Hi ya all. Here's a detailed method of etching that I use. In this How To, I'll explain what's going on from a chemistry point of view, and what are the dangers that you might need to protect from. There are many
different ones already all over the internet, but I hope this one would be clear and helpful to many of us... (edit: you can find some similarities with bajaman's thread here
, though the etchant is not the same...
So here we go.
- Your circuit laser-printed on a transparency (reversed so that the printed side is in contact with the copper).
- UV light (I use an adapted facial sun lamp mounted as an UV box).
- Presensitized copper clad.
- A 7g/L sodium hydroxide solution (made from a more concentrated solution that's quickly available in DIY stores).
- Hydrogen peroxide (I use a 110vol (=33%) solution) (10€/L)
- Chlorhydric acid (23%) from the DIY store (1€/L)
- A bucket of water (you never know).
- Some acetone and cold tinning solution if you want your PCB to be cold tinned.
- Gloves and glasses
in a open area...Nota bene: you may use a less concentrated peroxide solution (like in the video above). I have to try it myself to tell, but it may be less harmful and provide a more gentle etching...1) Preparing the PCB:
Cut the PCB to size, and file the edges with sandpaper or a file...
Then peel off the protective film.
Place the resin-side onto the transparency.
Close the box an turn the UV light on for the appropriate time (For me it's 1'45", but it depends on your equipement).What's happening:
well, the UV light will degrade the exposed resin. Since your printed image blocks the UV light, then it will remain intact, which will be useful afterwards.
You can now put your gloves and glasses.2) Removing the exposed resin:
When the exposure is done, you have to dip your PCB into the sodium hydroxide solution to get rid of the degraded resin. This step takes up to 30 seconds.
From the start:
And then the circuit lightly appears:
And it's over now:
You rinse it nicely, and you can see now the copper sheet with your circuit in resin up above. This resin will protect the future tracks from being etched... 3) Etching the copper:
I use a 50/50 of acid and peroxyde mix. Recipes may change, affecting mostly the speed of the etching, but the chemistry is the same.
For this How To, I used 25mL of each reactant. No more is needed. You can even lower the quantities provided your etching tank is deep enough...Open the window or go outside
. Dip your PCB in the mix. It bubbles instantly and the solution turns green-blue.
Very soon (10" in my case) it's all done. I did it at 15°C/60°F, but it was slower this winter...
Dispose of your etchant by pouring it in the bucket of water. This turns your etchant in a harmless solution.
You have it now. You can solder on the resin if you like. I'd rather tin the PCB, but I'll detail it after the chemistry part...
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