Reusing PCB echant.

Dgswaner

I just talked one of the guy at the electronics supply shop when I buy parts, He told me that it's possible to reuse PCB etchant (the dark Iodine looking stuff). you can remove the suspended copper through electrolysis. I haven't tried this yet so I don't know the ins and outs of it yet but that will save me a few bucks!!!. ThHought I would share the info.

anyone else try this?

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"A complex design is the sign of an inferior designer." - Jamie Hyneman, Myth Buster

DGSwaner

Chris Savage

I don't know about that, but the following link should give you some interesting information. Take care.

http://en.wikipedia.org/wiki/Iron(III)_chloride

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Chris Savage
Parallax Tech Support

Leon

You can also use cupric chloride as an etchant. As it is used it becomes cuprous chloride, which can be regenerated to the cupric form with hydrogen peroxide and hydrochloric acid. You end up with more etchant than you start with.

Leon

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Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle

Steve Joblin

I've heard of a lot of folks using 2 parts muriatic acid (a gallon at Home Depot is $6) to 1 part Hydrogen Peroxide (a quart at the drug store is $2). The great part (in addition to the rediculously low price) is that unlike the brown echant, it is clear so you can see your progress to avoid over etching.

Phil Pilgrim (PhiPi)

I used the muriatic/peroxide mix to etch some brass recently. It was ponderously slow, and I wonder if it was because the drugstore peroxide is so dilute (3%). The problem with slow etching isn't just the wait, but the fact that you get undercuts and feature thinning when your work is in the etchant so long. I tried to find an authoritative answer as to what strength peroxide to use in the 2:1 formula, but came up empty.

-Phil

Dgswaner

now that I think about he told me another thing. if you use electrolysis while etching, I forget if you use the copper clad board as the anode or cathode, but the board will etch really fast.

I almost went with the muriatic acid route because of cost, but I decided to stick with what I'm familiar with and reclaim the copper

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"A complex design is the sign of an inferior designer." - Jamie Hyneman, Myth Buster

DGSwaner

LoopyByteloose

A little chemistry might help. The brown stuff is Ferric Chloride and the iron is replaced with the Copper ions as it etches. I suppose that you can reverse the equation with electrolysis, but a by product could be chlorine gas which is poisonous. So why bother?

Sure, muratic acid works, but it is very aggressive and easily over-etches. I suppose that it is buffered with the peroxide to prevent this. The ferric chloride is a traditional etchant from intaglio printing on copper plate and offers more control of fine details.

Artist occasionally add lemon juice - citric acid - to enhance the ferric chloride. They claim this is a better formula, but it is hard to objectively document. The point is that the art world has a lot of information about etching copper plate which has evolved over centuries. If you want the best detail and tips on handling, it wouldn't hurt to consider their knowledge.

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PLEASE CONSIDER the following:

Do you want a quickly operational black box solution or the knowledge included therein?······

···················· Tropically,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan

Post Edited (Kramer) : 2/2/2008 8:35:55 AM GMT

Leon

There is *lots* of info on various etchants here:

http://tech.groups.yahoo.com/group/Homebrew_PCBs/

Leon

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Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle

LoopyByteloose

Regarding the muratic acid and peroxide being too slow, one can easy adjust all these etchants to suit your particular needs. But Muratic acid general undercuts more than ferric chloride and is considered unsuitable for intaglio printing because of that.

There really isn't a 'set formula' as temperature is a big factor. Dilution is another factor. Some people use an aquarium heater to speed up the ferric chloride and the actual strength of the solution varies with use. In fact, a new solution seems to go slower than one that has some copper ions in suspension.

Nonetheless, there is always the problem of your quality going to nil if you speed things up too much with a 'hot batch'.

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PLEASE CONSIDER the following:

Do you want a quickly operational black box solution or the knowledge included therein?······

···················· Tropically,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan

skylight

I have reused ferric chloride many times over, each time I strain the liquid through paper towel or gauze to remove the smeggy bits and it works fine time after time though it loses strength with each etching so longer etching times are needed but i found warming up the solution contained in a bottle warmed under hot water revives the solution to keep etching times reasonable eventually you will have to throw it away.

One factor for prolonged or uneven etching is not making sure that the copper board is spotlessly clean before application of transfer tracks ie after a period of storage the copper tarnishes.

better still use photo resist board which tends to not tarnish like clean copper does as it comes with a plastic peel off film.

Post Edited (skylight) : 2/3/2008 10:37:19 PM GMT

pwillard

I've had very good results with Muriatic Acid with hydrogen peroxide and it only seems to undercut if you agitate "a lot" in addition to leaving it to etch too long.· It etches quite fast and that alone makes it preferrable to the "heat required" slow ferric chloride approach.· The fact that you can see what you are doing (being a clear versus opaque liquid) is a plus...

