How to make your own etching solution for cheap - Page 1
Forum section: electronics / general

author: Beamin
author_rank: Super Contributor
timestamp: March 23, 2019, 11:56:17 pm
content: I realized by playing around with chemicals from the pool store you can make etching solution for about $6.00 a gallon. Buy concentrated HCl or muriatic acid then take nails or steel wool and add to the solution. Take some 3% hydrogen peroxide solution at 10:1 hcl to h2o2. You can go by the color of the acid to see when its done. The aacid will go from clear to yellow then green. the exact color doesn't matter as long as you let it react for about ten minutes. Be careful with the HCl the fumes even with a fan (not having a fume hood) ruined every metal object in the room like usb cables and all my aluminum tools, razor blades turned to dust after a few hours. Do out side or in a very well ventilated area. This solution will dissolve an entire circuit board of given enough time.

author: German_EE
author_rank: Super Contributor
timestamp: March 24, 2019, 03:45:49 pm
content: Hmmmmm, let me think about this..................Option AMess around with chemicals so reactive they will corrode everything metal in the room, no idea what will happen to my lungs and eyes but it can't be good.Option BSend my PCB design to a local board house and get ten finished PCBs back in less than a week.Sorry Beamin, I'll pass on this one.

author: Benta
author_rank: Super Contributor
timestamp: March 24, 2019, 04:20:41 pm
content: The classic is HCl, hydrogen peroxide and water in a 1:1:1 mix. Etches your circuit board in 20 seconds. Outside use only!!!

author: Refrigerator
author_rank: Super Contributor
timestamp: March 24, 2019, 06:08:16 pm
content: My recipe:Step 1)HCl + peroxideStep 2) add a bunch of raw copper in.Step 3) the stuff turns vivid green and you now have copper chloride.Basically now you have an etching solution that makes itself and all you have to do is to add a little HCl once it gets weak and let it breathe some oxygen.Works great and you never run out of it because, as mentioned, it keeps making itself.The HCl + peroxide mix is good but you can't keep it because it goes weak after some time, the green copper chloride mix becomes stronger as it sits because it absorbs more oxygen.You can also do it without peroxide, it just takes much longer.

author: KL27x
author_rank: Super Contributor
timestamp: March 24, 2019, 10:50:38 pm
content: Theoretically, i think you can make ferric chloride with this method, peroxide oxidizing the iron and then the acid dissolving it into ferric chloride. But if the stuff turns green not brown, the amount of iron you are getting in there are perhaps superfluous. It sounds like you are reinventing the wheel and are off to a slow start.

author: magic
author_rank: Super Contributor
timestamp: March 24, 2019, 11:40:14 pm
content: This copper chloride process is actually neat. I've never used it but I like the idea of it as it effectively boils down to dissolving copper in HCl without any other consumables besides O2 to tie up the leftover H2.The only problem I see is that, as you say, it just keeps making more and more of itselfI wonder if a completely closed-loop process would be possible, where spent oxidizer is regenerated with electrolysis and the only output is the same metallic copper which has been removed from the PCB.Perhaps spent B327 could be regenerated that way but AFAIK it could equally well turn into plain H2SO4 which is useless and dangerous at that.

author: hendorog
author_rank: Super Contributor
timestamp: March 24, 2019, 11:55:48 pm
content: Quote from: magic on March 24, 2019, 11:40:14 pmAnd if the metallic copper is output in the form of blank PCB's that would be extra convenient

author: nctnico
author_rank: Super Contributor
timestamp: March 25, 2019, 12:37:38 am
content: Quote from: magic on March 24, 2019, 11:40:14 pmAn easier way is to start with Ferric chloride. This will turn into Cupric chloride. Adding HCl (Hydrochloric acid) revives the solution. Because there will always be some evaporation and loss of liquid due to what sticks to the board the HCl just replaces the lost liquid. You can use the same etchant during a lifetime. I've been using this method for decades.

author: nctnico
author_rank: Super Contributor
timestamp: March 25, 2019, 01:04:16 am
content: FeCL is corrosive too. If you don't have an outside shed to use it in, then don't consider it.

author: artag
author_rank: Super Contributor
timestamp: March 25, 2019, 01:42:12 am
content: I don't think it vapourises. It creeps. Evil stuff.

author: artag
author_rank: Super Contributor
timestamp: March 25, 2019, 01:49:21 am
content: I've got a tank of cupric chloride as described above. It's made of HCL and copper, pretty much. It's in a small cupboard and has been for 5 years or more. Nothing has corroded. Nothing is stained a revolting yellow. It doesn't smell bad. It just works.

