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PCB Glossary

At MPCS we believe communication is key to achieving expected results. Below is a list of terms you may find useful in understanding the complexities of the technology we use:


Activating: A chemical treatment that allows non-conductive laminate to accept electroless. Also called, catalyzing, seeding and sensitizing.

Additive Process: A process in printed circuit board manufacturing where the circuit pattern is produced by the addition of metal rather than etching metal away.

Analytical Services Lab: Performs various tests such as plating thickness, inner layer connections to hole walls, photos or x-rays of circuit boards when required.

Annular Ring: Conductive material around a hole which creates a pad.

Anode: The positive element used in the plating tank. The power supply is connected to the positive potential. The anodes are used to supply and accelerate the metal ion towards the panel being plated.

Aperture: An indexed shape with a specified X and Y dimension, or line-type with a specified width, used as a basic element or object by a photo plotter in plotting geometric patterns on film. The index of the aperture is its D code. A line of textual data in an aperture list describing the D code and position, the shape, flash or draw and the X and Y dimensions of an aperture.

Aperture List: An ASCII text data file, which describes the size and shape of the D codes.

Array: A group of circuits arranged in a pattern.

Artwork: A photo plotted film 1:1 pattern, which is used to produce the Diazo production master.

ASCII: American Standard Code for Information Interchange; pronounced “ass-key.” It is the character sets used in almost all present-day computers. US-ASCII uses only the lower seven bits (character points 0 to 127) to convey some control codes, space, numbers, most basic punctuation, and unaccented letters a-z and A-Z. Newer codes use more bits in a RS 274x format for more object definition.

Aspect Ratio: The ratio of the circuit board thickness to the smallest drilled hole diameter.

Assembly Drawing: A drawing showing the locations of components, with their reference designators, on a printed circuit. Also called component locator drawing.

AutoCAD: A drawing software standard which is used by RF and silicon chip packaging designers, saved in a DFX format to convert to Gerber for PCB manufacturing.

Automatic Optical Inspection: (AOI) computerized inspection of circuit boards to find shorts and opens.

Auto-router: Automatic router, a computer program that designs or routes the traces in a design automatically.


B-Stage Material: Sheet material (fiberglass cloth) impregnated with a resin cured to an intermediate stage (B-stage resin). Pre-preg is the preferred term.

Back Planes: Interconnection panels onto which printed circuits, other panels, or integrated circuit packages can be plugged or mounted. Typical thickness is 0.125″-0.300″.

Backup Material: A .093 mil thick layer of Phenolic, paper or wood by products, to protect the drill plate and prevent exit burrs.

Ball Grid Array: BGA. A chip package in which the external terminals form a grid-style array in contact with solder balls which carry the electrical connection to outside of the package. The PCB design will have round landing pads to which the solder balls are soldered when the PCB is heated in a reflow oven.

Barrel: The wall formed by plating a drilled hole.

Base Copper: Copper foil provided in sheet form to clad one or both sides of piece of laminate used as either internal or external layers.

Base Laminate: The dielectric material upon which the conductive pattern may be formed. The base material may be rigid or flexible.

Base Material: See Base Laminate.

Bed-of-Nails: A method of testing printed circuit boards that employs a test figure mounting an array of contact pins configured to engage plated thru-holes on the board.

Bevel: An angled edge of a printed circuit board for gold fingers.

Bleeding: A situation where a plated hole emits electroless solution from crevices or voids.

Blind Via Hole: A plated-through hole connecting an outer layer to one or more internal conductor layers of a multilayer printed board but not extending fully through all of the layers of base material.

Blister: An area of swelling and separation or delamination between any of the layers of a laminated base material or between base material and copper foil.

Blow Hole: A solder joint void caused by out-gassing of process solutions during thermal cycling.

Board House, Vendor: A manufacturer of printed circuit boards.

BOM: Bill of Materials; pronounced “bomb”. A list of components of the 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, along with an assembly drawing.

Bond Strength: The force in pounds per square inches required to delaminate two adjacent layers of a board when attempting to separate the layers. See Peel Strength.

Bow: The measurement of flatness of a circuit board between corners and the center.

Breakdown Voltage: The voltage at which an insulator or dielectric ruptures or at which ionization and conduction take place.

Bridging, Electrical: The formation of a conductive path between two insulated conductors such as adjacent traces on a circuit board.

BT/EPOXY: The blending of bismaleimide/triazine and epoxy resin provides enhanced thermal, mechanical and electrical performance over standard epoxy systems.

Buildability: Team meeting to review customer designs against manufacturing process capabilities. Used to identify possible failure modes prior to fabrication.

