Slightly OT?: CuCl PCB heater & bubbler

I was wondering, if one were using a typical aquarium-style heater in a cupric-chloride etching tank, could the bubbler be placed underneath the heater during operation? (Would the "cool" bubbles cause any problem with the "hot" heater?)

Furthermore, did I read somewhere that PCB's should not be bubbled in CuCl etchant?

Thanks.

Reply to
Mark Jones
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No sir, I'm indeed designing a Cu+++Cl etching tank. I've used ferric chloride in the past and while cheap and effective, its messy, slow, non-renewable, and a disposal hazard. CuCl has its drawbacks too, but it also has several marked advantages like its renewability and neturalization characteristics. Perhaps I am a little insane. :)

Indeed! Anyone here not experience "orange finger" syndrome yet? I'm designing this new tank with a sealed cover to avoid this very issue. For the bubbler I was thinking of a length of polypropylene tubing with many fine holes drilled in it. The exhaust will be further filtered to remove the HCl fumes.

Thank you, I will look into it. :)

-- "God might not play dice with the universe, but he sure can bowl when it's raining!" MCJ 20041222

Reply to
Mark Jones

AFAIK: Etching with CuCl is not something to be done at home. The process requires constant balancing of the chemicals. It is a very good production process and environmentally friendly (the etchant is constantly recycled).

Aren't you referring to ferric chloride (FeCl)?

Anyway, I don't think placing the bubbler underneatch the heaters is a problem. Depending on the size of you tank you may need quite big heaters though. My tank needed 2 300W heaters to get 12 liters (small miscalculation) of etchant warm in 20 minutes.

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Reply to
Nico Coesel

No sir. I'm aware of the necessary parameters for CuCl3 etchant. With the assistance of a microcontroller, maintaining the etchant should be pretty straightforward.

Oh good, that simplifies things. 12L is a big tank! I'm aiming for a board capacity of 12"x9" with intermittent use, so only a fraction of that volume should be required.

I saw a design on the web where someone converted a plastic cooler (ice chest) into a CuCl etching tank. (Heaven forbid anyone thinking there were party punch in there!) The website is gone, but you can still see thumbnails if you google for images called "CuCl etching".

Regards, Mark Jones

Reply to
Mark Jones

I would assume you are talking about FeCl (Radio Shack stuff ;-) )

The aquarium bubble stone will work for awhile, but is not reliable (at least to me). Just make sure you cover the container: the bubbles produce VERY nasty mist. You don't want it to get on anything around the tank.

There is a newsgroup that's more narrowly focuses on PCBs and related stuff: sci.electronics.cad We keep its Web interface here:

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You may want to try your question there as well.

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Dmitri(Cabling-Design.com

Yes, that was probably my web page. I copied that stuff from a book published in 1983, but I did get permission from the author.

I have used it to etch with a bubbler. It worked but seemed slower than FeCl. I still have all the stuff, but haven't found the reason to use it lately. In theory, you can rejuvenate the solution just by bubbling air through it (to add O2) but in emails with the author, he says he now uses strong hydrogen peroxide. You also need to add HCl and water either way.

I got myself a web domain and a place to resurrect my pages, but after dumping my old ISP, I have been lazy about putting up pages. I want to redo them using CSS but I haven't found a style I like yet. When I get it finished, I'll post a message here with CuCl in the subject, and give a link.

Reply to
xray

Oh cool. From what I've found, it looks like the optimum temperature for Cu++Cl2 etchant is 130 degrees F. Were you using a heater? (Could an ice chest withstand a heater?)

H2O2 would be an ideal rejuvinator. That extra oxygen atom would really do the trick. It seems like nearly all reactions involving CuCl produce H20 - with the addition of H2O2 doesn't the solution end up being "watered down?"

This fall I etched a board outside using FeCl... it took nearly 50 minutes with no heater. I even put a lamp over it, but it still undercut noticably. I used a ziplock baggie so no yellow finger syndrome and poured the used etchant back into the bottle. Eventually it will have to be disposed of. I've learned that if you neutralize FeCl etchant with sodium hydroxide, it produces NaCl and Fe3(OH)2, which can be burned (reduced) to rust and hydrogen gas. This is still a big hassle, and one reason CuCl is looking so interesting. :)

Great, thanks. Eventually I'll put my design up on the web also. It's gonna take awhile though.

