Etching PCB - dealing with anhydrous ferric chloride - Page 1
Forum section: electronics / beginners

author: shaheansar
author_rank: Contributor
timestamp: October 23, 2020, 08:35:53 am
content: I'm looking into PCB etching,which requires ferric chloride (There are other etchants, but they're pretty hard to come by where I live and too expensive if I can find them).The issue is that where I live, only anhydrous ferric chloride is sold (Which is stupid. They don't even label it properly as anhydrous - got exposed to HCl fumes for 2-3 hours, thankfully the doctor found nothing abnormal with me and I got sent off with some anti allergy meds).I'd like to know what equipment I'll need to deal with this stuff safely. I always use nitrile gloves with these, but in particular what kind of respiratory protection will I need? I plan on just having 4 PC fans blow these fumes outside the window. If I must, I will invest in respiratory protection (It's very expensive where I live, the NIOSH approved ones at least). I'm assuming a 3M 6002 will be enough. Please keep in mind I will be using this stuff at home. If you have any suggestions regarding alternatives, do mention them. If I can find it, I'd rather use that than this.If this isn't the proper place to ask these questions, please direct me to a place more suitable for these questions.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: October 23, 2020, 08:42:06 am
content: Anhydrous FeCl (dark green/brown) is no good for etching. The Hexahydrate form (yellow) is normally used.I have a vague recollection that adding Hydrochloric acid to the solution made from anhydrous makes it work as an etchant.

author: Siwastaja
author_rank: Super Contributor
timestamp: October 23, 2020, 08:44:19 am
content: IMHO, invest some time into building a proper fume hood. Doesn't need to look fancy, just a closet where you suck air out, and have a sliding door made of transparent plastic or glass. Keep the door as far down as possible, with just enough gap to operate things with your hands. This way, no further personal protection needed.This is assuming you don't generate huge amount of nasty gases and blow them directly at your neighbor's open window.

author: shaheansar
author_rank: Contributor
timestamp: October 23, 2020, 08:45:50 am
content: This guy is from the same country as me and from what I can tell, it's just anhydrous ferric chlorideI myself have also successfully etched a PCB with it (Was quite slow at 10 mins though)

author: shaheansar
author_rank: Contributor
timestamp: October 23, 2020, 08:47:21 am
content: Is that kind of a rudimentary fume hood good enough? This stuff does release nasty HCl fumes after all. Will the plastic even be stable with those fumes floating around?

author: Siwastaja
author_rank: Super Contributor
timestamp: October 23, 2020, 08:54:34 am
content: HCl isn't a super poison. Get the level down enough and it's fine. You have a strong concentration of it (some 2% IIRC) in your stomach! Having too much airborne causes eye/skin/lung irritation and rusts metal objects in your room. This rusting is also why I'd recommend getting rid of the fumes (using fume hood) instead of just protecting your eyes and airways.I'd trust a fume hood over a potentially leaky gas mask with potentially insufficient or worn-out filters any day; if you go the personal protection way, it's going to be expensive, and you need to get new filters all the time.What comes to the fume hood, obviously it's up to you to do it properly. It has to be mostly airtight with no large gaps, then have strong enough exhaust fan(s). I think it is fairly easy to get rid of 99% of the fumes so that 1% leaks to the room.AFAIK acrylic won't last forever, nor will polycarbonate, if you use those as a window material. But I bet they will still last for years given just occasional fumes.

author: shaheansar
author_rank: Contributor
timestamp: October 23, 2020, 09:10:47 am
content: Quote from: Siwastaja on October 23, 2020, 08:54:34 amHow would I go about making airtight sliding doors? If it was static good ole silicone will do the job (Assuming it's stable under HCl fumes), but how would sliding ones work?

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: October 23, 2020, 10:52:16 am
content: According to this, if you leave anhydrous out for long enough it turns into hexahydratehttps://www.chemicalforums.com/index.php?topic=96911.0

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 23, 2020, 12:27:34 pm
content: Yes, it's deliquescent so it will make a solution by itself. Pouring water on it releases quite a bit of heat, and HCl fumes as you noted. Do it slowly and do it outside. The release of HCl means some rust will be left in suspension. Add more HCl (or muriatic acid or whatever it's sold as) to dissolve it.You also need to top it up with HCl from time to time, as dissolving Cu (and oxidizing everything back fresh, with exposure to air or preferably a bubbler) will precipitate more rust.Tim