author: KL27x
author_rank: Super Contributor
timestamp: March 25, 2019, 05:51:24 am
content: HCl and peroxide is more corrosive, but for the occasional board where you mix it and then throw it out, it can be convenient. It is also a less accurate etchant with more undercutting.QuoteThe Real Elliot's Instructable page might give the impression that HCl and peroxide is the same thing as cupric chloride, that they're just two faces of the same etchant. They are a bit different. Going from one to the other, things change.HCl and peroxide has the advantages of speed and amount of copper that a given volume of etchant can dissolve without exogenous support.Cupric chloride etches slower, and, devoid of effective aeration, you need a relatively large volume to etch the same amount of copper.But cupric chloride is a more accurate and forgiving etchant, almost as good as ferric chloride. You do not need a heater to use cupric chloride. Even at 50 degrees Farenheit, it will etch just fine, albeit slower. It might seem like this is a big drawback, but because of the accuracy/forgiveness, you do not need to hover over your board while it etches, or even watch the clock. On say a 1 oz board with sub 10 mil traces, HCl and peroxide might not give great results, even if you pull the board out at exactly "the right" time. You can be left with bridges, still, while some parts of the resist have already lifted, and traces already showing chewy edges. With the cupric (or any "proper" etchant), you can have a large window where the board is good. Say the total etch time of cupric is X, and X is a relatively long time compared to acid peroxide. Anything between X and 2X might produce a perfectly good board with higher fidelity and resolution than possible with acid peroxide, at all. X is a function of temperature. So while cold etchant will take longer, the window of success is also larger. This is based on real world experience.So in practical terms, HCl and peroxide is like putting an egg in a microwave oven, except unless you have some system to pull the board out of the etchant at a certain time, you have to stand there and watch it. A little too long and the egg explodes. Even if you get it right, some parts might be overcooked and some parts still raw. The first few times you make a board, this might be fun to stand there and babysit. After you've done it a bunch of times, it is not. Proper cupric etching is like hard boiling an egg in a pot of water. You just leave it in the tank and forget about it for awhile. Then come back, later, and it is all good. Even if you left it boiling way too long, it will still probably come out better than any egg that was cooked in a microwave.In any of the videos or pics you see of boards that etch in seconds and leaves a good result, I bet the copper is half oz. Half oz ismucheasier to etch, accurately, and it etches way faster. It's not twice as fast as etching 1 oz; it is about 1/4 to 1/3 the time, IME.Notice, if you use cupric by adding peroxide, the acid in your solution will etch like acid peroxide. You may not see the full difference in accuracy and forgiveness. The HCl will not be able to etch as much if you use only aeration. (The more acid you have in there, the etching accuracy drops a bit, but it's linear and gradual; it doesn't have to be titrated exactly right.) So for the best etching accuracy and forgiveness, you might want to try aeration and leave the peroxide for the cuts (and for cleaning up any etchant stains).You can try this experiment without aeration: Add peroxide to recharge your solution, then leave it uncovered for a couple days. Then try to etch a board. Chances are the amount of "cupric" you have previously been etching with will peter out and you will be left waiting for a long time for your board to etch. It'll turn dark green and basically stop. That's cuz you have been etching with a mix of both acid peroxide and cupric. The peroxide you add not only (continually) recharges the cupric etchant as long as it remains in solution; it also oxidizes the solid copper on the board, itself, allowing HCl to eat it away, directly. In regenerative cupric etching, the air predominantly recharges the etching solution, and the board is primarily etched with cupric, not HCl, because solid copper oxidizes relatively slower than does the reaction of cuprous to cupric when exposed to air. (Ideally, in a professional setup, the aeration/regeneration should be done away from the board, altogether, so the board isn't exposed to that air, at all, let alone peroxide).QuoteI also had the same experience. But I eventually started a fresh batch of cupric. The original iron from the ferric dilutes over time, but even a very tiny bit of residual iron leaves some of that iron stain in addition to the cupric stains.

author: magic
author_rank: Super Contributor
timestamp: March 25, 2019, 07:37:00 am
content: Quote from: nctnico on March 25, 2019, 12:37:38 amOr with off the shelf CuCl2 I suppose.Quote from: nctnico on March 25, 2019, 12:37:38 amNot exactly what happens here. The H+ from HCl works as electron acceptor which indirectly oxidizes metallic copper:H⁺ + Cu⁺ → Cu²⁺ + H (becomes H₂O)Cu²⁺ + Cu → 2Cu⁺or, if you don't believe in that ionic garbage,HCl + CuCl + ¼O₂ → CuCl₂ + ½H₂OCuCl₂ + Cu → 2CuClHCl is a consumable and must be added in proportion to dissolved copper.Er, wait, you talk about FeCl3. So, perhaps the regeneration works only like above, or maybe it also regenerates FeCl3 exactly the same way:H⁺ + Fe²⁺ → Fe³⁺ + HFe³⁺ + Cu → Fe²⁺ + Cu⁺At any rate, HCl is consumed and the end product is an ever growing solution of Cu and Cl ions.

author: KL27x
author_rank: Super Contributor
timestamp: March 25, 2019, 08:10:01 am
content: HCl dissolves the whitish dust-looking copper compounds that precipitate out of solution in used ferric and turns it into cuprous/cupric.Cupric is a byproduct of the ferric reaction. This cupric also etches copper and turns into cuprous, and when the free acid is used up, it starts to precipitate out into some other copper compound I won't pretend to know.If you use ferric long enough, iron compounds will also precipitate out.You might think, why not just siphon off the liquid fraction and discard the sediment? You could probably remove some of it, but you still want to leave some when you add acid. You need free acid for the reaction to occur, at all, but if you add the HCl after removing all of the precipitate, you might over-dilute your etchant. I was never good in chemistry, and I probably have got some of this wrong. But this is pretty much how it works in practice, IME.

