This is why there are PCB fab services

So the kid decided to teach a soldering workshop at geek camp. Of course that means a custom PCB (and custom firmware, but that’s not my department). Which meant that I finally got to test all those tutorials about etching your own PCB with vinegar, peroxide and salt.

You know what, it’s an effing pain. The kid’s CAD program exports SVG, so I thought at least that part would be easy: export, hand the file to the Glowforge, zap away the resist, done. But no, the SVG is one of those cobbled-together things with black traces and and little white areas covering the parts where there shouldn’t be any copper. But the Glowforge doesn’t care what color an area is: if it’s filled, it zaps it. Oh, and layers so that the white areas are hiding a bunch of lines the CAD developers didn’t want to bother drawing to the right length. So it turns out the least brain-melting way to get an image for zapping is to export the design as a bitmap, import to inkscape, trace it, and then subtract the traced version from a big colored rectangle.

Then: you coat your PCBs with nail polish or spray paint and zap the spray paint back off. (I had this idea I could zap a layer of masking tape and use it to pattern the paint/polish, but not, the dried stuff sticks to the edges of the tape much better than to copper.) Then use some alcohol to wipe off the zapping residue and you’re good to etch. But wait! Hardware store spray paint dissolves in isopropyl alcohol, so nail polish it is.

Then the etching, which takes a whole lot longer if there’s a few days of cold weather. And more vinegar, peroxide and salt than you think, even for a handful of 2×3-inch boards. Oh, yeah, and then the drilling. I knew that dremel drill press would come in handy one of these decades. And the surplus-store sets of teeny-tiny refurb bits. And the magnifying clip-on for my glasses. And a slightly steadier hand…

Was it worth it? Good question. I certainly learned a lot. If you don’t count the dremel, or the dremel drill press, or the high-power magnifier, it was probably cheaper than getting boards from one of the usual suspects (except when one of the usual-suspect PCB houses has a getting-to-know you sale). And if you don’t count having to redo a couple of the steps, it might have been faster.

I’m glad I learned how to do this, and I might want to do it again some time, but I’m not in any hurry. On the other hand, I can see a bunch of ways we might have done things better if only we had known beforehand what he know now. So if I just gin up a little project to test out some different ways of doing the resist and the etching, and maybe build just a little numerically-controlled X-Y stage for the drill press…

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