author: Siwastaja
author_rank: Super Contributor
timestamp: October 23, 2020, 02:46:44 pm
content: Quote from: shaheansar on October 23, 2020, 09:10:47 amObviously a standard fume hood isn't airtight, it doesn't need to be. The idea is you can bring stuff in and out, operate things with your hands, and so on, necessitating a significantly large opening on the bottom. The idea is that the exhaust fans pull air from the hood, so air only goes in from the openings; the inside of the hood have lower air pressure than the room. This idea can be extended: if there are some holes elsewhere, they also suck air from your room, not the other way around.In simplified theory, this is. Real fluid dynamics is complex, and in practice if you have a hole to an area with lower air pressure in it, airmostlygoes one way, but along the edges, eddy currents and whatnot mix some of the air so a minuscule percentage of air flows to the opposite direction.Or, if the total area of the openings is just way too large, then there is no pressure difference anymore.Hence, if you have real dangerously poisonous gases, don't try to build a simple DIY fume hood.But for PCB etchants causing some fairly low amount of HCl droplets and gas, that's fine. It's possible even just standard kitchen hood would be almost good enough. Add some walls to it, open the front wall from the bottom for access, and likely some 99% of the air will flow from your room, to the hood, then outside the duct. Pay attention where you push the air, preferably not to your neighbor's open window, or such way that it immediately gets sucked back to your house.You can test it opening some smelly thing in the hood, smoking a cigarette if you like or ask someone who does that shit to themselves do that for a demonstration.Obviously, as with all Internet advice, the responsibility is yours.

author: Cerebus
author_rank: Super Contributor
timestamp: October 23, 2020, 03:20:52 pm
content: Quote from: T3sl4co1l on October 23, 2020, 12:27:34 pmSo don't! Add itslowlytowater rather then the other way around. That way there's all the bulk of the water to take up the heat. This is exactly the same situation that the rule "Add acid to water, not water to acid" was invented for.I haven't used Fe (III) Cl3for years but when I used to it was always the anhydrous form that turned up and I never had a problem with making a solution, or with HCl evolving, because I always added the Ferric Chloride to the water, just like my mum*taught me to.*Mum was an Analytical Chemist, but most people ought to have had this drummed into them by their secondary school chemistry teachers. I just got this particular bit of schooling a bit younger than most people do.

author: HB9EVI
author_rank: Frequent Contributor
timestamp: October 23, 2020, 05:42:21 pm
content: never got anhydrous FeCl3, always hexahydrate, but even this is hygroscopic; so just let it stand on a wet place like a cellar or garage; it'll soak itself the necessary water out of the air so that it can be easily solved in water without who knows what kind of exothermic reaction.

author: jpanhalt
author_rank: Super Contributor
timestamp: October 23, 2020, 06:10:21 pm
content: "Ferrous chloride" would be FeCl2 or Fe(II)chloride (synonyms). I suspect the bottle is likely mislabeled. If not, a solution with additional HCl to provide the additional chloride will convert to Fe(III) chloride in air.I suspect you really need Fe(III) as the etching reaction involves oxidation of the copper.

author: shaheansar
author_rank: Contributor
timestamp: October 23, 2020, 06:21:23 pm
content: Quote from: Cerebus on October 23, 2020, 03:20:52 pmI always added the powder to the water, in teaspoon quantities, and let each one mix well before adding more (That school education sure did save me). It still released enough HCl fumes that I still have some pain in my chest 2 days later, under meds. I'm not sure how safe it is.

author: Benta
author_rank: Super Contributor
timestamp: October 23, 2020, 06:51:40 pm
content: In the early years, I used ferric(III)chloride for PCB etching, I never do that anymore.It's incredibly messy and the remains need to be treated as chemical waste. Lose a drop of the brown goo somewhere, and you'll never remove it again. Also it gasses out (both in solid and dissolved form) and will corrode everything in the vicinity.I use two methods depending on accurace and urgency.1: For precise and controlled etching, Na2S2O8aka "disodium peroxodisulphate" aka "sodium persulfate" is perfect. It's a white powder to be dissolved water, 230 g to 1 l of water. The solution can be stored and reused.It does need some extra effort, though: the solution should be heated to 50 C, and aeration of the etching bath (aquarium pump) for homogene results is recommended.Downside: as you have problems getting ferric chloride, sourcing this might be impossible in your location.2: Brute force etching with stuff you can probably get without problems:~30% hydrogen peroxide, ~30% hydrochloric acid and tap water.0.25 l H2O2, 0.25 l water and 0.5 l HCl.Always add the acid last!!!ONLY DO THIS OUTSIDE AND WEAR PROTECTION GLASSES AND PROTECTIVE CLOTHING!!!The etching is hard to control and will take around 20 seconds. As the process is exotherm, the etching bath will get warmer and warmer, so if you're doing serial etching of several PCBs, the last one could take only 5 seconds.Expect underetching of the tracks, as pulling out the finished PCB and washing it in water takes a little time. Meaning this process it not suitable for fine geometries. Track width should be 0.25 mm or more.The solution can be diluted with water after etching and is then pretty harmless. Depending on your local laws, it might even be allowed to flush it in the toilet.

author: mag_therm
author_rank: Frequent Contributor
timestamp: October 23, 2020, 07:51:10 pm
content: I use MG Chemicals Positive Developer and Ferric Chloride, both in 475 ml containers which last a long time here .They give a Ferric Chloride disposal procedure on website FAQ.

