The width of the copper pad area that remains after a hole is drilled through a pad.
The photographic tool used to manufacture a printed circuit board. Usually this is film work, but could be hand laid with tape, or could refer to the gerber files themselves.
An array combines a single PCB multiple times to make a larger array of connected boards; or a “matrix” so to speak. This process is referred to as “stepping out” the individual boards and also often referred to as “step and repeat.” Other terms used to describe an array include: panelized, stepped out, palletized and rout and retain. An array is used to make the assembly process faster.
Rails are extra PCB material that are added to the sides of an array to allow for easier handling during the assembly process. The rails could be on all four sides of the array or only on two sides. Array Rails is also called Break-away.
The ratio of the circuit board thickness to the smallest hole diameter.
This is the material which forms the structural and insulating layer between the copper layers.
This is a copper plated hole which passes from the surface of a PCB and terminates at a copper feature on an inner layer. It does not pass all the way through the PCB.
A buried via is a copper plated hole which interconnects between two internal layers of a multilayer PCB. They are not visible externally.
When drilling a PCB there is often a ridge or piece of material that is left connected to the drilled hole. The burr will need to be removed to not cause any problems in the rest of the manufacturing process.
Bow references the flatness of a printed circuit board. In the case of a bow all four corners of the board would be able to touch a flat surface equally but the middle area of the board would not be touching.
Usually referring to the final thickness of the printed circuit board. This would include the fiberglass, soldermask and silkscreen and the board finish. The most commonly used thickness is 0.062″ but many options are available
Also called Prepreg. The condition of the fiberglass material used on multi-layer PCBs that is placed between the core layers of the board. It is still pliable and soft until it is heated and pressed in a lamination press. The heat causes the material to “flow” and then it will harden as it cools.
This is the final hardened stage of the resin used during the lamination process of the multi-layer PCB.
CAM(Computer Aided Manufacturing)
CAM refers to the software used by PCB manufacturers to prepare customers engineering files (See Gerber Files Blog Post) for the final manufacturing process.
These are the files that provide the needed information for the manufacturing of the printed circuit board.
A clearance (also called isolation) is space used to create a separation from a power or ground layer near a plated hole on an inner layer. A clearance will prevent a short from the plated hole to either the power or ground plane.
Coefficient of Thermal Expansion(CTE)
A measurement of the amount the PCB material will change per degree of temperature. This is a key factor in when determining which material is the best one to use for a given circuit design. Material manufacturers will provide these details in their material specifications sheet.
Comparative Tracking Index(CTI)
Is used to measure the electrical breakdown properties of the insulating material used in PCBs. It is primarily used to assess electrical safety especially for human users of electrical devices. Material manufacturers will provide these details in their material specifications sheet.
A plated hole on the circuit board that is intended to have a component pin placed in it. This could include the component pin, terminations or wires. It is good to designate if a hole is a component hole or not because the size of a component hole is more critical than a hole that will not have a component placed in it.
This is the pattern of the copper on the final circuit board. This would include the traces, pads, etc. that make up the circuit on the board.
Computer Numerical Control(CNC)
Refers to the computer control that is used with modern day machinery. It is most often used in the PCB manufacturing process with CNC Drill Machines as well as Rout machines that cut the individual boards away from the production panels.
A counterbore is cylindrical flat-bottom hole that enlarges another drilled hole. It is typically used when a fastener, such as a socket head cap screw, is required to sit flush with the surface of the PCB.
A countersink is a conical hole added to a drilled hole to allow the head of a countersunk screw to sit flush with the surface of the PCB.
Often used in multilayer printed circuit board construction, copper foils are commonly available in 18 micron, 35 micron and 70 micron thickness.
The Date Code is added to the copper or silkscreen of the PCB during the manufacturing process. The date code shows the week and year that PCB was made.
When any copper or laminate materials in a PCB begin to separate after the boards have been manufactured.
The chemical process of removing drilling debris that is left in the holes of a production PCB panel after being drilled.
Dielectric refers to the fiberglass material in a PCB. The material is non-conductive and acts as an insulator for the electrical circuit in the PCB. The properties of the dielectric material can have an effect on the electrical circuit.
DRC(Design Rule Check)
A DRC is performed with CAM software to verify the continuity of all conductors and routing within the manufacturers design rules.
That property of a dielectric that determines the electrostatic energy per unit volume for unit potential grade. The transmission speed of an electromagnetic wave in a dielectric medium is the speed of light divided by the square root of DK. Air has a DK of 1.0, FR4 has a DK of 4.4.
Coating material in the form of laminated photosensitive sheets specifically designed for use in the manufacture of printed wire boards and chemically machined parts. They are resistant to various electroplating and etching processes.
Electrical Test is the process of testing the board for continuity and isolation. (opens and shorts). Typically the end points of all nets are checked for opens and shorts. It does not include functionality testing of the PCB.
