which is designed for a specific test or tests, but which were all made in the same manufacturing lot. (see also "Test Coupon")
An uninterrupted path for the flow of electrical current in a circuit.
Continuity Test
Resistance test to insure all the required points have electrical continuity.
Copper Island (Layer)
A portion of a single plane layer that is physically separated from the rest of the circuitry, intended to perform a shielding or copper distribution function, and may be electronically connected in order to provide a circuit return path. Several methods of plane generation exist that can generate copper islands.
Copper Weight
The mass of copper per unit area for a foil, typically expressed in ounces per square foot or micrometers.
(see "Test Coupon")
Coverlayer (Flexible Circuit)
The layer of insulating material that is applied totally or partially over a conductive pattern on the outer surfaces of a printed board. (Also referred to as "coverlay")
Crazing (Base Material)
An internal condition that occurs in reinforced laminate base material whereby glass fibers are separated from the resin at the weave intersections. (This condition manifests itself in the form of connected white spots or crosses that are below the surface of the base material.) It is usually related to mechanically-induced stress. (See "Measling.")
Creepage Distance
The shortest path between two conductors, which includes traces, terminals and structures, measured along the surface of the insulation.
The breaking up of large conductive areas by the use of a pattern of voids in the conductive material.
The undesirable interference caused by the coupling of energy between signal paths.
Current-Carrying Capacity
The maximum electrical current that can be carried continuously by a conductor, under specified conditions, without causing objectable degradation of electrical and mechanical properties of the product.


Date Code
Marking of products to indicate their date of manufacture.
The theoretically-exact point, axis or plane that is the origin from which the location of geometric characteristics of features of a part are established.
Datum Reference
A defined point, line or plane that is used to locate a pattern or layer for manufacturing purposes, inspection purposes, or both.
The absorbing of noise pulses in power supply lines, that was generated by switching logic devices, so as to prevent the lines from disturbing other logic devices in the same power-supply circuit.
A separation between plies within a base material, between a base material and a conductive foil, or any other planar separation within a printed board.
Dendritic Growth
Metallic filaments that grow between conductors in the presence of condensed moisture and an electric bias. (See also "Whiskers.")
Design-Rule Checking
The use of a computer-aided design program to perform continuity verification of all conductor routing in accordance with appropriate design rules.
A condition that results when molten solder coats a surface and then recedes to leave irregularly-shaped mounds of solder that are separated by areas that are covered with a thin film of solder and with the basis metal not exposed.
A material with a high resistance to the flow of direct current. In circuit boards, the dielectric is the insulating material that separates conductive layers.
Dielectric Constant
A property of insulating materials which allows us to compare their ability to support or propagate an electric field. The dielectric constant of a material is in relation to a complete vacuum, which has a dielectric constant of 1.00. The dielectric constant of a material must be known to make signal impedance calculations.
Dielectric Strength
The maximum voltage that a dielectric can withstand under specified conditions without resulting in a voltage breakdown, usually expressed as volts per unit dimension.
Dimensional Stability
A measure of the dimensional change of material that is caused by factors such as temperature changes, humidity changes, chemical treatment (aging), and stress exposure.
Discrete Component
A separate part of a printed board assembly that performs a circuit function, such as resistors, capacitors, diodes, etc.
Double-Sided Assembly
A packaging and interconnecting structure with components mounted on both the primary and secondary sides.
Double-Sided Printed Board
A printed board with a conductive pattern on both of its sides.


Electromagnetic Interference (EMI)
Unwanted electromagnetic energy that may couple into electrical circuits and adversely affect their performance.
Electrostatic Discharge (ESD)
The rapid spontaneous transfer of electrostatic charge, induced by a high electrostatic field.
Embedded Component
A discrete component that is fabricated as an integral part of a printed board.
Embedded Passive
A sheet of resistive, capacitive or inductive material which is laminated onto a dielectric, and either etched or lased away to define individual resistors, capacitors or inductors.
Epoxy Glass Substrate
A two-part epoxy resin reinforced with glass fiber to form an insulating material used to separate conductive layers and provide stability and strength.
Etch Factor
The ratio of the depth of etch to the amount of lateral etch, i.e., the ratio of conductor thickness to the amount of undercut.
Etch Resist
An organic or metal plated material used to protect the conductive pattern image from the etching chemistry. The organic material may be photosensitive.
Eutectic (Solder)
A mixture of substances (in fixed proportions) that melts and solidifies at a single temperature that is lower than the melting points of the separate constituents or of any other mixture of them. Eutectic solder composed of 63%Tin and 37%Lead melts/solidifies at 183 degrees Centigrade without going through a pasty (partially solid) phase.


