etching tanks and room corrosion? - Page 1
Forum section: electronics / general

author: coppercone2
author_rank: Super Contributor
timestamp: April 20, 2020, 01:34:49 am
content: Have you actually noticed corrosion from using a PCB etching tank indoors? Is there some minimum safe distance from objects that can be used (i.e. put in center of garage and mop floor afterwards?)Just how insidious is the bubble mist? I always did it outdoors but its annoying. I thought maybe just to put a towel over the top on a wire frame to act as a 'filter'.

author: jpanhalt
author_rank: Super Contributor
timestamp: April 20, 2020, 02:35:40 am
content: It could vary depending on what etchant you use. Even when I was making PCB's relatively frequently, I removed the etchant and stored it in another container when it would be a few days between uses. I tried various etchants including the "per-xyz" types and kept returning to ferric chloride or cupric chloride. When I regenerated the copper baths, I did it in an open room.Never had any problems with corrosion. I don't think it would be a good idea to store in an enclosed area. Remember that HCl is volatile while H2SO4 is not. So, if there were a problem, I suspect it would be worse with HCl _ hydrogen peroxide than with H2SO4-based etchants.It may also depend on what else is stored in the area. Ammonia (like liquid ammonia in water for cleaning) and HCl or FeCl3 (etc. ) stored in close proximity to each other will often get a gooey haze on the bottles and everything else in the area from reaction of the small amounts of free HCl and NH3 released.

author: coppercone2
author_rank: Super Contributor
timestamp: April 20, 2020, 02:43:54 am
content: nah there is no problems with storage, I store the space I want to etch in. I mean the actual bubble part. The only problem I had with storage is when a milk jug leaked (was very cheap). (40% ferric chloride).I am just worried about the bubbler during operation for 6 minutes. (I don't plan to keep it in the tank either). I know the open container is not going to effect anything, based on ~4 years storage with little/no issues. Actually left the cap off a jug for a year by accident, with no real issues (well the can of WD40 next to it rusted hard..but that was within like 1 foot away). (this is stuff that was 'regenerated' with h2o2 and hcl.I can hit things with a wire wheel grinder.. I just don't want it crazy.

author: jpanhalt
author_rank: Super Contributor
timestamp: April 20, 2020, 02:51:33 am
content: Quote from: coppercone2 on April 20, 2020, 02:43:54 amThat seems to answer your question.

author: coppercone2
author_rank: Super Contributor
timestamp: April 20, 2020, 03:24:20 am
content: its not misting though, as far as I know the stuff just evaporates water slowly leaving behind fecl3 hydrate. does it decompose or something?bubbles might make aerosol.

author: rdl
author_rank: Super Contributor
timestamp: April 20, 2020, 08:45:23 pm
content: Quote from: coppercone2 on April 20, 2020, 03:24:20 amBubblers are what cause really bad problems. The aerosols they create can travel farther than you would think and corrode everything.

author: jpanhalt
author_rank: Super Contributor
timestamp: April 20, 2020, 08:55:09 pm
content: Here's a short lesson in chemistry. Take this equation:a_FeCl3 + b_HOH == c_Fe(OH)x + d_HCl + e_xxHere are the rules:OH always was 1 negative chargeH always has 1 positive chargeFe always has 3 positive charges (I want to avoid changes in oxidation states)The final solution must be neutral for + and - chargesCan you come up with any equation that releases HCl? Why does ammonium carbonate release ammonia ("smelling salts")? (https://en.wikipedia.org/wiki/Smelling_salts)

author: coppercone2
author_rank: Super Contributor
timestamp: April 20, 2020, 09:04:39 pm
content: thats what I thought..do you know exactly what happens when you add HCl and H2O2 to 'refresh' it? I seen simple equations but also think I read something that it forms more complicated complexes or something that makes it 'unstable', i.e. its only refreshed for some period of time.Anyway, I determined already that the slight addition of HCl does not really corrode anything if its sitting (at least in a narrow neck bottle).. however the mist is still ominous.I guess I should keep doing it outside... unless a standard rag would act as a good enough filter. I assume the bubble mist dimensions are based on some kind of probability density function and there will be some small particles that would require something like hepa to catch (way too complicated at this point). Unless its some trick like a wet rag?I know it can't work THAT well because gas masks are complicated. But maybe..

