PCB etching  - Page 1
Forum section: electronics / beginners

author: megahz
author_rank: Regular Contributor
timestamp: April 05, 2013, 01:58:03 am
content: I wana etch a circut with HCl and H2O2 (because ferrachloride is bad for the environment), how pure do they have to be because I have 1m HCl, and I can concentrate it to 5M, do they have to be an exact ratio?

author: ivan747
author_rank: Super Contributor
timestamp: April 05, 2013, 02:28:59 am
content: I just use the HCl I can find as the supermarket. And I get H2O2 at the drug store. Nothing special. Takes a while and a lot of shaking for me but it's ok. I'm guessing that's because the concentration of both of the chemicals is very low.

author: Psi
author_rank: Super Contributor
timestamp: April 05, 2013, 02:38:03 am
content: I use 35% HCL from the hardware store and 6% peroxide from the pharmacy/drug storeIf you want to reuse the solution forever then more concentrated chemicals are better because you're not diluting the solution with water every time you top it up. (It also etches faster)However highly concentrated HCL and peroxide are dangerous to work with so i recommend starting with the normal stuff.It's fast enough and safer to mix.Just keep the chemicals away from your metal sink, it will ruin the polished metal finish.

author: megahz
author_rank: Regular Contributor
timestamp: April 05, 2013, 02:56:35 am
content: Lolz caus i have 12molar stuff, which is almost pure HCl, (well sorta the most pure you can get cuaz HCl is a gas)

author: Resistoid
author_rank: Contributor
timestamp: April 07, 2013, 08:40:48 pm
content: Hello megahz.There's a description of how to do it and what you need here:http://www.instructables.com/id/Stop-using-Ferric-Chloride-etchant!--A-better-etc/?ALLSTEPS- I've followed the recommendation of using 2 parts peroxide to one part HCl.My HCl was relatively weak in concentration at 25%, while the peroxide was 9%. If memory serves, I think I've also used 6% and probably even 3% peroxide in the past. It appears that the ratios of these two chemicals are not particularly critical.However, be prepared for your boards to etch much more quickly than with ferric chloride. Given the seeming aggressiveness of this method it may be advisable to monitor the process continually to avoid potential damage.Hope that helps.Resistoid.

author: darko31
author_rank: Regular Contributor
timestamp: April 07, 2013, 08:49:22 pm
content: Eh, I don't know, I just pour them in 1:3 ratio, and if things are going slow add some more of HCl and peroxide. It's like cooking

author: nukie
author_rank: Frequent Contributor
timestamp: April 09, 2013, 12:18:10 am
content: Is this formula better than Persulphate based acid because the ammonium persulphate I use sucks under etch a lot.

author: Psi
author_rank: Super Contributor
timestamp: April 09, 2013, 02:25:49 am
content: Quote from: nukie on April 09, 2013, 12:18:10 amAmmonium persulphate must be very hot to work properly.Unless you have the etch container sitting inside another container full of boiling water it wont stay hot long enough.For that reason alone i really hate ammonium persulphate.HCL+peroxide will work at room temp just fine.

author: nukie
author_rank: Frequent Contributor
timestamp: April 09, 2013, 04:05:36 am
content: I have been on ammonium persulphate for years because I bought a kilo of it from a photographic film developing supplies. I use it in glass on a hotplate with thermometer at 60c, the acid goes off after a while so storage is not a idea. Im going to try HCL peroxide next.

author: megahz
author_rank: Regular Contributor
timestamp: April 10, 2013, 02:43:57 am
content: I might buy the hcl online, any links?

author: Psi
author_rank: Super Contributor
timestamp: April 10, 2013, 02:46:55 am
content: you may have issues getting them to ship it due to being hazardous.

author: notsob
author_rank: Frequent Contributor
timestamp: April 10, 2013, 02:51:24 am
content: Go to the hardware store, it's used to wash down brickwork, they should have bottles in stock.

author: smashedProton
author_rank: Frequent Contributor
timestamp: April 10, 2013, 05:56:29 am
content: A trick I use to puriftly h2o2 is to freeze the water out and drip the liquid peroxide into your etchant. That may speed it up. Also, dispose of the stuff with sodium carbonate and a coffee filter

author: peps1
author_rank: Regular Contributor
timestamp: April 10, 2013, 11:07:22 am
content: Am I the only one who found HCl and H2O2 overrated as a sustainable etching solution?I found it next to imposable to keep a small tanks worth at a usable strength, and just ended up with larger and larger containers of the stuff.