A Ferric Chloride stain is also the most unforgiving stain you could ever create.· I continue to prefer the risk of undercutting to the annoyances of ferric chloride.· I also re-use my etchant and will only start fresh when it gets to be an unearthly shade of green.

As I've stated in the past...· Ferric Chloride gets it's color by an infusion of RUST.· It is essentially weaker·Hydrochloric Acid·[noparse][[/noparse]unlike the watered down·Hydrochloric Acid·we call·Muriatic Acid] (HCl) with rust in it·(FeO(OH)).· Why is that?· In steel rolling mills, they clean the rust (oxides) off sheet metal while it's being processed·with hydrochloric acid.· What we etch with is the liquid that results from that process...· a weakened acid.. There is nothing magical about the Iron in it.

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There's nothing like a new idea and a warm soldering iron.

Post Edited (pwillard) : 2/4/2008 4:44:00 AM GMT

Phil Pilgrim (PhiPi)

pwillard,

So what kind of peroxide do you use: the drugstore 3% stuff, or something stronger?

-Phil

Steve Joblin

The following excerpt was taken from "Easy Printed Circuit Board Fabrication Using Laser Printer Toner Transfer" by Thomas P. Gootee, (C) Copyright 2007 which can be found at http://www.fullnet.com/~tomg/gooteepc.htm#1


"I've found a new home-made etchant that I really, really like. And it's very cheap, and widely available. It's made by adding 1 part Muriatic Acid (the common kind that's sold in hardware stores, which is actually 28% Hydrochloric Acid) to 2 parts Hydrogen Peroxide (the common 3% kind that's sold in drugstores and pharmacies). This etchant can etch a 1-oz board in about five minutes, at room temperature, with gentle mechanical agitation. And it's almost transparent. I mix it in a small plastic food-storage container and wear rubber gloves so I can use a balled-up paper towel to gently wipe the surfaces of the board, as it etches, which seems to speed up the etching time, considerably. (Caution: The concentrated acid's fumes would be very bad to breathe, or to have around metallic items. And the acid would be very bad to get onto anything that's not plastic.)"

LoopyByteloose

FYI... In intaglio printing, the undercut is a very undesirable property as it holds too much ink and creates unexpected variations in the printing as it colapses under use. Thus, there has been a lot of investigation into avoiding it. Copper plate is coincidentially the most desirable because of the finest lines and least undercut.

With most circuit boards, we have a lot of lattitude in the quality that is acceptible. So, the choice of etchants may simply come down to clear or that soupy rust colored stuff. [noparse][[/noparse]Yes, ferric chloride certainly stains quite well, but muratic acid eats holes in your shirts that don't appear until the next wash cycle and the fumes can permanently ruin your sense of smell.]

But as images get smaller and tighter, all aspects of quality control become more important. There are a lot of factors. I prefer the photo resist boards because they produce a near perfect image when used with a good transparency. Others use the laser transfer method. But I've never had the crisp, clean images that I enjoy with my prefered method, though some claim Pulsar's laser transfer system is excellent.

It is all about finding a method that suits your personal preferences.

Incidentally, ferric chloride is a wonderful solution to artifically age a bronze statue or brass hardware as it can create a powdery blue-green patina streaked with rust in a few minutes that would take years of weathering. Adding common table salt aids the process.

Be wary of anyone that is quite glib about working with strong acids, bases, solvents, etc. There are important proceedures for dilution and mixing to avoid fumes, explosions, and burns. The easiest precaution is to mix and use in an outdoor space. A plastic or rubber apron and gloves are always welcome. Chopsticks are handy for handling.

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PLEASE CONSIDER the following:

Do you want a quickly operational black box solution or the knowledge included therein?······

···················· Tropically,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan

Dgswaner

Kramer you made me think of a job I had a while back, I had to etch aluminum parts in vats of acid. I had use a full rubber suit and gas mask. I forget all of the acids we used but the "bad" one was hydrofluoric acid, if you got that on you it was a fast ride to the emergency room! the bottle would "smoke" as you proud it out. We had a whole procedure on cleaning the empty bottles and throwing them away, they got thrown out in a regular dumpster, and if someone dumpster dove and got those it could be fatal.

everyone talking about reusing enchant. from what I gather your just talking about taking a bottle etching a board and then reusing the same liquid the next go around? so your not actually reclaiming the copper and making the enchant usable again.

I didn't try the electrolysis method, due to chemical hazard concerns, but when the weather isn't so bad and I can go outside I'll try it.

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"A complex design is the sign of an inferior designer." - Jamie Hyneman, Myth Buster

DGSwaner

KatyBri

Please be careful with peroxides, especially if you get higher concentrations. These are oxidizers, which if stored for longer than stated times or at above stated temperatures can become explosive.