EE CAD Terminology


General EE CAD terminology

' Kicad centric

back-drilled via
back-drilled via is a normal through-hole via in a PCB that connects two signal layers, but the dangling stub hanging down from the last signal layer to the bottom of the board has literally been drilled out. A drill bit with a diameter a few mils larger than the drilled and plated hole drills a "blind" via to within a few mils of the lowest signal layer. This removes the copper stub and prevents a potentially disastrous resonance in the 5 to 10 GHz range. All high-performance backplanes use back-drilled vias.
Component

An object which can be placed into a design. Examples : a Resistor, Capacitor or chip.

Copper
Connections between pads on a PCB. What makes up what is normally called tracks, routes, or traces.
ECO
ECO stands for Engineering Change Order and refers to design changes to circuits after they have been wholely or partially completed. ECOs document the approval of changes that correct design errors or changes of part type sometimes made due to part availability. The term ECO has come to mean the process of making a change to a design - not only the paper work involved. It also can mean a file type that contains information to make the change in a schematic or layout.
There are two kinds of ECOs referred to in EE CAD systems: Forward and backward
Good design practice often uses revision numbers in a decimal form '2.3' - the major number (2) refers to the revision of circuit board and the minor number (3) would be the changes in the schematic and parts list. (Some minor revisions are made to the circuit board in the form of cut traces and tacked on jumpers). By renaming the schematic and circuit board file after every change, one has a history to look at. ECOs would also have text file explaining the what and why things were changed and sometimes someone signs off on approving the changes. (This keeps purchasing from replacing a 10uf/10V tantalum with a 10uf/6V tantalum!)
Fields 
Fields AKA part attributes in other CAD packages - includes things like value, tolerance, footprint, price, manufacturer, vendor, description.
Gate
See Unit
Footprint 
Kicad sometimes calls these modules - they are also known as a decals, or patterns. A footprint is the graphics that represents the component in the PCB layout program ( pcbnew). A footprint is a grouped set of PCB pads and component overlay shapes that define the space required to mount and connect the physical component on the board layout.
Gate-Swap
In Kicad this might be thought of as unit swap. Two identical Units can be swapped during layout to facilitate routing. This changes the reference numbers of the schematic. (not yet supported)
Modules
Modules are foot-prints or PCB decals - the art work that appears on the PCB for each component. (AKA: asdecals, land patterns, cell, model)
Pin-swap
When there is a part with two pins that can be interchanged ( the inputs of an and gate) they are swappable within a Unit(gate). Being able to swap pins during layout helps untangle the rats-nest of connection and helps with routing. The swapping causes the schematic to change. Examples of swapable pins - the two terminals of a resistor, or-gate. (not yet supported)
Reference numbers
Designators, such as R1 or U2 that refer to parts and the associated schematic element.
Solder-Mask
An outer layer of a circuit board that covers areas of copper that should not get solder - also helps prevent solder bridging. The mask is represented in the negative sense - What you see in CAD programs is where it ISN'T.
Symbol
A graphical representation of the component, that is placed on the schematic. The symbol can include drawing objects that define the shape, and pins that define the electrical connection points.
Tented Via
A blind or thru-via that has the exposed surface on the primary, or secondary , or both sides of packaging and interconnecting structure fully covered by a masking material such as a dry film polymer covering (solder mask), etc., in order to prevent hole access by process solution solder, or contamination.
Units
Units known to the rest of the EE CAD world as gates! Certain components, such as a quad op-amp, resistor network or even a relay, can be drawn as a series of separate parts, which can be placed independently on the schematic (referred to as a multi-part component). The component is made up of these Units (or gates).
Value
value eeschema uses the field name 'value' to mean part-name or part-type.

File Formats

Gerber File format

D codes (See "Gerber RS-274X format" docs and http://en.wikipedia.org/wiki/Gerber_File)

HPGL

PostScript

SVG


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Disclaimer

This information may have errors; It is not permissible to be read by anyone who has ever met a lawyer.
Use is confined to Engineers with more than 370 course hours of electronic engineering for theoretical studies.
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