author: poorchava
author_rank: Super Contributor
timestamp: April 10, 2013, 12:44:15 pm
content: Same impression here: I have tried the HCL/H2O2 method a while ago and liked it, but i wasn't able to get the "reusable etchant" to work. Maybe because I'm using 3% pharmacy grade peroxide. Hydrochloric acid that i have is 30-36% technical (industrial) grade. Re-used etchant seems to attack the PCB (surface turns dark immediately) but it doesn't seem to etch at any reasonable rate. Who cares... ingredients are cheap and it takes only like 50cc of acid + 100cc of peroxide to etch even a fairly large pcb.

author: hlavac
author_rank: Frequent Contributor
timestamp: April 10, 2013, 01:35:46 pm
content: Quote from: peps1 on April 10, 2013, 11:07:22 amI'm using it and it works quite well. Started with 30% HCl and 30% peroxide 1:1.You need the technical kind of peroxide (30%) not the pharmacy diluted kind (3%).Etched quite a bit of boards in it and now I'm at a nice green CuCl etchant.It keeps etching nicely, not too fast, and you can see clearly whats going on as the etchant is perfectly transparent, not like the ferric chloride mess.All I do is add a few ml of peroxide when it starts being slow and brownish.Do not add more HCl unless the etchant is bright green but not etching!Attached is a photo of my CuCl etchant container so you can judge the correct color.

author: BravoV
author_rank: Super Contributor
timestamp: April 10, 2013, 01:43:08 pm
content: Quote from: hlavac on April 10, 2013, 01:35:46 pmWhen to add HCL then ? Mind explain a bit detail there ? I'm interested.

author: hlavac
author_rank: Frequent Contributor
timestamp: April 10, 2013, 02:22:41 pm
content: Basically the HCl is a source of Cl ions and gets decomposed in the process. It's not the HCl acid that is etching the copper.The etching is done by the emerald green cupric chloride (CuCl2) ripping copper from the board and forming brownish cuprous chloride (Cu2Cl2):CuCl2+ Cu -> Cu2Cl2The HCl combined with oxygen then makes cuprous chloride back into more cupric chloride, regenerating the etchant:2 Cu2Cl2+ 4 HCl + O2-> 4 CuCl2+ 2 H2OThe great thing is you end up with what you had in the beginning, just more of itOxygen is not very well soluble in the bath, you would have to bubble air thru it and it is slow.Adding peroxide helps to get some oxygen in fast (it decomposes to water and oxygen).Now when you run out of HCl or oxygen in the solution, the regeneration stops working, concentration of brownish cuprous chloride rises and the solution changes color brom bright green to somewhat brownish.I prefer to run out of HCl as it makes nasty fumes (HCl, chlorine), I have less problem with some extra oxygenI'm trying to have as little of HCl in the solution as needed but not more. Hence I add more peroxide first, and only when it does not help I know I have run out of HCl so I add some too. I avoid having to do any measurements of density or titration that wayWhen making the initial etchant, make it outside, it stinks badly and gets hot a bit as it mixes together. Pour peroxide first, HCl second, 1:1. Don't fill the container to the top, leave space for the extra etchant that will result from usage. And it is very aggressive, you can overetch your board quite easily, only do thick traces in the initial etchant. Or cheat and just drop a piece of copper in it end leave it until it greens upBut hey, its etching, may as well use it right?

author: BravoV
author_rank: Super Contributor
timestamp: April 10, 2013, 02:42:36 pm
content: Thanks for the explanation.So the HCl + H2O2 solution, say we only used it once and still usable for next etching, can we keep & store it ? Or it will lose its etching power through time ?Also store it in non-sealed storage cause its gassing ?

author: darko31
author_rank: Regular Contributor
timestamp: April 10, 2013, 03:07:31 pm
content: I've never actually stored H2O2 and HCl etchant before, always used smaller amounts and throw away the rest as it's quite cheap. Anyway, another good source if H2O2 is your local hair dresser, it's used for bleaching hair.Also when etching with this stuff, it's good idea to wear old clothes, I've ruined my good shirt last time. Another tip is to always have some water around you whether a sink or in some glass/container, you can touch the stuff with hand but better wash hands quickly after or it will burn your skin a bit. One more thing, don't use anything that is made of metal, glass or plastic is the way to go, if you borrow a good spoon, you'll return half of it, after some use.