author: shaheansar
author_rank: Contributor
timestamp: October 23, 2020, 08:01:27 pm
content: Quote from: Benta on October 23, 2020, 06:51:40 pmI'm unable to get my hands on any sodium persulphate, as you guessed. I'll have to contact actual chemical suppliers, but they are very industry oriented and the quantities sold are very much unreasonable as a single person IMHO. I am able to source some ammonium persulphate though (It's kinda expensive, but safety first). How dangerous would these chemicals be? The reason I want to get away from FeCl3 is that this chemical is only sold in it anhydrous form and it released HCl fumes when mixed with water, so going the second route you suggested is not ideal even if it's easy to source. The other issues I can deal with. If sodium/ammonium persulphate don't vaporize into something that'll eventually eat through my lungs, it'd be nice. If there are other safety precautions I should take when dealing with them, do mention them.

author: jpanhalt
author_rank: Super Contributor
timestamp: October 23, 2020, 09:21:09 pm
content: In the US, 41% ferric chloride is used by the barrel in sewage treatment plants as a flocculator. Sure, if your area has a law against it, you don't want to do it, but disobeying such laws will not bring Armageddon to your county.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: October 23, 2020, 09:37:33 pm
content: Quote from: jpanhalt on October 23, 2020, 09:21:09 pmISTR reading that the issue with disposing of used FeCl3 is not the FeCl3 itself, but the dissolved copper after being used for etching

author: sleemanj
author_rank: Super Contributor
timestamp: October 23, 2020, 09:39:50 pm
content: Quote from: Benta on October 23, 2020, 06:51:40 pmUse less concentrated components and you will have etching as slow as you like.

author: Benta
author_rank: Super Contributor
timestamp: October 23, 2020, 09:44:37 pm
content: I've only worked with sodium persulphate and have had no problems with gases or odors.Ammonium persulphate could be an option, but I've no experience with this.

author: Benta
author_rank: Super Contributor
timestamp: October 23, 2020, 09:47:06 pm
content: Quote from: sleemanj on October 23, 2020, 09:39:50 pmDid you try?Please come back with your results.

author: Cerebus
author_rank: Super Contributor
timestamp: October 23, 2020, 09:56:22 pm
content: Quote from: jpanhalt on October 23, 2020, 09:21:09 pmThere's a world of difference between controlled dosing of raw water in a water treatment plant with pure ferric chloride (with, no doubt, subsequent testing to make sure that unacceptable residual levels are absent), and dumping used, contaminated, ferric chloride etchant in an uncontrolled manner into waste water and hoping that it doesn't cause trouble. Dumping chemical waste may not necessarily cause "Armageddon" but it would still show a callous disregard for what that pollution might do to other people downstream of you and to the environment.

author: shaheansar
author_rank: Contributor
timestamp: October 23, 2020, 10:30:02 pm
content: Quote from: Benta on October 23, 2020, 09:44:37 pmThat's quite nice. Is it usable indoors? I might actually look into industrial chemical suppliers and pay the ridiculous amount for 25Kg if it's that safe compared to what I currently have on hand. I live in an apartment with my family so I'm quite concerned about the odors and fumes as they may negatively affect their health. I've only been able to find Sodium Persulphate in powdered form (25Kg of that stuff, unfortunately. Not going to be cheap to say the least), are there any concerns regarding adding it to water - exothermic reaction or release of fumes for example? Will I have to invest in any sort of respiratory protection?

author: jpanhalt
author_rank: Super Contributor
timestamp: October 23, 2020, 10:37:41 pm
content: Quote from: Cerebus on October 23, 2020, 09:56:22 pmYou have been well indoctrinated. FeCl3 is used very commonly as a home treatment to clear roots from drains. I am not talking about treating drinking water. I am talking about treating raw sewage.

author: sleemanj
author_rank: Super Contributor
timestamp: October 23, 2020, 11:12:43 pm
content: Quote from: Benta on October 23, 2020, 09:47:06 pmI don't etch much any more, but using what I had stashed in the shed...Single sided PCB with hand-drawn pen resist, excuse the poor representation and quality of resist, I'm too lazy to do a proper UV mask and exposure for this.* 1/4 Cup of hardware store HCl marked as 280g/L (I don't know what that is in a percentage concentration)* 1/4 Teaspoon of 35% H2O2 (many years old so could be degraded considerably less than 35% now)* 3 minutes and 50 seconds etching time"Waste" now added to my etchant bottle for re-use someday.

author: Benta
author_rank: Super Contributor
timestamp: October 23, 2020, 11:15:41 pm
content: Quote from: shaheansar on October 23, 2020, 10:30:02 pmI attach the EU safety regulations document. I'll leave it up to you to make decisions as to the way you want to use it.Cheers

author: sleemanj
author_rank: Super Contributor
timestamp: October 23, 2020, 11:21:41 pm
content: Quote from: shaheansar on October 23, 2020, 10:30:02 pmThis is important information.I wouldn't use HCl+H2O2 in that setting, I wouldn't store HCl inside your apartment let alone use it. It lives in my shed for a reason, well sealed and as far away from the tools as possible.Same goes for Ferric Chloride, keep that away from things you care about, anything it touches is forever brown.