Oh, and for CSS perhaps you'd like

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- they have a demo, very handy for rapid CSS design.

Regards, Mark Jones

-- "If necessity is the mother of invention, then is experimentation the father?" MCJ 20041116

Reply to
Mark Jones

In the one I built, I went to the aquarium supply store and found some stuff designed for bubbling. Its some kind of porous plastic tubing about .25 in dia. I think it is meant for burying under gravel in a fish tank. In the bubbler, I ran several rows of it in parallel about 1 in apart. Needs a strong pump to feed it all.

It seems to survive in the etchant ok.

Reply to
xray

I read in sci.electronics.design that Mark Jones wrote (in ) about 'Slightly OT?: CuCl PCB heater & bubbler', on Tue, 11 Jan 2005:

There wouldn't be much water produced if there was no peroxide. The basic action is:

Cupric chloride CuCl2 + Cu -> 2CuCl Cuprous chloride

You need other stuff, including HCl, because the basic reaction goes slowly and CuCl is poorly soluble in water so the reaction stops. The peroxide, and oxygen from the air, help to re-convert the CuCl and HCl into CuCl2.

The etchant is ferric chloride, FeCl3. You don't need to use sodium hydroxide to kill it, the carbonate (washing soda) is quite OK and less dodgy to handle. You get a disgusting-looking mass of ferrous hydroxide Fe(OH)2 and carbonate FeCO3. You don't need to burn it; just heat it up well until it's dry.

No hydrogen; you get salty rust (Fe(OH)3 mixture with Fe3(OH)4) or salty ferric oxide if you heat it strongly, and water (steam). (In any case, burning is oxidation, not reduction.)

It's not much of a hassle. You could use excess powdered slaked lime instead of the soda, which gives a solid mass without heating, but it still looks disgusting. It disintegrates as the calcium chloride attracts water from the air and dissolves in it.

The majority advice seems to be that cupric chloride etching is not really suitable for small-scale use, but this year is Y MMV.

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Reply to
John Woodgate

You'll need at least a heater and a pump. The best way to use FeCl is in a spray etching machine though. Etching times of 5 minutes or less are achievable.

You don't need to dispose FeCl. It can be regenerated with Hydrochloric acid (HCl). 10% HCl is available in a lot of stores. Don't worry about the extra water, you'll need it to compensate for loss of fluid due to evaporation.

I have been using the same FeCl for about 12 years (or more) now.

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Reply to
Nico Coesel

I read in sci.electronics.design that Nico Coesel wrote (in ) about 'Slightly OT?: CuCl PCB heater & bubbler', on Tue, 11 Jan 2005:

How do you get rid of the dissolved copper? If you don't, you may actually be using CuCl2 as the etchant without knowing it!

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Reply to
John Woodgate

I know, but it is not quite the same. When the solution is regenerated, a mix from FeCl and CuCl is doing the etching (if I remember correctly from my etching bible).

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Reply to
Nico Coesel

I took a fish tank heater -- adjusted to some hottish temp (I can't remember the details) and replanted it in a large test tube with chemistry rubber stopper and tight sealing enforced for wires and all junctions with some kind of "glue" - might have been silicone. I think I sealed it hot to minimize expansion pressure.

With the tight sealing, I got the whole heater horizontal at the bottom of the tank. The cooler container has survived so far - only a few attempts really, but I don't see problems from the heat.

On the rejuvenating -- the original article (none of it my work-I just provided what I found interesting) has the details. It is not simple. You need to monitor both specific gravity and the acid level, by titration.

I accumulated enough chemical supplies and kludgy apparatus to get it done. It is not simple. I doubt if a dash of this or that each time would suffice very long.

On the FeCl side, the original author of my method offered one of the best sounding suggestions I ever heard for disposing of spent FeCl solution -- Use it to mix with cement (concrete). Send the resulting brick to the dump. Any bad stuff should be tied pretty tightly inside this brick. Way better than pouring down the drain or somewhere else.

All these methods have potential negatives. It was mentioned earlier that either solution in a bubbler creates corrosive or staining spray if not carefully contained or cleaned. The HCl in in the CuCl will creap out and attack nearby metals if not tightly sealed, even just sitting there.

I'm no real expert on any of this, but I have tried it.

Reply to
xray

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