Ferric chloride is a traditional home-use circuit board etchant. It's easy enough to come by, and the Ferric by itself is no big environmental problem. However, once you've etched a board with it, you're left with a solution with a bunch of copper chloride in it. This dissolved copper is an environmental problem, and you can't just pour it down the drain (legally) -- you're supposed to take it to a hazardous waste facility. (For instance: How to Dispose of Ferric Chloride in this FAQ. )
Wouldn't it be nice if there were an etchant that you could re-use indefinitely so that you don't have to worry about disposing of the copper, and that could be made in lifetime supply for like $10.00 with ingredients bought at hardware and drugstores? (And it's prettier too.)
I got seven words for you: Copper Chloride in Aqueous Hydrochloric Acid Solution! (Exclamation point!)
But how're you going to get CCiAHAS? Conveniently enough, by starting out with a simple two-ingredient starter etchant, and doing a bunch of etching.
Wouldn't it be nice if there were an etchant that you could re-use indefinitely so that you don't have to worry about disposing of the copper, and that could be made in lifetime supply for like $10.00 with ingredients bought at hardware and drugstores? (And it's prettier too.)
I got seven words for you: Copper Chloride in Aqueous Hydrochloric Acid Solution! (Exclamation point!)
But how're you going to get CCiAHAS? Conveniently enough, by starting out with a simple two-ingredient starter etchant, and doing a bunch of etching.
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Signing UpStep 1: Ingredients: The Starter Etchant
For the starter etchant itself, you only need two ingredients: hydrochloric acid and hydrogen peroxide.
(OK, actually three. But the third one's copper. See the chemistry section for an explanation.)
Hydrochloric (muriatic acid, "pool acid", etc.) is available at a hardware store. The acid I got is 31.45% (or 10M) and should run around $5 per gallon. Which is more than you'll ever, ever need.
The peroxide is normal 3% for mouthwash or cleaning cuts, and can be bought at a drug store for $2-3 for a big bottle.
You'll also need a non-metallic container that fits your PCB and two standardized measuring cups.
As long as you're in the hardware store, pick up some acetone if you don't already have some. It's useful for removing the etch resist. (That's for another instructable.)
(OK, actually three. But the third one's copper. See the chemistry section for an explanation.)
Hydrochloric (muriatic acid, "pool acid", etc.) is available at a hardware store. The acid I got is 31.45% (or 10M) and should run around $5 per gallon. Which is more than you'll ever, ever need.
The peroxide is normal 3% for mouthwash or cleaning cuts, and can be bought at a drug store for $2-3 for a big bottle.
You'll also need a non-metallic container that fits your PCB and two standardized measuring cups.
As long as you're in the hardware store, pick up some acetone if you don't already have some. It's useful for removing the etch resist. (That's for another instructable.)
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Make sure that you're constantly agitating the solution so that fresh etchant is always exposed to the copper, and be patient. On the other hand, if it's taking longer than 15 minutes, something's wrong.
Keep the solution sealed when not in use -- strong hydrochloric solutions like this tend to fume, making the solution weaker and corroding all metal in the surroundings.
If it's green, and not etching well, add a little acid. If brown, add a tiny bit of peroxide. That's all I've ever needed to do...
Good luck! And if you figure out what's going on, post back?
downside - it is not fast (etching time 10-20min depending on temperature and use) and it is not clear so one normally takes PCB out for inspection.
the good side - cheap, easy to get, lasts for years and hundreds of PCBs, no maintenance (no mixing, measuring, shaking, bubbling or whatever). when you think you had it for too long, drop it off at a recycling place and buy new bottle.
etching time can be reduced by using air bubbler or agitator and warming up the etchant before use. another thing i am doing more often is to just let someone else manufacture my PCBs. then you get through hole plating, solder mask and silkscreen...
(I'm curious how you get your Ferric solution to last for "years" and "hundreds of PCBs".)
In contrast, I've used the same batch of this stuff that I made for this Instructable up until I left the US in 2011. So say from 2007 to 2011. Probably not "hundreds" of boards, maybe like 80-100. And as far as I know, they're still using my batch at my old hackerspace.