After an image pattern as been applied to a panel of copper clad fiberglass the unwanted copper is chemically etched away.
Excellon Drill File
The data file that defines the drill hole sizes, X & Y coordinates, and tool numbers for a circuit board. Also called a NC (numerically controlled) drill file.
The electro-deposition of metal coating on a conductive object. The metal may be conductive or non-conductive. The object 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. This creates a current flow from the metal to the conductive material thus depositing the material. In PCB manufacturing it is used to apply copper to the hole walls and copper conductor pattern.
Electroless Nickel Immersion Gold(ENIG)
ENIG is a very thin amount of Gold applied over Nickel. The nickel is plated onto the copper prior to the application of Gold and acts as a barrier to prevent the Gold and the Copper from migrating into one another. The gold will disappear when soldered, as it is absorbed in the process. Excellent for very fine pitched components.
A device that enables interfacing a printed circuit board with a spring-contact probe test pattern. It contains either a dedicated head or an interface for interchangeable test heads and means of keying the product to be tested.
A drawing that is used to provide additional information for the correct manufacturing of the PCB. It may include the location of holes, sizes and tolerances, board dimensions, material to be used, finish choice and any other important information not included in the gerber files.
The fiducial is a circle that is a copper pad with the same finish as the rest of the board and provides alignment targets for automated assembly equipment. A fiducial may be on the rails of the array, on individual boards or next to special components. Typically three fiducials are needed on an array and the ideal size is 0.050”.
This is an electrical test method of bare circuit boards. The flying probe machine uses several arms with probes on the end that work together to touch the test points on the circuit board to determine if there are any opens or shorts on the board.
FR-4 is fiberglass material that has a specific standard for flammability. It is the most common material used in the manufacturing of printed circuit boards.
A laser cut stencil that will be placed inside a universal frame. A frameless stencil will have holes cutout along the each edge of the stencil so that it can be attached to a universal frame.
Gold Fingers are gold plated connectors on an edge of the PCB. The hard gold plating allows for the PCB to be inserted into a connector without damaging the surface of the connections. An example would be a PCI card inserted into a PCI slot in PC.
In PCBs this is a conductive area of the board, often an entire layer, that is usually connected to the power supply ground of the circuit.
The temperature at which an amorphous polymer ( or the amorphous regions in a partially crystaline 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.
An orthogonal network of two sets of parallel, equidistant lines used for locating points on a printed circuit board.
Hard Gold is an electrolytic process and has hardeners in it for durability. It is plated over a nickel finish and may also be referred to as Deep Gold. (The term Deep Gold is used to indicate that full panels are placed in the plating tank prior to the application of soldermask.)
HASL, Hot Air Solder Level is a common finish type for PCBs. The PCB panel with exposed copper is lowered into a liquid bath of solder then quickly raised out of the bath and moved passed jets of hot air that clear off the excess solder leaving only the solder on the exposed copper areas.
Heating Sinking Plane
A continuous sheet of metal on or in a printed board that functions to dissipate heat away from heat sensitive components.
A condition in which a hole is not completely surrounded by the land.
Electrical impedance is the measure of the opposition (resistance) that a circuit presents to the passage of a current when a voltage is applied in an alternating current circuit.
Institute for Interconnecting an Packaging Electronic Circuits(IPC)
Primary industry governing body and often, the final authority on how to design and manufacture printed circuit boards.
A plating process that does not use electroplating to transfer various metals to the copper base of a PCB. Most commonly used to apply Gold or Silver in an immersion process.
A conductive pattern which is contained entirely within a multilayer printed board.
An electrical connection formed by wire between two points on a printed board added after the intended conductive pattern is formed.
Liquid Photo Imageable(LPI) Ink
LPI is an epoxy based ink that is applied to a PCB for solder mask or silkscreen through photographic imaging techniques. The PCB panel is covered in the ink then the image is exposed and developed. This method allows for a very precise thickness and accuracy for the solder mask application.
Refers to the fiberglass material used in a PCB. Typically in reference to a multi-layer circuit board.
Laser Photo Plotter
As opposed to a vector plotter, a laser plotter is able to produce very fine lines and dots to create a more accurate photo plot.
The process of preparing a laminate; also, any layer in a laminate.
A format of lettering or symbols on the printed board; i.e.,., part number, component locations, and patterns.
The technique of registering and stacking layers of multilayer board materials ( laminate and prepreg ) in preparation for the laminating cycle.
A Multi Layer PCB is a PCB that has more than two layers.
This is an unplated hole (meaning it will be non-conductive) that is used to secure the circuit board to its final assembly.
Part of the quality or inspection process will often require a Micro-Section of the circuit board. A small rectangular area of the board is punched out of the board in order to inspect the quality of the hole walls and plating. It allows for a look at the inner layers of the board to verify the overall process.
The lack of dimensional conformity between successively produced features or patterns.