author: Cerebus
author_rank: Super Contributor
timestamp: October 23, 2020, 11:45:20 pm
content: Quote from: jpanhalt on October 23, 2020, 10:37:41 pmWeirdly enough so was I, where did I say drinking water? Amazingly people who run water treatment works want their discharge water to be safe. Try reading an MSDS for Ferric Chloride -here'sone dedicated to an FeCl3solution intended for water treatment, you might like to note the aquatic toxicity figures quoted.The suggestion that chucking FeCl3down the drains to deliberately kill roots is evidence of its harmlessness to the environment seems a deeply perverse claim to make. Again, even if pure FeCl3is actually used to remove roots in drains*it is not loaded with copper ions and anything else that might have leached into it during the etching process. "Cu is acutely toxic (lethal) to freshwater fish in soft water at low concentrations ranging from 10 – 20 part per billion (US NAS 1977)." - cited fromEffects of Copper on Fish.pdfIndoctrinated? You have weird a view of the world where basic science and having a little bit of respect for what one does to other people or flora, fauna and watercourses becomes somehow political instead of simply being, at the least, good manners or, more selfishly, enlightened self interest.*I can find no actual evidence for claim that this is a common method, a google search for "Ferric chloride drain roots" returns no results to support that in the first two pages, but does come up with other "common" methods. A search on ebay.com for "ferric chloride root" returns zero results, which is unexpected if it's a "common" method of clearing roots from drains and is sold for that purpose.

author: shaheansar
author_rank: Contributor
timestamp: October 24, 2020, 12:13:52 am
content: Quote from: sleemanj on October 23, 2020, 11:21:41 pmPrecisely why I'm trying to get away from FeCl3. Thankfully sodium persulphate seems to be fine, although I'd like to do more research on it before jumping in.

author: coppercone2
author_rank: Super Contributor
timestamp: October 24, 2020, 07:43:54 am
content: to safely dilute it, get yourself a 1 gallon jug filled with water, then add the correct amount of FeCl3 in 3-4 parts, each time making sure the water is down to refrigerator temperature before you start, and shaking it after you add it with a cap. You need to add it slow because if you throw a whole bunch in, it can settle to the bottom and make a hot mass that does not wanna break apart. The idea is each time you only get the water warm, then cool it down again (capped). Keep in mind it takes a while to cool down in a plastic jug, but its quite safe this way. What can happen is the reaction can release heat in a non linear way based on surface area / mass transfer, so take it very easy.. don't decide that its not hot and to add a whole bunch more. I measure out the total quantity I plan on adding to that jug cycle, then put a scoop in with a dry funnel, cap it, shake it up, add another scoop and so on, till I added 1/4 of the total quantity, then I put it in the refrigerator for a long while, and repeat.As you have more cold ferric chloride in there, it adds mass to the vessel, so you will get less heating because effectively the iron ions that you added are cooled down, so in addition to warming up the water, the stuff needs to warm up the iron present (you will notice its quite a bit of anhydrous substance you need to make the correct etch concentration), so it gets safer as you go. Adding the last 1/4 should make the water substantially less hot then adding the first 1/4 if you always start the water at the same cold temperature. But keep in mind you are cooling more substance. You can add slightly less water then you need to begin with so you have room for shaking, and make it extra concentrated by a small amount, then add more water at the end when its all dissolved. I use empty plastic hardware store pouring vessels (i.e. the white ones in the paint section used for de greasers, but the rectangle ones, with the cap off to the side, not the conical top ones).You can probably expedite this with ice but I recommend just taking it easy and to use a minifridge.Do not use a milk jug because for whatever reason I left a milk jug of the stuff on a shelf and eventually it corroded through, after a few years, maybe from frost (stored outside).Also, replace the gasket in those containers with a proper plastic one, do not use the paper gasket that comes with the bottle. It requires cleaning the cap and precisely cutting a new gasket with sharp scissors or a exacto being sure not to make any creases or whatever in the cut out. Also, check for any mold flash along the top side of the cap, to make sure the gasket seals properly.. they don't pay too much attention to soap containers.Keep in mind if the plastic inside gets above 70 degrees C it begins to weaken, I think permanently, so add small scoops with a spoon and shake well every time, to prevent hot spots.Now you need to be smart when you do this and use a thermometer, because the 1/4 rule might be not perfect because the stuff I gotten could have been already partially hydrated, so it could have made less heat then very pure anhydrous chemical would make. I am not sure how sure you can be of purity of anhydrous chemicals you buy for cheap, they could have been stored improperly during whatever part of the supply chain and partially converted to hydrate giving you a false sense of thermal behavior, and generated less heat then anticipated.Also, if you get a tall container, the top layer might be more hydrated, and the bottom layer less hydrated, so be sure to cool it down to the same cold temperature every time you add your portion, to maintain safety.You should already have a thermometer for doing the etch, so it does not add any cost to measure it.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 24, 2020, 01:26:44 pm
content: Note that you can assist disposal by soaking the solution over iron scrap -- filings, steel wool, (cleaned) soup cans, etc. First the ferric chloride is reduced to ferrous, then the copper is precipitated out, electroplated loosely onto the steel. Filter to remove insoluble rust (FeOOH), copper metal, and any crud left from dissolving the steel (often some black stuff, carbon and other impurities). The resulting solution is... at the very least, less toxic to dump -- much better than dumping it straight, for sure.Same is true of the persulfate solution, you may want to add a little acid (HCl or H2SO4 is fine) to ensure everything stays in solution. The "per" part is what gets spent, same as the H2O2 used in other formulations. You'll be left with copper metal, and ferrous sulfate and sodium sulfate in solution. (The solution will be a light bluish to greenish color.)You can also add a base (sodium hydroxide, carbonate, even calcium carbonate (lime(stone)) will do) to neutralize the acidic metal salts, precipitating metal oxides or carbonates, leaving a clear salt solution that can be dumped.If you had industrial quantities, the copper can be sold for scrap. You'll be doing a lot of etching to get to that point though,so the residue can be filtered off and landfilled.But still, if you have a waste disposal location to take it to, do that.Tim