author: Canis Dirus Leidy
author_rank: Regular Contributor
timestamp: March 25, 2019, 09:05:06 am
content: Hydrochloric acid may well be replaced by citric acid (Typical solution: 100 ml of 3% peroxide, 30 gram of citric acid and 5 gram of kitchen salt). Not so fast, but much safer at home. Another option: two parts of blue-stone with one part of kitchen salt (very slow at room temperature, so use hot water).

author: Ian.M
author_rank: Super Contributor
timestamp: March 25, 2019, 10:38:51 am
content: The white crystalline precipitate isCupricCuprousChloride or in modern nomenclature Copper (I) Chloride. It requires free acid to stay in solution, so if you are getting it, either your acid is low or your copper concentration is too high and the bath hasn't been aerated. Assuming your etchant is just acid cupric chloride (i.e no significant proportion of other metal ions), you can use density as a proxy for copper concentration, so weigh a known volume or use a hydrometer to determine the density before you add acid and turn on the bubbler to redissolve the Copper (I) Chloride. If its on the high side of the recommended density range and the etchant is dark brown/green (See link below), scoop out the crystals. If its on the low side, you need to get them back into solution, so its add acid and aerate.Low concentration Hydrogen Peroxide is not useful for etchant maintenance - it dilutes the etchant too much vs the quantity of oxygen it contributes. Aeration is far more practical. However its a quick way to kick-start a new etchant bath, as you would be diluting the acid anyway. Conc. Hydrogen Peroxide is extremely dangerous and tends to decompose violently and exothermically in the presence of heavy metal ions. Don't mess with it unless you are an expert chemist, with experience with strong oxidisers.For a scientific approach to acid cupric chloride etchant bath parameters, see Adam Seychell's notes at:http://techref.massmind.org/techref/pcb/etch/CuCl2.htmThe problem with all non-regenerating etchants is safe disposal. Even if you start off with lemon juice and salt in some misguided attempt to be 'green' and 'safe', as soon as you've etched a few boards the copper concentration in the etchant makes it toxic waste, hazardous to kids, pets and aquatic ecosystems. Minimise the quantity of chemical waste you produce!Edit: Thanks Kl27x for correcting my Cupric/Cuprous confusion.

author: KL27x
author_rank: Super Contributor
timestamp: March 25, 2019, 06:37:56 pm
content: QuoteThis sounds wrong, because there is a lower oxidized state of the copper called cuprous. Logic dictates cupric must be at least copper (II), so that cuprous can be higher than zero. Copper with zero oxygen would not be oxidized.The precipitate comes out of solution after using the etchant a lot without maintaining it. It looks like fine white sand. When you evaporate the etchant, it crystallizes into vibrant translucent green crystals. Same thing, different shape?QuoteAnd not only does it dilute the concentration of cupric/cuprous, it also increases the acid and copper oxide etching path (at least while there's peroxide still in solution, before it inevitably decomposes and gases off). For the cleanest etch, you want to minimize the acid path and etch with the cupric. Yet, adding 3% peroxide to recharge the solution and not using aeration is exactly how theRealElliot has taught hundreds of thousands of people to do it. It can apparently work and not get too diluted, if you do it just right, but it is not the way to get high fidelity. He advocates allowing air to recharge the solution between uses as much as possible and adding only a small bit of peroxide to help it recharge when you're in a rush. But in my experience, even using his full fifth (1/5th gallon liquor bottle) of fully charged cupric, it would greatly slow or stall out on even a single 6 x 9" 1 oz board sans aeration, if it were not for adding peroxide immediately before or during the etching. IOW, the way he is advocating/demonstrating would only really work like proper cupric if you used a (really) huge volume of cupric for (really) small boards, letting this large volume of cupric recharge between uses. He suggests that he adds the peroxide only when he is in a hurry, but the truth is that maybe only a scant few squares inches of board could be properly etched with his full bottle of cupric before it "hit the wall," and heating it would just make it hit the wall faster. It would work much better if he poured a little into the tank, dumped this into the "used container" after 30 seconds to a minute, and continually replaced with fresh etchant several times along the way to keep the concentration of charged etchant high. But that would be a pain. Effective aeration is the end game.Adding a bit of HCl and peroxide is how I eeked out a little bit of extra life out of spent ferric (spent ferric is basically dirty, iron contaminated cupric/cuprous chloride) to get a halfway etched board to finish. This is very suboptimal without aeration and does not produce clean traces. It might work well enough for your immediate needs, but it is a hack. With adequate aeration, spent ferric works just as well as the cupric that it essentially has become after you add some acid; it's just dirtier if you spill it.

