Etching question - Page 1
Forum section: electronics / beginners

author: Jimbz
author_rank: Contributor
timestamp: June 21, 2013, 08:13:45 pm
content: Greetings all, Id like to start etching my own pcbs, since using perfoboards is getting cumbersome for my hobby stuff. The process of etching is nothing complicated and Ive used some of the software for single layer tracing, nothing hard.Id like to use ferric chloride for etching, and my main question concerning this is: what do you do with the chemical after you have etched it ? Dump it down the toilet, throw it out of the window, add water to it and then flush it down the drain ? Where do you put it ?Also, aside from the expensive cnc tracing and forementioned ferric chloride, what would you recommend as a decent safe-for-health etching method ?Thank you for reading

author: Alana
author_rank: Frequent Contributor
timestamp: June 21, 2013, 09:54:44 pm
content: I usesodium persulfateand this stuff can be dealt with at home.I try to separate as much of CuSO4 as possible usinghttp://en.wikipedia.org/wiki/Fractional_crystallization_%28chemistry%29- comes in handy for copper plating or other chemistry stuff and rest goes back to etching bath. If its totally used you may add baking soda to get rid of copper ions. Any copper will become solid stuff and rest of solution is mostly sodium sulfate that is quite harmless to environment and can be put down the drain.And for etching - sodium persulfate likes to be hot and i mean at least 40-50 deg celsius hot. Otherwise etching is so slow that you may end up with washed away toner from toner transfer before board etches completely.

author: c4757p
author_rank: Super Contributor
timestamp: June 21, 2013, 09:58:03 pm
content: Quote from: Alana on June 21, 2013, 09:54:44 pmSo, has your first board finished etching yet?QuoteAh, yes, you've figured it out. Even when it's good and hot it still takes ages...

author: TerminalJack505
author_rank: Super Contributor
timestamp: June 21, 2013, 10:04:25 pm
content: So far as ferric chloride goes, use a funnel and put it back in the bottle it came out of and re-use it. You can get a lot of use from one bottle. Especially if you use one of those cheap sponge brushes to scrub the board when you etch. You can etch a double-sided board in 5 minutes with fresh ferric chloride that way. It will take longer with re-used stuff but not that much longer.

author: Jimbz
author_rank: Contributor
timestamp: June 21, 2013, 10:12:49 pm
content: Quote from: TerminalJack505 on June 21, 2013, 10:04:25 pmAnd what do you do if you have compleately exhausted the reusability ? Down the toilet it goes or dig a hole i nthe ground and bury the bottle there ? Legit question tho, how should I rid of it ?Quote from: Alana on June 21, 2013, 09:54:44 pmI dont really have a bath, all I can think of right now is putting the sodium container into a hot water container, how long does this process take ?

author: TerminalJack505
author_rank: Super Contributor
timestamp: June 21, 2013, 10:21:45 pm
content: I'm not going to advise you on disposal but, according to Dave, ferric chloride is actually one of the things the water treatment plants add to water. In Australia, anyway. I don't know about other countries.

author: ampdoctor
author_rank: Frequent Contributor
timestamp: June 21, 2013, 10:27:09 pm
content: I've personally always been a fan of the Muriatic acid/hydrogen peroxide solution. It's dirt cheap, works well at most temperatures and is easily obtainable. In theory you can recharge the etchant and reuse it indefinitely, however I've never managed to get it to work. Also, I've found that magazine paper tends to work better than the photo paper method a lot of people endorse. Again, your mileage may vary. You just have to try different things and see what works best for you.As for disposal, well this is I'm sure a bit controversial and I'm sure it's still illegal, but the old old old school method is to save up your spent etchant in a plastic milk jug. Once you've accumulated a fair amount of the stuff head over to the hardware store and get a small bag of concrete or mortar mix. Now make a small brick using the etchant and extra water. Let it cure hard then just dump it in the trash. The mix will neutralize the acid and the copper ions will get sealed up inside the brick so it's "relatively" environmentally safe. Yea, over time I'm sure it'll leach out into the water supply, but this will take decades as opposed to minutes if you were to just dump it down the drain.The "legal" way in most areas is to contact a hazmat disposal company, store the etchant in "approved" containers, and schedule a pickup or drop off. Some places will charge you for the service while others wont. The other solution is to contact your local water treatment plant and ask them what their procedure is. Problem here is that more often than not the person you talk to wont have a clue as to environmental impact, local state or federal law, or anything else for that matter and YOU are still the one that's responsible no matter what they tell you.

author: Unknown
author_rank: Unknown
timestamp: June 21, 2013, 10:54:39 pm
content: Quote from: ampdoctor on June 21, 2013, 10:27:09 pmMuriatic acid eats concrete i believe sodium carbonate (NOT sodium bicarbonate) is the proper way to neutralize.

author: nukie
author_rank: Frequent Contributor
timestamp: June 21, 2013, 11:36:53 pm
content: Why throw away muratic when you can 'recharge' it? It's something renewable that's what made me move away from other acids and it etch much faster than ferric.

author: Stonent
author_rank: Super Contributor
timestamp: June 21, 2013, 11:38:29 pm
content: Sylvia says to pour it back in the bottle.

author: TerminalJack505
author_rank: Super Contributor
timestamp: June 22, 2013, 12:19:04 am
content: Don't tell Dave but that kid's videos gets more views than his.*snicker*

author: Stonent
author_rank: Super Contributor
timestamp: June 22, 2013, 12:25:21 am
content: Well I'd be interested in Dave's demographics. I don't know if he has the "tween" girl category quite sewn up yet.... He's a bit PG-13 to R at times.But I do watch Sylvia's videos, it sometimes motivates me when I think "Well if she can do it, I can too"

author: c4757p
author_rank: Super Contributor
timestamp: June 22, 2013, 12:29:13 am
content: Quote from: TerminalJack505 on June 21, 2013, 10:21:45 pmThis is true. Ferric chloride with copper in it, though? Big difference.

