Making Your Own Circuit Boards
I originally wrote this article for the December 2018 issue of Channel M, the newletter of Channel Islands Mensa.
Back when I was growing up in the 1980s, the only way to make your own circuit boards was to etch the board at home using acid. While you can still do that, there’s now another way: you can design your circuit board on your computer using a CAD program, and then send your design off to a fab. (A fab is just a company that makes circuit boards.) The fab will then mail your finished boards to you.
Having boards produced professionally means that you don’t have to deal with nasty chemicals, toxic fumes, and hazardous waste. It also means you get higher quality boards than you could make at home:
They will be two-sided, and you can even do four layers or more for an additional charge.
The holes will already be drilled for you.
The holes will be plated, meaning that both sides of the hole are electrically connected.
The board will be covered in soldermask, which insulates the entire board except for the pads that you will actually want to solder.
The board will have a silkscreen, which allows you to label which components go where, and how they should be oriented.
The trace width and spacing can be much thinner than what’s possible if you etch your boards at home.
I design my boards with a free, open-source program called KiCad. It’s cross-platform, and runs on Windows, Mac, and Linux.
First, you will draw your circuit schematic in KiCad. The schematic is made up of symbols, such as resistors or capacitors. KiCad comes with a library of commonly-used symbols, but you can also create your own symbols if needed.
When you’re done with your schematic, you will associate each symbol with a footprint. A footprint designates the actual shape the component will have on your board. For example, you might have a pushbutton symbol in your schematic, but pushbuttons come in various sizes, so you would need to choose the correct footprint for the pushbutton you intend to use. Once again, KiCad comes with a library of common footprints, but you will probably need to create some footprints yourself. If you’re feeling generous, you can contribute the symbols and footprints you create back to the KiCad library for others to use.
The next step is to lay out your circuit board. The first thing you need to do is set up the design rules. Design rules tell KiCad how wide traces must be, how close the spacing can be, and so forth. You will need to find out the design rules from the fab you intend to use.
KiCad will import the footprints you are using onto a blank screen. You can then move the footprints around to position the components on the board. KiCad draws a set of lines called a ratsnest, which shows which components are connected to which other components. Once you’ve positioned the footprints, you can draw the outline of your board on the Edge.Cuts layer.
Next, you must draw traces to wire all the components together in the correct way. As you complete each trace, the corresponding line will disappear from the ratsnest. KiCad contains a new feature called the “Interactive Router” or “Push-Shove Router”, which allows you to draw traces in a way that automatically comply with the design rules. Unfortunately, the interactive router isn’t yet covered by KiCad’s written documentation, but there are several videos on the KiCad website which demonstrate its use.
When you think you’re done, you run the Design Rules Check, or DRC. DRC makes sure that your board conforms to the design rules, and it also makes sure the board is wired up in the way specified by the schematic.
KiCad comes with fairly good documentation, but it doesn’t cover every possible case, and learning a new, complex software package can be daunting. However, KiCad has a very useful forum site where you can ask questions. I’ve found the people on the forum to be very friendly and knowledgeable, and they tend to answer questions quickly.
Once you’ve completed your circuit board, you’ll need to send it off to a fab. There are many fabs to choose from, all over the world. Some fabs will accept your .kicad_pcb file directly, but most require you to generate Gerber files and submit those. (Despite sounding like baby food, Gerber is an industry-standard file format for exchanging circuit board designs.)
One fab which is easy-to-use and is inexpensive for small boards is OSH Park. They have a simple pricing model: $5 per square inch, for three copies of your board. Free shipping via US First Class Mail is included. (OSH Park manufactures boards in the US, and ships from Oregon.)
There are a number of fabs based in China. They can be more cost-effective for larger boards. I have used one called JLCPCB, but there are many to choose from. JLCPCB’s prices are much lower than OSH Park’s, but that is offset by the cost of shipping from China. Shipping from China via DHL can be around $20-$25, so for boards less than four or five square inches, OSH Park with free shipping can be more cost effective.
Once you receive your boards, you can solder your components on!