author: coppercone2
author_rank: Super Contributor
timestamp: March 25, 2019, 06:52:08 pm
content: iron chloride in its hydrated form is hydroscopic. I noticed it gets wet much like many hydroscopic chemicals in the presence of humidity.The anhydrous variant is going to be a dull yellow powder, which rapidly reacts with atmospheric air to form the hydrate. Like other metal chlorides it fumes heavily on contact with air.http://www.rod.beavon.org.uk/AlCl3_and_water.htmThe reaction chemistry is similar to this.

author: KL27x
author_rank: Super Contributor
timestamp: March 25, 2019, 07:15:49 pm
content: QuoteI'm not good at chemistry, but I think you mean that in its anhydrous form it is hygroscopic.

author: bd139
author_rank: Super Contributor
timestamp: March 25, 2019, 10:32:11 pm
content: I don't get all the faff with etching boards. I just buy bottles of ferric chloride off ebay. They usually turn up ready mixed up inside a thin bottle with a jiffy bag around it which is the only scary thingThen I etch in the kitchen sink using a tupperware pot floating in boiling water:When you're done, pour it back into the bottle. When the bottle is knackered, take it the local recycling centre and they dispose of it for me (properly and safely).Edit: don't do this if you have a plastic sink. If you drop any in it, your other half will beat you to death. If it's metal, a couple of drops won't hurt.

author: apis
author_rank: Super Contributor
timestamp: March 25, 2019, 10:41:51 pm
content: Quote from: bd139 on March 25, 2019, 10:32:11 pmIsn't it the other way around? The plastic tupperware container looks like it's doing fine, but since the iron chloride is supposed to corrode metal I would have thought it was the metal sink that was at risk (and potential metal pipes)?

author: bd139
author_rank: Super Contributor
timestamp: March 25, 2019, 11:04:39 pm
content: If you poured it all down the sink yes but I wouldn't do that. Goes back in the bottle.If you spill some on metal you can rinse it off quick and it just looks cleaner than the rest of the sink. Quick scrub and it's gone.Plastic, human flesh, clothes etc are yellow for at least a monthIncidentally one of the things with ferric chloride is if you spill it on your hand you can just wash it off with no major side effects if you don't hang around. Using HCl etc can cause serious burns instantly. I know. I burned my left hand when I was in A level chemistry on HCl and it got infected and took 4 years to heal totally.

author: james_s
author_rank: Super Contributor
timestamp: March 30, 2019, 04:29:35 pm
content: My old stainless sink had several rust pits in it from where I spilled a few drops of ferric chloride years ago. Now I use cupric chloride which started out as HCl and peroxide about 8 years ago. I've been using the same batch ever since, adding a bit of fresh HCL a couple of times and a capful of peroxide any time I'm in a hurry to regenerate it.I don't etch boards often these days but when I need a board now it's an indispensable resource to have on hand. Also it's just kind of fun to make something myself from scratch.

author: Refrigerator
author_rank: Super Contributor
timestamp: March 31, 2019, 07:54:56 pm
content: I only made my own etching solution because i couldn't get any of the ferric chloride stuff that all the cool kids had.I also like the green color of the etching solution.

author: Gerhard_dk4xp
author_rank: Frequent Contributor
timestamp: March 31, 2019, 09:04:25 pm
content: I really don't know why people use those highly corrosive chemicals.I just juse NaOH for developping and Ammonium or Natrium persufateas an etchant. And FR4 material from Bungard that is already light sensitive.I also use PCBway. They are good but it takes usually 1.5 weeks becausethe customs office questions the prices or finds something else to beobnoxious. This here works from layout in computer to soldering inless than 2 hours.Pics:layout in Altium Designerlayout printed to Zweckform/Avery foil. That is somewhat roughso the laser printer toner attaches better.mounting the board between 1 sheet of glass and one or two layout foils.For two-sided boards you can align the top & bottom foil in through-light.Use left-over epoxy around the board location as spacer. Fix everythingwith duct tape. When top & bottom match, slip the board into the poach.The toner side(s) must touch the board. Be sure that the spacer + duct tapeare not thicker than the board. There should be no air gap betweentoner and photo resist.Add the second sheet of glass, press gently and use more duct tape tocomplete the bundle.I usually reserve the bottom side for a GND plane that needs no etching.

author: Gerhard_dk4xp
author_rank: Frequent Contributor
timestamp: March 31, 2019, 09:05:21 pm
content: use a face tanner from local tronics market as a UV sourceTakes 12 minutes per side in my setup.Develop in NaOH. About a teespoon full per liter of water.Etch in ammonium persulfat solution. I use a bowl of Pyrex glassWhen I bought it, i selected one where a Eurocard (100*160 mm)sits on its 4 corners with just 5 mm of free space to the bottom.That makes sure that the bottom of 2 sided boards is not scratched.and I don't need too much etching solution.I fill in abt. 15 mm of water and 2 or 3 spoons of Ammoniumpersulfate.That looks like salt, the solution stays clear and later turns bluish fromthe solved copper. Working temperature is abt 45°C, maybe 50.It must not boil. It won't do harm to your fingers, unless hot.I now have an induction stove which complicates things since theglass pot won't get hot. So I use a noble Fissler enameled fryingpan with 2 cm of water in it for heat transfer. It's chromium ringhas not taken the slightest stain in several years. Goes into thedishwasher after use for ritual cleanliness.Etching takes abt. 8 minutes; the solution lasts for abt. 4 boards.The easiest way to remove the photo resist after etching is anotherdose of UV and another bath in the NaOH. You cannot get it thatclean with any solvent.Sometimes I use "SENO Glanz-Zinn" tinning solution, but that is nowharder to get. It needs really clean surfaces, that's where NaOHstripping really helps.