Fabrication Allowance
A dimensional value added to a printed board feature or feature location intended to assure that manufacturing variations can maintain certain physical or performance characteristics of the end product.
Fiducial (Mark)
A printed board feature 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 Technology (FPT)
A surface-mount assembly technology with component terminations on less than 0.65 mm [0.025 in] centers.
First Article
A part or assembly that has been manufactured prior to the start of a production run for the purpose of ascertaining whether or not the manufacturing processes used to fabricate it are capable of making items that will meet all applicable end-product requirements.
Flexible Printed Board
A printed board using a flexible base material only. May be partially provided with electrically non- functional stiffeners and/or coverlayer.
Flow Soldering
A wave, drag or dip soldering process where the product is brought into contact with molten solder in order to attach electronic components to the interconnecting surface.
The physical area of a component that touches the surface of a circuit board. (For example, if you pressed a component into wet sand and then removed it, the size of the depression area would be the component's footprint. However, the term footprint is also used by many in the electronics industry to mean the size of the circuit board land pattern, which can be a significantly larger area for soldering purposes) See "Land Pattern"


Gerber Data
A type of data that consists of aperture selection and operation commands and dimensions in X- and Y- coordinates. (The data is generally used to direct a photoplotter in generating photoplotted artwork.)
Glass Transition Temperature (Tg)
The temperature at which the circuit board material changes from being in a hard and relatively stable condition to being in a viscious or rubbery condition.
Ground Plane
A conductor layer, or portion thereof, that serves as a common reference for electrical circuit returns, shielding, or heat sinking. (See also "Signal Plane" and "Voltage Plane.")
Ground Plane Clearance
Removed portions of a ground plane that isolate it from a hole in the base material to which the plane is attached. (See also "Signal Plane" and "Voltage Plane.")
Gull Wing Leads
An SMT lead form. Leads extending horizontally from the component body centerline, bent downward immediately past the body and then bent outward just below the bottom of the body, thus forming the shape of a gull's wing (a type of bird).


A mechanical device that is made of a high thermal- conductivity and low specific-heat material that dissipates heat generated by a component or assembly.
Heatsink Plane
A continuous sheet of metal on or in a printed board that functions to dissipate heat away from heat generating components.
Heel Fillet
The solder fillet formed in the land area behind the lead.
Hole Breakout
A condition in which a hole is not completely surrounded by the land.
Hole Filling Process
A process of adding a conductive or non-conductive fill material to a plated through-hole, followed by adding an etch resist that covers the hole and its land. The process also includes etching away of the unwanted copper and subsequent stripping of the etch resist. (see also "via" definitions)
Hole Plugging Process
A process of plugging a plated through-hole with liquid solder mask material after the circuit configuration has been completed in order to prevent chemistry from entering the hole during the assembly process. (see also "via" definitions)
Hot Air (Solder) Leveling (HAL or HASL)
A physical deposition process using a solder bath into which the printed board is dipped into a molten solder bath and withdrawn across a set of hot air knives (forced hot air flow) used to remove excess solder.


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.
The resistance to the flow of current (represented by an electrical network of combined resistance, capacitance and inductance) in a conductor as seen by an AC source of varying time voltage. The unit of measure is ohms.
In-Circuit Testing
The application of test signals directly to a device's input terminals and sensing the results directly from the device's output terminals.
Intrusive Soldering
A process in which the solder paste for the through- hole components is applied using a stencil or syringe to accomodate through-hole components that are inserted and reflow-soldered together with the surface- mount components.


The preferred surface mount lead form used on PLCCs, so named because the lead departs the package body near its Z axis centerline, is formed down then rolled under the package. Leads so formed are shaped like the letter "J."


Known Good Board (KGB)
A correctly fabricated printed board that serves as a standard unit by which others can be compared.