Buried Vias: Vias which start and end in the middle of the board.

Burr: A ridge left on the surface copper after drilling.


C-Stage: The condition of a resin polymer when it is in the fully cured, cross-linked solid state, with high molecular weight.

CAD: Computer Aided Design. A software which allows engineers to create and design a printed circuit layout.

CAD CAM: Simply a combination of the two terms CAD and CAM.

CAE: Computer Assisted Engineering. In electronics work, CAE refers to schematic software packages.

CAF: Conductive Anodic Filament (or Conductive Anodic Filament Growth) -An electrical short which occurs inside the PCBs when a conductive filament forms in the laminate dielectric material between two adjacent conductors under a DC electrical bias and humidity.

CAM: Computer Aided Manufacturing.

CAM Files: The data files used directly in the manufacture of printed circuits. One type of CAM files is a Gerber file, which controls a photo plotter, drill or LDI exposure unit.

Capacitance: The property of a series of parallel conductors between a dielectric to store electrical signals when a potential difference exists between them.

Card: An older name for a printed circuit board.

Card-edge Connector: A gold plated connector which is fabricated on the edge of a printed circuit board.

CEM-1: An older NEMA grade of printed circuit laminate having a substrate of woven glass surfaces over a cellulose paper core and a resin binder of epoxy. It has good electrical and mechanical properties. It is inexpensive and can be punched.

Center-to-Center Spacing: The nominal distance between the centers of adjacent features or traces on any layer of a printed circuit board. Also known as “pitch.”

Chamfer: A corner that has been rounded to eliminate an otherwise sharp edge.

Characteristic Impedance: A compound measurement of the resistance, inductance, conductance and capacitance of a transmission line expressed in ohms. In printed circuits, its value depends on the width and thickness of the conductor, the distance from the conductor to ground plane(s), and the dielectric constant of the insulating media.

Chase: The aluminum frame used in screening inks onto the board.

Check Plots: Photo plots that are suitable for checking only. Pads are represented as circles and thick traces as rectangular outlines instead of filled-in artwork. This technique is used to enhance transparency of multiple layers or may be holes only for drill checking.

Chip-on-board: COB, Integrated circuits or bare die are glued and wire-bonded directly to printed circuit boards instead of first being packaged and then glob topped. It can be identified by the black glob of plastic covering the chip on the board.

Chip Scale Package: A chip package in which the total package size is no more than 20% greater than the size of the die within, e.g. micro BGA.

Circuitry Layer: The layer of a PCB containing copper conductors, including signal, ground and voltage planes.

Clad or Cladding: A thin layer or sheet of copper foil, which is bonded to a composite laminate core to create the base material for printed circuits. See Base Copper.

Clean Room: A room with very low specified limits concentration of air born particles is controlled to lessen the effect dust has on imaging.

Clearance Hole: A hole in the conductive pattern larger than, but concentric with, a hole in the printed board base material.

CNC Drill File: Programs in Exelon format which a CNC drill machine use to drill the holes in the panel.

Coefficient of Expansion: Thermal fractional change in dimension of a material for a unit change in temperature.

Component Hole: A through hole for the attachment and electrical connection (soldering) of component terminations, including terminals and wires, to the printed circuit board.

Component Side: That side of the printed circuit board on which the majority of the components will be mounted.

Computer Aided Design: (CAD) a software program that calculates impedance modeling and providing graphical creation of a printed circuit board’s conductor layout and signal routes.

Computer Aided Manufacturing: (CAM) The use of computers to crate tooling data and transfer the electronic design (CAD) to the manufacturing machines.

Conductive Pattern: The configuration or design of the conductive material on the base laminate through which electrical energy passes. Includes conductors, lands, and through connections.

Conductor: A copper area on a PCB surface or internal layer usually composed of lands (to which component leads are connected) and paths (traces).

Conductor Base Width: The conductor width at the plane of the surface of the base material. See Conductor Width.

Conductor-to-Hole Spacing: The distance between the edge of a conductor and the edge of hole.

Conductor Thickness: The thickness of the trace or land including all metallic coatings.

Conductor Width: The observable width of the pertinent conductor on the printed circuit board.

Conformal Coating: An insulated protective coating that conforms to the components and is applied on the completed board assembly.

Contaminant: An impurity or foreign substance whose presence on printed wiring assemblies could electrically, chemically, or galvanically corrode the system.

Continuity: An uninterrupted flow of electrical current in a circuit.

Controlled Impedance: The matching of substrate material Dk with trace dimensions and locations to create specified electric impedance as required by the designers.

