Virtual Exhibition

Glossary

 

A B C D E F G H I J K L M N O P Q R S T U V W

 
 А

ACAS, Automatic components assembly system

An automated system for mounting of electronic components

 

ACCEL, Automatic Circuit Card Etching Layout

An automated wiring of printed circuit boards, brand name of CAD and manufacturing company.

 

Accordion

A method of wire routing in a form of meander (Fig. 1). It is used to align lengths of the wires by increasing of their lengths and wave resistances. It is characterized by amplitude and gap between fragments of the meander (a term of SPECCTRA system).


B

Balanced daisy chain topology (a term of SPECCTRA system)

A method of net routing where each net has at least one start lead or source and two or more end leads or receivers (Terminators). In this case, the sources (if more than one) are connected in a single net by a chain which then is splitted into several branches extending to the receivers, in contrast to daisy chain technique where total length of wires connecting pairs of leads is minimized, and each lead can not belong to more than two segments of the net. This topology allows to balance load on source leads and to facilitate routing of nets combining benefits of Daisy and Chain topologies. As a rule, the sources are leads of the chips and the receivers are their inputs.

 

BBB, basic building block

A basic building block.

 

BGA, ball grid array

A ball lead array package.

 

Bill of Materials

A list of used materials and components, specification.

 

Blind vias

Blind vias

 

 

C

Capacitors

In SPECCTRA system it means a filter (blocking) capacitor for power nets (decoupling capacitor). The blocking capacitor may be connected to component whose power nets it filters (see large components, small components, associate components). When placing components in automatic mode, SPECCTRA system is seeking to position it as close as possible to power leads of the components (a term of SPECCTRA system).

 

Checkpoint file

A file of routing results saved after completion of each pass of autorouter (a term of ACCEL EDA).

 

Cerdip

A glass-ceramic package with dual-in-line leads.

 

Circuit

A circuit is an aggregate of nets and net segments connecting the adjacent leads (fromto) for which electric restrictions are defined (a term of SPECCTRA system).

 

D

Daisy

A routing rule of daisy (star) type at which net has only one source lead and several receiver leads, and T-shaped wiring (T-routing) is not allowed if max_stub rule is not defined (a term of SPECCTRA system).

 

Daisy chain

A net routing method at which component leads are connected so that length of the connections between pairs of leads is minimized, and each lead belongs to not more than two segments of the net.

 

Deposit Height, height of deposition

An average height of material deposited on PCB (solder paste or glue).

 

Design file

A text file used as input file of autorouter. A project file defines size of PCB, components, net list, project routing rules, pre-laid routes, definitions of vias and contact pads (a term of SPECCTRA system).

 

 

E

ECO, engineering change ordering

A mechanism of making changes to a project.

 

EDA, electronic design automation

CAD of electronic devices

 

Electroformed Stencils

Stencils made by electroforming. Stencils made by electroforming are produced from nickel and have wedge-shaped (trapezoidal) walls of apertures for improvement of paste transmission ability. Such stencils are produced without "lugs" on the side contacting with PCB. Thereby stencil "laying" effect is improved that reduces the need in frequent cleaning of bottom of the stencil and prevents leakage of solder paste under its bottom. In case of stencils made by electroforming, a little force for applying of solder paste is required. Owing to these excellent solder paste transmission characteristics, these stencils are typically used in products with a linear printing step (water injection).

 

Electropolishing

A process of reverse coating eliminating minor irregularities from inner walls of apertures and soot deposit from the stencil base causing that its surface becomes shiny.

 

Escape wires

A short length of wire between planar contact pad and via, the same as Fanout or Stringer.

 

 
 

F

Fanout

A short length of wire with a via at the end, designed to simplify automatic routing of components with planar leads. It is similar to term "stringer". Usually, automatic routing program automatically generates stringers for all planar contact pads at initial stages of the routing, and after its completion removes extra vias.

 

Fence

A routing prohibition area, virtually the same as Keepout (see Hard Fence and Soft Fence) (a term of SPECCTRA system).

 

Fiducial, calibration point

A tag introduced into stencil design, etched next to apertures. It is used by automated vision systems for alignment of stencil with respect to PCB, control of its orientation and location of image deposited. Calibration points may be completely or partially etched, and placed on lower or upper sides of the stencil. Sometimes calibration points are filled by black epoxy mass to increase contrast between the stencil and the calibration point for the automated vision systems. "Common" calibration points are located at an outer boundary of print area, while local points - as close as possible to the image, normally close to chips.

 

File Layer

Describes PCB layer comprising Gerber data. A layer describing overlay of solder paste is 1:1 reflection of contact pads on PCB.

 
 

G

Gap

A distance between parallel or tandem (parallel on adjacent layers) wires (a term of SPECCTRA system).

 

Gap (differential pair and bundle)

A distance between wires in a pair (bridge). Autorouter provides a support for this gap (a term of SPECCTRA system).

 

Gasketing, laying effect

An extent to which stencil aperture contacts with contact pad and seals it from leakage of solder paste. Good fit of the stencil reduces effect of solder balls' formation during the printing.

 

Gate

A logical section which under certain conditions (logical equivalence) can be rearranged to optimize net routing on the board.

 

Gerber Data

A standardized language for PCB design and set of operating commands that uniquely determine slope and position of apertures in the base of stencil.

 
 

H

Hard fence

A hard routing barrier where all connections are made within the prohibition area without any penetration to the outside (a term of SPECCTRA system).

 

Hatching

A polygon hatching. Reduces time of photostencil execution on photoplotter and improves adhesion of solder mask with PCB.

 

Heterogeneous component

Heterogeneous components comprising gates (logical sections) of different types.

