Ordering Circuit Boards

Ordering PCBs

When actually placing an order for PCBs, the main consideration (besides the options discussed previously) is making sure that you provide the correct files for the circuit board. These files are typically in the standard Gerber file format, which encodes a series of shapes using vector coordinates. Gerber files are generated from the original circuit design files, which are typically stored in a proprietary format specific to the software used (Eagle, Altium, etc.) If you want to edit the design of the circuit board, you’ll want to get the original design files. If you’re just looking to order a copy of an existing design, however, you’ll want the Gerbers, because that’s what you send to the manufacturer. The current version of Gerber is known as extended Gerber, or RS-274X. You may also see an older format known (misleadingly) as “standard Gerber” or RX-274D. Some manufacturers still accept the older, standard Gerber format but, in general, you should probably be working with extended Gerber.

A screenshot from the AP Circuits online order form showing the individual files for each layer of the PCB.

There’s one Gerber file for each layer of the PCB:

Note that none of these files specifies the outline of the board. Typically, the board dimensions will be included in one of the other files. As far as I can tell, the manufacturer usually just figures this out by looking at the files for something that seems like the outline of the board. Again, if there are internal cut-outs you may want to mention this in your comments when ordering, as they sometimes get missed otherwise.

In addition to the Gerber files, you’ll need an additional file that specifies where the holes should be drilled in the board. This is usually referred to as an NC or Excellon or, simply, drill file. It may have the extension “.drd” or “.xln”.

Typically, you’ll zip up these files and upload them to your manufacturer (or upload them one at a time). Then, you’ll probably have to specify which file corresponds to which board layer. Specify the other PCB options and you should be all set to order your boards.

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