If you've been reading my blog for a while, you've probably noticed that I typically make my own PCBs for my projects. I've gotten much better at this process over the past few months, and I've been promising a "super awesome writeup" on my techniques for almost a year now. I figured that a video would do more than a writeup and spent the weekend producing one for you.
So here you have it! The video is a good 40 minutes long, but it's packed with details that should hopefully help you avoid some of the time consuming mistakes I've made.
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Just a note: Bubbling air through the FeCl actually causes a chemical reaction in the FeCl which makes it last longer (I read this in a magazine about 20 years ago). It also is a much better method of agitating the etchant. I have built several etching tanks, one of which was triangle crossection with the punctured air tube at the vertex of the triangle and the board placed copper-side down over the air tube. It etched very quickly. Sorry I don't have pictures.
You know, I haven't heard that before. I know that's the case with CuCl as I wrote about before, so I suppose it makes sense that it applies to FeCl. I'll have to ask a chemist.
Regardless, considering how small my typical board is, I imagine that some rough agitation or stirring will be sufficient.
I know this is antique, but I just saw the tutorial.
Doesn't FeCl react with copper to become CuCl2 or CuCl3? At that rate, used FeCl looks exactly like CuCl2 etchant. The bubbling air, if I recall, reduces CuCl2 to Cu2Cl2, which then reacts with HCl to become CuCl2 again. Something like that.
Really helpful tutorial, thanks, mostly due to the pro/cons comparisons you did about the different transferring and etching methods.
I just have a quick question: do you not plate the exposed copper with a tin solution (like liquidtin)? I read somewhere it was a really good idea (protects the copper against oxidation, and eases soldering).
I actually haven't tried tinning any boards. You're right about the benefits, though I'm yet to have a circuit board last long enough to start oxidizing. I might look into tinning for my future PCBs.
You might want to also try using the foam brush when etching as you do with your photoresist step. Also you can use the brush to just etch the areas that are taking the longest by holding it above over the container.
I also use a hair dryer or heat gun to heat the etchant from above periodically to keep it warm(er) -- probably less obnoxious than the lamp.
Very nice job on the video.
If you're using FeCl, take a look at the Edinburgh Etch. Basically you add some citric acid to the mix and it makes things work better. Citric acid is a chelant, so it pulls etched copper away from the surface so more ferric can get in and work.
The mix also regenerates, so you can keep using it longer before having to neutralize it and dispose of it.
Here's a link to the basic recipe:
and here's one to a page with more detail:
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