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Topic: switching to Ferric Chloride, could do with some words of wisdom! (Read 1 time) previous topic - next topic

n00b

Been using Copper Chloride (hydrochloric acid and hydrogen peroxide) to etch for a couple of years now, as wonderful as it is I had a few problems with using it to etch large volumes, so have decided to try switching to Ferric Chloride for my next run of PCBs to see the comparison.

Having never used Ferric Chloride (well once when I was at school, and totally uninterested) so just had a few question.....so here i go.

1:Will it be fine in the same tank, plastic with two 8inch bubbler strips and aquarium heater.

2:Is there a sweet spot temp for etching?

3:How long will each batch last for, say 4 liter in the tank etching A4 sheets will i get 5-10-50-100+ sheets out of it?

4: what the best way to store it?

Thanks in advance!  : :*

westfw

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Been using Copper Chloride (hydrochloric acid and hydrogen peroxide)

Those aren't the same things, BTW...  You can make copper chloride etchant (eventually) starting with HCl and H2O2, but actual CuCl etchant works differently.

I always thought Ferric chloride was usually considered a disposable etchant.  You use enough to cover your board in a tray, and "properly dispose" of it after the one board.  More recently I see reports of reuse, but I have no actual experience.

Ferric chloride is generally more aggressive than CuCl or persulphates, and works OK at room temp with mere agitation, rather than needing heater+bubbles.  Not that it won't work faster with the features...

n00b

Thanks westfw, always appreciate you help!

What etching solution would you recommend for higher volumes, Im doing 100+ boards a week at the moment (10+ 233 x 220mm).

The ability to recharge the CuCl, and keep everything in on tank bubbling away has been really handy (but with higher etching activity I get more and more surpluses solution), and every now and then I get a really strange thick creamy white residue that clouds up the whole tank sticking to the copper and preventing etching, as a result I have to start the mix all over.

         

westfw

I've never made, nor expect to make, boards in that quantity...  Sticking with CuCl sounds like a good idea, but you may need to tune it a bit more...

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I get a really strange thick creamy white residue that clouds up the whole tank

But THIS I had happen while generating my CuCl from HCl, H2O2, and scrap coppy.  I believe it to be "coppy oxychloride",
generated when you bubble TOO much air through a CuCl solution with extra copper and with not enough acid.  Or some such; the air bubbling in CuCl systems is important to the chemistry as well as providing agitation.   Oxygen from the air is what re-generates the CuCl part of the etchant. (given excess acid to do so.)


Have you seen http://members.optusnet.com.au/~eseychell/PCB/etching_CuCl/index.html
It seems to have nice quantitative advice about maintaining the solution.

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