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Step 5Save the etchant for next round. You're done.
Once you're done etching, pour the etchant back into your storage bottle, rinse off the board, flux, drill, populate, and solder.
Some final notes here:
1) You can make quite a bit of this stuff very easily, and since you're re-using it, there's no real reason to skimp; put plenty of etchant in your "tank." When you use too little FeCl etchant, for instance, it can get saturated with copper and slow down which can result in long etching times and pitting or undercutting or worse. When I'm etching a board with copper chloride, I'll pour a couple extra inches of solution into the container. It's reusable anyway, and the extra exposure to oxygen just regenerates it. Live large.
2) Don't make too much. As you keep re-using the solution, you're going to need to add a little more acid and a little more peroxide every once in a while. If you've got a 750 milliliter container, start out with less than 500 milliliters of solution. Give yourself some room to grow over time. After all, the main point is to avoid having to dispose the copper in spent etchant.
3) If you've got too much volume of etchant (it will happen eventually) you can evaporate out the extra water by putting it in a shallow (non-metallic) pan or beaker or whatever and letting it sit for a while. This concentrates the copper in solution, giving you a stronger etchant. It'll also re-oxidize some of the copper for you, a bonus. Remember when you're adding the peroxide that you're actually adding 97% water.
4) The linked website suggests that the acid levels in the etchant are not critical as long as there's some acid in solution to do the CuCl2 regeneration. The amount of CuCl2 (vs CuCl) present is easy to diagnose by the color of the solution. Add oxygen to re-green, and add a bit of acid if that's not working. Worst case is that you may have to wait a few more minutes per etch with a sub-optimal bath. This isn't rocket surgery.
5) I do have an aquarium pump ($6 at fish store) that I've used to re-activate my solution. Sometimes I'd leave it on for a few hours while I'm at work if I've been etching a lot. But lately I've been lazy/impatient and tossed in a couple capfuls of peroxide. Both seem to work just fine.
6) The environmental benefit of etching with copper over ferric lies mostly in not having to dispose of the copper that comes off your boards every few times you etch. When and if you do end up with too much copper etchant, please treat it like the hazardous waste that it is -- look into your local hazardous chemical disposal options. There's no getting around the fact that copper salts are (for instance) poisonous to fish even in very dilute concentrations.
Some final notes here:
1) You can make quite a bit of this stuff very easily, and since you're re-using it, there's no real reason to skimp; put plenty of etchant in your "tank." When you use too little FeCl etchant, for instance, it can get saturated with copper and slow down which can result in long etching times and pitting or undercutting or worse. When I'm etching a board with copper chloride, I'll pour a couple extra inches of solution into the container. It's reusable anyway, and the extra exposure to oxygen just regenerates it. Live large.
2) Don't make too much. As you keep re-using the solution, you're going to need to add a little more acid and a little more peroxide every once in a while. If you've got a 750 milliliter container, start out with less than 500 milliliters of solution. Give yourself some room to grow over time. After all, the main point is to avoid having to dispose the copper in spent etchant.
3) If you've got too much volume of etchant (it will happen eventually) you can evaporate out the extra water by putting it in a shallow (non-metallic) pan or beaker or whatever and letting it sit for a while. This concentrates the copper in solution, giving you a stronger etchant. It'll also re-oxidize some of the copper for you, a bonus. Remember when you're adding the peroxide that you're actually adding 97% water.
4) The linked website suggests that the acid levels in the etchant are not critical as long as there's some acid in solution to do the CuCl2 regeneration. The amount of CuCl2 (vs CuCl) present is easy to diagnose by the color of the solution. Add oxygen to re-green, and add a bit of acid if that's not working. Worst case is that you may have to wait a few more minutes per etch with a sub-optimal bath. This isn't rocket surgery.
5) I do have an aquarium pump ($6 at fish store) that I've used to re-activate my solution. Sometimes I'd leave it on for a few hours while I'm at work if I've been etching a lot. But lately I've been lazy/impatient and tossed in a couple capfuls of peroxide. Both seem to work just fine.
6) The environmental benefit of etching with copper over ferric lies mostly in not having to dispose of the copper that comes off your boards every few times you etch. When and if you do end up with too much copper etchant, please treat it like the hazardous waste that it is -- look into your local hazardous chemical disposal options. There's no getting around the fact that copper salts are (for instance) poisonous to fish even in very dilute concentrations.
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Excellent tips, tried it and etched a few boards with very good results and this could be the answer to my problem of now having to get Ferric Chloride (crystal form) by mail order in my locality.
Just one thing someone may be able to clear up for me though.
Adding the peroxide to my HCl which is 280-300g/litre makes the etchant dark brown so there's no way to assess the 'green-ness' of the mix. Tried with 2 different concentrations of standard hardware store acid with the same result but the etchant certainly does its job well so my only way of checking its state would be via specific gravity and ph. No amount of aeration with an air pump and a porous stone makes any difference to the colour or clarity.
Is there iron or some other contaminant in my HCl?
(Both the acid and the 6% peroxide appear perfectly clear & clean prior to mixing)
Also did some sample tests in test tubes with the resulting brown colour starting to develop from just a single drop of peroxide in 10ml of HCl.
It might still be poisonous, though.
The author mentioned that he was using "fuming HCl" - that's about as concentrated as you can get, and the fumes are HCl gas. If it redissolves in the liquid on your mucous membranes (eyes, nose, throat), it will form concentrated acid.
I had an incident in the university lab where I accidentally inhaled a _small_ amount of HCl gas from a chemical reaction and had to rinse out my nasal passages. Took 1/2 an hour before the stinging stopped, and the "taste" to disappear. :/
The issue is the copper - even tiny amounts in water supplies are very poisonous to fish.
What procedure should be used in washing off the board?
I usually shake/drain the board afterwards and there's only a few drops of etchant left on it. Rinsing with running tap water dilutes it sufficiently that there's no worries.
This necessitates that you store a second chemical. But it's worth it if you etch more than once a blue moon, because it serves other purposes, as well. I use it to prep boards and to clean tank/utensils. This further recovers copper ions. Eventually, the bath becomes etchant, itself, and you pour it into your etch tank and make some more.
and may also attack stainless
to make it inert treat it with washing soda.
http://www.taster-wine.com/shop/prodimg/mellem2512017.gif
i assume that would be good for storage?
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.