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Gerber File Format and ODB++ File Format

Gerber File Format

Gerber is an open ASCII vector format for printed circuit board design that shows parts of a board like copper layers, solder mask design, etc. Many applications can read this format because it simple, has detailed specifications, and has few bugs because of its wide use and subsequent debugging. The simple format of a Gerber means it is easy to identify and fix bugs as well. There are three Gerber generations: Gerber X2 (current format), Extended Gerber, or RS-274X, and Standard Gerber, or RS-274-D, which is now obsolete. The Gerber X2 format contains layer stackup information, which was not in previous versions. Software that supports the X2 format will read and identify each item's function in the file.
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.

Remember to include the following when submitting Gerbers:
  • All copper layers (inner & outer)
  • Soldermask layers
  • Silkscreen/legend layers
  • Via plugging layers (if applicable)
  • Solder paste layers (for assembly)
  • Aperture list if apertures are not embedded in Gerber data

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

ODB++ File Format

There has been a lot of debate between whether Gerber format or ODB++ formats are better for PCB design. Some designers and shops prefer one format over the other. At Sierra, we prefer ODB++ formats. Here's a summary of both formats and their pros and cons.

ODB++ stands for Open Database and serves as a way to exchange data between computer-aided design (CAD) and computer-aided manufacturing (CAM) formats for circuit boards. This format was first introduced as ODB, and the "++" was added after a new version included components. ODB++ is an ASCII file that has all the information pertaining to the circuit board design. Printed circuit boards are designed in CAD and transferred into CAM. CAD and CAM programs are usually made by different companies, so they need to agree on the type of data exchange. ODB++ is a manufacturing-oriented program. Many shops prefer this format for this reason because one file can consolidate all the information needed for the job, whereas some Gerbers need additional information from several files to make sense of the image layers. This eliminates the need to analyze each file to eliminate bugs.

Read our IPC-2581 blog to learn more.

This chart gives a brief summary of the pros and cons of the ODB++ and Gerber format.
ODB++ Gerber
Pros Cons Pros Cons
One file includes stackup, layers, drilling, masking, net data Different image format Simple Multiple files needed
Widely used More complex format than Gerber Widely used Requires examination of all files at fabricator
Undergoes DFM / quality checks Specification is precise
Easy to transfer to fabricator Format supported by free viewers

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