Etchants: How many are there?

[Somicide]

We've got our basic Ferric Chloride and Ammonium Persulphate, but what are our other alternatives?  I recently read an old post in the archives discussing the use of Muriatic (Hydrochloric) acid (30% concentration) and Hydrogen peroxide (3% concentration) as etchant and was wondering if there are any other alternate etchants as well.  I also seem to have misplaced my Ferric Chloride, so go figure. 

[Paul Perry (Frostwave)]

There are MANY possible etchant mixes, but a better question might be: How many etchant mixes are there that are reasonably safe if it spills on your arm, and do not generate poisonous fumes? That cuts the field right down.
In fact I think it cuts it down to what we already know about...

(by 'reasonably safe' I mean if you spill it on your arm, it hasn't burnt the skin off by the time you have run to the bathroom & washed it off. Personally, I'm sticking with persulphate.)

[Somicide]

True, true.  But, if your conditions permit (in my case, a well-ventilated garage with a conviently placed sink for rinsing said arm ) they very well could be safer.  I'm going to try the muriatic/H2O2 mixture in a 3:1 ratio (H2O2:muriatic) since I have it on hand, and as I said earlier, I've misplaced that damn Ferric Chloride.

[Paul Perry (Frostwave)]

OK Somicide! If you want to live dangerously, you could always add pool chlorine to the devil's brew.....
And you might find sodium perborate somewhere as a laundry aid, in solution it hydrolyses to give some hydrogen peroxide.
One of the nappy washing mixtures contains mostly sodium percarbonate (a hydrogen peroxide & sodium carbonate crystalline mix) but, if you use that as a source of peroxide, you would have to neutralise the carbonate which would be a waste of acid.
Note I havn't tried any of the above, and people have died from randomly mixing domestic cleaning agents (I remember one case of someone removing stains from a toilet bowl using muriatic (hydrochloric) acid & White King (hypochlorite) bleach.. the chlorine in a confined space got him

[Somicide]

I did it tonight, and it worked out really well, actually!

The 3:1 mix made the acid fairly mild (that's 3:1 Hydrogen Peroxide to Acid), no fierce bubbling (heck, none really) and I left it to etch outside where any fumes vented safely.  Save for some poorly touched-up PnP, the etch was fantastic, certainly no worse than I could've done with the usual etchants.  If I can get ahold of a digicam, I'll post some pictures of the board (my Dr. Boogey finally takes shape!). 

I appreciate the concerns, but I know well the dangers of mixing bleach and anything, or strange chemicals, etc.  I found a safe looking recipe for this etchant and gave it a go, and it worked ok for me (not that I'm saying I'd rather use this over etchant intended for this).

[alfonso_pola]

As far as I know, if you pour iron in that solution you get Ferric Chloride. By iron I mean nails, or any other iron thing. Though it may take a while to dissolve a nail...

[Seljer]

I just found this among the RSS feeds I'm subscribed too:
http://www.instructables.com/id/EKVI03SL4PEV2Z566X/?ALLSTEPS

etching with electrolysis

[R.G.]

If all you want to do is get the copper etched away, you have the choice of many chemicals.

Most chemicals that react with copper and don't also eat the resist will eventually etch. In fact, if you are truly desperate, I believe that ordinary water will eventually dissolve the copper, although this will take centuries.

And that's the difference in the processes - speed of etch and cleanliness of the cutting. Modern etching chemicals are optimized for speed and cleanness of cut. It's not easy to see on our stone-axe produced circuit boards, but the etchant also eats away at the side of the copper being etched as it eats toward the board. The faster the stuff cuts, the less the undercut in general. This is important with thin traces.

I think that the main industrial processes are persulphate-peroxide and sulphuric acid-peroxide baths. If I remember correctly, these baths can be regenerated easily because they eventually form copper sulphate crystals on the bottom which can be recycled. Ferric Chloride is harder to regenerate, and was discarded by industry because of that. Electrolytic baths are ideal... except that they can't etch isolated islands of copper because the current stops to the islands when the last molecule in the last thread connecting the island opens. This generally leaves many threads just about ready to short. It would have to be followed up by a chemical etch to clear those away.

