Making PCBs with simple tools

I’ve seen lots of guides and how-tos for making Printed Circuit Boards (PCBs) at home using the toner transfer method but they all seem to revolve around buying some expensive chemical or specific type of printer paper.

So here is my two cents (Euro) worth for using the toner transfer technique on plain old magazine paper.

This follows the development of my v2 LED analogue clock. I wanted to make it a bit more professionally so I needed a PCB. The circuit was a mix of surface mount (SMD) and through the hole components. It has some pretty hairy routing to link up the 60 LED to the LED driver. I try to make my traces as wide as possible, I think the narrowest in this case is 12mil on a 50 mil spacing I also like to use ground planes to fill up as much space as possible to save etchant.

The routing was done using the free version of Eagle CAD by CadSoft which meant my design was limited to 100mm x 80mm, but to be honest how you arrive at the circuit is not that important, it’s how you make the PCB that counts here.

The chemicals I am using are bought from my local supplier here in Barcelona (Spain) and are a mix of Hydrochloric Acid and Sodium Perborate. It’s a bit weird but I can’t find any references online to anyone else using these chemicals to etch circuit boards. I can find lots of references to tooth whitening and concrete cleaning, but not PCB production… Weird.

The Sodium Perborate comes as a dry crystalline powder that you mix in relative proportion to the Acid. It doesn’t seem to last long once the solution is mixed, even stored in an airtight container (or near as damn it) it only lasts a few weeks. However with gentle agitation it etches quite fast, 10 minutes is enough time for most boards, and you only need to make enough solution to cover the board. So all in all it’s pretty good fairly cheap (12 Euros for the set above, 1liter HCL plus sodium crystals) and a lot cleaner that the traditional Ferric Chloride that I used to use at college. I don’t know exactly how many boards you could etch with the kit as I tend to do small batches with large timespans in between and the etchant seems to die during that gaps.

Here’s a test etch with various trace sizes all at 100 (or 50 mil for the narrower traces) spacing. You can click the image for a larger view. As you can see the narrower traces came out really well. 12mil is no problem, I probably could go narrower if needs be. There’s a bit of blurring between 16mil tracks but a bit longer in the etch bath would probably sort that out.

You can download the Eagle file for the test
board if you want to have a look.

So with the success of this test in mind I re-worked my Eagle file to use some narrower traces that allowed me to route things a bit more easily.

Now on to the actual production stage.