DirtyPCBs.com offers super cheap PCBs for up to 10 cm x 10c m through Chinese fabrication houses . Despite their dirt cheap approach, the options are still plentiful for the average hobbyist. All PCBs, 2-layer or 4-layer, are of FR4 material with selectable thickness, color and finish. Even electroless nickel immersion gold (ENIG) finish is offered. Also available super cheap are solder paste stencils. Dirty PCBs stresses that you shouldn’t expect much and that this is a real “as cheap as it gets” approach. It’s a great service for prototyping inexpensive prototyping and hobbyist use though.
Dirty PCB differentiates between the different layers by the file extension of the Gerber files. The following extensions are used for each layer:
Extension – Layer
GTO – Top Silkscreen (text)
GTS – Top Soldermask (the ‘green’ stuff)
GTL – Top Copper (conducting layer)
GBL – Bottom Copper
GBS – Bottom Soldermask
GBO – Bottom Silkscreen
GML/GKO/GBR* – Board Outline*
TXT – Routing and Drill (the holes and slots)
This is different from the default DipTrace setup. By default, DipTrace uses the .gbr extension for all Gerber files and differentiates between layers by file name. So before exporting one needs to click on the “Files” button in the Gerber export menu and enter the above nomenclature. Furthermore, please deselect layers that are unnecessary. The following picture shows the correct setup:
The most important file is the board outline. According to Dirty PCBs, forgetting to include this file is a common error that leads to designs being rejected. Technically speaking, a board outline is the only required file. However, this would be an extremely boring board. But it might be useful if you need someone to cut some FR4 material to size for some strange reason.
The next common problem Dirty PCBs mentions is missing drill files. They require an Excellon drill file (also called NC drill file) with either a .TXT or .DRI file extension and embedded tooling information. DipTrace accomplishes this as follows:
All the files generated by the Gerber and Excellon export need to be combined in a .zip archive. That is really all of the magic behind exporting a layout for Dirty PCBs. Just upload the .zip archive to Dirty PCBs, select a package size and send off the order. Dirty PCBs will offer you a preview of your uploaded design. They stress that this feature is experimental, however, it is probably a useful tool to see if something went horribly wrong.
One really cool feature of Dirty PCBs is the ability to share one’s design with the whole wide world. For instance, my design from a previous article on how to use DipTrace can be ordered here. Perfect for Open Source Hardware (OSHW). You can even collect $1 every time somebody orders your design. But don’t be greedy; Dirty PCBs doesn’t make much money of orders. If you intent to get rich with your design, I suggest you order a larger quantity and sell it at a profit yourself.
Another feature is the fact that you can upload new design files at all times until Dirty PCBs sends them off to the fabrication house. Seems like no big deal but every design engineer knows that almost always at least one improvement comes to mind just after submitting the design files. As you can see from the previous image, I actually revised the uploaded design files 3 times. It’s a real life saver.
That’s it. Assuming that your design is abiding their design rules, not much can go wrong from here. Enjoy!
Links and Sources:
 Dirty PCBs: http://dirtypcbs.com//