Glossary of PCB from M-P

Manhattan length —The length of the two sides of a right triangle as a distance between two points, as opposed to the hypotenuse.. (Derived from the Manhattan Alogorithm for determining the length of a taxicab trip following streets and avenues on the island of Manhattan, NY.)  Routing of traces in orthagonal patterns in a PCB design, or in a semiconductor chip, follows the same pattern as streets and avenues in a city.  The minimum distance between two component leads, or two nodes on a chip, when routing on 90 degrees is the Manhattan length .

 Advanced PCB auto-routers permit specification of maximum length of classes of nets as a percentage of Manhattan length . For example, one could specify clocks as 120% and random nets as 160% of Manhattan length . (This percentage, expressed as a ratio, becomes the "Manhattan coefficient", ie. a Manhattan coefficient of 1.2 means the routed length is 120% of the Manhatten length .) Specifying such limits on the auto-router prevents long and circuitous routes.

Master aperture list —1. An aperture list which is used for every PCB designed by a PCB design service bureau or department.  If a new design requires one or more new apertures, they are added to the list, either at the end or in some previously unused positioned set aside for that purpose. The previously used aperture positions are never edited to change their parameters. Thus the updated list can still be used as a master for any previous PCB's designed. This type of master aperture list became possible only with the advent of laser phottoplotter, which can have upwards of 1000 positions if need be.  2. Any aperture list which is used with two or more PCB's would be called the master aperture list for that set of PCB's.

MCR —Molded Carrier Ring. A type of fine-pitch chip package named for the method of supporting and protecting the leads. The leads are left straight; the ends of the leads are embedded in a strip of plastic, which is the Molded Carrier Ring. Just before assembly (placing on a PCB for soldering), the MCR is cut off and the leads are formed. In this way, the delicate leads are protected against damage in handling until just before assembly.

MELF —Metal ELectrical Face - A surface mount discrete part, usually a diode, that is barrel shaped, or cylindrical. The ends of the "barrel" are capped with metal, the "metal electrical face." The "barrel" is laid on its side, the metal ends upon landing pads, and the part is soldered that way. The two most common sizes are MLL34 and MLL41, which are roughly MELF versions of a DO-35 and DO-41 respectively.

MIC — Monolithic Integrated Circuit.

Micro ball grid array —A fine pitch ball grid array. Fine pitch for BGAs is anything less than 1.27 mm [50 mil] (some say 1.00 mm [39 mil]). 

Mil —One thousandth of an inch (0.0254 mm). [From abbreviation of mil li-inch, which means one-thousandth of an inch.]

MLC —Multi-Layer Ceramic

Monolithic —1.  Existing as one large, undifferentiated whole.  2.  (of an integrated circuit or its elements) built upon or formed within a single slice of silicon substrate.

Monolithic integrated circuit —1.  Abbreviated MIC. An integrated circuit formed upon or within a semiconductor substrate with at least one of the circuit elements formed within the substrate.    2.  A complete electronic circuit fabricated as an inseparable assembly of circuit elements in a single small structure. It cannot be divided without permanently destroying its intended electronic function. 

  

MTF —Multi-layer Thin film.

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

   

NC drill —Numeric Controlled (computer controlled) drill machine. A machine used to drill the holes in a printed board at exact locations, which are specified in a data file. Also known as "CNC drill."

NC drill file —A text file which tells an NC drill where to drill its holes.

negative 1. n . A reverse-image contact copy of a positive, useful for checking revisions of a PCB. If the negative of the current version is superimposed over a positive of an earlier version, all areas will be solid black except where changes have been made. 2. adj . (Of a PCB image) Representing copper (or other material) as clear areas and absence of material as black areas. Typical of power and ground planes and solder mask.

NEMA — National Electrical Manufacturer Association.

Net —A collection of terminals all of which are, or must be, connected to each other electrically. Also known as a signal.

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.

Node — A pin or lead which will have at least one wire connected to it. In a netlist, a node is described by a component reference desginator together with a pin number.

     

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

   

Package —1) Decal or PCB component.  2) A type of PCB component which contains a chip and acts to make a convenient mechanism for protecting the chip while on the shelf and after attachment to a PCB. With its leads soldered to a printed circuit board, a package serves as the electrical conduction interface between the chip and the board. An example is a DIP.

