Not sure if vertical etching is for you? Try it out! Make a small scale, pint-sized, leak-proof etch tank in about 10 minutes, with 2 things you already have lying around: a DVD case and a 2L bottle.
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What you'll need:
scissors
DVD case
heat gun
Now go buy:
an aquarium bubbler - $15.00
aquarium tubing - $3.00
a 2L bottle of soda - $2.00
scissors
DVD case
heat gun
Now go buy:
an aquarium bubbler - $15.00
aquarium tubing - $3.00
a 2L bottle of soda - $2.00
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There are already several good websites and instructables that cover the basics of making a pcb, including choosing/making etchant, toner transfer method, UV exposure method, et al.
@ ydeardorff - The toner transfer method involves printing an image onto a piece of paper (you can even use glossy magazine paper) with a laser printer, then transferring the image onto the copper using either a laminating machine or household iron. The areas that have the toner protect the areas under it from being etched during the etching process. You can use a green scour pad to remove the toner and Voila! You have a very nice circuit board! I DID want to add my two cents that I've been using the Pulsar products and ( http://www.pulsarprofx.com/ ) and I've been VERY happy with the results! I don't have any more undercutting or botchy so-so areas of copper. I no have very few areas of the board that need touch-up after etching.
I just figured I'd throw that in! I use the muriatic acid method and have been very happy with that too! Be-Gone GREEN SLUDGE!!!! ;-)
Pulsar pros: it's coated paper. It handles like coated paper. It's easy to cut and handle. PnP is plastic, so it curls, generates static cling, and attracts dust/hairs. It is much harder to cut. The easiest way I've found is with a very sharp knife over a cutting board.
Pulsar pro: it transfers very easily. But if you don't transfer well, the transfer may be damaged by minimal handling or even while in the tank. So this isn't a huge pro for me. PnP takes a lot more heat and pressure to transfer. But once it's on, it's on for good.
Pulsar pro: If your technique is bad, you still get great results. With PnP, too much heat and pressure can result in artifacts, where the blue sticks to the board, even where there's no toner. Dextrin paper can't produce artifacts.
PnP pros: It's more stable for long-term handling and storage. If you get it wet/damp then you just have to let it dry off. If you get the dextrin paper wet, it messes up the coating and the backing can distort. And if you have a humid environment, you have to keep dextrin paper sealed. PnP has an additional layer over the toner. It seems to me like the traces come out just the tiniest bit sharper. And it's cheaper.
So if you an learn how to use PnP effectively, it is basically the same thing, maybe just a hair better finished result for cheaper. But Dextrin paper is very nearly the same finished result and is much easier to achieve.
To make your first batch, you mix the HCl and H2O2 together (the H2O2 adds the oxygen). Next you throw in some copper wire over night until it is dark brown. Now put your aquarium pump in the solution until it turns bright green.
I bought a 2L bottle of HCl a few years ago. I have still only used about 250 - 400 mL of it. It cost $20NZD (About $15USD). The H2O2 costed $2 a bottle, and I have used two bottles over the years. You really only need one bottle, and it is for putting the initial oxygen in the solution. After that you just need an aquarium pump.
The cost means that I can have a nice large tank, have it really full of acid, and drop my board in. The acid is completely re-usable. In fact, it gets stronger with use (as long as you don't use the hydrogen peroxide to re-add the oxygen).
What you're describing is copper chloride etchant.
Indeed, I use copper chloride, as it is the by product of etching with ferric chloride. My larger plexiglass tank is filled with about 1.5L of etchant. Roughly 1/2 to 2/3 of that starting volume was ferric chloride. The rest is copper chloride, stretched with muriatic acid over the years as needed to keep the concentration right.
You're correct. If maintained, a batch of copper chloride will last forever. So will ferric chloride (plus copper chloride).
The topic is heavily debated here :-). I myself have been the instigator a couple of times.
The was an awfully large board you used. Was that expensive..? In NZ, boards are about $20NZD a pop. 300mmx300mm
Etching with ferric chloride is almost exactly the same thing as etching with pure copper chloride.
There is one difference. When copper chloride solution gets too concentrated, it simply stops etching. You add some HCl, and it's good to go, again.
