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Ferric Clorhidre

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patroclus

New Member
It's the first time I build myown PCB (before, I just wired circuits in perforated boards). I have already drawed the pads and lines on the copper surface, and now I need to etch it before drilling. I bought some Ferric Clorhidre (a little pack, in brown pieces, not liquid).

How should I do this?

* I disolve all content of the pack and after etching, preserve the liquid in a bottle to reuse it?
* or either I only disolve some ferric clorhidre, and preserve the rest (and also the liquid from the etching).

The PCB is quite small (50x65 mm) and the ferric pack is small.
Also, where should I put the liquid after etching? Just any plastic bottle??

Thanks!
 

Johnson777717

New Member
Howdy!

If it were me, I would only mix enough Ferric Chloride to etch the board that you have already setup, and save the other tabs for later PCB's that you'll make. Plus, if you mix all of the tabs, and accidentally mix in too much water, you''ll pretty much have to go down to the store and get some more Ferric Chloride tabs. Mixing a little at a time and making a mistake wont put you out a whole pack of tabs.

I use a tupperware container to store my Ferric Chloride. In the case that you may not be familiar with tupperware, tupperware is a plastic container that is used to store food, or other products in. The plastic container has a lid that fits tightly in order to keep most liquid from leaking out. I'm sure any plastic container will do okay, as long as the thickness of the container isn't very thin (Like those disposable plastic containers).

I keep my ferric chloride in a cabinet away from other chemicals such as bleach or amonia. If these two chemicals (Ferric Chloride, and amonia or bleach) were to mix, I'm sure the gasses that would be produced, would be pretty nasty, and possibly lethal.

Good luck!
 

patroclus

New Member
Thanks :)
By the way, how much ferric clorhidre ? I mean, I should use enough water to cover the board, isn't it? but how many quantity of ferric?
 

Johnson777717

New Member
That's correct. I use just enough fluid to cover the board, but no so much that you can't see that how the copper is coming of your board. Otherwise, you might etch everything off of the board, and then you're left with nothing.

As far as how many tabs should be used, I'm not sure. You may have to read the directions on the package to determine how many tabs you need per the amount of water that you are using.

I hope this helps. good luck!
 

vaineo

New Member
If anyone know the mixture rate for the powder, that would be useful too. I got a big package but it didn't say how much to put in how much water.
 

Dean Huster

Well-Known Member
Ferric Chloride

If a 140°F ferric chloride bath doesn't etch the board in less than five minutes, the solution is 'way too weak .... add more powder/tabs.

I wouldn't consider storing the solution in Tupperware or any other plastic left-over-food container. I've seen too many of those lids not seal well and leak. Better yet a wide-mouth plastic WELL-MARKED jar-type container, such as a 3-liter plastic soft-drink bottle or a Gatorade bottle. Just remember that it's VITALLY IMPORTANT to remove the label and relabel the bottle to indicate the contents and store the bottle up high in the shop where a little kid or feeble-minded adult can't get to it and drink it.

I prefer ammonium persulfate as an etchant, myself. Much cleaner, doesn't stain like the ferric chloride and you can see through it to see how the board is doing as opposed to that near-opaque ferric chloride.

Dean
 

patroclus

New Member
Thanks for the tips.
I think I'll use a wide mouth plastic bottle with good seal and, of course well labeled. Also, have it far away from other quemical compounds. And I think that is all..

By the way, I had never heard about amonium persulfate, just ferric clorhidre and Clorhidric Acid (H Cl). Is it more expensive, more toxic, or anything?
 

tavib

Member
8)
For ferric chloride the mixture rate is 33%, in other words at 1 part ferric chloride powder put 2 parts water, but not put water over ferric chloride, put ferric chloride into water. Consider the mass of powder and water e.g. at 1kg powder 2kg water.
 
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