author: Gerhard_dk4xp
author_rank: Frequent Contributor
timestamp: March 31, 2019, 09:06:06 pm
content: That Proxxon drill can do 0.3mm holes without problems.I use WireWrap wire for vias. it can be easily cut with a scalpel.

author: M4trix
author_rank: Frequent Contributor
timestamp: April 01, 2019, 12:15:43 am
content: Quote from: Gerhard_dk4xp on March 31, 2019, 09:05:21 pmHave no fear m8 ! 81 bottles in stock.https://www.buerklin.com/en/tin-powder-for-solder-baths/p/13l217

author: Beamin
author_rank: Super Contributor
timestamp: April 10, 2019, 01:22:24 pm
content: Quote from: nctnico on March 25, 2019, 12:37:38 amThat's what I was doing. You just add HCl or h2o2 to it when it wears out but at 6.00$ a gallon you could make new solution each time. I would start with the iron/nails/steel wool etc rather then copper as the replacement reaction works better. The stuff you buy has HCl in it so that's not safe either. They kust sell for more because HCl is scary to the untrained and people don't want to mess with chemicals but really its the same thing.

author: KL27x
author_rank: Super Contributor
timestamp: April 10, 2019, 09:11:16 pm
content: It reckon it sells for more because there's a much smaller market for ferric chloride in non-industrial quantities than for muriatic acid, which you can find in any hardware store in gallon jugs.I doubt you're making much ferric chloride if your etchant is GREEN. You can't see any green in used ferric until you have used and stretched/retitrated it with HCl many times. If you have anything resembling ferric chloride, it is brown. And you can etch a 4x6" board (maybe 3) in a pint of it after storing it for a week and without adding any additional peroxide.If your ferric turns green after one or two uses, you are most certainly just etching primarily with muriatic and peroxide, as are many of the folks who think they're using cupric chloride in the last decade. For a disposable etchant, I think adding some nails to it will make it etch better. But if you want an infinitely reusable etchant, I'd skip that part, and use cupric. The iron floating around in there doesn't do you any favors in the long run.QuoteIn some professional etching systems, peroxide is used to recharge the cupric, but it's carefully titrated and done separate from the tank. The peroxide doesn't go right into the tank, oxidizing the board, directly. H2O2 "recharged" cupric (which is all the rage, of late) doesn't etch for shit, unless you're doing significant etching with acid peroxide, directly, by dumping in the peroxide just before or while the board is in there. Even 2L of charged cupric might stall out on a 4x6" board without some way to regenerate it. Aeration can be used to regenerate cupric without decreasing the etching accuracy the way adding peroxide does. It can be very effective, allowing even a small tank to etch continuously and with high accuracy.

author: taydin
author_rank: Frequent Contributor
timestamp: July 14, 2019, 11:33:49 pm
content: I have just prepared CuCl2 solution in my vertical etch tank which also has a sealed top. Is it safe to store the solution sealed? Or will gases be produced and the thing will blow up?

author: coppercone2
author_rank: Super Contributor
timestamp: July 14, 2019, 11:52:00 pm
content: put a stopper

author: KL27x
author_rank: Super Contributor
timestamp: July 16, 2019, 05:44:32 pm
content: QuoteToday, "CuCl2" is poorly defined.99% chance, today, you actually mean you are putting peroxide in it (which makes the etching happen partly/largely via HCl and peroxide rather than the slower CuCl2 reaction with copper). This will gas off some O2. Peroxide degeneration has killed a bunch of people... by making poorly maintained torpedoes blow up, sinking their own subs.I wouldn't store it airtight, personally. CuCl2 doesn't need to be stored in a sealed container to "keep." There isn't enough acid to fume away. If you have peroxide in there (or if the temp of the air sealed in there increases), it will increase the pressure, and that won't help your chances of your tank not leaking. (I am sure your tank doesn't leak, today. I'm curious what you will find 4 years from now!)What's with the fancy airtight lid, though? It looks like you have taken serious trouble to make an airtight lid complete with a gasket. But it looks like you have made brackets to hole an air tube and a bubbler? There must be air outlet? Or are those brackets for a heater?You can't really etch with that volume of CuCl2 without some form of regeneration which will need venting. So the gasketed top is really curious to me. Most people using CuCl2 "only add a bit of peroxide when they are impatient," which is curious statement for me. IME, using even a full liter of fully charged cupric without regeneration (by air or whatnot), you won't etch even a modest sized PCB without waiting hours. It'll start at a good rate but come to a crawl just a little ways in. If you use add just enough peroxide to let your full tank recharge, then let it sit for a few days for any excess peroxide to degenerate and then try to etch a board, you might understand you're not adding peroxide just when you're impatient. Unless you are etching only very tiny boards in very large volumes of cupric, you are adding and etching with acid peroxide every damn time, and you probably gravitate towards excessively high acid concentration compared to pure CuCl2 etching.