Coordinate Tolerance: A method of qualifying hole locations in which the variance is applied directly to linear and angular dimensions, usually forming a rectangular area of allowable variation.

Copper Foil: See Base Copper and Clad or Cladding.

Core Group: Daily operational meeting held on each shift to communicate current status of the plant in terms of producing and delivering high quality, cost-effective circuit boards on time.

Cosmetic Defect: A defect such as a slight change in its usual color that doesn’t affect a board’s functionality.

Coupon: See test coupon.

Cover Lay, Cover Coat: Outer layer(s) of insulating material applied over the conductive pattern on the surface of a printed circuit board.

Crazing: A condition existing in the base material of connected white spots or “crosses” on or below the surface of the base material, reflecting the separation of fibers in the glass cloth and resin material.

CTE: Coefficient of thermal expansion expressed as ppm or percentage.

Current Carrying Capacity: The maximum current which can be carried continuously, under specified conditions, by a conductor without causing degradation of electrical or mechanical properties of the printed circuit board.


D code: A datum in a Gerber file which acts as a command to a photo plotter. D code in a Gerber file takes the form of a number prefixed by the letter. “D20”.

Datum Reference: A defined point, line, or plane used to locate the pattern or layer for manufacturing inspection.

Deburring: Process of removing burrs of base copper material that remain around holes after board drilling.

Defect: Any deviation from the normally accepted characteristics of a product or component. Also see Major Defect and Minor Defect.

Definition: The accuracy of pattern edges in a printed circuit relative to the master pattern.

Delamination: A separation between any of the layers of a base material or between the laminate and the conductive foil, or both.

Design Rule Check: The use of a computer program to perform continuity and spacing verification of all conductor routing on all layers in accordance with appropriate design rules.

De-smear: Removal of epoxy smear (melted resin) and drilling debris from a hole wall.

Destructive Testing: Sectioning a portion of printed circuit panel and examining the sections with a microscope. This is performed on coupons, not the functional part of the PCB.

Develop: An imaging operation in which unpolymerized (unexposed) photo-resist is dissolved or washed away to produce a copper board with a photo-resist pattern for etching or plating.

Dewetting: A condition that occurs when molten solder has failed to properly coat a metal a surface and then recedes, leaving irregularly shaped globules of solder separated by areas covered with a thin solder film; base metal is not usually exposed.

DICY: Dicyandiamide, common cross-linking agent used in FR-4.

Dielectric: An insulating medium, which occupies the region between two or more conductors.

Dielectric Constant: The ratio of permittivity of the material to that of a vacuum (referred to as relative permittivity).

Dielectric Strength: a measurement of the voltage required to create an arc inside the dielectric.

Differential Signal: A method of signal transmission through two wires, which always has opposite states. The signal data is the polarity difference between the wires.

Digitizing: A computerized method of converting feature locations on a flat plane to digital X-Y coordinates.

Dimensional Stability: A measure of dimensional change caused by factors such as temperature, humidity, chemical treatment, age or stress.

Dimensioned Hole: A hole in a printed circuit board where the means of determining location is X-Y coordinate values not necessarily coinciding with the stated grid.

Double-Sided Board: A circuit board with conductive copper patterns on both sides.

Drills: Circuit board solid carbide cutting tools with four facet points and two helical flutes designed specifically for the fast removal of chips in extremely abrasive materials.

Dry Film: A photo imageable material, which is laminated onto a bare copper panel. It is exposed with 365 nm UV light through a negative photo tool. The exposed dry film is hardened by the UV light.


Edge Bevel: A bevel operation performed on edge connectors to improve their wear and ease of installation.

Edge-Board Connector: A connector designed specifically for making removable and reliable interconnection between the edge board contacts on the edge of a printed board and external wiring.

Edge Dip Solderability: A solderability test performed by taking a specially prepared specimen, fluxing it with a nonactivated rosin flux, and then immersing it into a pot of molten solder at a predetermined rate of immersion for a predetermined dwell time, and then withdrawing it at a predetermined rate.

Electroless Plating/Electroless Deposition: The deposition of metal from an auto-catalytic plating solution without application of electrical current. Short for “electrodeless.” This process is required to plate the nonconductive hole walls in order that they may be subsequently electroplated. Also called “PTH.”

Electroplating: (1) The electrodeposition of a metal coating on a PCB. The board to be plated is placed in an electrolyte and connected to one terminal of a DC voltage source. The metal to be deposited is similarly immersed and connected to the other terminal. Ions of the metal provide transfer to metal as they make up the current flow between the electrodes. (2) The electrolytic process used to deposit a metal on a desired object by placing the object at one electrical polarity and passing a current through a chemical solution to another electrode. The metal is plated from either the solution or the other electrode.