Laminate (noun)
A product made by bonding together two or more layers of material.
A portion of a conductive pattern usually used for the connection and/or attachment of components.
Land Pattern
A combination of lands that is used for the mounting, interconnection and testing of a particular component.
Layer-to-Layer Registration
The process of aligning circuit features (lands) on individual layers of a printed board through the use of tooling image location features (fiducials) or tooling holes.
Layer-to-Layer Spacing
The thickness of dielectric material between adjacent layers of conductive patterns in a printed board.
A length of insulated or uninsulated metallic conductor that is used for electrical interconnections.
Lead-Free Solder
An alloy that does not contain more than 0.1% lead (Pb) by weight as its constituent and is used for joining components to substrates or for coating surfaces.
Least Material Condition (LMC)
The condition in which a feature of size contains the least amount of material within the stated limits of size.
A format of letters, numbers, symbols and patterns that are used primarily to identify component locations and orientations for convenience of assembly and maintenance operations.
Local Fiducial
A fiducial mark (or marks) used to locate the position of a land pattern for an individual component on a printed board. (See "Fiducial Mark")
Lot Size
A collection of units produced in one continuous, uninterrupted fabrication run.


Mass Lamination
The simultaneous lamination of a number of pre- etched, multiple-image, C-staged resin panels or sheets that are sandwiched between layers of B-staged resin and copper foil.
A condition that occurs in laminated base material in which internal glass fibers are separated from the resin at the weave intersection. (This condition manifests itself in the form of discrete white spots or "crosses" that are below the surface of the base material. It is usually related to thermally-induced stress.) (See also "Crazing")
The preparation of a specimen of a material, or materials, that is to be used in a metallographic examination. (This usually consists of cutting out a cross-section, followed by encapsulation, polishing, etching, staining, etc.)
A transmission line (see Transmission Line) structure that consists of a signal conductor that runs parallel to and is separated from a much wider reference plane.
Microvia (Build-Up Via)
A blind or subsequently buried hole that is < 0.15 mm [< 0.006 in] in diameter and formed either through laser or mechanical drilling, wet/dry etching, photo imaging, or conductive ink-formation followed by a plating operation.
Minimum Annular Ring
The minimum width of metal(s) at the narrowest point between the edge of a hole and the outer edge of a circumscribing land. (This determination is made to the drilled hole on internal layers of multilayer printed boards and to the edge of the plating on external layers of multilayer and double-sided printed board.)
Minimum Electrical Spacing
The minimum allowable distance between adjacent conductors, or between conductors and non-common conductors such as mounting hardware, ground, etc., at a given voltage and altitude, that is sufficient to prevent dielectric breakdown, corona, or both, from occurring between the conductors.
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.
Multilayer Printed Board
The general term for a printed board that consists of rigid or flexible insulation materials and three or more alternate printed wiring and/or printed circuit layers that have been bonded together and electrically interconnected.


An artwork, artwork master, or production master in which the pattern being fabricated is transparent to light and the other areas are opaque.
Net List
A list of alphanumeric representations, each of which is used to describe a group of two or more points that are electrically common.
The endpoint of an electrical network branch or the junction of two or more branches.
The design target dimension for a physical characteristic of a product or a feature to which a tolerance may be applied that establishes the limits of variation from the target that are acceptable.
Nonfunctional Land
A land that is not connected electrically to the conductive pattern on its layer.


Organic Solderability Preservative (OSP)
An organic compound that reacts selectively with copper surfaces forming a thin, uniform film that prevents copper oxidation and maintains solderability after extended printed board storage.


Pallet (Printed Board)
The printed board image or images plus the additional contiguous deliverable material from the panel. This may include tabs, fiducials, tooling holes, etc.
A rectangular sheet of base material or metal-clad material of predetermined size that is used for the processing of one or more printed boards and, when required, one or more test coupons.
A phototool is a physical film, Mylar (or similar), which contains the pattern that is used to produce a circuitry image on a photo-sensitive material by way of exposure to light-energy such as UV light. (see also "Artwork")
See "Intrusive Soldering"
The nominal center-to-center distance between adjacent features. (When the features are of equal size and their spacing is uniform, the pitch is usually measured from the reference edge of the adjacent features.)
Plastic Leaded Chip Carrier (PLCC)
A surface mount family of integrated circuit packages with leads exiting from all four sides of the package, generally with a 1.27 mm [0.050 in] lead-to-lead pitch.
Plastic QUAD Flat Pack (PQFP)
A surface mount family of integrated circuit packages, bounded on all four sides by bumpers, with leads exiting from all four sides of the package and formed into a "gullwing" lead format.
Plated-Through Hole (PTH)
A hole with plating on its walls that makes an electrical connection between conductive patterns on internal layers, external layer, or both, of a printed board.
Polarized Component
A component wherein the terminations are assigned as positive or negative electrical polarity.
A sheet of material that has been impregnated with a resin cured to an intermediate stage, i.e., B-staged resin.
Pressfit Contact
An electrical contact that can be pressed into a hole in an insulator or printed board with or without plated- through holes.
Printed Board (PB)
The general term for completely processed printed circuit and printed wiring configurations. (This includes single-sided, double-sided and multilayer boards with rigid, flexible, and rigid-flex base materials.)
Printed Circuit Board
Printed board that provides both point-to-point connections and printed components in a predetermined arrangement on a common base.
Printed Wiring Board
A printed board that provides point-to-point connections but not printed components in a predetermined arrangement on a common base.
Probe Point
The predetermined location on a printed board where electrical contact can be made to exposed circuitry for electrical diagnostic purposes.
Probe, Test
A spring-loaded metal device used to make electrical contact between a test equipment and the unit under test.
Propagation Delay
The time from output to input required for a signal to travel along a transmission line, or the time required for a logic device to receive an input stimulus, perform its function, and present a signal at its output.


