Gerber format PCB files

The Gerber file format is the most widely used specification for printed circuit artwork drawn by the vector method. Today there exists two variants known by their EIA designations EIA-274-D and EIA-274-X. When you prepare board artwork for fabrication by Technical Services or elsewhere you need to be sure to use the latter variant.

Both variants are plaintext which can be viewed in Notepad or any application able to open ASCII format files. The files normally have a filename suffix of .gbr, but Technical Services may change this to .gerber.

EIA-274-D

This format, also known as 'Gerber original' or 'Gerber plain', is the older of the two. A typical file looks like this -

G75*
G54D20*
X39646Y-12502D02*
Y-10002D01*
X29843D01*
Y-12502D01*
X39646D01*
G54D21*
...
...
...
X19314Y-1439D02*
X18715D01*
D02*
Y-1002D01*
X19314Y-1439D02*
Y-1002D01*
X19914Y-1439D02*
Y-1002D01*
D02*
X19314D01*
X19914Y-1439D02*
X19314D01*
D02*
Y-1002D01*
M02*

Note that the file begins with a G code.

The disadvantage of the Gerber original format is that it relies on the provision of a second file called an 'aperture table' which usually is given the extension .apt, .apr, .rep or .tab. Standardisation of the aperture table files is weak to non-existent, which makes it impossible for Technical Services to produce a board successfuly using EIA-274-D.

EIA-274-X

This format, also known as 'Gerber extended', is more recent. A typical file looks like this -

%IPPOS*%
%FSLAX34Y34*%
%MOMM*%
%ADD10C,0.02500*%
%ADD11C,0.05000*%
%ADD12C,0.10000*%
%ADD13C,0.20000*%
%ADD14C,0.40000*%
%ADD15C,0.80000*%
%ADD16C,1.50000*%
%ADD25C,0.02500*%
%LNCOND*%
%LPD*%
G75*
G36*
X-2029000Y2419000D02*
Y2255000D01*
X-2159000D01*
Y2419000D01*
X-2124640D01*
Y2376015D01*
...
...
...
X-2098837Y2402524D01*
X-2098893D01*
Y2419000D01*
X-2029000D01*
G37*
M02*

Note that the file begins with several instructions enclosed by % characters. The original format does not have these extended instructions.

Gerber extended format files do not require a separate aperture table and can give good results following conversion to .pdf format. If you are able to generate .pdf format directly then that is still prefered.


[ PCB production home] [ Gerber format at Wikipedia] [ CircuitPeople]

E-mail:R.Clarke@surrey.ac.uk
Last modified: 2008 June 17th.