Reading time ( words)
There has been a lot of activity by the intelligent design data formats over the past year, and the newcomers (which are not really that new) are gaining users. But the overwhelming majority of PCB designs are still output in Gerber, a 60-year-old format that was never meant to convey PCB designs to manufacturers.
The I-Connect007 Editorial Team recently spoke with Karel Tavernier, managing director of Ucamco, which now takes care of the Gerber format; and Gerber advocate Dirk Stans, managing director of Eurocircuits. They discuss why Gerber continues to be the most popular format for PCB designers, the advantages it offers designers and fabricators, and what the future holds for this resilient format.
Andy Shaughnessy: Karel, would you walk us through the history of Gerber and the most recent revisions?
Karel Tavernier: Gerber goes back a long time. It was originally the input format of the Gerber line of photoplotters. It was a pure image format. There were a lot of photoplotter-specific variants. Gerber was very successful; many people adopted a Gerber format or variants of it as their image format. Ucamco took over Gerber Systems Corp. in 1998. At that time, we brought out Extended Gerber, which, essentially, was a unification and simplification of the Gerber family of image formats. A lot of machine-specific stuff was thrown out, and it became a simple and clear unified format. It was wildly successful, and everyone adopted it.
That’s about the same time that ODB came out, around 1995. Extended Gerber came to be the dominant format—not that it was necessarily better or worse than ODB, but because it was simple to adopt and largely compatible with existing software. For a long time, nothing changed from the Gerber format. ODB added component information, and this was a very positive thing. Around 2010, Ucamco again took up evolving the Gerber format.
In a first phase, we simplified it by throwing out everything that was very rarely or never used. Simplify before you extend. In a second phase, we added information that Gerber lacked as a CAD-to-CAM data transfer format. It was already a perfect image format but lacked design intent information; it did not contain the information about which drilled holes were vias or component holes, for example. Gerber X2 was brought out in 2014. Gerber X2 added extra information to the Gerber file so that from within the Gerber file you can see whether it’s positive or negative, if it’s a copper layer or a solder mask, which pads are component pads, and what’s top or bottom, etc. This has been very widely adopted, and most Gerber files today are X2 files.
The reason for its quick adoption, again, is simplicity. The difficult part of output is the image; getting that right is difficult. For a CAD-vendor that already has an Extended Gerber output (and that is all of them), generating the extra X2 information is straightforward. If Gerber software outputs a top copper layer in Gerber, for example, chances are that software knows it’s outputting the top copper layer; adding a line saying, “I am the top copper layer” is not rocket science.
Gerber X2 is compatible on input. The simplest is to ignore the X2 lines; then you have gained nothing, but it continues to work as before. Plenty of people receive Gerber X2 files without having updated software, and they do not even know it’s an X2 file. They don’t derive the benefit, but they have no disadvantage.
To read this entire conversation, which appeared in the October 2021 issue of Design007 Magazine, click here.