Exporting for fabrication¶
The purpose of a PCB layout program is to allow you to make PCBs. CPCB can therefore export your design to the industry-standard “Gerber” file format [1]. To export a Gerber file, press “Control”+“E” or choose “Export fabrication files” from the “File” menu.
Gerber files can be uploaded to a variety of fabricators on the internet. A useful website to compare offers from many sources is https://pcbshopper.com. Pro tip: Be sure to select lead-free surface finish as well as lead-free solder. Don’t poison youself.
Most fabricators have a way to verify that their interpretation of the file you uploaded matches your intentions.
Caution
Please use those tools, and note that by using CPCB, you accept the terms of the GNU General Public License. That means, among other things, that the author cannot accept any liability for incorrect fabrication, even if, for instance, CPCB exported patently incorrect Gerber files.
In the “Export” dialog, you have the option of exporting several additional types of files that can be used in the fabrication process
Bill of materials (BOM)¶
This is a CSV file mapping component identifiers in your design to part numbers from manufacturers and vendors. If you are shopping for parts yourself, the “Compact” option is useful. If you are outsourcing your part placement, it may be better to export the long-form list. PCB assemblers are very picky about the format of the BOMs they accept, and they do not seem to agree on the preferred format. You should compare CPCB’s output with their published examples and be ready to reformat the file. LibreOffic Calc is very useful for that.
Pick-and-place (P&P) table¶
This is a CSV file listing the positions and orientations of all your components, for automated PCB assembly. As for BOMs, assemblers are very picky about the format of P&P files they accept.
A common problem is confusion about which orientation for a part constitutes “up”. Always check whether the assembler correctly interprets your design before submitting for actual fabrication. The “PNP mode” (see CPCB’s user interface) can be used to set the nominal orientation of parts within CPCB.
You have a choice of exporting placement for all parts, or only for surface-mounted parts.
List of unplaced items¶
This is a simple CSV file listing any parts not exported into BOM or PNP files. This is a useful final check on whether you have put all the requisite information into the BOM table.
Solder paste mask¶
If your layout involves any surface-mount components, you may wish to produce a solder paste mask, for laser cutting. The number to the right specifies the allowance for paste mask shrinkage. This number can be used to make the holes slightly smaller than the solderable area, to compensate for the kerf of a laser cutter. My procedure for SMT soldering explains how I make masks out of transparency film.
Front panel stencil¶
A small selection of connectors in CPCB’s component library include drawings of their front panel placement, comprising a line marking the top of the PCB and outlines of the holes that need to be cut into the front panel to accommodate the part. You can export an SVG file with these markings as a starting point for designing a front panel for your project. The produced SVG file looks at the panel from the outside-in, and is thus a mirror image of the markings you see in the “Panel” layer within CPCB.