author: akimpowerscr
author_rank: Regular Contributor
timestamp: October 24, 2020, 02:16:20 pm
content: I used hydrochloric acid (HCL) mixed with hydrogen peroxide (H²O²) and I have always been very satisfied with the result.I noticed that the speed of the reaction depends mainly on the amount of H²O² that is added to the HCL acid.Initially, I used 33% hydrochloric acid, without diluting it, adding a small amount of concentrated H²O² (35%).Concentrated hydrogen peroxide should be used so as not to over-dilute the acid.Thus, we can reuse the same solution dozens of times, it suffices to add a little H²O² again for each use.The problem of waste disposal is thus considerably simplified.The acid can easily be neutralized with caustic soda. (NaOH).Regarding the gas release, it seems to me that it is chlorine and not HCL.

author: shaheansar
author_rank: Contributor
timestamp: October 24, 2020, 04:25:44 pm
content: Quote from: akimpowerscr on October 24, 2020, 02:16:20 pmCorrect me if I'm wrong but isn't Chlorine gas far more dangerous than HCl?I really hope this is regarding the HCl + H2O2 etching method and not my FeCl3 mixture because if it is, I'm going to the doctor's again

author: Siwastaja
author_rank: Super Contributor
timestamp: October 24, 2020, 04:39:04 pm
content: We (a club) had great results with cupric chloride. You can "naturally" convert from HCl + H2O2 process to cupric chloride by reusing the "waste" infinitely, adding less and less H2O2 each time until the cupric chloride takes over completely; at high enough copper concentration, no H2O2 is needed at all, anymore. When reaction rate diminishes, a bit of fresh HCl needs to be added. When copper concentration goestoohigh (it has a sweet spot), reaction rate starts going down again but we never reached this point during my time, and it wasthousandsof PCBs (for some 5 liters of etchant). At that point, you would ditch say half of the solution and add (diluted) HCl.This process requires control, in theory, but we had great results with almost no control. Zero waste in many years and thousands of PCBs! Added a bit fresh HCl about once-twice a year, basically when the etching time exceeded some 20 minutes (compared to the initial 12 minutes IIRC)...Compare this to HCl+H2O2 where 95% of the chemicals you use go directly to waste "unused". Amount of waste is some 100x.Another difference to HCl+H2O2 is you need strong bubbling (agitation + aeration), so yeah, a bit more tank design necessary, but as a positive side effect, your etching resolution goes way up; HCl+H2O2 is totally useless below 10 mil / 10 mil process in my experience. It's FAST and self-agitating but that comes with a price (overetching / underetching depending on the PCB pattern). With cupric chloride, OTOH, we had no problem withactually reliable8mil/8mil on 1oz or 6mil/6mil on ½oz clad.

author: Cerebus
author_rank: Super Contributor
timestamp: October 24, 2020, 04:53:03 pm
content: Quote from: shaheansar on October 24, 2020, 04:25:44 pmYes, Chlorine gas is more toxic than HCl gas. I can speak from personal experience that accidental exposure to Cl2gas isdeeplyunpleasant. Even transitory exposure to harmful levels leaves you feeling like someone has scrubbed out the insides of your lungs with coarse steel wool.HCl gas - OSHA PEL (permissible exposure limit) = 5 ppm (ceiling), NIOSH IDLH (immediately dangerous to life or health) = 50 ppmChlorine gas - OSHA ceiling = 1 ppm, NIOSH IDLH (immediately dangerous to life or health) = 10 ppmIt's come to my attention that it's also possible for phosgene (COCl2) to be emitted when wetting anhydrous commercial grade Fe (III) C3, so for good measure let's add figures for that to the list:Phosgene gas - OSHA PEL (permissible exposure limit) = 0.1 ppm (averaged over a 8-hour workshift), NIOSH IDLH (immediately dangerous to life or health) = 2 ppm

