Printed Circuit Boards (PCB)
Designing and Procuring Custom PCBs
The purpose of this page is to collect information about designing custom PC boards and submitting your design to a fab house, or etching or milling the boards from raw stock. The intent is to make this software and fab method agnostic, with instructions and tips for all of the resources that make up the tool chain. Without further ado, let's get started.
A very popular software tool for designing PCBs is Eagle CAD. This tool allows you to design the schematic, lay out the board (including an auto-router), and generate the Gerber files that commercial fab houses require to fab your boards for you. Eagle has several license levels. The free version is limited to 2 layers and a relatively small board. i3 Detroit has a full license until August 2012 for a single seat that is available if you need to do more. Please check the Eagle site for current license details.
There are many sites that provide tips on using Eagle. Sparkfun has tutorials on using Eagle, including how to make your own custom component library. It's worth a read.
Once you've created the Gerber files that you need to send to the PCB fab, take a few minutes to check them using the Viewplot application. Tip: Be sure to set the drill file parameters correctly when you load the file. The SparkFun CAM file script generates a "2.4 Leading" format, so choose the "2.4" option when prompted, but leave the type as "Normal" not "Leading". Otherwise, your drill holes will not be displayed in the right place. It's pretty obvious when you see it and it's wrong: the drill hits are not even close to the traces.
Making PCBs from Your Design
There are several options for turning your design into a physical board. The easiest is to send it off to a commercial fab house and have them make it for you. This sounds daunting and expensive. It's NOT! It's amazing that you can get custom prototype boards made for under $100 and in some cases for less than $20! What are you waiting for?
A less easy, but to some people more rewarding, way to realize your design is to make it yourself. The options included here are etching and milling. Both require some experience and trial and error. Both have potential safety issues which are not insurmountable.
Now we get into a potentially heated discussion. The cheapest fab houses are in China. Some people refuse to have their designs fabbed outside the US for two main reasons: intellectual property concerns, and foreign trade, i.e., make it in the USA principles.
When you submit a PCB design, you typically provide a set of 7 files in "Gerber" format that are produced in Eagle by a CAM job. Gerber is standardized a way of describing how you would draw all the traces and lines, and where you will place holes. The files you need for a two-layer board are: top copper, top soldermask, top silkscreen, bottom copper, bottom soldermask, bottom silkscreen, and the drill file. There is another file, for paste application, that is typically produced, but you would not use it unless you are going to make or have a template made for applying soldering paste to the board when you populate it.
Each fab house has a slightly different submission process, so you will need to carefully review their submission guidelines. They also often provide a design rules file, and sometimes a Gerber rules file, that you can use during the checking process to ensure that your board can be fabbed.
Before you submit your files, you should review them using the ViewPlot application. Sometimes there are artifacts that are not obvious in the board design software, but are easy to spot once you look at each layer in the Gerber files.
Here are some possible sources for getting your boards fabbed:
Etching Your Own
A couple of i3 Detroit members have done this many times and understand the safety requirement and can likely provide tips or instruction to get you started etching your own boards with Ferric Chloride or other solution. Paul or Keenan, here's your space. :)
Milling Your Own
Other members have been following the milling process, notably on Paul's mini-mill. Trevor or Paul: here you go.