Homebrew PCBs

Which is safer to use and easiest to dispose of? i.e. which can I flush down the toilet ;-)

I've used the Muriatic Acid / Peroxide solution for a couple of boards, but I'm really worried because I've read how dangerous it is to use. I'm making PCBs in my basement which is not well ventilated and I'm close to a gas furnace, so I'm worried that the fumes might ignite.

I'm just looking for advice.. Thanks for your help.

"nathan_h_tna" <nathan_h_tna@...> writes:
> Which is safer to use and easiest to dispose of? i.e. which can I
> flush down the toilet ;-)

Both have copper in them after being used, so they're both considered
hazardous waste.

> I'm making PCBs in my basement which is not well ventilated and I'm
> close to a gas furnace, so I'm worried that the fumes might ignite.

Chlorine gas doesn't burn.

Well, it burns your lungs, but it won't catch fire.

Oxygen doesn't either, but accelerates any fire.

I don't think there is a danger.

ST

On Wed, Feb 3, 2010 at 5:32 AM, DJ Delorie <dj@...> wrote:

>> I'm making PCBs in my basement which is not well ventilated and I'm
>> close to a gas furnace, so I'm worried that the fumes might ignite.
>
> Chlorine gas doesn't burn.
>
> Well, it burns your lungs, but it won't catch fire.
>

Stefan Trethan wrote:
> Oxygen doesn't either, but accelerates any fire.
> 
> I don't think there is a danger.

Though arguably that would make the HCl+H2O2 mix more risky near 
furnaces, etc. (though isn't the combustion section of most modern 
boilers effectively sealed off from the outside air?)

Academic point, really. I'd be more worried about high-concentration 
HCl+H2O2 -- isn't that a so-called "piranha acid" mix, or am I thinking 
of something else?

(But from what I've heard it's also a precursor to CuCl etchant, which 
is -- AIUI -- about as hazardous as FeCl, so it all goes full-circle in 
the end).

If you're using FeCl, I've been told mixing it with Plaster of Paris 
will neutralise it (this was in the datasheet for a bottle of FeCl I 
bought years ago). Though IIRC the more commonly accepted method is to 
mix it with sodium carbonate or sodium bicarbonate until the pH drops a 
little past neutral, then filter out the precipitate. The liquid is salt 
water (NaCl+H2O) and the precipitate is an iron-copper mix of some 
description.

Been a while since I did chemistry though, and I wasn't terrifically 
good at it to begin with...

-- 
Phil.
ygroups@...
http://www.philpem.me.uk/

High concentrations are definitely nasty. The stuff heats up on it's
own then and releases lotsa fumes. I've tried with a tiny amount once
and after only 10 seconds immersion the board I inserted was etched
clean, including much of the resist covered traces ;-)

I think the thermal runaway is even worse with sulphuric peroxy stuff.

Not a problem with reasonable concentrations, even less so as you
develop towards CuCl.

ST

On Wed, Feb 3, 2010 at 2:50 PM, Philip Pemberton <ygroups@...> wrote:

> Academic point, really. I'd be more worried about high-concentration
> HCl+H2O2 -- isn't that a so-called "piranha acid" mix, or am I thinking
> of something else?
>

Hi,

 

I googled "neutralizing ferric chloride" and found the following Q&A article, which seems pertinent. In college, my physics was much better than my chemistry, so I'm not clear on the conclusion. That was a looong time ago, anyhow. Perhaps someone with better chemistry smarts could tell us if NaOH is the FeCl3 disposal solution.

 

It sounds like a ph meter may be a good addition to my lab. Does anyone have a good, CHEAP design for one that we could make into a PCB? J

 

Jim

 

============== <article>

 

What is the best way to dispose of used ferric chloride PCB etchant?

I know of at least one method, diluting it and slowly pouring into the drain, but it can still stain and eat away metals in the pipes a bit. Is there something else I could use to possibly just "neutralize" it? I think an alkaline metal nitrate would work (Li;Na;K) or some other salt. That or maybe even just try to get the pH as neutral as possible.

*	3 years ago 

Additional Details

Note: PCB is an acronym electrical engineers/hobbyists etc used to stand for PC-board, a.k.a Copper-clad board. 

I also now realize a nitrate salt, as well as many other salts, would only form complex ions/ligands. Especially since the used ferric chloride would already contain complex ions due to the copper dissolved off the board (copper and chlorine like to do that a lot). Although, even that might bring the pH closer to 7.

3 years ago

Best Answer - Chosen by Asker

PCB enchant is Ferric Chloride (as you said), with a chemical formula of FeCl3...Iron (III) Chloride.

When you pour the Iron (III) Chloride on to a Copper-clad computer board with your circuit traced out on it, the enchant will eat away the undesired Copper by Oxidizing it to the very soluble CuCl2 and reducing the FeCl3 to FeCl2.

After you use your enchant, you will have a solution of FeCl2, CuCl2, and probably some remaining FeCl3.
All of these can be removed from solution by precipitating the metal ions out using a Hydroxide.

All of the Iron/Copper Chloride salts in your used etchant solution are quite soluble, but their Hydroxides are barely soluble.
if you add some Sodium Hydroxide ('lye', commonly found in drain cleaner), you can form the metal Hydroxide precipitates which can be filtered or decanted off, leaving a much milder solution behind.

