Products Quality Process Technology News Company EDUCATION Commonly Used PCB Production Terms and PCB Definitions A B C D E F G H I J K L M N O P R S T U V W Z TERM DESCRIPTION A Activating A chemical treatment that allows non-conductive laminate to accept electroless coated. 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 surrounding 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 supply and accelerate the metal ion towards the circuit 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. Â 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. Â 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. ASTM American Society of Testing and Materials. Â https://www.astm.org/index.shtml. Auto-router Automatic router, a computer program that designs or routes the traces in a design automatically. AutoCAD A drawing software standard which is used by RF and silicon chip packaging designers, saved in a dxf format to convert to Gerber for PCB manufacturing. Automatic optical inspection (AOI) computerized inspection of circuit boards to find shorts and opens. B 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"â€“0.300." Backup material A .093 mil thick layer composed of Phenolic, paper or wood by products, to protect the drill pate and prevent exit burrs. Ball grid array BGA . Â A chip package in which the external terminals form a grid-style array, and are 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 will be soldered when the package and PCB are heated in a reflow oven. Barrel The wall formed by plating a drilled hole. Base Copper Copper foil provided in sheet form or clad to one or both sides of piece of laminate used as either internal or external layers of a circuit board. 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 so as to engage plated thru-holes on the board. Bevel an angled edge of a printed circuit board usually for gold fingers . Bleeding A situation where a plated hole discharges 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 of the board. Blister A 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 Printed circuit board. comprised of laminate and copper traces with interconnecting holes. Board house, Board 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 and, along with an assembly drawing. Bond Strength The force in sq 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 in a gas or vapor. 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 end in the middle of the board. Burr A ridge left on the surface copper after drilling. C 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 create and design a printed circuit layout. CAD CAM Simply a concatenation 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 an DC electrical bias and humidity. CAM Computer Aided Manufacturing. Â CAM files CAM stands for Computer Aided Manufacturing. which are the data files used directly in the manufacture of printed wiring. The types of CAM files Gerber file, which controls a photo plotter or LDI exposure unit. Capacitance The property of a series of parallel conductors between a dielectric to store electrical signals when a potential difference between them exists. 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 A 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 wiring 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 surface. 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 scale package A chip package in which the total package size is no more than 20% greater than the size of the die within. Eg: Micro BGA. Chip-on-board COB. Â Integrated circuits or bare die are glued and wire-bonded directly to printed circuit boards instead of first being packaged. And then glob toped It can be identified by the black glob of plastic sitting on the board. Circuitry Layer The layer of a PCB containing conductors, including ground and voltage planes. Clad or Cladding A thin layer or sheet of copper foil, which is bonded to a laminate core to form the base material for printed circuits. See Base Copper. Clean room A room in which the concentration of air born particles is controlled to very specified limits 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 which an CNC Drill machine and fabrication and assembly drawings in paper or PDF form. Coefficient of Expansion Thermal fractional change in dimension of a material for a unit change in temperature. Component Hole A through hole used for the attachment and electrical connection of component terminations, including pins and wires, to the printed circuit board. Component Side That side of the printed circuit board on which most of the components will be mounted. Computer aided Manufacturing (CAM) The use of computers to analyze and transfer the electronic design (CAD) to the manufacturing machines. Computer aided design (CAD) a soft ware program with algorithms for drafting , modeling and providing graphical representation of a printed circuit boards conductor layout and signal routes. 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 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. Conductor-to-Hole Spacing The distance between the edge of a conductor and the edge of hole. 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 properties with trace dimensions and locations to create specified electric impedance as seen by a signal on the test trace coupon. Coordinate Tolerance A method of tolerancing hole locations in which the tolerance is applied directly to linear and angular dimensions, usually forming a rectangular area of allowable variation. Also see Positional Limitation Tolerancing and True Position Tolerance. Copper Foil See Base Copper and Clad or Cladding. Core Group Daily operational meeting held on each shift to communicate current status of plant in terms of producing and delivering high quality, cost-effective circuit boards to customers 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. Crazing A condition existing in the base material in the form 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. Cover Lay, Cover Coat Outer layer(s) of insulating material applied over the conductive pattern on the surface of a printed circuit board. CTE Coefficient of thermal expansion expressed as ether ppm or a 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 D code A datum in a Gerber file which acts as a command to a photo plotter.Â 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, or for both purposes. Deburring Process of removing traces 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 verification of all conductor routing in accordance with appropriate design rules. Desmear 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 coated a surface and then recedes, leaving irregularly shaped globules of solder separated by areas covered with a thin solder film; base metal is not exposed. DICY Dicyandiamide, the most 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). Differential signal A method of signal transmission through two wires which always have opposite states. The signal data is the polarity difference between the wires. Â Digitizing Any method of converting feature locations on a flat plane to digital representation in x-y coordinates. Dimensional Stability A measure of dimensional change caused by factors such as temperature, humidity, chemical treatment, age or stress; usually expressed as units/unit. 