author: ace1903
author_rank: Regular Contributor
timestamp: October 24, 2020, 05:05:14 pm
content: I use hydrochloric acid (HCL) mixed with hydrogen peroxide (H²O²) and I have always been very satisfied with the result.I use 20% hydrochloric acid and H²O² (9%).Here actually to obtain a concentrated H²O² degree in chemistry and special permission is needed.That is why I am using hair bleach 9% or rarely 12%. Sometimes even hair bleach with oils in it.The trick is to look at the color of copper during etching.Starting with HCL and adding H2O2 gradually. H202 is an oxidizing agent causing dark brown color and HCL is a reducing agent returning the shine of the copper. Best results are obtained when reaction speed is a rate that causes copper to lose shine and have a light brown color.If too much H2O2 is added HCL is needed to slow down the speed and prevent under etching and high temperature that will damage photoresist.When 12% H2O2 is used it is very easy to get the best result. I tried with 35% H2O2 but it is very difficult to add it in a controlled manner (small drops and not directly on the PCB).I think that during reaction oxygen is released in form of ozone O3 and not chlorine. This activated version of oxygen is unpleasant but not damaging as chlorine. I have seen and experienced chlorine gas and I think it is a completely different smell and feeling compared to smell when etching PCBs.Started with making PCBs at home 25years ago and never used ferric chloride or anything other than hcl+h2o2.Cheap PCB services are nice but in this part of the world, shipping is always more than a month and the price of DHL service somehow always ends to be ~100EUR. PCBs are cheap but procedure and annoyances with custom and paperwork procedures put PCB services as the last option.

author: shaheansar
author_rank: Contributor
timestamp: October 24, 2020, 06:47:19 pm
content: Quote from: Cerebus on October 24, 2020, 04:53:03 pmWell that's delightfully dangerous. Thankfully I'll be switching over to a glove box + sodium persulphate to make my life easier.

author: shaheansar
author_rank: Contributor
timestamp: October 24, 2020, 06:50:10 pm
content: Quote from: ace1903 on October 24, 2020, 05:05:14 pmOzone is quite toxic to us humans. I'm not sure how toxic it is compared to chlorine, but nonetheless something to avoid. I'd rather stay away from anything that releases nasty fumes - learned it the hard way. As I said, I don't have much in the way of ventilation - an open window is about all I can manage in my apartment.

author: Benta
author_rank: Super Contributor
timestamp: October 24, 2020, 07:29:27 pm
content: Sodium persulphate is the way to go - with caveats...You need heating and stirring while etching.Something like this:https://el-supply.dk/shoppix/8545og46.PDFIt's not hard to build one yourself using acrylic sheets, profiles and suitable glue. Air pump (for stirring/aerating) and heater are standard accessories for aquariums.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 25, 2020, 12:01:18 am
content: Ferric chloridedoes not producephosgene. I don't see any mention of this save for thecombustion hazardin the SDS, which is plausible by donating chlorine to burning carbon species. So, don't toss it in a fire, easy enough...Most obvious, phosgene contains carbon, which neither ferric chloride nor water contain. Phosgene is patently impossible to produce from these ingredients, at any proportion or rate of reaction.Water sometimes contains carbon in the form of dissolved CO2 gas, or carbonate ions; these are already oxidized forms of carbon, and it would be quite a stretch to form phosgene from these ingredients.As for oxidizing gasses -- chlorine and ozone -- ozone is absolutely not produced from H2O2 or a chloride solution. H2O2 has 1.77V of oxidizing potential. Chlorine is readily oxidized (1.36V), ozone is not (2.08V).Chlorine, ozone and nitric oxide all have similar smells -- probably something about smell receptors being oxidized. Nitric oxide is actually familiar from some combustion processes, diesel exhaust for example. All are rather toxic, for similar reasons (nitric being the worst).When you add H2O2 to HCl(aq), what you're actually doing is converting some H2O2 to dissolve chlorine gas. This attacks the copper, and as the copper dissolves (as Cu(I) and Cu(II)) it catalyzes further oxidation, hence why the solution stays clear and green when enough H2O2 is present. (In strong chloride solution, Cu(I) has a strong brown color.)Persulfate has nearly (but just not) enough potential to generate ozone, interestingly enough. Ozone is produced in small amounts when synthesizing it; but it doesn't stick around in the finished product, of course.Note that chloride salts should not be used with persulfate, because... you guessed it, they'll make chlorine.And yes, chlorine gas is only produced when H2O2 is added to an acid chloride solution. Ferric chloride by itself does not produce chlorine. H2O2 can be used to speed up its reaction, but an excess will release chlorine.Chlorine and HCl fumes are easily avoided. They'reunpleasant.If your body is telling you"the air is hurting me"just walk away from the stuff. Do it outside, preferably with a modest breeze. We're not talking industrial quantities that you can't run away from, here!Tim

