I use the pre-mixed Ferric Chloride solution from MG Chemicals in a photographic tray, float the tray in a sink of hot water and rock it back and forth. Takes 15 to 20 minutes. When it's done, I pour as much as possible of the FeCl back in the bottle.
(To prepare the boards, I use the MG Chemicals positive resist boards, laser or inkjet printer on transparencies and a single UV tube about 6 inches over the board for their recommended exposure time, then their developer diluted as recommended.)
If the etching (or developing come to that) gets slow, it's time to replace the solutions.
So, if etching is taking longer than 30 minutes at room temperature, there is something really wrong...
I'm also using MG Chemicals Ferric Chloride. I'm afraid of putting the used etchant back into the bottle. I worry that bits of the paint I used as resist will contaminate the solution. For now I'm just keeping the used etchant in a separate container.
if you have easy access to cheap 30% peroxide.
Unfortunately, here in Croatia you can find 30% hydrogen peroxide only on the black market or if you have a friend who works in a hair salon. The drugstores sell only 3%. Well, there were times when you could buy 30% peroxide in drugstores but the lady behind the desk asks for your ID and asks for what purpose you're buying peroxide. Sometimes they give it without questions but that's rare.
Next problem: is 35% hydrochloric acid available where you are?
QuoteI'm also using MG Chemicals Ferric Chloride. I'm afraid of putting the used etchant back into the bottle. I worry that bits of the paint I used as resist will contaminate the solution. For now I'm just keeping the used etchant in a separate container.FYI, I wouldn't worry about that, at all. I read somewhere that aside from contamination with solvents, there's not much you can do to screw up ferric chloride etchant. I would add soap to the list, if you use a bubbler. And w/e is in Kemtech 15% muriatic acid.
If you don't want to waste it, just use the whole 1L* bottle of it. And pour it back in a bottle or next time. Trying to use a little of it at a time and then disposing of it is more wasteful, in the long run.
*Or w/e volume will reasonably fill your container without fear of spilling. You can try the whole, put the pcb in a bag and a few mL or ferric, but this is not creating less mess or using less ferric. This is just dumb.
Well, that's why I stashed on time some 40-50 liters of 35% HCL and 6 liters of 30% peroxide. Just in case if bad time comes.
Soap, bubbler? Is this from experience?
Ah, but that's not really a problem. 50 ml of 30% peroxide contains 15 ml of peroxide (approximately). However, 500 ml of 3% peroxide also contains 15 ml of peroxide. So you just adjust the proportions in the above recipe:
250 ml - distilled water
250 ml - 35% hydrochloric acid
500 ml - 3% hydrogen peroxide solution
Watch the shelf life of your peroxide !, it will slowly decompose when sealed, much faster after being opened.
@dsharp02,
I don't wanna sound like a smartass but do yourself a favor... ditch the ferric-chloride etchant and use 'modern' etchants like sodium persulphate or HCL+ hydrogen peroxide. The second one doesn't even need to be heated. The downsides of ferric-chloride are already mentioned in this thread so I'll skip that part. If you want to use HCL+HP then this is my recipe which always work:
For 1L etchant -->
700ml - destilled water
250ml - 35% HCL
50ml - 30% hydrogen peroxide
The only downside of this etchant is a nasty odor like vomit.
just don't go dumping a pile of H2O2 in at once, especially if it's 30% (excitement for sure!)
I still haven't found out what is being given off in that video. It obviously isn't Chlorine gas or we'd have heard about it. I'm thinking it must be water vapor as steam. I think if it was me I'd be using less concentrated peroxide just to slow things down a few notches.
Try:
Vinegar
Hydrogen peroxide
Salt. Add more salt to get more etching.
>Quote from: cdev on Yesterday at 18:29:32Try:
Vinegar
Hydrogen peroxide
Salt. Add more salt to get more etching.
Don't think that you are environmentally friendly or safer just because you use vinegar instead of "chemicals" such as hydrochloric acid, ferric chloride or sodium persulfate. Especially the copper salts formed in any of these etching methods are environmental hazards and need to be taken care off properly.
Also in Europe - at least Sweden and Germany - it is much easier to buy ferric chloride (if you want to stain yourself, your clothes, everything) or sodium persulfate than hydrogen peroxide.