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A
Analog Circuit
A circuit in
which the output varies
as a continuous function of the input, as contrasted
with digital circuit.
Assembly Drawing
A drawing
depicting the locations of
components, with their reference designators (q.v.), on a
printed circuit.
Assembly House
A manufacturing
facility for attaching
and soldering components to a printed circuit.
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B
Board printed
circuit board. Also, a CAD database which
represents the layout of a printed circuit.
Board house Board vendor. A manufacturer of printed
circuit boards.
Body The
portion of an electronic component exclusive
of its pins or leads.
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C
CAD Computer
Aided Design. A system where engineers create a design and see
the proposed product in front of them on a graphics screen or
in the form of a computer printout or plot.
In electronics, the result would be a printed circuit layout.
CAE Computer
Assisted Engineering. In electronics work,
CAE refers to schematic software packages.
CAM Computer
Aided Manufacturing. (See CAM files)
CAM files CAM means Computer Aided Manufacturing.
These are the data files used directly in the manufacture of
printed wiring. . The types of CAM files are 1) Gerber
file,
which controls a photoplotter, 2) NC Drill file, which controls
an
NC Drill machine and 3) fab and assembly drawings in soft form
(pen-plotter files). CAM files represent the valuable final
product of PCB design. They are handed off to the board house
which further refines and manipulates CAM data in their processes,
for example in step- and-repeat panelization. Some PCB design
software companies refer to all plotter or printer files as
CAM files , although some of the plots may be check plots
which are not used in manufacture.
Card Another
name for a printed circuit board.
Card-edge Connector A connector
which is fabricated as an integral portion of a printed circuit
board along part of its edge. Often employed to enable a daughter
or add-on card to be plugged directly into another much larger
printed board, the motherboard or backplane. See finger .
Capture Extract information automatically through the
use of software, as opposed to hand-entering of data into a
computer file.
Check Plots Pen 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.
Chip On Board In this technology integrated circuits
are glued and wire-bonded directly to printed circuit boards
instead of first being packaged. The electronics for many mass-produced
toys are embedded by this system, which can be identified by
the black glob of plastic sitting on the board. Underneath that
glob (technical term: glob top ), is a chip with fine wires
bonded to both it and the landing pads on the board.
Clad A
copper object on a printed circuit board. Specifying certain
text items for a board to be "in clad" means that
the text should be made of copper, not silk-screen .
Component Any of the basic parts used in building electronic
equipment, such as a resistor, capacitor, DIP or connector,
etc.
Component Library A representation
of components as decals, stored in a computer data file which
can be accessed by a PCB CAD program.
Connection One leg of a net . Also called a "pin
pair."
Connectivity The intelligence inherent in PCB
CAD software which maintains the correct connections between
pins of components as defined by the schematic.
Connector A plug or receptacle which can be easily joined
to or separated from its mate. Multiple-contact connectors join
two or more conductors with others in one mechanical assembly.
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D
Database A collection of interrelated data items stored
together without unnecessary redundancy, to serve one or
more applications.
Decal A
graphic software representation of a component, so named because
hand tape-up of printed circuit boards employed the use of pull-off
and paste decals to represent components. Also called a part,
footprint or package . On a the manufactured board the body
is an epoxy-ink outline.
Digital Circuit A circuit which operates like a switch
(it is either "on" or "off"), and can make
logical decisions. It is used in computers or similar decision
making equipment.
DIP Abbreviation
for dual in-line package. A type of housing for integrated circuits.
The standard form is a molded plastic container of varying lengths
and 0.3 inch wide, with two rows of pins space 0.1 inch between
centers of adjacent pins.
DOS Disk
Operating System. A program that controls the computer 's transfer
of data to and from a hard or floppy disk. Personal computers
that are IBM-compatible run DOS rather than other early varieties
of operating systems.
DOS-Formatted (Of magnetic data storage media,
such as floppy disks.) Prepared for storage of data in such
a way that DOS transfer can occur.
Double-track Slang for fine line design with
two traces between DIP pins.
Dry film solder mask
A solder
mask film applied to a printed board with photographic methods.
This method can manage the higher resolution required for fine
line design and surface mount. It is more expensive than liquid
photoimageable solder mask.
DUT Device
Under Test. A DUT board is used in automated testing of integrated
circuits. It is part of the interface between the chip and a
test head, which in turn attaches to computerized test equipment.