Embedded: Resisters, capacitors and small chip die are placed inside the PCB to increase density.

Entrapment: The damaging admission and trapping of air, flux, and/or fumes; it is caused by contamination and plating.

Entry Material: A thin layer of composite material or aluminum foil or paper products that is placed on top of the boards to be drilled to improve drill accuracy and prevent burrs and dents.

Epoxy Smear: Epoxy resin that has been deposited onto the surface or edges of the conductive inner layer pattern during drilling. Also called Resin Smear.

Etch: Chemical removal of copper to achieve a circuit pattern.

Etch Back: The controlled removal of the glass fibers and epoxy of the base material by a strong chemical process on the sidewall of holes to expose additional internal conductor copper.

Etch Factor: The ratio of the depth of etch (conductor thickness) to the amount of lateral etch (undercut).


Fab: Short for 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.

Fiducial: Etched features or drilled hole used for optical alignment during assembly operations.

Film Artwork: A positive or negative piece of film containing a circuit, solder mask, or nomenclature pattern.

Fine Line Design: Printed circuit design permitting two to three traces between adjacent chip pins. Typically, 2 mil line, 2 mil space is considered fine line.

Fine Pitch: Refers to chip packages with lead pitches below 0.050″. The largest pitch in this class of parts is 0.8 mm, or about 0.031″. Lead pitches as small as 0.2 mm (0.008″) are used.

Finger: A gold-plated terminal of a card-edge connector.

First Article: A sample part or test board manufactured prior to the start of production to assure that the vendor is capable of producing a circuit that will meet specified requirements.

Fixture: A device that enables interfacing a printed circuit board with a spring-contact probe test pattern.

Flat: A standard size sheet of laminate material, which is processed into one or more circuit boards. Also called panel.

Flex Circuit: Flexible circuit, a printed circuit made of thin, flexible material.

Flux: A substance used to promote or facilitate fusion such as a material used to remove oxides from surfaces to be joined by soldering.

Flying Probe Tester: A electrical testing machine that uses multiple moving arms to make contact with two spots on the copper circuitry and send a electrical signal between them. A procedure that determines if a short or open exists.

FR1: A low-grade version of FR2. Tg 130°C.

FR2: A grade of flame retardant industrial laminate having a substrate of paper and a resin binder of Phenolic. It is used for PCB laminate and cheaper than the woven glass fabrics. Tg 105°C.

FR4: A grade of Flame-Retardant industrial laminate having a substrate of woven-glass fabric and resin binder of epoxy. FR4 the most common dielectric material used in the construction of PCBs. Its dielectric constant is from 4.4 to
5.2 at below-microwave frequencies. As frequency climbs over 1 GHz, the dielectric constant of FR4 gradually drops. Tg 150°C to 175°C.

FR6: Fire-Retardant glass-and-polyester substrate material for electronic circuits. Inexpensive; popular for automobile electronics.

FR404: A multifunctional epoxy system that is a standard multilayer material.

FR406: A multifunctional epoxy laminate and prepreg that has a Tg of 170°C. It is used in applications where a higher temperature material is needed.

FR408: A high-performance FR4 epoxy laminate and prepreg that has a Tg of 180°C. The low dielectric constant is an ideal for faster signal speed and improved signal integrity.

Fused Coating: A metallic coating (usually tin or solder alloy) that has been melted and solidified, forming a metallurgical bond to the base material.


Gerber File: Data file used to control a photo plotter, named after Gerber Scientific Co., who manufactured the original vector photo plotter.

GIL Grade MC3D: A composite laminate comprised of woven glass surface sheets on both sides of a glass paper core. MC3D exhibits excellent electrical properties with a low and stable Dk and Df.

Glass Transition Temperature: Tg The temperature at which a polymer changes from a hard and relatively brittle condition to a viscous or rubbery condition. When this transition occurs, many physical properties undergo significant changes. Some of those properties are hardness, brittleness, coefficient of thermal expansion, and specific heat.

Grid: An orthogonal network of two sets of parallel, equidistant lines used for locating points on a printed circuit board.

Ground Plane: A copper conductor layer, used as a common reference point for circuit returns, shielding or heat sinking.


Haloing: Mechanically induced fracturing delimitation on or below the surface of the base material. It is usually exhibited by a light area around holes or other machines areas, or both.

HDI: High Density Interconnect. Very fine lines and thin dielectrics, made with sequential lamination.

Heavy Copper PCB: Circuit boards with more than 4 oz. of copper for power circuits.

