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Topic: Questions about an etching solution for PCB making  (Read 9211 times)

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Offline sstbrg

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Questions about an etching solution for PCB making
« on: February 05, 2011, 01:29:06 PM »
Hello guys, I need your help.
I want to make my own PCBs at home and I'm planning to use an HCl and H2O2 solution for the etching process, in a Brita plastic container (click for an image).
I was foolish enough to pour some acid (30% of concentration) into the container and saw that nothing spectacular happens, as I heard that mosts plastics don't react (much?) with HCl (or vice versa?).

I would like to ask if I may use distilled water instead of H2O2 and what difference will it make (if any) ?

If you need more info, please ask!

Offline Borek

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Re: Questions about an etching solution for PCB making
« Reply #1 on: February 05, 2011, 04:08:06 PM »
I would like to ask if I may use distilled water instead of H2O2

No.

Quote
and what difference will it make

It won't work.
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Offline hobobot

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Re: Questions about an etching solution for PCB making
« Reply #2 on: February 05, 2011, 06:38:42 PM »
Larger electronics stores like Fryes usually sell the stuff you need to make a PCB. Strong stuff even by my standards.

Offline Zerm

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Re: Questions about an etching solution for PCB making
« Reply #3 on: February 07, 2011, 11:38:38 AM »
H2O2 is required to oxidize the copper so that the HCl can attack it to form CuCl2.

H2O2 + Cu -> CuO + H2O

CuO + 2HCl -> CuCl2 + H2O

The copper chloride can easily enter solution and is thus removed from the PCB.  Alternatively, the ferric chloride I've seen in most PCB etching kits works without the need for hydrogen peroxide since it is thermodynamically favorable for copper to donate an electron to iron(III) cation, reducing it to iron(II) while oxidizing the copper.  The end result being:

FeCl3 + Cu -> FeCl2 + CuCl

FeCl3 + CuCl -> FeCl2 + CuCl2

Offline sstbrg

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Re: Questions about an etching solution for PCB making
« Reply #4 on: February 11, 2011, 01:45:05 PM »
OK, thanks for the useful information guys.
I can purchase some H2O2 (18%), and I'll try using that.

Offline mnakhla

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Re: Questions about an etching solution for PCB making
« Reply #5 on: February 20, 2011, 02:19:03 AM »
I would be wary of adding too much H2O2 and HCL together as it will release a nice amount of Chlorine gas. Also I was under the impression that the nascent chlorine formed insitu was the reactive species in this system.
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