FeCl3 (aq) + 3 NaOH (aq) --> Fe(OH)3 (s) + 3 NCl (aq)
FeCl2 (aq) + 2 NaOH (aq) --> Fe(OH)2 (s) + 2 NaCl (aq)
CuCl2 (aq) + 2 NaOH (aq) --> Cu(OH)2 (s) + 2 NaCl (aq)

Make sure and dilute the solution before you add the NaOH (preferably a NaOH solution). Dissolving NaOH in water is a very exothermic process, so the solution's temperature will rapidly rise if you are not careful. It is also a very bad idea to get any NaOH in your eyes or on your skin, so be careful but when used responsibly NaOH is fine. 

When the Hydroxide precipitates are heated, they will form the metal Oxide salts. So for example, by heating Cu(OH)2, you will form CuO. The heat generated by the above reactions might also be enough to convert the Hydroxides into Oxides, so that is certainly a possibility but disposing of Fe2O3, FeO (or the combination of the two, Fe3O4), and CuO should be no problem.

The remaining NaCl solution will be no problem disposing of down the drain, as would any excess NaOH which happens to remain.

*	3 years ago 

============== <end of article>

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com] On Behalf Of Philip Pemberton
Sent: Wednesday, February 03, 2010 5:46 AM
To: Homebrew_PCBs@yahoogroups.com
Subject: Re: [Homebrew_PCBs] Is Ferrich Chloride safer than Muriatic Acid / Peroxide?

 

  

Stefan Trethan wrote:
> Oxygen doesn't either, but accelerates any fire.
> 
> I don't think there is a danger.

Though arguably that would make the HCl+H2O2 mix more risky near 
furnaces, etc. (though isn't the combustion section of most modern 
boilers effectively sealed off from the outside air?)

Academic point, really. I'd be more worried about high-concentration 
HCl+H2O2 -- isn't that a so-called "piranha acid" mix, or am I thinking 
of something else?

(But from what I've heard it's also a precursor to CuCl etchant, which 
is -- AIUI -- about as hazardous as FeCl, so it all goes full-circle in 
the end).

If you're using FeCl, I've been told mixing it with Plaster of Paris 
will neutralise it (this was in the datasheet for a bottle of FeCl I 
bought years ago). Though IIRC the more commonly accepted method is to 
mix it with sodium carbonate or sodium bicarbonate until the pH drops a 
little past neutral, then filter out the precipitate. The liquid is salt 
water (NaCl+H2O) and the precipitate is an iron-copper mix of some 
description.

Been a while since I did chemistry though, and I wasn't terrifically 
good at it to begin with...

-- 
Phil.
ygroups@... <mailto:ygroups%40philpem.me.uk> 
http://www.philpem.me.uk/





[Non-text portions of this message have been removed]

"Jim Barnes" <jim@...> writes:
> It sounds like a ph meter may be a good addition to my lab. Does
> anyone have a good, CHEAP design for one that we could make into a
> PCB? J

I've never needed one.  CuCl becomes CuOH when the pH rises above 7,
and precipitates.  You can just watch and see, it's its own indicator.
If FeCl does the same thing, no pH meter needed.

--- In Homebrew_PCBs@yahoogroups.com, "nathan_h_tna" <nathan_h_tna@...> wrote:
>
> Which is safer to use and easiest to dispose of? i.e. which can I flush down the toilet ;-)
> 
> I've used the Muriatic Acid / Peroxide solution for a couple of boards, but I'm really worried because I've read how dangerous it is to use. I'm making PCBs in my basement which is not well ventilated and I'm close to a gas furnace, so I'm worried that the fumes might ignite.
> 
> I'm just looking for advice.. Thanks for your help.
>


I've recently switched to CuCL which starts out as acid and peroxide. So far I'm quite impressed, the stuff is certainly less messy, you can see the board as it etches without pulling it out.

As someone else said, the dissolved copper is the problem with disposal, it's highly toxic to marine life even in very dilute quantities. Either solution can be neutralized and/or evaporated and the solids disposed of in the trash.

On 4/02/2010 13:39, James wrote:
>
>
>
>
> --- In Homebrew_PCBs@yahoogroups.com
> <mailto:Homebrew_PCBs%40yahoogroups.com>, "nathan_h_tna"
> <nathan_h_tna@...> wrote:
>  >
>
> As someone else said, the dissolved copper is the problem with disposal,
> it's highly toxic to marine life even in very dilute quantities. Either
> solution can be neutralized and/or evaporated and the solids disposed of
> in the trash.

CuCl2 is hygroscopic and difficult to evaporate. Garden or builders lime 
is a cheap source of impure calcium hydroxide and is good way to 
nutralize (i.e -> copper hydroxide and calcium cloride) followed by 
evaporation to a solid. Another way is to not neutralise and throw in 
excess scrap aluminium, in a closed container.  After a few days you 
should have crystal clear liquid with a brown sediment of copper metal 
sludge plus some unreacted aluminium.

Adam

Adam Seychell <a_seychell@...> writes:
> Another way is to not neutralise and throw in excess scrap
> aluminium, in a closed container.

"Pipe bomb" if you do that to CuCl etchant.