Hole Breakout: A hole which is not completely surrounded by the land.

Hole Density: The quantity of holes in a PCB per unit area.

Hole Void: A void in the metallic deposit of a plated-through hole exposing the base material.

Hot Air Solder Leveling: (HASL) a method of coating exposed copper with solder by inserting a panel at 45 degrees into a bath of molten solder, then passing the panel rapidly past a series of hot air jets to remove excess solder.


Image: That portion on artwork masters, working tools, silk screens, or photo masks that would be considered the photographic image. Also would include images created with photo-resists or silk-screening techniques. Generally, “one image” refers to a single circuit board image; thus there may be several images per flat.

Impedance: A capacitive opposition to the flow of AC electrical current. This term is used to describe how high frequency circuit boards will react.

Ink: Common term for screen resist.

Inner Layer: Any layer that will be laminated into the inside of a multilayer board.

Inspection Overlay: A positive or negative transparency made from the production master and used as an inspection aid.

Insulation Resistance: The electrical resistance of the insulating material as measured between any pair of contacts or conductors.

IPC: The Institute for Interconnecting and Packaging Electronic Circuits.

ITAR: International Traffic in Arms Regulations (ITAR) control the export and import of defense-related articles and services on the United States Munitions List (USML).


Jumper Wire: An electrical connection formed by wire between two points on a printed board added after the intended conductive pattern is formed.


Kerf: A widening of the rout path which allows extra space for hardware to be attached to the board.

Keying Slot: A slot in a printed circuit board that polarizes it, thereby permitting it to be plugged into its mating receptacle with pins properly aligned, but preventing it from being reversed or plugged into any other receptacle.


Laminate: A product made by bonding together two or more composite layers of material.

Laminate Thickness: Thickness of the base material, not including metal-clad, prior to any processing. Applies to single or double-sided material.

Laminate Void: Lack of laminate material or epoxy in an area that normally should contain laminate material.

Laminating Presses: Multilayer equipment that applies both pressure and heat to laminate and pre-preg to make multilayer boards.

Lamination: The process of pressing a laminate.

Land: A portion of a copper conductive usually, but not exclusively, used for the connection and/or attachment of components. Also called pad.

Landless Hole: A plated-through hole without land(s). Also referred to as padless plated holes.

Laser Direct Imaging: The most recent development related to photoplotting is LDI (Laser Direct Imaging) which utilizes a high-power laser to directly expose photoresist on a coated substrate instead of exposing photographic film.

Laser Photo Plotter: A photo plotter which uses a laser on a X-Y computerized table to expose film to create the image.

Layer-to-Layer Spacing: The thickness of dielectric material between adjacent layers or conductive circuitry in a multilayer printed circuit board.

Lay-Up: (1) The technique of registering and stacking layers of materials (laminate and pre-preg) for a multilayer board in preparation for the laminating cycle. (2) The laying out of repeat images on film to create multiple groups of circuit boards.

LPI: Liquid Photo Imageable refers to liquid photo imageable solder mask.


Major Defect: A defect that could result in a failure or significantly reduces the usability of the circuit for its designed purpose.

Mask: A material applied to create selective etching, plating, or the application of solder or solder mask to a printed circuit board.

Measling: Condition existing in the base laminate in the form of discrete white spots or “crosses” below the surface of the base laminate, indicating a separation of fibers in the glass cloth at the weave intersection.

Met Lab: Metallurgical Laboratory refers to the process of inspecting internal board quality characteristics through the use of micro sections.

Metal Foil: The thin sheets or rolls of conductive material of a printed circuit board from which circuits are formed. Metal foil is generally copper.

Micro BGA: micro Ball Grid Array.

Micro Circuits: Very fine lines, 2 mil and less, and small micro vias 3 mil and less.

Micro Sectioning: The creation of a specimen for the microscopic examination of the material to be examined, usually by cutting out a cross section, followed by encapsulation, polishing, ammonia etching, staining.

Microvia: A via used to make connection between two adjacent layers, typically less than 6 mils in diameter. May be formed by laser ablation, plasma etching, or photo processing.

Mil: One-thousandth of an inch 0.001″ (0.0254 mm); abbreviation of milli-inch.

MIL-PRF-31032: This specification establishes the general performance requirements for printed circuit boards or printed wiring boards (hereafter designated printed board) and the verification requirements for insuring that these items meet the applicable performance requirements. Certification and qualification to this specification allows manufacturer’s to apply the QML program to printed boards procured to non-QML documents such as MIL-PRF-55110 and MIL-P-50884. The intent of this specification is to allow the printed board manufacturer the flexibility to implement best commercial practices to the maximum extent possible while still providing product that meets military performance needs.