author: SiliconWizard
author_rank: Super Contributor
timestamp: July 16, 2019, 06:14:51 pm
content: How about nitric acid?It's nasty though. Don't try this at home without adult supervision.

author: magic
author_rank: Super Contributor
timestamp: July 16, 2019, 09:04:43 pm
content: Quote from: SiliconWizard on July 16, 2019, 06:14:51 pmWhat are you, a terrorist?Try to buy it in concentration higher than 3% anywhere in the EUSSR and report back.And yeah, the nitrogen dioxide fumes are sorta poisonous. I have heard of people who ended up in the hospital trying to distill that stuff

author: james_s
author_rank: Super Contributor
timestamp: July 17, 2019, 12:02:35 am
content: It's a shame really, because nitric acid is really useful stuff, particularly for de-capping ICs. I don't even know what use it is to terrorists although I'm pretty sure it isn't too terribly difficult to get in the USA, it's not cheap though.

author: SiliconWizard
author_rank: Super Contributor
timestamp: July 17, 2019, 12:40:22 am
content: Quote from: james_s on July 17, 2019, 12:02:35 amOf course you won't find that in your local hardware store, but it's not that difficult to get in Europe and in the USA. Not cheap but not *that* expensive either:https://www.chemicals.co.uk/nitric-acidAnd yes, it has many uses. It can dissolve many metals including copper. To dissolve gold, it must be mixed with hydrochloric acid. Dangerous stuff.As I hinted, it's very corrosive and can react producing very dangerous fumes, so that's certainly not something to toy around with if you don't know how to handle it.I have no clue what use it could be to terrorists either. @magic seems to know more about it than we do.

author: coppercone2
author_rank: Super Contributor
timestamp: July 17, 2019, 07:18:52 am
content: lol it sounds like you are playing dumb, most people know nitric acid is one of the best base ingredients to make explosives with in 99% of casesother routes are finicky industrial level stuff

author: magic
author_rank: Super Contributor
timestamp: July 17, 2019, 07:20:44 am
content: I'm pretty sure I have heard of things like TNT, nitrocellulose or dynamite even at school. Maybe your governments didn't want you to knowQuote from: james_s on July 17, 2019, 12:02:35 amI don't think it's banned in the US yet. And technical grade 65% isn't very expensive, $10/l here if they will sell it to you. Fuming NA is used for professional decapping and that can be expensive. I have heard that chemistry hobbyists synthesize and distill it themselves because it's cheaper that way, and comes without weird questionsTo etch copper you would use 65%. Maybe even slightly less would work too, IDK. Fuming OTOH almost doesn't attack metals at all, and that's why it's used for decapping and useless for etching.Quote from: SiliconWizard on July 17, 2019, 12:40:22 amThat's a wise response. Not so far away, in the homeland of George Orwell, even reading about it on the Internet may land you in jail.Quote from: SiliconWizard on July 17, 2019, 12:40:22 amQuote

author: magic
author_rank: Super Contributor
timestamp: July 19, 2019, 10:58:49 pm
content: I had an opportunity to play with 65% nitric. I didn't really attempt to etch anything, just stuck a copper wire in it. The reaction is quite fast, lots of bubbles, might be too fast for reliable etching. And NO₂ released in the process sure enough stinks like chlorine and is harmful, although apparently not in quantity just sufficient to detect its smell and back offAll things considered, there are better solutions out thereBy the way, I can add that it does nothing to stainless steel and aluminum, at least at room temperature and in the short term.

author: Beamin
author_rank: Super Contributor
timestamp: July 20, 2019, 01:59:30 am
content: Quote from: taydin on July 14, 2019, 11:33:49 pmI wouldn't keep it sealed as gas can be produced. You can put it in a larger container to catch any spilling and leave out in the garage to vent.

author: Beamin
author_rank: Super Contributor
timestamp: July 20, 2019, 02:05:54 am
content: Quote from: SiliconWizard on July 17, 2019, 12:40:22 am

author: Beamin
author_rank: Super Contributor
timestamp: July 20, 2019, 02:15:13 am
content: Quote from: SiliconWizard on July 17, 2019, 12:40:22 amOne of the most stable bonds is a N N triple bond in N2 a double or single bond with N to C is usually unstable when large shocks are produced perfect for explosives hard to set off but massive conversion of gas made. Unlike gun powder where 3 chemicals have to touch and be mixed together; huge boulders in the chemical realm high explosives have the oxygen nitrogen and fuel all in one molecule.At each unlabeled intersection there is a carbon atom with the top of TNT having a CH3 group at 12:00. Look at how much O and N the petn has super powerful. The RDX is almost perfect balance of N2 CO2 and H20At each intersection there 2 H single bonded to the carbons.Look at how elegant and unstable these molecules are the nitrogen's just want to be left alone to form N2 the carbon wants to be CO2; desirable but TNT is also oxygen poor creating black smoke as opposed to white which is complete combustion. Burning TNT in air actually produces more energy but no explosion. The trick is cramming as much n o and c in a perfect ratio while keeping it stable. So the molecule itself breaks apart. You can nitrate all kinds of carbon compound with sulfuric and nitric acid like cotton or paper.

