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Typical Gerber file format extensions for different software packages

During the PCB layer assignment in our Auto File Verification, you will have to tell us which gerber file is which layer. This table will help you for some common packages.

Software: Eagle

File Extension Description
 cmp  Top Copper
 sol  Bottom Copper
 stc  Top Soldermask
 sts  Bottom Soldermask
 plc  Top Silkscreen
 pls  Bottom Silkscreen
 drd  NC Drill

Software: Orcad

File Extension Description
 top  Top Copper
 bot  Bottom Copper
 smt  Top Soldermask
 smb  Bottom Soldermask
 sst  Top Silkscreen
 ssb  Bottom Silkscreen
 thruhole.tap  NC Drill

Software: Protel

File Extension Description
 gtl  Top Copper
 gbl  Bottom Copper
 gts  Top Soldermask
 gbs  Bottom Soldermask
 gto  Top Silkscreen
 gbo  Bottom Silkscreen
 drl  NC Drill


What are Gerber Files?

Gerber is a family of file formats used by printed circuit board (PCB) industry software to describe the electrical connections of a printed circuit board (the traces, vias, pads or component footprints and planes) as well as the drilling and milling data.
There are two distinct Gerber formats: RS-274X and the obsolete RS-274-D.
RS-274X or Extended Gerber or X-Gerber is a fully fledged bi-level image description format. It is the de-facto standard image description format for the PCB industry.
RS-274X is a human readable ASCII format consisting of a sequence of commands and coordinates.
A RS-274X file contains the complete description of a PCB layer image without requiring any external files. It has all the imaging operators needed for a PCB image. Any aperture shape can be defined as well as positive and negative objects. Planes can be specified without the need to "paint" or "vector-fill" as in RS-274-D.
RS-274X is a complete, powerful and unambiguous standard to describe a PCB layer. It can be input and processed fully automatically. This makes it well suited for fast and secure data transfer and for reliable and automated workflows.
(Reference: Wikipedia. For more details go to http://en.wikipedia.org/wiki/Gerber_format)