MIL-PRF-55110: This specification establishes the performance and qualification requirements for rigid single-sided, double-sided, and multilayer printed wiring boards with or without plated through holes (see 6.1). Verification is accomplished through the use of one of two methods of product assurance (appendix A or appendix B). Detail requirements, specific characteristics, and other provisions which are sensitive to the particular intended use are specified in the applicable master drawing. [Inactive for new design after 31 December 1997. For new design use MIL-PRF-31032.]

MIL-PRF-50884: This specification establishes the performance and qualification requirements for flexible and rigid-flex printed wiring boards with or without plated through holes. Verification is accomplished through the use of one of two methods of product assurance (appendix A or appendix B). Detail requirements, specific characteristics, and other provisions which are sensitive to the particular intended use are specified in the applicable master drawing.

Minimum Annular Ring: The minimum metal width, at the narrowest point, between the circumference of the hole and the outer circumference of the land. This measurement is made to the drilled hole on internal layers of multilayer printed circuit boards and to the edge of the plating on outside layers of multilayer boards and double-sided boards.

Minimum Electrical Spacing: The minimum allowable distance between adjacent conductors that is sufficient to prevent dielectric breakdown, corona, or both, between the semiconductors at any given voltage and altitude.

Minor Defect: A defect that is not likely to reduce the usability of the circuit for its intended design. It may be a departure from established standards having no significant bearing the operation of the circuit.

Misregistration: The lack of dimensional conformity between successively produced features or patterns.

Multilayer Circuit Board: A processed printed circuit configuration consisting of alternate layers of conductive patterns and insulating materials bonded together in more than two layers.


NADCAP: The National Aerospace and Defense Contractors Accreditation Program is a global cooperative accreditation program for aerospace engineering, defense and related industries.

Nail Heading: The flared condition of copper on the inner conductor layers of a multilayer board caused by hole drilling.

Negative: An artwork master or production master in which the intended conductive pattern is transparent to light and the areas to be free from conductive material are opaque.

Net List: List of names of symbols or parts and their connection points, which are logically connected in each net of a circuit. A net list can be “captured” (extracted electronically on a computer) from a properly prepared CAE schematic.

Nomenclature: Identification symbols applied to the board by screen printing or ink jetting.

Nonfunctional Land: A land on internal or external layers not connected to the copper conductive pattern on its layer.


Outer Layer: The top and bottom sides of a circuit board.

Outgassing: De-aeration or other gaseous emission from a printed circuit board when exposed to the soldering operation or to vacuum.

Overhang: Increase in printed circuit conductor width caused by plating build-up or by undercutting during etching.

Oxide: A chemical treatment to inner layers prior to lamination, for the purpose of increasing the roughness of clad copper to improve laminate bond strength.


Pad: The portion of the conductive pattern on printed circuits designated for the mounting or attachment of components. Also called land.

Panel: The square or rectangular base material containing one or more circuit patterns that passes successively through the production sequence and from which printed circuit boards are extracted, typically, 12˝ by 18˝ or 18˝ by 24˝. See back planes.

Panel Plating: The electrolytic plating of the entire surface of a panel (including holes).

Panelize: To lay up more than one (usually identical) printed circuits on a panel. Individual printed circuits on a panel need a margin between them. Lay up multiple printed circuits called modules, into a sub-panel so that the sub-panel can be assembled as a unit. The modules are then separated after assembly into discrete PCB.

Pattern: The series of conductive copper and dielectric materials on a panel or printed circuit board. Also the circuit design on related tools, drawings, and masters.

Pattern Plating: Selective electrolytic plating of a copper pattern.

PC Board: Printed circuit board also called PCB.

PCB Design: The creation of artwork for the manufacture of bare PCBs on a computer database used to generate such artwork as data files (CAM files). Also called PCB layout.

PCB Design Service Bureau: A business engaged in PCB design as a service for others, especially electrical engineers. Also called PCB design shop.

Peel Strength: The force required to peel the conductor or foil from the base material.

Permittivity Measure: The ability of a material to store electrical energy when exposed to an electrical field.

Photo Mask: A silver halide or diazo image on a transparent substrate that is used to either block or pass light.

Photo Plotter: A high-accuracy (>0.001 inch) flatbed or rotary plotter with a programmable, photo image projector assembly. It is most often used to produce actual-size master patterns for printed circuit artwork directly on dimensionally stable, high-contrast photographic film.

Photo-Resist: A light-sensitive material that is used to establish an image by exposure to light and chemical development.

Pilot Order: First production order going through process.

Pinhole: A minute hole through a layer or pattern.

Pitch: The nominal distance between the centers of adjacent features or traces on any layer of a printed circuit board. Also known as “center-to-center spacing.”

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: (PTH) A hole in a circuit board that has been plated with metal (usually copper) on its sides to provide electrical connections between conductive pattern layers.

Platen: A flat plate of thick metal within the lamination press in between which stacks of pre stacked circuits are placed to be pressed.

Plating: Chemical or electromechanical deposition of metal on a pattern.

Plating Resists: Material that, when deposited on conductive areas, prevents the plating of the covered areas. Resists are available both as screened-on materials and as dry-film photopolymer resists.

Plating Void: The absence of a plating metal from a specified plating area.

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

Polymerize: To unite chemically two or more monomers or polymers to form a molecule with a higher molecular weight.

Polyimide Resins: High-temperature thermoplastics used with glass to produce printed circuit laminates for multilayer and other circuit applications requiring high temperature performance.

Positional Limitation Tolerancing: Defines a zone within which the axis or center plane of a feature is permitted to vary from true (theoretically exact) position. Pre-clean cleaning steps taken prior to an operation to ensure success of the operation.

Pre-preg: Sheet material consisting of the base material impregnated with a synthetic resin, such as epoxy or Polyimide, partially cured to the B-stage (an intermediate stage). Short for pre-impregnated. See also B-stage.

Press-Fit Contact: An electrical contact that can be pressed into a hole in an insulator, printed board (with or without plated-through holes), or a metal plate.

Printed Circuit: A conductive pattern of printed components and circuits attached to a common base.

Printed Circuit Board: (PCB) The general term for a printed or etched circuit board. It includes single, double, or multiple layer boards, both rigid and flexible.

Printed Wiring Board: Another name for a Printed Circuit Board.

Production Master: A 1:1 scale pattern that is used to produce one or more printed boards (rigid or flexible) within the accuracy specified on the master drawing.

PTFE: Woven glass materials, with exceptionally well controlled electrical and mechanical properties. The dielectric constant range is 2.45 to 2.65 used for RF applications.

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


Quality Control (QC): A precise system of measurements to ensure the PCB meets the desired specifications. Also called Quality Assurance.


Reflowing: The melting of an electro deposit followed by solidification. The surface has the appearance and physical characteristics of being hot-dipped.

Registration: The amount of conformity of the true position of a pattern with its intended position or with that of any other conductor layer of a board.

Residue: An undesirable substance remaining on a substrate after a process step.

Resin Smear: Melted epoxy resin transferred from the base material onto the surface or edge of the conductive pattern normally caused by drilling. Sometimes called epoxy smear.

Resin-Starved Area: A region in a printed circuit board that has an insufficient amount of resin to wet out the reinforcement completely evidenced by low gloss, dry spots, or exposed fibers.

Resist: Coating material used to mask or to protect selected areas of a pattern from the action of an etchant, solder, or plating. Also see Dry Film, Plating Resists and Solder Resists.

Resistivity: The ability of a material to resist the passage of electrical current through it.

Reverse Image: The resist pattern on a printed circuit board enabling the exposure of conductive areas for subsequent plating.

Rework: Reprocessing that makes articles conform to specifications.

RF: Radio Frequency.

Rigidflex: A PCB construction combining flexible circuits and rigid multilayers, to provide a direct connection or to make a three dimensional form that may include components.

Robber/Thieves: An exposed area generally attached to a rack used in electroplating, usually to provide a more uniform current density on plated parts. Robbers are intended to absorb the unevenly distributed current on parts, thereby assuring that the parts will receive a uniform electroplated coating.

Router: A CNC machine that removes portions of the panel to release the board with the desired shape and size required.


Schematic Diagram: A drawing that shows, by means of graphic symbols, the electrical connections, components, and functions of an electronic circuit.

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

Screen: A cloth material (usually polyester or stainless steel for circuit boards) coated with a pattern that determines the flow and location of coatings forced through its openings.

Screen Printing: A process for transferring an image to a surface by squeezing suitable ink through a stencil screen with a squeegee. Also called silk screening.

Selective Plate: A process for plating unique features with a different metal than the remaining features will have. Created by imaging, exposing, and plating selected area and then repeating the process for the remainder of the board.

Shadowing: A condition occurring during etch back in which the dielectric material, in contact with the foil, is incompletely removed although acceptable etch back may have been achieved elsewhere.

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.

Silk Screening: See Screen Printing.

Single-Sided Board: Circuit board with copper conductors on only one side and no plated-through holes.