The specific test equipment used will determine the value of
the controlled impedance required for the chip tester boards.
Depending on which system it is designed for, one type of DUT
board is used in testing individual chips in a silicon wafer
before they are cut free and packaged, and another type is used
for testing packaged IC 's.
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E
ECL Emitter
Coupled Logic. Higher speeds may be achieved with ECL than are
obtainable with standard logic circuits.
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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. It relates the board edge to at least on hole location
as a reference point so that the NC Drill
file can be properly lined up.
Fine Line Design Printed circuit design permitting
two (rarely three) traces between adjacent dip pins. It entails
the use of a either dry film solder mask or liquid photoimageable
solder mask (LPI), both of which are more accurate than wet
solder mask.
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 0.5mm (0.020")
are used.
Finger A gold-plated terminal of a card-edge connector.
[Derived from its shape.]
Footprint 1. The pattern and space on a board taken up
by a component. 2. Decal .
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G
Gerber File Data file used to control a photoplotter.
Named after Gerber Scientific Co., who made the original
vector photoplotter .
Glob Top A blob of non-conductive plastic, often black
in color, which protects the chip and wire bonds on a packaged
IC and also on a chip on board . This specialized plastic has
a low coefficient of thermal expansion so that ambient temperature
changes will not rip loose the wire bonds it is designed to
protect. In high-volume chip on board production, these are
deposited by automated machinery and are round. In prototype
work, they are deposited by hand and can be custom-shaped; however,
in designing for manufacturability, one assumes a prototype
product will "take- off" and ultimately have high
market demand, and so lays out chip on board to accommodate
a round glob top with adequate tolerance for machine-driven
"slop-over".
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H
Header The portion of a connector assemble which is
mounted on a printed circuit.
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I
IC Integrated
Circuit.
IPC The
Institute for Interconnecting and Packaging Electronic Circuits,
the final American authority on how to design and manufacture
printed wiring. In 1999, IPC changed its name from Institute
of Interconnecting and Packaging Electronic Circuits to IPC.
The new name is accompanied with an identity statement, Association
Connecting Electronics Industries.
(IPC Home Page)
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J
K
L
Laser Photoplotter (also "laser
plotter")
A photoplotter which simulates a vector photoplotter by using
software to create a raster image of the individual objects
in a CAD database, then plotting the image as a series of lines
of dots at very fine resolution. A laser photoplotter is
capable of more accurate and consistent plots than a vector
photoplotter.
Lead (pronounced "leed")
A terminal
on a component.
Liquid Photoimageable Solder
Mask (LPI) A
mask sprayed on using photographic imaging techniques to control
deposition. It is the most accurate method of mask application
and results in a thinner mask than dry film solder mask. It
is often preferred for dense SMT.
LPI stands
for Liquid PhotoImageable. Refers to liquid photoimageable solder
mask.
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M
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.
Mil One
thousandth of an inch.
MultiMate A portable test instrument which can be used
to measure voltage, current, and resistance.
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N
NC Drill Numeric Control drill machine. A machine used
to drill the holes in a printed board at exact locations, which
are specified in a data file.
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.
Net A
collection of terminals all of which are, or must be, connected
electrically. Also known as a signal.
Netlist List of names of symbols or parts and their
connections points which are logically connected in each net
of a circuit.
A netlist can be captured from properly prepared schematic-drawing
files of an electrical CAE application.
Node A
pin or lead which will have at least one wire
connected to it.
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O
open Open
circuit. An unwanted break in the continuity of an electrical
circuit which prevents current from flowing.
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P
Package 1) Decal or printed wiring board 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 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 epoxy-copper laminate known as FR-4) sized
for fabrication of printed circuit boards. The most common panel
size is 12" by 18", of which 11" by 17"
is 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.
PCB Printed
circuit board.
PCB Database All of the data fundamental to a
PCB design, stored as one or more files on a computer.
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 A
terminal on a component, whether SMT or through-hole. [Derived
from its physical shape on through-hole components, which predated
SMT.] Also called lead.
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.
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.
Positive n. 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. adj. (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. See QFP.
Printed Circuit Board
A flat plate
or base of insulating material containing a pattern of conducting
material. It becomes an electrical circuit when components are
attached and soldered to it.
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.
PWB Printed
Wiring Board; same as PCB.