author: taydin
author_rank: Frequent Contributor
timestamp: July 20, 2019, 08:53:44 pm
content: Quote from: KL27x on July 16, 2019, 05:44:32 pmI have bought 250g of Copper II Chloride Dihydrate. It's turquoise colored crystals. I will mix this with distilled water and then add some HCL and H2O2 to it.Quote from: KL27x on July 16, 2019, 05:44:32 pmInitially, my plan was to use HCL and H2O2 as the etching solution. I know that HCL fumes out even if the bottles cap is closed (from experience lol). I don't have any place (garage etc) to store the acid, so I wanted to make a well sealed container for it to store it in the house. But then I found out about CuCl2 which is looked much safer, so I just changed plans.The brackets are for air bubbles and the intention is to etch PCB's with the lid open and close the lid only for storage.Quote from: KL27x on July 16, 2019, 05:44:32 pmThe tank looks smaller than it actually is. It's about 3 liters of volume, and the target PCB size is close to 180 x 180 mm.If I can store the CuCl2 solution in the house without closing the lid (no nasty fumes) then I can Just put the lid on and tighten it just a little bit so that some gas can escape.

author: taydin
author_rank: Frequent Contributor
timestamp: July 20, 2019, 09:02:47 pm
content: Quote from: magic on July 16, 2019, 09:04:43 pmI was able to buy 40% HCL and 50% H2O2 from an internet merchant here in Turkey with no questions askedAnd I also see 56% Nitric acid on the same merchant's websiteConsidering how many dummies are out there, this should be better controlled.

author: coppercone2
author_rank: Super Contributor
timestamp: July 21, 2019, 12:13:34 am
content: lets go hire professionals to do everything why don't wewelders cry

author: IanB
author_rank: Super Contributor
timestamp: July 21, 2019, 12:30:54 am
content: Quote from: Beamin on July 20, 2019, 02:15:13 amWhat has that got to do with etching? Do you want blow up your failed circuit boards maybe to let out your frustration?

author: magic
author_rank: Super Contributor
timestamp: July 21, 2019, 08:33:23 am
content: Quote from: taydin on July 20, 2019, 08:53:44 pmI don't think you need H2O2 yet, it's used to convert CuCl and HCL to CuCl2 when the solution turns brown after use. Alternatively, air can be used instead.Quote from: taydin on July 20, 2019, 08:53:44 pmThere is no escape from HCl, you will need to add more of it once in a while in order to restore CuCl2 from CuCl.Quote from: taydin on July 20, 2019, 09:02:47 pmSo be glad you haven't joined.I don't think it needs to be controlled, the only acid dummies tend to play with is LSDDifferent thing for countries affected by terrorism or those dumb enough to have open borders with the formerQuote from: IanB on July 21, 2019, 12:30:54 amThermite would be easier and safer

author: taydin
author_rank: Frequent Contributor
timestamp: July 21, 2019, 10:51:53 am
content: Quote from: magic on July 21, 2019, 08:33:23 amYes, after the first preparation, the solution is ready to go. I do want to use an aquarium air pump to refresh the solution, mainly because it isn't possible to add too much oxygen using this method, whereas with H2O2, there is always the question of how much to add.Quote from: magic on July 21, 2019, 08:33:23 amI have seen metal stuff that is close to the HCL bottle corrode, even though the bottle cap was closed tight. But I think you are talking about the HCL that's in the CuCl2 solution.Quote from: magic on July 21, 2019, 08:33:23 amThere are a disturbing number of cases where disgruntled boyfriends throw nitric acid at their girlfriend's face when the girl dumps him, so I think acid should be strictly regulated here. These cases are getting less and less, but even one case always makes headlines and people take out to the streets. I think the best punishment for these fuckers is to make the same treatment to their face as they did to the poor girl.

author: Beamin
author_rank: Super Contributor
timestamp: July 21, 2019, 11:48:31 am
content: Quote from: taydin on July 21, 2019, 10:51:53 amNitric acid isn't that bad if you get it off quick, but we shouldn't ban things because 1/10,000,000 misuse it. Drano or sulphuric will do the same.As far as the HCl fumes go even with the bottle capped and fans just opening it will ruin all the metal, even aluminum, in the room. I made the mistake of using it in the house. I have all kinds of USB cables ruined, cabinet hinges, which I have never seen rusted and things like razor blade crumble apart.