author: coppercone2
author_rank: Super Contributor
timestamp: October 25, 2020, 12:31:08 am
content: its really not that bad other then the stains, i don't see what the crazyness is about, all the people freaking out over it made me think i was dealing with a bad process or something lolits mild as far as anhydrous chemicals go and mild in terms of working with itnot too much worse then coffee?if you want a damage report, I had a leaky gallon of it on a shelf next to a craftsman tool chest filled with welding stuff for a few years, the only thing that happened was the bottom of the shelf that it leaked on is messed up. The toolchest was 1 foot away, and it gets hosed down during cleaning, and the slide rails are fine, the paint job is fine, the casters appear fine, the welding equipment inside appears fine, last year I polished all my brass stuff to make it look nice, but I think most of the tarnish was from being basically outdoors in a concrete structure with no heating (single car garage).I just never did a etch indoors, I did those outdoors.. I think so long you don't mist it, its not nearly as corrosive as people say.Also the garage door hardware is fine considering how old it is, other then frayed cable lines which need replacement.I saw damage to tools that I dipped in ferric chloride to fish things out, but a wire wheel took care of that.I think you really need to mist it in order for it to cause damage. It does not really do that much if its sitting open so long its fully hydrated.

author: Cerebus
author_rank: Super Contributor
timestamp: October 25, 2020, 01:26:26 am
content: Quote from: T3sl4co1l on October 25, 2020, 12:01:18 amWell there's at least one MSDS that would disagree with you (http://www.waterguardinc.com/files/90276626.pdf) which says, and I quote: "Fire and Explosion Hazards: Substance itself does not burn, but may decompose upon heating to produce corrosive and/or toxic fumes, such as hydrogen chloride and phosgene gas.". I'm sure the risk is minor, but it's there in the MSDS.Add water to anhydrous commercial ferric chloride and it will get hot, very hot. Needs carbon you say? Yes, that's kind of obvious, the hint is in the formula, COCl2. Have you perhaps not considered that commercially pure Iron used to prepare it is likely to have some carbon in, carbon being intrinsic to the production of Iron? Sigma'sReagentgrade Fe (III) Cl3is only listed as 97% pure, that other 3% has to be something. Lord knows how impure commercial grades are likely to be if Sigma's basic laboratory grade is only 97% pure. Furthermore, the atmosphere is ~400ppm CO2, there's another carbon source immediately to hand as is the dissolved CO2in the water.Given a choice of trusting an MSDS or you about chemical hazards, I'm going with the MSDS. Now, if it had been an electronic component data sheet, you'd probably get the benefit of the doubt.

author: S. Petrukhin
author_rank: Super Contributor
timestamp: October 25, 2020, 01:43:57 am
content: Quote from: shaheansar on October 23, 2020, 09:10:47 amThe door must not be sealed. Air tightness is provided by the fan, creating a reduced pressure that does not allow gases and particles to fly out of the сabinet. Instead of a сabinet, you can use a hood, even a vacuum cleaner with a horn, putting its exhaust on the window.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 25, 2020, 02:17:50 am
content: Quote from: Cerebus on October 25, 2020, 01:26:26 amYes, like I said, what's doing the heating? Typical MSDS conditions will be in a fire. That provides all the elements needed: hydrocarbon radicals, hot volatile ferric chloride, and steam, or a low amount of oxygen. The yield is probably pretty small, and probably much of the phosgene is further decomposed by the heat of the fire.Needless to say, it's not somewhere you want to be. Fires produce lots of toxic fumes, and when chlorinated materials are present, phosgene is among them.PVC electrical wiring is a more topical example, but I've never seen you go off ranting about its flame hazards for some reason.QuoteYou're a much better electrical engineer than an organic chemist. Let's stick to topics we have lab experience in.Tim

author: coppercone2
author_rank: Super Contributor
timestamp: October 25, 2020, 02:39:41 am
content: guys, they sell big jugs of HCl in most home improvement stores, only recently did they decrease the strength to 20%, in some places, mostly to make work more pleasant for home owners that just want to clean concrete (they titrate it so it does not fume under most conditions). It stores OK. I never saw a trashed store isle from it yet. They do not store it in a fume hood. I suspect its mostly because people don't want to mix it up in a bucket prior to use, mixing chemicals is slightly time consuming, which is not good for people trying to make a living cleaning driveways fast.If you decided to store it in the same room as your metrological K-type connectors for microwave work, then maybe you are onto something with the fume hood. But that is insane. If you have concentrated HCl you want to store more safely, just dilute it with distilled water to 20% or so and it will no longer fume but still be just as useful for adjusting pH in most cases.Nothing with carbon is going to happen unless some of these crazy assertions are correct and you happen to put it in a kiln, and likely that would destroy phosgene as it was made. The closest people are going to get to those toxic gases is burning a frying pan some how. Not to mention if you spend any time in eastern europe you will see the smog that is produced from burning garbage illegally in the winter in a stove is worse then anything you will make with small scale PCB production. I bet its the same thing in china.I think people are confusing common chemicals with 2-4-5 Trioxin.When you decide to go into commercial scales and involve OSHA then you might need to worry about this stuff a little bit more.If you want to avoid rusting stuff, be sure to EVAPORATE it gently and do not boil it. Boiling bubbles is what causes the corrosive mists to form and deposit on stuff. If its slowly evaporated the solids are not leaving the container, it will only splash if there are solids formed on the wall of the container and you evaporate it way down then it decides to break off and splash the container (so don't screw with it until its done evaporating totally trying to make the sides of the vessel easier to clean, it is not some kind of rye bread production tank that you should scrape the walls down to protect the baking pan).