author: george graves
author_rank: Super Contributor
timestamp: June 22, 2013, 12:33:24 am
content: Quote from: TerminalJack505 on June 22, 2013, 12:19:04 amHa! I hope the parents have that channel set up for ad money!Dave - it's time to put Segan to work! Pimp that kid out and you'll get rich!

author: Thor214
author_rank: Newbie
timestamp: June 22, 2013, 01:30:53 am
content: NurdRage has a series of 10 etchants to use and he quickly mentions what to do with the spent reagents afterwards (recycle or dispose of).

author: george graves
author_rank: Super Contributor
timestamp: June 22, 2013, 01:41:38 am
content: 3% peroxide is what I was using until I found 30% stuff at a hair salon supply place. It etcches like no one's business. I can etch ~100 sq inches of copper in about a 60-120 seconds.

author: bluesmoke
author_rank: Contributor
timestamp: June 22, 2013, 01:44:12 am
content: Thanks for making me laugh!Quote from: TerminalJack505 on June 22, 2013, 12:19:04 am

author: ampdoctor
author_rank: Frequent Contributor
timestamp: June 22, 2013, 02:03:26 am
content: Quote from: CompElitePCAnything that's going to eat away a whole chunk of concrete is going to require a very large quantity of it relative to the size of the block. It will also need to be almost completely undiluted. And yes there are textbook proper ways to neutralize the stuff but you're still left with the copper which is toxic as hell and most people that home roll pcb's don't have access to shelves of chemicals for 'proper' neutralization, base metal recovery, and disposal. The mortar trick has worked pretty good for probably half a century or more to effectively dispose of, and make almost completely immobile, all sorts of etchants especially if it's been contaminated over time.Quote from: nukie on June 21, 2013, 11:36:53 pmLike I said you're supposed to be able to recharge it. However I personally have never been able to recharge it to the degree that it's functional again. Given that a gallon of the stuff costs a whopping 5 dollars at the hardware store an a bottle of peroxide is 2 dollars at walmart, I really can't get my panties in too big of a knot over it. If you have a method that consistently gives good results and is cost effective, please share it with the class. And no I'm not being sarcastic. I'd really like to know.

author: Unknown
author_rank: Unknown
timestamp: June 22, 2013, 02:41:40 am
content: Quote from: ampdoctor on June 22, 2013, 02:03:26 amcorrect me if i am wrong... however it is my understanding if the solution is neutralized... its should drop the copper out? I personally would not know because I have never needed to dispose of it, I use it multiple times a day. and no complaints here!This I do know: copper can be removed by adding aluminum (such as soda/ beer cans) until it drops all the copper out of solution and can be recovered.We have used copper(II) acid for well over five years, and it still works a treat. all you need is oxygen, i am curious to what your doing incorrectly...

author: ampdoctor
author_rank: Frequent Contributor
timestamp: June 22, 2013, 03:07:57 am
content: I might be wrong but I can't see how the copper would drop out if it was ph neutral. I've had 2 classes in P chem and 1 organic and that was nearly 20 years ago so I'm more than willing to admit being mistaken.As far as rejuvenating the etchant, I have no idea what I'm doing wrong. If I did, then I'd have fixed that problem a long time ago.

author: Unknown
author_rank: Unknown
timestamp: June 22, 2013, 03:32:08 am
content: Quote from: ampdoctor on June 22, 2013, 03:07:57 amWell your classes paid off!you are absolutely correct, and i am SO wrong about that. (brainfart)However I might be able to regain some composure/confidence by helping you out pertaining to Copper(II)

author: westfw
author_rank: Super Contributor
timestamp: June 22, 2013, 06:27:53 am
content: I say flush it down the toilet.Ferric chloride is used in water treatment.Copper isn't good for the environment, but people dump copper sulfate down their drains BY THE KILOGRAM to keep roots out of their pipes. (not to mention spraying or dusting it on assorted foliage.) If the quantity of copper you're etching away gets above to 500g/year (more than a square meter), or if you're in a location that specifically prohibits copper sulfate root killer, then you should probably search for a better way.

author: sleemanj
author_rank: Super Contributor
timestamp: June 22, 2013, 07:59:24 am
content: Do NOT flush spent up ferric chloride.Brand spanking new Ferric Chloride is one thing, but used Ferric Chloride is a whole different kettle of (dead) fish (http://www.diystompboxes.com/smfforum/index.php?topic=50426.msg377115#msg377115)Neutralise it with soda. Mix it with some plaster. Cast it into a brick. And put it in your bin. Landfills are designed to contain this sort of thing. Sewer systems are not.

author: sleemanj
author_rank: Super Contributor
timestamp: June 22, 2013, 08:03:48 am
content: Quote from: westfw on June 22, 2013, 06:27:53 amI think you'll find there is a substantial difference between Copper Sulphate, and Copper (II) Chloride.Copper (II) Chloride, as Wikipedia will tell you: "is toxic and only concentrations below 5 ppm are allowed in drinking water by the US Environmental Protection Agency."Compare:" Upon oral exposure, copper sulfate is only moderately toxic. According to studies, the lowest dose of copper sulfate that had a toxic impact on humans is 11 mg/kg. "

author: IanB
author_rank: Super Contributor
timestamp: June 22, 2013, 08:24:41 am
content: Quote from: sleemanj on June 22, 2013, 08:03:48 amActually there is no effective difference at all. Once dissolved in water, both copper sulfate and copper chloride will produce the same copper ions. Since it is copper that has the toxic properties it is unimportant whether the accompanying anion is chloride or sulfate.