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Q
QFP Quad
Flat Pack, a fine-pitch SMT package that is rectangular or square
with gull-wing shaped leads on all four sides. The lead pitch
of a QFP is typically either 0.8mm or 0.65mm, although
there are variations on this theme with smaller lead pitches:
TQFP also 0.8mm; PQFP tooled at either 0.65mm (0.026")
or 0.025" and SQFP at 0.5mm (0.020"). Any of these
packages can have a wide variety of lead counts from 44 leads
on up to 240 or more. Although these terms are descriptive,
there are no industry- wide standards for sizes. Any printed
circuit designer will need a spec sheet for the particular manufacturer's
part, as a brief description like "PQFP-160" is inadequate
to define the mechanical size and lead pitch of the part.
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R
Ratsnest A bunch of straight lines (unrouted connections)
between pins which represents graphically the connectivity of
a PCB CAD database. [Derived from the pattern of the lines:
as they crisscross the board, the lines form a seemingly haphazard
and confusing mess similar to a rat 's nest.)
Reference Designator (abbrv. "ref
des") The
name of component on a printed circuit by convention beginning
with one or two letters followed by a numeric value. The
letter designates the class of component; e.g.. "Q"
is commonly used as a prefix for transistors. Reference
designators appear as usually white or yellow epoxy ink (the
"silk-screen") on a circuit board. They are placed
close to their respective components but not underneath them,
so that they are visible on the assembled board. By contrast,
on an assembly drawing a reference designator is often placed
within the boundaries of a footprint — a very useful technique
for eliminating ambiguity on a crowded board where reference
designators in the silk-screen may be near more than one component.
Register In printed board manufacture, many terms are
borrowed from the subject of printing. Register
has the following specialized printing definition from
Macmillan Dictionary for Students:
(noun)
proper alignment of various plates, stones, or screens to
assure clear and accurate reproduction, as of color. Examples:
in register, off register.
In
printed circuit design, the designer gets his photoplot files
in register before he views them with his Gerber file
viewer. The board manufacturer produces film from the
Gerber files and uses them in register with respect to
the panels of material from which he will build the boards.
He is going to want the pads on both sides and on internal
layers to be in register before he drills holes in the
panel. [Usage note: The term registration is sometimes
used mistakenly for this sense of the noun register.
Register, already being a noun, doesn't need the suffice -tion
added to it to make it a noun. You wouldn't say, "Count
the money in the cash registration."]
Registration See register .
RF Radio
Frequency.
Route 1.
n. A layout or wiring of a connection. 2. v. The action of creating
such a wiring.
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S
Schematic A diagram which shows, by means of graphic
symbols, the electrical connections and functions of a specific
circuit arrangement.
Short Short
circuit. 1. An abnormal connection of relatively low resistance
between two points of a circuit. The result is excess (often
damaging) current between these points. Such a connection is
considered to have occurred in a printed wiring CAD database
or artwork anytime conductors from different nets either touch
or come closer than the minimum spacing allowed for the design
rules being use.
Signal 1. A net. 2. A net other than a power or ground
net.
Silicon Wafer A thin, iridescent, silvery disk
of silicon which contains a set of integrated circuits, prior
to their being cut free and packaged. A silicon wafer will diffract
reflected light into rainbow patterns and, being a similar size,
looks so much like a music CD that it could be mistaken for
one (except that it has no label or hole in the middle). On
closer inspection, one could see the individual integrated circuits,
which form a uniform patchwork quite unlike the surface of a
music CD.
Silk-screen (Also called "silk-screen legend")
1. The decals and reference designators in epoxy ink on a printed
wiring board, so called because of the method of application—the
ink is "squeegeed" through a silk screen, the same
technique used in the printing of T-shirts.
The silk mesh size commonly used is 6 mils. Thus,
the absolute minimum line width of any silk-screen legend artwork
is 6 mils, which leaves a very faint line. 7 mils works better
for a practical minimum line width.
2. A Gerber file controlling the photoplotting of this legend.
Single Track PCB design with only one route between
adjacent DIP pins.
SMD Surface
Mount Device.
SMT Surface
Mount Technology.
Soft Pertaining
to or consisting of software.
Software Programs, data files, procedures, rules, and
any associated documentation pertaining to the operation of
a computer system or of a computer application.
Solder Mask A technique wherein everything on a circuit
board is coated with a plastic except 1) the contacts to be
soldered, 2) the gold-plated terminals of any card-edge connectors
and 3)fiducial marks.