 

Highlight

A color highlighting of PCB element in CAD.

 

Histogramm

A histogram of link densities destined for visual evaluation of possibility of board routing under chosen coordinate grid.

 

 

I

Image

An image of a component, typical package including a unique name and definition of leads. In addition, component image may include image of dimensions of the component, side of installation of the component on PCB, rotation angle and routing barriers relating to the component (cf. Physical Part) (a term of SPECCTRA system).

 

Initial autorouting phase

An initial stage of the autorouter consisting of the first five routing passes. The purpose of the initial stage routing is to create wires for all links not paying much attention to conflicts (a term of SPECCTRA system).

 

Initial via grid

An initial grid of vias (a term of SPECCTRA system).

 

 

J

Jumper layer

An imaginary layer on which jumpers are assigned (a term of SPECCTRA system).

 
 

K

Keepouts

Routing barriers.

 

KPCR, Kodac printed circuit resist

Kodak photoresist for manufacturing of printed circuit boards.
 
 

L

Land, contact pad

A conductive portion of PCB on which individual components or chips are fastened.

 

Large components

Large components in SPECCTRA are defined as components with more than three leads or components with three leads or less for which a high type priority was assigned (cf. Small components) (a term of SPECCTRA system).

 

Layer

A layer. Represents a set of objects denoted with the same color and having certain common properties (for example, a layer of PCB wires, a layer of component mounting seat graphics, and so on).

 

Layout

A figure of PCB wires.

 

Leading Edge

PCB edge which first enters a printer or positioned along an assembly line's travel.

 

Lee algorithm

Lee automatic routing algorithm.

 

Library

CAD component library.

 

Line spacing

A distance (gap) between PCB wires.

 

Line width

Printed wire width.

 

Locked component

A locked component that can not be moved during automatic placement in SPECCTRA program. Unlike Fixed component, a connection may be laid to the locked component.

 

Logical part

A mounting seat (package) of a component for which a description of individual logic gates is defined (a term of SPECCTRA system).

 
 

M

Manhattan length

A distance between two points defined as the sum of the legs between them. The term is derived from calculation of distances under taxi traveling in Manhattan which is known to have strict quarterly layout. This term is commonly used in PCB CAD and, in fact, refers to the actual length of wires between two points.

 

Manual routing

A manual routing of PCB.

 

Manufacturing

An optimization of automatic routing results for improvement of PCB appearance and manufacturability consisting in sharp edge mitering, removal of unnecessary segments of wires, minimization of number of vias.

 

Memory routing

A routing of memory type connections.

 

Mid-driven daisy chain topology

A method of net routing wherein sources connected in a chain are in the center of the net, and two receivers (Terminators) are at its ends as shown in Fig. 5 (a term of SPECCTRA system).

 

 
 

N

Net

A net.

 

Net class

A net class for which routing rules may be defined.

 

Netlist

A project net list which is the base for component placement and PCB routing.

 

Non-signal layers

PCB non-signal layers carrying service information.

 

Nonuniform grig

A nonuniform grid under which various distances between nodes are used thereby enabling increase of the number of channels available for routing. However, it is not recommended to use nonuniform grid under placing of components.

 
 

O

On-Contact Printing

A contact printing. Stencil is in direct contact with PCB during the print cycle.

 

Off-Contact Printing

An off-contact printing. Stencil is slightly raised above PCB and is not it in direct contact with it during the print cycle.

 

Off-grid items

PCB items located outside of routing grid.

 
 

P

Pad

A contact pad.

 

Padstack

A contact pad stack that contains information about contact pad shape and apertures of photoplotter exposure in various layers.

 

Pad style

A contact pad style.

 

 
  

Q

QFP, quad flat pack

A flat package with quadruple layout of leads.

 

 
 

R

Ratsnet (literally, "rat hole")

An electrical connection between leads showed by straight line in CAD indicating presence of connection between leads.

 

Reference designator

A position notation of component.

 

Region

A term of SPECCTRA system indicating a rectangular area on PCB where net routing rules are defined. It is close in meaning to term "room" in ACCEL EDA.

 

Resistors

Any component that should be handled separately from the rest.

 

Rip-up

An autorouting algorithm with breaking of drawn connections and redrawing of the topology.

 
 

S

Seedvia

A splitting of diagonal connection of two orthogonal segment with addition of via. Provides an increase of the number of free routing channels (a term of SPECCTRA system).

 

Shape

Shape, a basic concept of PCB CAD. Includes circles, arcs, polygons, rectangles, etc.

 

Shielding

A shielding of sensitive signal circuits using wire loops connected with earth (a term of SPECCTRA system).

 
 

T

Tandem

Wires being parallel in different layers (a term of SPECCTRA system).

 

Tandem segment crosstalk rules

Rules of SPECCTRA system for assessment of mutual interference in wires laid in parallel layers.

 

Teadrop

A teardrop smoothing of transition when connecting wire to round contact pad. Improves PCB manufacturability reducing possibility of undercut etching.

 

Terminal

A point to which wire may be attached, for example, contact pad, via, T-junction, pseudo-pin, polygon associated with net (wiring polygon) (a term of SPECCTRA system).

 
 

U

Uniform grid

A regular grid with equal distances between the nodes.

 
 

V

Verification

A verification (validation) of implementation of circuit diagram and technological norms under PCB design.

 

Vertex

A breaking point (corner point) of a printed wire or line.

 

Via

A by-pass orifice.

 
 

W

Wire

A conductor.

 

Wire grid

A grid for placement of printed wires.

 

Wiring polygon

A metallized polygon connected to a net.