Both speed of etch and lack of undercutting are important, as is the disposal of the resulting gook. Sulphuric-peroxide is good because (a) the basic bath is easy to make from battery acid stock (b) it's cheap (c) it can be regenerated forever (d) it cuts fast (e) it does not undercut. The only reason this doesn't get much amateur play is that as a practical matter you have to keep a five gallon jug of battery acid in your garage forever. Persulphates tend to need heating to get to high etch rates. FeCl is about the only minimally corrosive stuff that etches cleanly and fast at room temperature and can be kept in small bottles, doesn't need regeneration, and is relatively benign to dispose. (Yes, compared to some of the other etchants, it's not all that bad.)

[Somicide]

I've got a 5-gallon bucket with about 16oz of liquid etchant in it now, sitting outside the garage, waiting to be neutralized (baking soda should work, but I'll research before throwing it in there.  I've also heard that Ferric Chloride is alkalai rather than acidic, though I'm not sure where.

[ubersam]

There was a thread a while back where someone mentioned etching with some kind of salt (copper salts?), the kind that you can get from feed stock suppliers.

[Minion]

I have been useing the Muriotic Acid and Hydrogen peroxide etchant for quite a while Now and it has become my main etchant now...

It is mostly because I use so much etchant that it is getting expensive when a Litre of Feric Chloride is about $10 were I live and I can make about 5 Gallons of Acid mixture for the same price....

I also notice that for small boards that the acid is very fast ,Like a couple minutes if you agitate it well.....

I have gotten the acid on my skin a couple of times but I allways have a bucket of water close by so I haven"t really gotten burned yet....

It works well if you are safe....

[Somicide]

It works well if you are safe....

Exactly!  I work near a sink, so I can wash my hands/arms frequently.  Rubber gloves would've been a good idea, but I seem to be out.  Dr. Boogey PCB was done in less than ~5 min!

[MikeH]

I don't think Ferric is alkalai... baking soda produces a pretty good reaction; that's how I've been neutralizing my ethchant.  Think baking soda and vinegar times 10.  And it turns from liquid to sludge afterward.

[Somicide]

like I said, I could be wrong.  But then again, aren't bleach and ammonia both alkalai? 

[JimRayden]

I just found this among the RSS feeds I'm subscribed too:
http://www.instructables.com/id/EKVI03SL4PEV2Z566X/?ALLSTEPS

etching with electrolysis

A million thankses! Enough with acids and alkali for me, Jim goes electro!

If it does work, I don't understand why it isn't the preferred method for everyone (especially newbs) in electronics, as it seems way safer than the usual "evil liquid" we use.

---------
Jimbo

[Minion]

I just found this among the RSS feeds I'm subscribed too:
http://www.instructables.com/id/EKVI03SL4PEV2Z566X/?ALLSTEPS

etching with electrolysis

A million thankses! Enough with acids and alkali for me, Jim goes electro!

If it does work, I don't understand why it isn't the preferred method for everyone (especially newbs) in electronics, as it seems way safer than the usual "evil liquid" we use.

---------
Jimbo

I don"t know but that board was pretty ugly looking or maybe I"m not used to that "Style" of PCB Design, The etching method it"s self looks pretty cool though...I might have to try it.....

Thanx

[Peter Snowberg]

P'n'P probably holds up to salt water too.

[markm]

 
I'll stick with Ferric Chloride myself.
If I didn't have a day job and a Wife and 2 kids well then, I may have the time to mess with the alternative methods but for now,
Ferric Chloride works fine.

[Somicide]

pnp is awesome stuff, especially once you finish the transfer, and you can see through it!

[Paul Perry (Frostwave)]

There was a thread a while back where someone mentioned etching with some kind of salt (copper salts?), the kind that you can get from feed stock suppliers.

That was in the context of etching stomp boxes, that is, etching aluminum, a different matter.