SQFP Shrink
Quad Flat Pack. See QFP .
Stuff Attach
and solder components to (a printed wiring board).
Sub-panel A group of printed circuits (called modules)
arrayed in a panel and handled by both the board house and the
assembly house as though it were a single printed wiring board.
The sub-panel is usually prepared at the board house by routing
most of the material separating individual modules, leaving
small tabs. The tabs are strong enough so that the sub-panel
can be assembled as a unit, and weak enough so that final separation
of assembled modules is easily done.
Surface Mount Surface mount technology. The technology
of creating printed wiring wherein components are soldered to
the board without using holes. The result is higher component
density, allowing smaller PWB 's. Abbreviated SMT.
Symbol A simplified design representing a part in
a schematic circuit diagram.
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T
TAB Tape
Automated Bonding.
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.
TDR Time
Domain Reflectometer, a device which a board house can use for
measuring characteristic impedance of a conductor on a printed
board, thus insuring an accurate build for controlled impedance.
Terminal A point of connection for two or more conductors
in an electrical circuit; one of the conductors is usually an
electrical contact or lead of a component.
Test Coupon An area of patterns on the same
fabrication panel as the PWB, but separate from the electrical
circuits and outside the actual board outline. It is cut away
from the printed wiring board prior to assembly and soldering
of components.
It can be used for destructive testing.
Through-hole (Of a component, also spelled
"thru-hole"). Having pins designed to be inserted
into holes and soldered to pads on a printed board. Contrast
with surface mount .
Thru-hole Same as through-hole.
TQFP Thin
Quad Flat Pack. Essentially the same as a QFP except low-profile,
that is, thinner.
Trace Segment of a route .
Track Trace .
Trillium A company that makes DUT systems.
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U
UL Underwriter's
Laboratories, Inc., a corporation supported by some underwriters
for the purpose of establishing safety standards on types of
equipment or components.
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V
Vector Photoplotter (also
"vector plotter", or "Gerber photoplotter"
after Gerber Scientific Co., which built the first vector photoplotters
for commercial use) It plots a CAD database on photographic
film in a darkroom by drawing each line with a continuous lamp
shined through an annular-ring aperture, and creating each pad
by flashing the lamp through a specially sized and shaped aperture.
The "apertures" are thin trapezoidal pieces of plastic
which are mostly opaque, but with a transparent portion that
controls the size and shape of the light pattern. The apertures
are mounted on an "aperture wheel" which can hold
up to 24 apertures. Gerber photoplotters, if set up by
an experienced craftsman, are well-suited for printed circuit
artwork generation. Compare with laser photoplotter , which
is faster and has largely replaced the vector photoplotter.
There are still vector photoplotters in use. Some
manufacturers take advantage of the large bed size of the largest
Gerber photoplotters, roughly the size of a full-sized billiards
table. This enables the production of very large photoplots.
An example is Buckbee-Mears, which makes large antenna boards,
and the USGS (United States Geological Survey) which has used
them in map-making.
Via Feed-through.
A plated-through hole in a PWB used to route a trace vertically
in the board, that is, from one layer to another.
VLSI Very
Large Scale Integration.
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W
X Y Z
Wet Solder Mask Applied by means of distributing
wet epoxy ink through a silk screen, a wet solder mask has a
resolution suitable for single-track design, but is not accurate
enough for fine-line design.
Wire Besides
its usual definition of a strand of conductor, wire on a printed
board also means a route or track .
Wire Wrap Area A portion of a board riddled
with plated-through holes on a 100-mil grid. Its purpose is
for accepting circuits which may be found necessary after a
PWB has been manufactured, stuffed, tested and debugged.
Top Number of terms
defined: 109
For hard-to-find words related
to PCB Design and Manufacturing, please email us,
info@accucircuits.com,
and We will respond promptly with the term defined and update
this glossary as well. Some of the terms used in electronics
and printed circuitry are defined adequately in a common desk
dictionary, and so would not be included in this glossary. I
recommend the Macmillan Dictionary for Students , William
D. Halsey/ Editorial Director; Macmillan Publishing Company,
New York and Collier Macmillan Publishers, London. It is that
dictionary We have used to determine whether or not to include
any particular term in this glossary. So please check a good
dictionary before requesting a term be defined herein.
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