author: hlavac
author_rank: Frequent Contributor
timestamp: April 10, 2013, 03:14:30 pm
content: I'd pour it back into a sealed container after use. Preferably something like what the HCl came in.I did leave it in the plastic food storage box with a sealed lid that I used to do the etching in (as seen in above photo). But then the corrosive HCl fumes turned the rubberish plastic sealing on the lid into a white crispy dust in a few weeksIt does not seal anymore, but on the other side, the etchant stopped fuming as well so who cares as long as it does not stink - i just lay the lid onThe normal expected etching time is something like 20 minutes when you just leave it sitting at room temperature and I like it that way, nice and gentle. It does not undercut much.It may be interesting to look at ways of recovering the copper and turning this into something harmless like table salt solution that can be disposed of safely

author: BravoV
author_rank: Super Contributor
timestamp: April 10, 2013, 03:36:48 pm
content: hlavac, did you need to add more H2O2 or HCL at the "used" solution after it was stored for a while ?

author: hlavac
author_rank: Frequent Contributor
timestamp: April 10, 2013, 04:01:53 pm
content: I have had no problems storing the solution. I have been using my solution for almost a year, seems to work fine so far, sometimes i get impatient and add a few drops of peroxide when I think it is not etching fast enough. Only had to add a bit of HCl once so far.When you add a drop of peroxide onto the submerged board it makes a dark area that should disappear quickly. If it does not disappear within second or two you probably need more HCl.

author: megahz
author_rank: Regular Contributor
timestamp: April 10, 2013, 09:48:19 pm
content: Well I did it with 2m hcl and alot of peroxide, I don't know the proportions but it took forever

author: AndrejaKo
author_rank: Frequent Contributor
timestamp: April 11, 2013, 07:09:51 am
content: Just a small note about hair-dresser's H2O2: Make sure it's real, dumb H2O2and not some new fancy emulsion for hair bleaching or similar. Last time I tired to use hair-dressing H2O2, I could only find new, fancy kind and there was no easy way to deemulsify it.

author: poorchava
author_rank: Super Contributor
timestamp: April 11, 2013, 07:34:03 am
content: QuoteExactly the same thing here. Actually the only two ways to get 'real' peroxide was to either buy it from pharmacy as 3% solution, or from chemical supply wholesaler, but the minimum quantity of technical grade is 20L and it's not that cheap (around 17€ / 20L).In Poland companies dealing in chemicals generally refuse to sell acids to private people, because those are perceived as dangerous/toxic substances. In most cases giving your personal information (name, address etc) is enough, but then not many companies are willing to sell so low volumes (where low volume = less than 200 liter barrel)

author: flolic
author_rank: Frequent Contributor
timestamp: April 11, 2013, 08:23:40 am
content: Up until few years ago, here in Croatia you could buy 30% peroxide in every pharmacy. Then they change some rules and now you can buy only diluted 3% "safe" concentration.But if you know right people...

author: Resistoid
author_rank: Contributor
timestamp: April 13, 2013, 10:22:23 pm
content: Quote from: megahz on April 10, 2013, 09:48:19 pmmegahz, if you just stick to the concentrations and proportions I gave you earlier you should not have any problems etching your boards.What I am telling you is verified by personal experience:Peroxide: 2 parts (160 ml). Concentration 6% - 9%. - You can almost certainly buy this from a pharmacy.HCl: 1 part (80 ml). Concentration at least 25%. - You can almost certainly buy this from a hardware store.You'll have to decide the volume of a "part" - use enough of the mixture to cover the surface of your board when it's lying flat in your etching tank.Agitate or swirl the etchant so it washes over the surface of your board and keep a close eye on proceedings.A double-sided FR4 board, roughly 14cm x 12cm etched in 5 to 10 minutes; probably closer to the former.This method is much more rapid than etching with ferric chloride under similar conditions.Good luck.Resistoid.

author: ptricks
author_rank: Frequent Contributor
timestamp: April 13, 2013, 11:48:28 pm
content: check out this video where the guy shows 10 different etchants and how to make them.The guy NurdRage has a lot of other interesting videos, most are chemistry type stuff.I found something interesting when I let my last batch of etchant dry out:The cystals are a couple inches tall and very detailed. The etchat I use is copper chloride.

author: megahz
author_rank: Regular Contributor
timestamp: April 14, 2013, 01:15:28 am
content: the pharmacy near me does not sell 6 or 9%, only 3%H2O2

author: ptricks
author_rank: Frequent Contributor
timestamp: April 14, 2013, 11:01:44 am
content: Quote from: megahz on April 14, 2013, 01:15:28 am3% will work for etchant , I use it all the time. The thing to remember is not to shake the container or leave it uncapped for long or it will revert to plain water.

author: ddavidebor
author_rank: Super Contributor
timestamp: April 14, 2013, 11:17:49 am
content: I use 30% hcl with 130vol h2o2, casual quantity.