Quad Flat Pack (QFP)
A generic rectangular component package, containing an electronic device, with leads on all four sides that are formed in a ''gullwing'' shape.
Quality-Conformance Test Circuitry
A portion of a printed board panel that contains a complete set of test coupons that are used to determine the acceptability of the board(s) on the panel.


Radial Lead Component
A component where the leads are located on the bottom, radially and parallel to the central axis.
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
The joining of surfaces that have been tinned and/or have solder between them, placing them together, heating them until the solder flows, and allowing the surface and the solder to cool in the joined position.
Reflow Temperature
The temperature range of a reflow soldering process during which the solder is in its liquidus phase.
The degree of conformity of the position of a pattern (or portion thereof), a hole, or other feature to its intended position on a product.
The probability that a component, device, or assembly will function properly for a definite period of time under the influence of specific environmental and operational conditions.
Rigid-Flex Printed Board
A printed board with both rigid and flexible base materials.
Rise Time (Transition Duration)
The time required for a logic-signal voltage to switch from 10 to 90 percent of the difference between logic states.
Router Bit
A straight or shaped rotary cutting tool used in a power router to cut, trim or shape materials by rotary action.
A mechanical method that removes a portion of the material outlining a printed board, using a cutting bit, in order to facilitate ease of breakout (removal) from the manufacturing/assembly panel.


Schematic Diagram
A drawing that shows, by means of graphic symbols, the electrical connections, components and functions of a specific circuit arrangement.
Screen Printing
The transferring of an image to a surface by forcing a suitable media with a squeegee through an imaged-screen mesh.
Self Declaration
The manufacturer's view of its products and process capabilities in order to meet the customer's requirements, the requirements of a standard, and/or the applicable associated specification sheet(s).
Semi-Additive Process
An additive process wherein the entire thickness of electrically- isolated conductors is obtained by the combined use of electroless metal deposition and electroplating, etching, or both. (See also "Fully-Additive Process.")
Sequential Lamination
The process of manufacturing multilayer printed boards in which multiple double-sided printed boards with interconnecting holes between conductive patterns on both sides are laminated or combined, after which additional layers (usually single-sided) are attached to the partially completed board stackup.
A physical barrier, usually electrically conductive, that reduces the interaction of electric or magnetic fields upon devices, circuits, or portions of circuits.
Short, Electrical
A fault that connects two or more points that should be electrically separated.
Skin Effect
The increase in resistance of a conductor at microwave frequencies that is caused by the tendency of electric current to concentrate at the conductor's surface.
Solder Ball
A small sphere of solder adhering to a laminate, resist, or conductor surface. (This generally occurs after wave solder or reflow soldering.)
Solder Bump
A round ball of solder used to make interconnections between a flip-chip component and a base material during controlled-collapse soldering.
Solder Connection
A metallurgical connection serving electrical/mechanical/thermal functions that employs solder for the joining of two or more metal surfaces.
Solder Fillet
Solder, with a normally concave surface, that is at the intersection of the metal surfaces of the solder connection.
Solder Joint
See "Solder Connection".
Solder Leveling
A solder coating process that causes redistribution and/or partial removal of excess molted solder from a printed board by applying sufficient heat and mechanical force (see also "Hot Air Solder Leveling")
Solder Mask
A heat-resisting coating material applied to selected areas to prevent the deposition of solder upon those areas during subsequent soldering.
Solder Paste
Finely divided particles of solder, with additives to promote wetting and to control viscosity, tackiness, slumping, drying rate, etc, that are suspended in a cream flux.
The ability of a metal to be wetted by molten solder.
Small Outline Package (SOP)
A generic rectangular component package, whose chip cavity or mounting area occupies a major portion of the package area, with leads or metal pad surfaces on two opposing sides.
Stencil (Solder Paste/Adhesive)
A thin sheet of material containing openings to reflect a specific pattern, designed to transfer a paste-like material to a substrate for the purpose of component attachment.
A method of dimensionally positioning multiples of the same or intermixed functional patterns accurately within a given area on the phototool or by repetitious contact, projection printing or photoplotting. Sometimes referred to as an "Array"
Stiffener Board
A material fastened to the surface of a printed board to increase its mechanical strength.
Stress Relief
The portion of a component lead or wire lead that is formed in such a way as to minimize mechanical stresses after the lead is terminated.
A transmission line structure that consists of a signal line that runs parallel to and is sandwiched between and separated by a dielectric from two reference planes.
Subtractive Process
The fabricating of a conductive pattern by the selective removal of unwanted portions of a conductive foil.
Supported Hole
A hole in a printed board that has its inside surfaces plated or otherwise reinforced.
Surface Mounting Technology (SMT)
The electrical connection of components to the surface of a conductive pattern that does not utilize component holes.