Industry switched from Ferric to more-easily renewable etchants in the late 1990s and early 2000s for environmental and cost reasons. I see no reason for the hobbiest not to do the same.
For some reason this process did not work for me. Even after 20 minutes, not the board was still looking pinkish, b/c not all the copper has been removed yet. The photo resist layer started dissolving on minute 10 of the etching, so I could not use this method at all. Here is the end result:
Does anyone know a possible reason for why this didn't work? Is the photoresist coming off too easily? Is the copper being removed much slower than it should be?
Did you use double-sided board? It looks like the top actually etched clean, but there's still some copper left on the back side. It's a lot easier on the etchant, and a lot quicker, if you mask off the back side of a double-sided board with tape or paint or anything, rather than etch it away. *And* then if you hook it up to your ground, you get a nice ground plane for free.
It is a double-sided board, with tracks on both sides.
Etching time can vary a lot depending on the thickness of the copper on the board, of course, but 20 minutes for fresh etchant mix seems very long to me as well. That's why I was wondering if you somehow the positive developer stage didn't go right or something? Maybe it the resist didn't get fully removed? (Like I said, I have _no_ experience with that stuff, I've always been an iron-on or sharpie kind of guy.) Can you test this with some clean copper? Maybe remove the photo-resist film with sandpaper or use un-treated board to be sure?
And here's all the rest I can think of: (shotgun-style, hoping something will hit)
Temperature? You're not doing this outside on a cold day, right?
Double-sided etches need 2x the solution as single-sided, and it's a lot harder to etch the downward-facing part of the board if it's resting on the bottom of a tupperware.
And then there's agitation. Even with a fresh solution, if you're not constantly swirling the solution around in the tray, it'll locally saturate with copper and slow down the reaction in the neighborhood of the traces. As you swirl it around, you'll see small dark clouds of dissolving copper coming off the traces that eventually dissappear into solution. Professional etching machines use pumps, bubblers, or spray-and-drip methods to keep fresh etchant in contact with the copper. We're stuck with emphatic swirling.
I was only able to arrange laboratory grade 30% h202 and some extra strong Muriatic acid used for toilet cleaning here in India. With 2:1 proportion, It barely took seconds to etch out the pcb, But I am having a hard time preserving it.
I kept it in a plastic bottle, but the mixture heated up by itself and exploded, costing a bucketful of sweat cleaning up the mess(excluding to the expenses of the chemicals). Can you please help me with proper guidelines on how to preserve it? It is creating a significant amount of fume and that's the reason for the explosion. but I am worried diluting the solution will affect the etching process. Please help.
Regards,
Shubhradeep
Second, I don't know how strong "extra strong" HCl is, but be aware that stuff used for cleaning toilets often has extra additives, and you'll have no idea what's going on chemically.
Anyway, it sounds like you've gone waaay too far in both possible directions. You're aiming for a 3M HCl solution with a tiny bit of excess oxygen. Dilute out your H2O2, and figure out how much of the diluted H2O2 solution to add to the acid, based on how strong the acid is.
Eg: I used 10M HCl, so to get it down to around 3M, I needed to dilute it 1/3, or one part in three, or 1:2 with a (weak) peroxide solution.
Hydrochloric Acid in Harpic Power Plus Original toilet cleaner. 9g HCL per 100g = 9% (Brick cleaner from builder merchants states 5-10% HCL)
Hydrogen Peroxide in Bausch & Lamb EasySept contact lens solution. States 5% Hydrogen Peroxide.
I finally got round to trying these as an etchant and got zero results. I added HCL (Harpic) to H20" (EasySept) then my copperclad. Even after 10 minutes there was no visible reaction, despite all info saying the first etch is super quick.
I'm not sure what to do from here, other than just buy some Ferric Chloride!
First off, it's thermally unstable -- the reaction generates heat and wants to run faster as it heats up. If you're doing this with more than a little bit of lye, you should have it in a cooling bath to limit the reaction speed and temperature,
Second, the end results are aluminum oxide (and your aluminum etched away), and hydrogen gas, probably with a bunch of lye/water vapor mixed in -- steam if it's hot enough. So you've got a potentially runaway exothermic reaction and a flammable (explosive if contained) gas, in a steam with caustic lye. Fun times.