The data file that defines the drill hole sizes, X & Y coordinates, and tool numbers for a circuit board. Also known as Excelon drill file,
List of names of symbols or parts and their connection points which are logically connected in each net of a circuit.
A Non-Plated hole is a hole that is drilled after the copper plating process so that there is no plating in the hole. Often used for mounting holes.
A NRE is any type of onetime costs related to the manufacturing of a printed circuit board. These costs will vary but could include Tooling or Engineering costs, electrical test etc.
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.
A land on internal or external layers, not connected to the conductive pattern on its layer.
Organic Surface Protectant(OSP)
OSP is an organic chemical finish that is applied to the copper. The shelf life is very short with OSP and the boards should be used very soon after applying the finish.
An open circuit is a break in the continuity of any given circuit on the board. This would be identified during the electrical test process which would result in a failed test.
The process to electroplate only select portions of a production PCB panel.
Used to print the patterns on the photo tools used to manufacture a PCB.
The condition of the fiberglass material used on multi-layer PCBs that is placed between the core layers of the board. It is still pliable and soft until it is heated and pressed in a lamination press. The heat causes the material to “flow” and then it will harden as it cools.
A Plated Hole is a drilled hole on a PCB panel that has completed a plating process to allow a copper connection with pads connected to the hole.
The force per unit width required to peel the conductor or foil from the base material.
An artwork master or production master in which the intended conductive patterns is opaque to light, and the areas intended to be free from conductive material are transparent.
Rout is the process of using a programmed rout machine to cut a PCB out of the manufacturing panel.
The reference designator is generated from the Gerber data to provided additional data when loading components on the printed circuit board. It defines the component and its placement on the board.
The melting of an electro-deposit followed by solidification. The surface has the appearance and physical characteristics of being hot-dipped.
The degree of conformity of the position of a pattern, or a portion thereof, with its intended position or with that of any other conductor layer of a board.
an inorganic substance of natural or synthetic origin which is polymeric in structure and predominantly amorphous.
A schematic is created as the first step of a PCB design. It includes graphic symbols of the electrical connections and functions of the circuit board.
Refers to a short circuit in the circuit board. A short could have been accidentally created in the design of the board or is a result of an error in the manufacturing process. An electrical test can be used to identify the short to prevent it from passing final inspection.
Also called Solder Cream, is used to solder a surface mount component lead to a corresponding land (pad) on a printed circuit board.
The solder side is the bottom side of the PCB.
Step and Repeat
The process of “stepping out” the individual boards in an array. Other terms used to describe an array are: panelized, stepped out, palletized and rout and retain.
A process for transferring an image to a surface by forcing suitable media through a stencil screen with a squeege. Also called Silk Screening.
The evaluation of a metal to determine its ability to be wetted by solder. Such evaluations include; the edge dip solderability test; the meniscus test; and the globule test.
Tab Rout is most commonly used when a single PCB is duplicated several times in an array. Tab Rout arrays will leave a small tab on all four sides of the board attached to the other boards or to rails.
There are a variety of tolerances in the printed circuit board manufacturing process. They are most often identified in a customer’s design files as + (plus) or – (minus) amount depending on the area and process of the board. For example the overall thickness of a circuit board is typically going to be a +/- 10% of the overall thickness. In this case a board requirement of .062” would still be within tolerance if the thickness was .068″.
Tooling holes are commonly used in four corners of the rails of a PCB array. They are used to aid in alignment and orientation when assembling the board. The typical size is .125” and they are non-plated.
TDR stands for Time Domain Reflectometer. When using Controlled Impedance in a PCB a TDR test is used to verify the specific impedance requirements as needed.
Twist references the flatness of a printed circuit board where not all four corners of the board are able to touch at the same time on a flat plane.
A printed board fabrication method of covering over plated through holes and the surrounding conductive pattern with a resist, usually dry film.
A portion of a printed circuit board or of a panel containing printed circuit coupons, used to determine the acceptability of such boards.
Polymerizing, hardening, or cross linking a low molecular weight resinous material in a wet coating or ink, using ultraviolet light as an energy source.
The reduction of conductor cross-section on a printed circuit board caused by etchant removal of conductive metal under the edge of the resist.
A plated-through hole used as a through connection, but in which there is not intention to insert a component lead or other reinforcing material.
A V-Score is a small grove that is cut into an array of PCBs so that after components are added they can easily be separated.
The formation of a relatively uniform, smooth, unbroken and adherent film of solder to a base material.
An X-Out occurs when on an array of PCBs a single board fails electrical test or final inspection and are “X’ed out” with a marker to designate that they are not to be used. Some customers or end users specify a percentage of X-Outs allowed while others require that there be no X-Outs in an array. This should be specified when quoting the PCBs because additional costs may be incurred.
The x-Axis is the horizontal (left and right) axis of a two-dimensional plot.
The Y-Axis is the vertical (up and down) axis of a two-dimensional plot.
Where the xy-plane is horizontal then Z-axis would point up from the point where x and y meet.
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