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 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 imagable material which is laminated on to a bare copper panel, it is exposed with 365 nm uv light through a negative photo tool, the exposed dry film is harden by the uv light , the unexposed film is washed away in a developer solution of .8 percent sodium carbonate E Edge Bevel A bevel operation performed on edge connectors to improve their wear and ease of installation. Edge Dip Solderability Test A solderability test performed by taking a specially prepared specimen, fluxing it with a non-activated 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. 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. Electroless Plating/Electroless Deposition The disposition 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 embedded 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 metal (copper) to achieve a desired circuit pattern. Etch Factor The ratio of the depth of etch (conductor thickness) to the amount of lateral etch (undercut). Etchback The controlled removal of the glass fibers and epoxy of the base material by a chemical process on the sidewall of holes in order to expose additional internal conductor areas. F 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 DIP pins. Typically 2mil 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 0.8mm, or about 0.031". Lead pitches as small as 0.2mm (0.008") are used. Finger A gold-plated terminal of a card-edge connector. First Article A sample part or assembly manufactured prior to the start of production for the purpose of assuring that the manufacturer is capable of manufacturing a product 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 or welding. Flying probe tester A testing machine that uses multiple moving pins to make contact with two spots on the electrical circuitry and send a signal between them , a procedure that determines weather a fault exists FR-1 A low-grade version of FR-2. Tg 130c. FR-2 A grade of Flame-Retardant industrial laminate having a substrate of paper and a resin binder of phenolic. It is suitable for printed circuit board laminate and cheaper than the woven glass fabrics such as FR-4. Tg 105 c. FR-4 A grade of Flame-Retardent industrial laminate having a substrate of woven-glass fabric and resin binder of epoxy. FR-4is the most common dielectric material used in the construction of PCBs in the USA. Â Its dielectric constant is from 4.4 to 5.2 at below-microwave frequencies. As frequency climbs over 1 GHz, the dielectric constant of FR-4 gradually drops. Tg 150 to 175 c. FR-404 A multifunctional epoxy system that is a standard multilayer material. FR-406 A Multifunctional Epoxy Laminate and Prepreg that has a Tg of 170 C (DSC used in applications where a higher temperature material is needed). FR-408 A high-performance FR-4 epoxy laminate and prepreg that has a Tg of 180 C (DSC). low dielectric constant is an ideal for faster signal speed and improved signal integrity. Used when layer counts begin to exceed 8 layers because it`s higher thermal properties minimize Z-axis expansion and the potential for barrel cracking and pad lifting in complex designs. FR-6 Fire-Retardant glass-and-polyester substrate material for electronic circuits. Inexpensive; popular for automobile electronics. Fused Coating A metallic coating (usually tin or solder alloy) that has been melted and solidified, forming a metallurgical bond to the base material. G Gerber file Data file used to control a photo plotter. Named after Gerber Scientific Co., who made 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 electricals with a low and stable dielectric constant and dissipation factor. Glass Transition Temperature Tg The temperature at which an amorphous polymer (or the amorphous regions in a partially crystalline 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 conductor layer, or portion of a conductor layer, used as a common reference point for circuit returns, shielding, or heat sinking. H 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 condition in which a hole is not completely surrounded by the land. Hole Density The quantity of holes in a printed circuit board 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 into a bath of molten solder then passing the panel rapidly past a series of hot air jets. I 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 The total passive opposition offered to the flow of electrical current , this term is generally used to describe high frequency circuit boards. Ink Common term for screen resist. Inner layer Any layer that will be pressed on 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. J Jumper Wire An electrical connection formed by wire between two points on a printed board added after the intended conductive pattern is formed. K Kerf A widening of the rout path as may be called out on the blueprint. 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. L Laminate A product made by bonding together two or more 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 Absence of laminate material in an area that normally contains 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 conductive pattern 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 photo plotter A photo plotter which uses a laser to expose film to create the image. 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. (3) The laying out of multiple layers in preparation for multilayer lamination. Layer-to-Layer Spacing The thickness of dielectric material between adjacent layers or conductive circuitry in a multilayer printed circuit board. LPI Liquid Photo Imageable. Refers to liquid photo imagable solder mask. M Major Defect A defect that could result in a failure or significantly reduces the usability of the part for its intended purpose. Mask A material applied to enable selective etching, plating, or the application of solder 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, reflecting a separation of fibers in the glass cloth at the weave intersection. Met lab Metallurgical Laboratory. (1) Refers to the process(es) of inspecting internal board quality characteristics through the use of microsections. (2) Used interchangeably with microsection. 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 preparation of a specimen for the microscopic examination of the material to be examined, usually by cutting out a cross section, followed by encapsulation, polishing, etching, staining, and so on. 