But this is my favorite way of filling up hydrogen balloons at parties. To be quasi-safe, the procedure goes like this: Use small amounts of lye -- I'll put 1 tbs in 500 ml of water, and that's probably on the high end. Keep the solution cool -- have the lye + aluminum reaction going on in something heat-proof, and have it submerged in another bucket with a lot of water to suck the excess heat away and keep the reaction under control.
So yeah. Long story short: if you want to etch aluminum, lye in water is great. Just keep the lye in small amounts, don't ignite the resulting hydrogen unless you want to, and keep it in a water bath with ice on hand if it gets crazy to keep the temperature and reaction speed under control.
In the end, pull the aluminum out with tongs or something and rinse it off. Dilute the lye/water/aluminum oxide mixture with a lot of water and toss it down the drain.
Ferric Chloride should be cheap it's the waste product from cleaning rust off of steel. They use HCl to do it.
I'd like to find out how to reclaim all that copper I will be etching away with HCl and H2O2
gr8 blog BTW
Also, with a 2 peroxide to 1 MA (30%), it keeps produceing gas. (on the second day) So I have to leave the solution outside, with the cap half on.
Other than that, I must say it's a great solution. I 5 by 5 cm board in 2-3 minutes, in -1°C So yeah. I just hope I wont run in to any issues with reuseing it like others have had.
Re: producing gas. Yeah, the HCl will probably fume. I've kept my solutions in sealed glass / plastic bottles which keep the fumes well contained.
Made the mistake of trusting the seal on some IKEA tupperware, left the solution in a cabinet, and ended up with a lot of very seriously rusted metal parts.
I secretly think that some of the stalled etches are due to lack of agitation of the solution. When there's excess O2 in solution, it doesn't matter as much, but in the long-run stable version of the etchant, you'll find that continually moving fresh solution over the copper is important.
The whole point was to not have to dispose of the solution for a long time (years? forever?) by re-using. And yeah, it does slow down after the first few times through, from around 2 minutes to around 10 minutes in my experience. But can't you wait another 8 minutes?
If not, you can try warming up the solution, to something like 100-120 degrees F (barely warm to the touch) in the microwave. Warming increases the HCl fuming, though, so you might want to etch with warmed solution in a ziplock bag or closed tupper or similar.
If you're getting etch times in the 20 minute or more range, something's wrong with your chemistry. Add acid or H2O2, or possibly let some of the water evaporate out over a couple days. That's all that can go wrong. (Note that adding low-concentration peroxide is basically adding water, so if you've done that a lot, you'll have a dilute solution which will etch slowly.)
And then finally, if you're really dead-set on disposing and starting again, you can call up your local firehouse -- they will know how to dispose of hazardous chemicals.
Or alternatively neutralize all the acid by adding enough lye (sodium hydroxide) and maybe some baking soda (calcium carbonate) to turn the solution a turquoise-blue, (copper hydroxide / carbonate) then let this dry out into a powder, and you can throw it in the trash. On the other hand, that's a lot more work than just getting the etchant back into shape chemically and waiting an extra 8 minutes per etch...
One word of caution though: the copper and zinc seem to etch at different rates. In one experiment, I was attempting to reduce the thickness of some brass sheet by a timed etch in this solution. The thickness was reduced, but the sheet's surface went from from having a uniform bright brass colour to having heterogeneous swirls and streaks of dark brown copper and silver-coloured patches of what I assume was zinc. This was using fresh etchant, at an elevated temperature, so the sample etched really quickly (under 2 minutes), When I used a "used" etchant bath, at a cooler temperature, the brass etched more slowly and evenly, and retained its homogeneous appearance and original colour. If you're trying to etch all the way through your brass sheet, though, this point is moot and I'm sure it will work fine at any etch rate.
I think the problem with the HCL based solution *might* be that you're more likely to evolve chlorine gas and get in trouble that way. Or it might just not give very good results finish-wise, or plating time wise. Or all three. Anyhow, I was hoping someone here might have experience with the technique.
Additionally, depending on a hundred different factors, the resulting copper plating will be a smooth finish, or a black, metallic powder that just falls off the metal. :(