author: Cerebus
author_rank: Super Contributor
timestamp: October 25, 2020, 03:28:53 am
content: Quote from: T3sl4co1l on October 25, 2020, 02:17:50 amI'm trusting the MSDS for the details that say the reaction can happen. You're the one saying it needs carbon, implying there is none therefore it cannot happen, I'm merely pointing out that there's carbon around. Note I didn't say elemental carbon.I'm not ranting, I merely said, some messages ago, answering a query about the relative toxicity of Cl2and HCl:Quote from: Cerebus on October 24, 2020, 04:53:03 pmYou gainsay that, categorically stating that "Ferric chloridedoes notproduce phosgene." . I supply the MSDS that points it out as a possibility. I didn't even use anyemphatic text. I even said "I'm sure the risk is minor".Hardly, ranting is it?. Why is it that peopleloveto use such emotive language around here?And yes, before you jump on it, I'm assuming that sufficientheating, as specified in the MSDS, can come from hydration. I've welded granules of NaOH to the bottom of the polythene container full of water that I'm adding it to by not stirring sufficiently soon or quickly, from past experience with the amount of heat evolved mixing up Ferric Chloride the right way I've very convinced that it can get 'orribly hot when being hydrated the wrong way.My chemistry is middling, it's a long time since it was put to more than trivial use. That's why I feel happier trusting an MSDS written by a qualified professional than my own judgement, or yours, as to what might happen. And stooping to the facepalm and the, admittedly relatively mild, put down? I'd rather hoped that was beneath you.I know there's a tendency around here to pooh-pooh "health and safety", and some people and places do take precautions to the ridiculous, but we ought to remember that this thread starts with someone going to the doctors for treatment after experiencing adverse effects from the substance under discussion.

author: shaheansar
author_rank: Contributor
timestamp: October 25, 2020, 10:54:25 am
content: Quote from: Benta on October 24, 2020, 07:29:27 pmThe heating shouldn't matter too much - where I live the temperature is routinely above 30C, and during summers can reach 45C. I will at some point build a heater of some sorts, but it's not strictly necessary now, I believe.Aerating on the other hand will be something I'll be investing in pretty soon.Thank you for your advice. Has been a real help.

author: Siwastaja
author_rank: Super Contributor
timestamp: October 25, 2020, 11:04:27 am
content: My experience with persulfate (decades ago, as a kid) was that you need to go way over your routine temperatures of 30 degC.I'd say it has to be somewhere around 50-60degC for good etching rate.Not a problem though heating that up on a stove; I remember no issues with fumes even when heated, it was very benign compared to ferric chloride or HCl+H2O2 I later used.

author: S. Petrukhin
author_rank: Super Contributor
timestamp: October 25, 2020, 11:19:00 am
content: Quote from: shaheansar on October 25, 2020, 10:54:25 amWhy do you bind to hydrochloric acid HCl?If you don't have access to iron chloride FeCl3. You can make a different composition from safe and affordable substances: copper sulfate CuSO4 (it is used in everyday life and is completely safe) and ordinary edible salt NaCl. In the proportion of 1 part CuSO4 and 4 parts NaCl. This composition is somewhat slower, but also not bad. A pleasant transparent solution of turquoise color, not poisonous (if you do not drink), not spewing vapors and smell, and not even burning through the color of everything in a row like iron chloride. For a home hobby, this is very good.There are even more accessible chemicals: hydrogen peroxide, citric acid, and salt.

author: shaheansar
author_rank: Contributor
timestamp: October 25, 2020, 12:52:35 pm
content: Quote from: S. Petrukhin on October 25, 2020, 11:19:00 amI don't. I very much want to get away from FeCl3 and HCl anything. Harming my health is not worth the possibilities etching PCBs gives access to. That is precisely why I'm trying to move away from it to Sodium Persulfate (Thankfully I've found a supplier near me willing to deal with 1Kg quantities which are very economical). I will look into Copper Sulphate as well, although I'm worried about disposal.

author: S. Petrukhin
author_rank: Super Contributor
timestamp: October 25, 2020, 03:04:50 pm
content: Copper sulfate is even good for the environment, as far as I know, it is used to treat plants.But the safest solution is hydrogen peroxide (hydroperite in the solid state) - it makes women blonde and used in medicine to treat wounds, citric acid, which can be eaten and edible salt.