The covering of holes in a printed board and the surrounding conductive pattern with a resist.
Test Coupon
A portion of quality conformance test circuitry that is used for a specific test, or group of related tests, in order to determine the acceptability of a product.
Test Point
A special point of access to an electrical circuit that is used for electrical testing purposes.
Thermal Coefficient of Expansion (TCE)
See "Coefficient of Thermal Expansion (CTE)"
Thermal Conductivity
The property of a material that describes the rate at which heat will be conducted through a unit area of the material for a given driving force.
Thermal Mismatch
Difference in coefficients of thermal expansion of materials that are bonded together. (See also "Coefficient of Thermal Expansion (CTE).")
Thermal Relief
The crosshatching of a ground or voltage plane that minimizes blistering or warping during soldering operations.
Thin Small Outline Package (TSOP)
A package that has the same features as the SOP package except that its thickness is reduced to 0.8mm - 1.2mm [0.0315 in ? 0.0472 in].
Through-Hole Mounting
The electrical connection of components to a conductive pattern by the use of component holes.
Through-Hole Technology (THT)
The electrical connection of components to a conductive pattern by the use of component holes.
Time to Decomposition (Td)
The time it takes a base laminate material to lose an established percentage of weight at a given temperature using Thermogravimetric Analysis (TGA).
The application of molten solder to a basis metal in order to increase its solderability.
The total amount by which a specific dimension is permitted to vary.
Tooling Feature
A physical feature that is used exclusively to position a printed board or panel during a fabrication, assembly or testing process.
Tooling Hole
A tooling feature in the form of a hole in a printed board or fabrication panel.
Transmission Line
A structure for guiding or conducting electromagnetic energy from one point to another. A transmission line consists of two or more parallel conductors each separated by a dielectric. (See "Microstrip" and "Stripline")
True Position
The theoretically-exact location for a feature or hole that is established by basic dimensions.


Underwriters Symbol
A logotype that denotes that a product has been recognized (accepted) by Underwriters Laboratories, Inc. (UL).
Unsupported Hole
A hole in a printed board that does not contain plating or other type of conductive reinforcement.


