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In case of zombie apocalypse, part 2


Alternative title: Minimalist PCB etching with vinegar, hydrogen peroxide and salt.

I usually order my PCBs from China or Malaysia, I never tried etching one myself. After hearing rumors about PCBs being etched with vinegar, I did some investigation and decided to try this out myself. But I wanted to raise the bar by doing it even simpler, using as few resources possible. You know, as if... well... as if a zombie apocalypse was around the corner.

I didn't want to use transparent or glossy paper and mess around with a clothes iron. Nor did I want to have potentially dangerous chemicals in my small, non-ventilated room when I have two kids running about. Vinegar, hydrogen peroxide and salt are three fairly innocent ingredients. Corrosive, but not I-will-burn-through-your-kids-and-down-the-floor-in-minutes corrosive. So I started out with this permanent marker and a copper clad board:

Here are the main ingredients, except salt, which I for some reason forgot to include in this picture. Oh, and by the way, the hydrogen peroxide expired 01/2011. Not that it mattered, though.

In the lack of a better idea, my first circuit was a simple 555 circuit for flashing an LED. Hand-drawn as I thought to myself, "I can't see how this would work at all." The tracks were drawn extra thick, just in case. Knowing it would turn out ugly, the board was already nicknamed "zombie".

The vinegar I bought was 35% concentration, so I had to dilute it down to ~5% with water. In spirit of the simplicity of this project, I used tap water. I proceeded to mix it (50/50) with hydrogen peroxide and a graceful pinch of salt, all in a plastic container. When I inserted the board, the corrosion was visible within seconds:

...and within half a minute, the PCB was almost pitch black. I used a plastic spoon to move the board around, to gain better access to the copper layer. I did this about every 30 seconds until it was done.

After about 5 minutes the board was done, and I scrubbed off the permanent marker using a scrubbing sponge. Yeah, it's ugly, but somehow it turned out better than I expected.

Soldering time. A 555, 10uF cap, 2x8k2 resistors, a 100R resistor and a LED are facing their final destination.

And when you don't have SMD parts, you SMD-ify your DIPs.

After a quick continuity check with a meter, it was time for preservation. To prevent further oxidation, I tinned the tracks. I kinda regret this, it turned even uglier, but at least it will live longer.

Wasn't so bad when the rest of the components were mounted, though. Now it looks like it's supposed to be this awful.

Voila, that's the first PCB etched by yours truly, ever! And as a bonus, it works!

Conclusion: It's safe for the home, safe(r) for the environment, safer for the kids (than ferric chloride or muriatic acid) - I love it. It worked much faster than I expected, but also slow enough to watch the process carefully. I don't think I'll be using the permanent marker next time, though. Looks like I'll be using the printer, but I'm keeping this vinegar cocktail - it's re-useable many more times.


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1 Comment

  • This is glorious, man! The ugly adds to the credibility, in my opinion, of a circuit meant to be thrown together under Zombie Apocalypse conditions.

    Zombiologists have shown that a flashing LED will buy you just enough time to reload your anti-undead artillery. The zombies get mesmerized, or something. Good show, and a great contribution to preparations for the great ZA.


    #65 | Comment by Dave Eaton on May 16, 2012 04:50pm

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