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). [From abbreviation of milli-inch]. 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 unit for its intended purpose. It may be a departure from established standards having no significant bearing on the effective use or operation of the unit. Misregistration The lack of dimensional conformity between successively produced features or patterns. Multilayer Circuit Board The general term for completely processed printed circuit configurations consisting of alternate layers of conductive patterns and insulating materials bonded together in more than two layers. N 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. Netlist List of names of symbols or parts and their connection points which are logically connected in each net of a circuit. A netlist can be "captured" (extracted electronically on a computer) from a properly prepared CAE schematic. Nomenclature Identification symbols applied to the board by means of screen printing ink jetting see legend. Nonfunctional Land A land on internal or external layers, not connected to the conductive pattern on its layer. O Outer Layer The top and bottom sides of any type of circuit board. Outgassing Deaeration 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. P 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. See Back Planes and Panels .typically 12" by 18" or 18" by 24". Panel Plating The electrolytic plating of the entire surface of a panel (including holes). Panelize 1. To lay up more than one (usually identical)printed circuits on a pans. Individual printed circuits on a panel need a margin between them of 0.3". Some board houses permit less separation. 2. Lay up multiple printed circuits (called modules) into a sub-panel so that the sub-panel can be assembled as a unit. The modules can then be separated after assembly into discrete printed circuits. Pattern The configuration of conductive and nonconductive materials on a panel or printed board. Also the circuit configuration on related tools, drawings, and masters. Pattern Plating Selective electrolytic plating of a conductive pattern. PC board Printed Circuit board also called PCB. PCB design 1. The creation of artwork for the manufacture of bare PCBs. 2. The artwork so created. 3. 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. The word bureau is French for desk, or office, and this service is indeed performed from an office while sitting at a desk. Also called PCB design shop. Peel Strength The force required to peel the conductor or foil from the base material. Permittivity Measure of 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 that been plated with metal (usually copper) on its sides to provide electrical connections between conductive patterns layers of a printed circuit board. Platen A flat plate of thick metal within the lamination press in between which stacks of 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 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. Polymide 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 Polymide, 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 A part manufactured from rigid base material upon which completely processed printed wiring has been formed. 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. (1) Single-Image Product Master: A production master used in the process of making a single printed circuit board. (2) Multiple-Image Production Master: A production master used in the process of making two or more printed circuit boards simultaneously. PTFE Woven glass materials 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 pulses instead of a direct current. R Reflowing The melting of an electro deposit followed by solidification. The surface has the appearance and physical characteristics of being hot-dipped. Registration The degree 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 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 Resists, 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 usually to provide a built in connection or to make a three dimensional form that includes components. Robber An exposed area generally attached to a rack used in electroplating, usually to provide a more uniform current density on plated parts. Thieves are intended to absorb the unevenly distributed current on parts, thereby assuring that the parts will receive a uniform electroplated coating. Router A machine that cuts away portions of the panel to release the board with the desired shape and size required. S 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 groves 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 forcing suitable media 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 etchback in which the dielectric material, in contact with the foil, is incompletely removed although acceptable etchback 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 conductors on only one side and no plated-through holes. SMOBC Solder mask over bare copper a method of fabricating a printed circuit board which results in final metallization under the solder mask 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 components . Solder Leveling The process of dipping printed circuit boards into hot solder and leveling with hot air. Solder Mask A 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 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 method by which successive copies of a single image are made to produce a multiple-up filling 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. T T/d Temperature of destruction, where the circuit looses 5 percent of its volume due to out gassing. T/g 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 in 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, but it also renders the via unusable as a test point. Sometimes vias are tented on the top side of the board and left uncovered on the bottom side to permit probing from that side only with a test fixture. 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 conductors. Traveler A "recipe" for the manufacture 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. It also provides information for traceability and history. Two-Sided Board See Double-Sided Board. U 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 Harding or cross inking a material by exposing to ultra violet light. V Via A plated thru-hole that is used as an inner-layer connection but doesn`t have component lead or other reinforcing material in it. Vias can make an electrical connection between layers on a PCB Void The absence of substances in a localized area (e.g., air bubbles). W 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. Z Zero Defects Sampling A statistical based attribute sampling plan (C = O) where a given sample of parts is inspected and any defects found are cause for rejection of the entire lot. 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