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A Gerber File is a standard file format used by printed circuit board (PCB) fabrication
houses that contains information necessary for computer controlled machines to draw
exact patterns for circuit boards. These patterns are typically used to assemble and
electrically connect electronics assemblies.
The patterns usually contain features such as pad patterns, signal traces, drilled holes,
milling and cutting information.
The Gerber Format is originally a subset of EIA RS-274-D. Later the format was then
extended by the so called "Mass Parameters" and was then also called RS-274-X.
Usage of the GERBER Format
These files are produced by PCB designers using specialized Electronic Design Automation (EDA)
software, such as OrCAD Layout, Mentor, Cadence Allegro, CadSoft EAGLE etc.
Since a PCB may have many layers, the older Gerber format EIA RS-274D always assumed
a set of command files (one for each PCB layer) and one "tool" description file.
The command files (consisting of short commands and X, Y coordinates) were called "Gerber files"
and the tool files were called "aperture files". A standard for the latter was never established so
every EDA software had its own file format which caused problems for the manufacturers.
Often the aperture information had to be re-entered manually.
The newer Gerber format RS-274-X, also known as X-Gerber or Extended Gerber,
includes the aperture information into the file headers. With embedded apertures, this makes every
X-Gerber file complete as to how each PCB layer should look.
However, there are still problems with the interpretation of these files, such as on polygons,
or the question of which file to use for which layer.
Gerber file extensions are often .GBR, .GBX, .PHD, .SPL or .ART.
Sometimes extensions such as .TOP and .BOT are used instead.
Some common XGerber extensions are: