Back in 2019, I went about designing a PCB ruler, inspired by so many others that came before, I wanted it well balanced between common footprints and electronic cheat sheet tables, while still trying to achieve a beautiful clean look. However, it wasn't really available for everyone to get their hands on, until now! I've decided it's time to share it with the world so everyone can get their own.

First I opened up KiCad and draw a 3 x 25 cm rectangle. I added the ruler marks in the silkscreen layer, metric system on the front face, imperial on the back. One detailed I noticed on most rulers I’ve seen, is that the zero is never placed on the edge of the PCB, so I wanted to do this, because it can be quite useful, when you just push the ruler against an object, you’ll get the exact measurement.

To keep it balanced, I decided to add the footprints on the front face, and the useful electronics cheat rule tables on the back. Regarding the footprints, I opted mostly for SMD to avoid interfering with whatever I was going to add on the back side. The footprints were organized by type: RLC, Diodes, Transistors, Capacitors, Crystals, ICs and other power packages. I used the default KiCad footprints for most components and also tried to title each one with their names and alternative references to be as clear as possible.

All of the footprints were lined up as tidy as possible and the Hackerspace logo added in the center. Each section title is also shown above in the copper layer. Since eLab’s colors are black and white, I decided to use black soldermask with white silkscreen. To give it some “bling”, I thought gold on black would look nice, so the Enig surface finish is my recommended choice. But it's up to you to choose your preferred color and material combination.

Now for the electronic and PCB cheat ruler things get a bit tricky. There are a lot of useful information that could be added but the space is limited. One thing I wanted to have on it for sure was the trace and via size vs amperage correlation. It’s a very useful cheat to have nearby when designing PCBs, specially when you have higher current applications, like motor drivers and such. I don’t mention it on the ruler itself, but all the current information is established for a copper thickness of 1 oz.

1 oz corresponds to 0.35 μm and by the way, a units conversion table is also available on the ruler, which shows some of the most common unit conversions used in PCB design, such as mil to mm, in to mm, oz to g, among others. Another tables included on the ruler, that are also useful while designing PCBs are a clearance distance between traces, according to the voltage and depending on the traces being uncoated (unc) or coated (coa); line width and text sizes for the silkscreen layer, which can be useful to check if the text is easily readable or not; and finally and layers/text indicator, which shows the different combination between layers on the PCB.

The last one says “silkscreen – no mask” is a good test to check if the PCB manufacturer used the mask while applying the silkscreen or not. If all goes well it should end up like the one that says “no copper – no mask”, if it ends up like the one “silkscreen – with mask” that means that they don’t use the mask stencil to apply the silkscreen, which means you can apply silkscreen on top the copper layers, and that can be very annoying, because if you need to solder something, the silkscreen on the copper won’t allow it, and it can be hard to scrape it out.

In terms of electronics design there are also some useful information such as typical BJT and MOSFET transistor diagram applications, SMD resistors, polarized capacitors and ceramic capacitors coding calculations, and finally LED typical forward voltages according to the LED color.

More Details: https://www.thefragmentationparadox.com/2019/08/elab-hackerspace-pcb-rulers.html