A mechanical method that removes a portion of the material outlining the board, in order to facilitate ease of breakout (removal) from the manufacturing or assembly panel.
Vapor-Phase Soldering
A reflow soldering method that is based on the exposure of the parts to be soldered to hot vapors of a liquid that has a boiling-point that is sufficiently high to melt the solder being used.
A plated-through hole that is used as an interlayer connection, but in which there is no intention to insert a component lead or other reinforcing material. (See also "Blind Via" and "Buried Via.")
Via, Filled (Type V Via)
A via with material applied into the via targeting a full penetration and encapsulation of the hole.
Via, Filled and Capped (Type VII Via)
A Type V via with a secondary metallized coating covering the via. The metallization is on both sides.
Via, Filled and Covered (Type VI Via)
A Type V via with a secondary covering of material (liquid or dry film solder mask) applied over the via. It may be applied from either one side or both sides.
Via Planarization
The process of removing metallization and/or organic materials associated with the surface of a via structure. It is most commonly employed in filled via fabrication.
Via, Plugged (Type III Via)
A via with material applied allowing partial penetration into the via. It may be applied from either one side or both sides
Via, Plugged and Covered (Type IV Via)
A Type III via with a secondary covering of material applied over the via. The secondary covering may be applied from either one side or both sides.
Via, Tented (Type 1 Via)
A via with a mask material (typically dry film) applied bridging over the via wherein no additional materials are in the hole. It may be applied to one side or both.
Via, Tented and Covered (Type II Via)
A Type I via with a secondary covering of mask material applied over the tented via.
Voids (Base Materials)
Circular pockets within the resinous area of the laminate, usually formed by entrapped air of volatiles; usually at or near the surface of the laminate.
Voltage Plane
A conductor layer, or portion thereof, that serves as a common voltage source at other than ground potential for an electrical circuit, shielding, or heat sinking. (See also "Ground Plane" and "Signal Plane.")
Voltage Plane Clearance
Removed portions of a voltage plane that isolate it from a hole in the base material to which the plane is attached.


Wave Soldering
A process wherein an assembled printed board is brought in contact with the surface of a continuously flowing and circulating mass of solder.
The distance an electromagnetic wave propagates during one full cycle. It is the ratio of the propagation velocity in length units per unit time to the frequency in cycles per unit time.


X Axis
The horizontal or left-to-right direction in a two- dimensional system of coordinates. (This axis is perpendicular to the Y axis.)
A method of identifying a defective part.


Y Axis
The vertical or bottom-to-top direction in a two- dimensional system of coordinates.


Z Axis
The axis perpendicular to the plane formed by the X and Y axes. This axis usually represents the thickness of the board.
see IPC-T-50 Terms and Definitions for more

Acronyms and Abbreviations

As Agreed Upon Between User and Supplier
Alternating Current
American National Standards Institute
Automated Optical Inspection
As Soon as Possible
American Standard Code for Information Interchange
Automatic Test Equipment
American Wire Gauge
Ball Grid Array
Bill of Material
Computer-Aided Design
Computer-Aided Manufacturing
Conformal Coating
Copper Foil
Computer Numerical Control
Certificate of Compliance
Coefficient of Thermal Expansion
Direct Current
Dual-Inline Package
Dielectric Constant
Design Rule Checking
Diameter True Position
Engineering Change Notice
Engineering Change Order
Electronic Design Automation
Electronic Design Interchange Format
Electromagnetic Compatibility
Electromagnetic Interference
Electroless Nickel/Immersion Gold
Relative Dielectric Constant
Electro-static Discharge/Electro-static Device
First Article Inspection
Fine-Pitch Technology
Hot Air Level
Hot Air Solder Leveling
Input/Output (Terminations)
Ionic Contamination/Interconnect/Integrated Circuit
International Electrotechnical Commission
Institute of Electrical and Electronic Engineers
Insulation Resistance/Infrared
International Standards Organization
Joint Electronic Device Engineering Council
Known Good Board
Leadless Chip Carrier
Leadless Ceramic Chip Carrier
Light-Emitting Diode
Least Material Condition
Liquid Photoimageable
Liquid Photoimageable Solder Resist
Multi Chip Module
Metal Electrode Face (Discrete Leadless Component)
Multilayer Board
Maximum Material Condition
Mean Time Between Failures
Not Applicable
Numerical Control
Nominal Hole Size
Non Plated
Non Plated Through
Original Equipment Manufacturer
Organic Solderability Preservative
Packaging and Interconnecting Assembly
Packaging and Interconnecting Structure
Printed Board Assembly
Printed Circuit Board
Plastic Leaded Chip Carrier
Parts Per Million
Plastic Quad Flat Package
Plated-Through Hole
Printed Wiring Assembly
Printed Wiring Board
Quality Assurance
Quality Control
Quad Flat Pack
Request for Quotation
Should/Shall Be
Single Inline Package
Surface Insulation Resistance (Resistivity)
Surface Mount Device
Surface Mount Equipment Manufacturers Association
Solder Mask Over Bare Copper
Surface Mount Technology
Small-Outline Integrated Circuit
Thermal Coefficient of Expansion
Time-Domain Reflectometer
Glass Transition Temperature
Tooling Hole
Transistor Outline
Underwriter's Laboratories
Impedance Value
see IPC-T-50 Terms and Definitions for more

(Thanks to the IPC for establishing a common foundation to build upon)
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