author: KL27x
author_rank: Super Contributor
timestamp: April 20, 2020, 09:22:43 pm
content: I lay/stuff a rag or paper towel over the top of my tank to catch the spray produced from the bubbles/head popping. I think it would be better to make a lid where this spray would collect/condense and drip back down into the tank. My tank has a lid with a beveled piece on the bottom for condensation to drip back down to the tank, but I can't use it with my PCB holder.These rags get soaked with etchant even 4 or 5" from the top of the etchant, so I don't suppose it's particularly practical to just make the tank taller. I etch outside. The rags prevent the side of my house from building up green salts.edit:Quoteif you are having to add peroxide, then ditch the bubbler. It's not doing anything particularly significant. You need a lot of surface area of contact to regenerate cupric, and holes poked in a tube won't do squat.

author: coppercone2
author_rank: Super Contributor
timestamp: April 20, 2020, 09:35:52 pm
content: I thought the main use of bubbler is mechanical motion (I can see vortex form in tank).fitting a condenser on the tank is a good idea, it looks like you would need to make an entire assembly that features tank lid + board holder with a adapter to a glass condenserGlue this into tank lidhttps://www.ebay.com/itm/Lab-Scientific-Glass-Ground-Joint-Adapter-Extender-18mm-Male-to-18mm-Female/124059810425?hash=item1ce28a7a79:g:RwUAAOSwK9heK378then fit something like a frederich condenser on it (think its the tightest, so vapor can't 'shoot through' the middle, and it has to spiral around some what.then you got 2 pumps and a heater and ice bathkind of wonder actually what would happen if you just bend titanium sheet into a V and put ice cubes in it, may be a 20$ solution

author: jpanhalt
author_rank: Super Contributor
timestamp: April 20, 2020, 09:44:14 pm
content: I use a horizontal tank, glass standoffs, Corning stirring hot-plate, and Teflon-coated stir bar. Very little splashing.

author: KL27x
author_rank: Super Contributor
timestamp: April 20, 2020, 09:52:36 pm
content: QuoteThat helps for most "real" etchants. It removes the salts from the board so that the traces will etch right. And it circulates fresh etchant to displace the spent etchant that diffuses relatively slowly in a static tank.Acid peroxide has no problem diffusing around salts (or under your resist) and etching whatever is wet. The concentration of H+ and H2O2 is pretty close to the same, everywhere. The acid proton and H2O2 molecules are tiny and won't form much of a gradient. They diffuse extremely fast.OTOH, if you get enough air exchange, you can actually etch with cupric. And now you're etching almost as accurately as with fresh ferric, each and everytime, without changing out the etchant. But you won't get there with a fish tank bubbler, so disavow yourself of that idea. If you are using acid peroxide with a bubbler, that might make it 3% better and save you 3 cents on peroxide per year. So if it's causing a problem, just don't do it?I've explained this in excruciating detail about a dozen times on this forum, and I'm sure you read most if not all of those explanations, Copper.

author: coppercone2
author_rank: Super Contributor
timestamp: April 21, 2020, 12:02:38 am
content: By regenerated I mean you add a little bit (because its probably a mixture of FeCl3 and CuCl2)I think I Have a very spent container thats mostly CuCl2. I think I was going to throw the container away, since it looked really ratty in a milk bottle and I threw some left over copper strips in there (and totally forgot about it). It stood for like 4 years, the bottom accumulated alot of sludge.. however recently I bought fresh anhydrous FeCl3 to make new solution, and I found this old shit, and I actually strained it to get rid of most of the brown mud, whatever a coffee filter can do. Now that solution is pretty green when it settles, so I assume its mostly copper chloride etchant.I actually don't know what to do, if I made a gallon of etchant, and it started at 40%, then it gets depleted eventually, I guess I would add some H2O2 and HCl to it eventually, because its kind of a pain in the ass to mix up fresh solution since it gets hot etc. I don't know when the bubbler stops being useful when you reinforce the solution.Bit of a problem, I don't know how to handle it/measure it (all I could think of is to use volumetric flasks and a precise scale to see how the mass of the solution changes). I don't know the history of the left over stuff.. I assume it evaporated to super concentrate whatever was in there and the crystals were mostly the less soluble copper chloride? Anyway its not imporant it must be worth less then 15$, I thought to keep it around for shop metal work (like etching a dial).