When ferric chloride gets too concentrated (I know you're not adding any additional ferric to the tank. I'm talking about the concentration of copper chloride + ferric chloride), the etching slows down and gross solid iron oxide particles start coming out of solution. If you do not maintain your tank, the etching will eventually stop, and a pile of iron oxide will settle on the bottom of the tank. Add some HCl and a bubbler, and this is reversed. You're good to go, again.
I think a lot of people are under the impression that ferric is disposable, because it etches so darn good with such a small volume, at first. But they mixed it from powder, and there are no excess Cl- ions in solution! So check it out. It works awesome at first, because Fe(III)chloride etches copper. Copper goes into solution as copper chloride. Now Fe(II) chloride is left, and there aren't enough Cl- ions to allow it to revert back to Fe(III), even with a bubbler. Same goes for the copper chloride produced. Some can be reverted to green copper(II) chloride, but it won't be efficient unless you add some Cl- ions to the mix. So things slow does, and eventually iron oxide starts precipitating out. So people throw it away because it's slow and gross.
Some people add table salt to ferric chloride baths. I prefer to use HCl. It speeds up the etching of copper chloride, but it also increases undercutting. So don't add too much.
http://en.wikipedia.org/wiki/Iron(III)_chloride
If you look at the reactions, it clearly shows how you can make ferrous chloride from iron oxide and HCl.
Furthermore, ferrous chloride turns into ferric chloride in the presence of chlorine.
Final piece of the puzzle:
http://en.wikipedia.org/wiki/Chlorine
Chlorine is produces by HCl + oxygen
So In my experience, ferric is indefinitely recycleable with a little HCl and a bubbler, and in the last 15 minutes (just cuz you seem skeptical), I backed that up with research.
I was under the impression you didn't need to maintain Copper Chloride(II) with HCl. I just added some the other night, as I needed more etchant to cover the board. It then got very fast. I hadn't done that for many, many boards. That explains why it got so slow. An etch would take up to an hour, or more! The most recent one turned out great, and took about 30minutes.
Thanks for doing all that research. It is very interesting to hear that FeCl(III) is actually re-usable. That makes life a whole lot cheaper for many people... Although, I'm sure that CuCl(II) is cheaper.
FYI, excess HCl does NOT etch copper directly, in absense of peroxide. But it does enhance the etching speed of copper chloride solution, partly for reasons I have just explained. But from what I read, too much HCl can cause excessive lateral etching/undercutting. So be warned.
1 hour etch? Wow, that's slow. I wonder what you're etching? If you're doing circuit boards, you will get cleaner edges if you speed up the etching with heat and agitation. A bubbler will work wonders, and will help to keep your etchant oxydized.
There is one benefit of copper chloride besides cost. Cuprous chloride regenerates faster when exposed to oxygen than does ferrous chloride. But as long as you keep the solution with excess HCl, ferrous does regenerate with a bubbler. And every time you add muriatic acid, you are adding some aqueous chlorine, which speeds up the regeneration. ?? (again, not a chemist, but it does work)
Either way, if you keep reusing ferric chloride etchant, you'll end up with mostly copper chloride. There ARE ways to get the copper chloride to precipitate out, if you want to repurify your ferric, though. Putting elemental iron in your tank with increase ferric content by addition of Fe ions and causing copper to precipitate out. Try putting a drop of your copper chloride etchant on a piece of iron/steel. Copper will plate out onto the object.
Pro's for vertical etching: 1. Space. I found out that as the size of your etchant tray gets bigger, it gets easier to accidentally spill etchant while you move it, even if you only keep a shallow amount in there. With a vertical tank, it's easy to move without having the skills of a waiter.
2. Air agitation: can be done with a horizontal tray, too, with a bit more effort. But with a vertical tank, air agitation is always going to be more efficient for the same amount of bubbling.
3. Heating: I've found that a vertical tank with a bubbler is easy to heat evenly, by putting a heater across the bottom of the tank.
My main purpose was convenience. I wanted to flip a couple switches, put my board in, and then come back in 10 minutes... and a vertical etch tank seems like an elegant, space-saving solution. I'm liking it, so far.