Panel —material (most commonly an glass/epoxy-copper laminate known as core) sized for fabrication of printed circuit boards. Panels come in many, many sizes, the most common being 12" by 18" and 18" by 24". Subtract 1/2" to 1" margins (check with your board house) from the panel size to arrive at the space available for printed circuitry.

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.

Part —1. Component. 2. A decal in a PWB database or drawing. 3. A symbol in a schematic.

Passive component —A device which does not add energy to the signal it passes. Examples: resistor, capacitor, inductor. 

PCB design —1. The creation of artwork for the manufacture of bare PCB's. 2. The artwork so created. 3. A computer database used to generate such artwork as data files ( CAM files). Also called PCB layout.

     

Photoplotter —Device used to generate artwork photographically by plotting objects (as opposed to copying an entire image at once as with a camera) onto film for use in manufacturing printed wiring.

Pin —1.  A terminal on a through-hole component. [Derived from its physical shape on through-hole components, which predated SMT.] Also called lead. 2. In the term "pin count,"pin refers to a terminal on any component, whether through-hole or SMT.

Pin-out —Pin-number assignment, the relation between the logical inputs and outputs of an electronic device and their physical counterparts in the PCB package. pin-outs will involve pin numbers as a link between schematic and PCB design (both being computer generated files). In more complicated packages, they may also involve pin names. Even for devices with only two pins and no polarity, such as resistors, the netlist extracted from a schematic will have a pin 1 and pin 2 for each resistor, even though the schematic might not show a pin number label as such. (The visibility in the schematic of the pin numbers can be turned on or off at will, but the significance of the pin number assignment is still there in the schematic and subsequently, through the netlist extracted from it, the PCB database.) For CAD CAE electronics to work at all, the pin-outs for the PCB database must agree with the schematic.

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

Plated-through hole —A hole in a PWB with metal plating added after it is drilled. Its purpose it to serve either as a contact point for a through-hole component or as a via.  In PCB vernacular and documentation, the spelling of the word through is sometimes shortened to thru.

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

Populate —Install (place, attach and solder) components onto PCB. This can refer to a single component, as in the acronym used in schematics "DNP", which means "Do Not Populate".

Position —A type of index for an aperture in an aperture list which is a number from 1 to the number of apertures in the aperture list. Position 1 is linked to D code D10, 2 is D11 and so on. Positions appear only in aperture lists, and never in a Gerber file.  Cadstar aperture lists use the column heading Position to mean D code.  Abbreviated "Pos" in GC-Prevue.

Positive — noun A developed image of photoplotted film, where the areas selectively exposed by the photo plotter appear black, and unexposed areas are clear. Board houses work from positives, and a photo plotter produces positives, thus one set of positives is all the film that is needed to produce a Printed wiring Board. modifier (of a printed wiring image) Representing copper as black areas and absence of copper as clear areas. Typical of images of routed layers of a PWB.

PQFP —Plastic Quad Flat Pack. 

Printed circuit board —

1.      A flat plate or base of insulating material containing a pattern of conducting material and components placed and soldered to it. It is an electrical circuit. It is a "Printed wiring Board" (PWB) that has been "stuffed." 

The conducting material is commonly copper which has been coated with solder or plated with tin or tin-lead alloy. The usual insulating material is epoxy laminate. But there are many other kinds of materials used in more exotic technologies. 

Single-sided boards, the most common style in mass-produced consumer electronic products, have all conductors on one side of the board. With two-sided boards, the conductors, or copper traces, can travel from one side of the board to the other through plated-thru holes called vias, or feed-throughs. In multilayer boards, the vias can connect to internal layers as well as either side.

2.      A PCB without the components, a "bare board" or a Printed wiring Board.

PWA —Printed Wiring Assembly.

PWB —Printed Wiring Board; a "bare board"; an unstuffed PCB. It is flat plate or base of insulating material containing a pattern of conducting material. It is not an electrical circuit until components are placed and soldered to it.

The acronynm PWB, followed by a part number, is commonly included in clad, sometimes in both clad and silkscreen, on a PWB

In this Article I have tried to explain the words from M to P. I am sure it will be helpful for the readers..

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