SMOBC: Solder Mask Over Bare Copper, a method of fabricating a printed circuit board with the final copper metallization under the solder mask 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 components which will reflow, causing a blemish.

Solder Leveling: The process of dipping printed circuit boards into hot solder and leveling with hot air.

Solder Mask: An ink coating applied to a circuit board to prevent solder from flowing onto any areas where it’s not desired or from bridging across closely spaced conductors.

Solder Masking Coating: A term for resist.

Solder Resists: Coatings that mask and insulate portions of a circuit pattern where solder is not desired.

Solderability Testing: The evaluation of a metal to determine its ability to be wetted by solder.

Squeegee: The tool used in silk screening that forces the resist or ink through the mesh.

Stacked Vias: Micro vias in HDI that are stacked one upon each other.

Starvation Resin: A deficiency of resin in base material that is apparent after lamination by the presence of weave texture, low gloss, or dry spots.

Step-and-Repeat: A computerized method by which successive copies of a single image are laid up to produce a multiple-up filling of the panel.

Strip: The chemical removal of developed photo resist or plated metal.

Substrate: See Base Material.

Subtractive Process: A process in printed circuit manufacturing where the product is built by the subtraction of an already existing metallic coating. The opposite of additive processing.

Surface Mount Technology: SMT defines the entire body of the process and components that create printed circuit board assembly with leadless components.


Td: Temperature of destruction, where the circuit loses 5% of its volume due to out gassing.

Tg: Glass transition temperature, in degree C, the point at which the material starts to become soft and plastic like. Also the point where the Z axis starts to expand non linearly.

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.

Test Coupon: A sample or test pattern normally made outside the actual board pattern that is used for testing to verify certain quality parameters without destroying the actual board.

Thief: See Robber.

Tooling Holes: Two specified holes on a printed circuit board used to position the board in order to mount components accurately.

Top Side: The component side.

Trace: A common term for the copper conductors.

Traveler: A “recipe” for the manufacturer of a board. It “travels” with each order from start to finish. The traveler identifies each order and gives instructions for each step in the process.

Two-Sided Board: See Double-Sided Board.


Underwriters Laboratory: Certifying agency for consumer electronics. See also Underwriters Symbol.

Underwriters Symbol: A logotype denoting that the product has been recognized by Underwriters Laboratory Inc. (UL).

UV Cure: Polymerizing hardening or cross inking a material by exposing to ultra violet light.


Via: A plated thru-hole that is used as an inner-layer connection but doesn’t have component lead in it.

Void: The absence of substances in a localized area (e.g., air bubbles).


Wave Soldering: A process wherein assembled printed boards are brought in contact with a continuously flowing and circulating mass of solder.

Wicking: Migration of conductive copper chemicals into the glass fibers of the insulating material around a drilled hole.

WIP: Work In Progress.


Young’s Modules: A measurement as to the amount of force a object applies as it contracts or expands due to temperature change, expresses in Mpsi or Gpa

Zero Defects Sampling: A statistical based attribute sampling plan where a given sample of parts is inspected and any defects found are cause for rejection of the entire lot.

One oz. of copper is 1.39 mils thick;
One mil is 24.5 mm
Voltage E=I / R
Notation and Formula
C capacitancefaradsF
E voltage sourcevoltsV
e Instantaneous EvoltsV
G conductanceSiemensS
I currentampsA
i instantaneous IampsA
k coefficientnumber#
L inductancehenrysH
M mutual inductancehenrysH
N number of turnsnumber#
P powerwattsW
Q chargecoulombsC
q instantaneous QcoulombsC
R resistanceohmsΩ
T time constantsecondsS
t instantaneous timesecondsS
V voltagevoltsV
v instantaneousvoltsV
W energyjoulesJ
Conversion Factors

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Medical Technology

Vast experience manufacturing sophisticated technology, coupled with unparalleled product reliability provides MPCS with the necessary foundation to be your trusted supplier for products to the medical technology industry.


With over 40 years of experience, MPCS has been manufacturing mission critical products for various levels of the aerospace industry, including NASA, the military, as well as numerous commercial clients. MPCS is certified and qualified to AS9100D, MIL-PRF-31032, MIL-PRF 55110, IPC-6012 Class 3 and IPC-6012 Class 3/A and is a recognized and approved provider for manned space flight.

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We are proud to provide our military with American made products of the highest quality and reliability on the market. MPCS is certified and qualified to the demanding performance standards of AS9100D, MIL-PRF-31032/1/2. MIL-PRF-55110 as well as IPC-6012 Class 3, IPC-6012 Class 3/A and can meet or exceed your specifications.