author: KL27x
author_rank: Super Contributor
timestamp: April 21, 2020, 01:18:05 am
content: QuoteOr just leave it be, and mix up straight HCl and H202 if you're going to etch with acid peroxide. If you use peroxide, the cupric is basically garbage byproduct that actually catalyzes the breakdown of the peroxide you're using.Adding diluted HCl to the sludgy, used ferric/cupric will restore it, only very slightly, and you will notice it will never etch a board unless you have very recently added peroxide. And the etch quality goes down.QuoteWell, if you etch with ferric, you should continue to use a bubbler.If you get the resolution you require when using any of these flavors of acid peroxide, that's great. And it would be more convenient for many people. But putting a fish tank bubbler in there is pointless. It'll turn the cuprous into cupric over several hours. But that will do 14 seconds etching of a 25 minute job.So when it turns from dark/brown to lighter/greener, that doesn't make a difference. The peroxide in there while you're etching is the only thing that matters.Etching with air-regenerated cupric is easy if you do it right. Air compressor, 20 psi through the aquarium bubble curtain wand. There are other ways to do it, including with peroxide, but not like what the internet does. But you will believe the internet because thousands of people can't be wrong. So you will guess that your mix is off. Maybe you have to add more water or more acid. And you think it is working, now. Because you ALSO added just a capful of peroxide.

author: coppercone2
author_rank: Super Contributor
timestamp: April 21, 2020, 01:55:37 am
content: I don't know if I ever even used it lol (I think I made it around the time I stopped doing microelectronics design). I think maybe I stopped doing it because I got greedy with buying chemicals and it destroyed a few boards being a franken solutionyou are right the circuit boards are expensive enough that trying to make some kind of mixed eternal soup is a bad idea. I will keep it for low res work like boilerplates or something

author: KL27x
author_rank: Super Contributor
timestamp: April 21, 2020, 02:16:53 am
content: QuoteYou're my twin brother in some ways. What with the garage workshop crap. Tell me you don't have an air compressor? All you need to buy is a regulator and a fish tank bubble wand, and you can etch with cupric. Takes 2-3x longer than ferric. But you only need add acid and water and it never slows down.

author: coppercone2
author_rank: Super Contributor
timestamp: April 21, 2020, 03:44:05 am
content: I have a compressor (rolair quiet nail compressor). Kind of scared to plug that into etchant without some kind of vapor trap/bubblerFor the etching I always used a aquarium pump. I am worried about the integrity of the film for long etches (my boards usually mix with TO220, DIP and weird packages like QFP-NL and weird nanosized stuff like filters.. i mix through hole, smd passive too (I like the idea of a one board design to minimize interconnectsI want to experiment with weird amplifiers connected to high res ADC/DAC (think like stanford research systems). This should stem into multi layer construction.. need to make glue jigs for that and do VIA platingI have alot of research to do with ground plane current mapping with field density probe scanner in regards to mixed signal stuff.unfortunately its like thisyoutube.com/watch?v=qXD9HnrNrvkwhat comes to mind now is multiple etching processes, i.e. use cheap solution on powerish then peel, remask and do fine traces (perhaps soft silicone tape would work for this).

author: KL27x
author_rank: Super Contributor
timestamp: April 21, 2020, 07:30:34 am
content: The air only goes one direction. And there's zero reason to leave it plugged in when you're not etching a board. If you leave the regulator with the tank gear, then you have to disconnect it, too. You can even buy a 5 gallon air tank for 20.00, if you're that worried. That will give enough regeneration for just about any reasonable board with room to spare. This is when you get tired of buying and mixing ferric. If you stick with ferric, then the fish tank bubbler is good enough... although if you used the setup I'm giving you, your ferric will never stop working just it will change to cupric.After that, you lost me.edit: You could probably use a small external tank, anyway. An external tank will hold that air for a really long time. The built-in tank on my compressor leaks anything over 30 psi, overnight. Before I got this portable tank, I would have to fire up my compressor everytime, just to blow chips out of my router plate and fence or to shoot 3 brads.