author: M0BSW
author_rank: Frequent Contributor
timestamp: April 14, 2013, 12:47:22 pm
content: What is this ho2o or hci anyways , is it somekind of secret code, or are you from those UFO's I saw.

author: Resistoid
author_rank: Contributor
timestamp: April 14, 2013, 01:19:17 pm
content: megahz, ptricks has told us that he uses 3% peroxide successfully. - I too have a vague memory that I may have done this in the past, as I mentioned in my first post on this subject.I suspect that the culprit is your 2M HCl: It's probably too weak.Allow me to explain: 2M HCl contains c. 72 grams of HCl per litre (1 mole of HCl weighs about 36 grams).Calculating the weight in volume concentration as a percentage gives: (72g / 1000ml) x 100 = 7.2% w/v.Your 2M HCl is the same thing as 7.2% HCl. - Apparently too weak. - Remember I recommended that you use 25% HCl, or higher.25% HCl contains 250 grams HCl per litre. Expressing that concentration as a molarity requires that we divide 250 grams by 36 grams (i.e. the weight of one mole of HCl):250g / 36g = 6.94.In other words, my 25% HCl is the equivalent of nearly 7M HCl.If I were you, I would try much stronger acid, at least 25% or 7M with the 3% peroxide your pharmacy sells.Let us know how you get on.Resistoid.

author: Resistoid
author_rank: Contributor
timestamp: April 14, 2013, 01:30:15 pm
content: Quote from: M0BSW on April 14, 2013, 12:47:22 pmM0BSW, I am from the UFO and I will let you in on the secret code:HCl =Hydrochloric acidH2O2 = Hydrogen peroxideResistoid.

author: M0BSW
author_rank: Frequent Contributor
timestamp: April 14, 2013, 02:36:10 pm
content: Quote from: Resistoid on April 14, 2013, 01:30:15 pmThank you space man na noo na noo

author: Resistoid
author_rank: Contributor
timestamp: April 14, 2013, 03:55:14 pm
content: You are most welcome, Earthling. Now, take me to your leaderResistoid.

author: chipwitch
author_rank: Frequent Contributor
timestamp: April 14, 2013, 07:17:12 pm
content: Anyone looking for HCl... just ask for Muriatic acid (another name for HCl) at the local pool supply. Costs about $3 US/gal. for 10M (about 32%).

author: Resistoid
author_rank: Contributor
timestamp: April 14, 2013, 10:45:19 pm
content: Quote from: chipwitch on April 14, 2013, 07:17:12 pmThat's right. - This information was included in the "Instructables" link I gave megahz in my first post on his problem (Reply #4 on: April 08, 2013, 06:40:48 AM).The only significant difference I can see is the price quoted by you, chipwitch, is evenmorereasonable than the $5 per gallon according to "Instructables".Moreover, Instructables' method specifies 3% peroxide, which is precisely what megahz says he can get.Resistoid.

author: megahz
author_rank: Regular Contributor
timestamp: April 15, 2013, 12:14:01 am
content: cool, the pool supply place down the street had some, now I just need another board to etch

author: IanB
author_rank: Super Contributor
timestamp: April 15, 2013, 01:06:08 am
content: It may have been said before, but if you buy muriatic acid (hydrochoric acid) at some strong concentration like ~35% and it comes in a plastic bottle, then don't store it anywhere near tools that you value, or anything that will rust. The best place to store it is outside, under cover. If you put it in your garage, then anything made of iron or steel nearby will crumble into brown dust in a matter of months. By the time you notice, it will be too late. HCl isevil!

author: amspire
author_rank: Super Contributor
timestamp: April 15, 2013, 01:43:36 am
content: Quote from: ptricks on April 13, 2013, 11:48:28 pmI took a look at the videos from this guy, and they are among the best I have seen. It is not just the different methods, but you can make your own ferric chloride pretty easily from iron (nails or steel wool), HCl and either air or H2O2. I love information like this that empowers me to do things I never thought of doing.Thanks to this thread, I am going put aside my current store-bought etchant for now to try some of the different etchants myself. I have never used the HCL/H2O2etchant before so that is the first test.Great thread!

author: ptricks
author_rank: Frequent Contributor
timestamp: April 16, 2013, 12:36:09 pm
content: Quote from: IanB on April 15, 2013, 01:06:08 amVery true. The acid I use even lets off a little puff of smoke like gas whenever I take off the lid. When I let my etchant dry out I had it below a piece of stainless steel, that steel is now coated in rust.