author: KL27x
author_rank: Super Contributor
timestamp: July 22, 2019, 11:23:24 pm
content: QuoteI'm obsessed with sharing my solution. There are these plastic bubble wands for fish tanks. They are supposed to make a tiny curtain of fine bubbles, using an aquarium bubbler. I've seen two varieties, one is real skinny, and the one I'm referring to is the large diameter, maybe 3/8" tube, comes in 14" lengths, i believe.If you try to use it in a cupric tank like this, chances are that it will not do very much good. And that it will eventually clog with sediment. In fact, I bought the biggest and most expensive multiple line out aquarium bubblers, and I could not produce a satisfactory cupric regeneration with any bubblers I tried. I was stuffing as many bubblers I could in a tank, and it was essential impractical. Even starting with 3L, you will likely reach the point where you want to etch a large board(s) and find where the reaction stalls and basically hits a brick wall; then you'll dump a bunch of peroxide AND acid in there just to get it to finish. An aquarium bubbler will recharge the etchant overnight or whatnot, but it can't sustain the etching. And cupric doesn't etch very much copper before it stalls.But if you have an air compressor and a regulator, you can force about 15-20 psi through this bubble wand and the bubbles still remain super tiny. The bubbles are so small, their surface area to volume is so insane that the bubbles barely have any buoyancy and just mill around with the current instead of rising and popping straight off. This makes a very fine frothy etchant that recharges cupric very well. The etch accuracy is fantastic. For a 3 L tank with large boards, I would suggest you might try to run as many as 3 of them across the bottom, but even one might be enough. Even a cheap nail gun compressor can run that easily with a very low duty cycle. I just run my 11" single wand, 0.4 liter (down from 2.5L tanks I initially played with; you really don't need that much with good regen!), vertical tank off a 125 psi 5 gallon air tank, and it will run for 45 minutes to an hour. Plenty time to etch a board. You actually have to be careful how much air you run, because the froth/head can reach at least 9" inches and overflow the tank. (My tank is 11.5" tall, and I've had the horror of finding 90% the contents have escaped, more than once; Key point: the froth gets frothier when the cuprous content rises.)This material does not degrade in acid. I've used the same wand for about a decade, now. It's been submerged in cupric for the past 4 years. This pushes the recharging so well that my tank etches with half inch of sediment in it, well past due for titration. I don't even use a heater.If you get sufficient regeneration to efficiently etch with purely cupric pathway, you need very little free acid in the tank. Fumes might be a bit corrosive very close to an unsealed tank, but diffusion would limit the danger zone. A close fitting lid and care what you put right next to the tank might be enough to deal with fumes, even without that crazy lid. I think your major worry would be the tank developing a leak in one of the seams.If you actually try this, be sure to disconnect the regulator when you're not using it. The vapor pressure in the tiny air hose will be the same as in the tank. So inside of the regulator will corrode over some months/years of being connected but not running. And, again, I'd warn you to keep the head under an 1" tall and well away from the top of the tank before walking away.The froth head etches just as well as the liquid fraction. The etch accuracy is so high that you don't need to worry about a "line" of over/underetching at this transition. It's all good. But if you have a tall board in there, it is way safer to fill the tank a bit higher and run a small head than to use less etchant and try to run a tall head.

author: magic
author_rank: Super Contributor
timestamp: July 23, 2019, 10:46:36 am
content: Quote from: taydin on July 21, 2019, 10:51:53 amSo be the change you want to see in the world. Dump your solution down the drain and scratch your PCBs with fingernailsYou know, in Europe that kind of gentlemen would have their asses beat by the father and brothers of the girl so that centuries later we could freely enjoy our chemicals without worry about them being misused. Until recently, at least

author: coppercone2
author_rank: Super Contributor
timestamp: August 01, 2019, 01:19:12 am
content: does nitric acid even burn you as a weapon? it will turn you yellow for a while, its weak on flesh compared to other acidsand it wont super heat if you try to wash it like other acids as much

author: magic
author_rank: Super Contributor
timestamp: August 02, 2019, 12:07:40 pm
content: You know, these days you can just go to google image search and type "xyz acid burns".

author: taydin
author_rank: Frequent Contributor
timestamp: August 03, 2019, 10:40:58 am
content: Ok guys, I have completed my acid tank.

author: taydin
author_rank: Frequent Contributor
timestamp: August 03, 2019, 10:46:30 am
content: It's basically 1.6 l distilled water, 125 g copper II chloride dihydrate, and about 350 ml of 40% HCL. I started out with just the distilled water and started adding the copper II chloride until I got a full turquoise color solution. Then I started to add HCL until it changed to a full green color solution. I know, not very scientificI just knew that I had to have green solution.This is a two sided PCB that I did just for experimentation. This PCB doesn't have to be two sided, but I made it that way so that I can see how the etching process goes. One thing that really threw me off was the shadow of the upper layer preventing me to see how far along the etching is. The upper layer is almost completely full copper, so it was shadowing the bottom layer view, and I kept thinking that the etching is not complete and kept it in the acid much longer (about 30 minutes). So, I don't know how long the etching really took.

author: taydin
author_rank: Frequent Contributor
timestamp: August 03, 2019, 10:52:05 am
content: The resulting PCB was visibly overetched

author: taydin
author_rank: Frequent Contributor
timestamp: August 03, 2019, 10:57:31 am
content: Then I drilled some holes to see how well they match. It didn't look great. The holes that I had used to align top and bottom layer matched quite well (see the TO-220 holes on the right). But other holes had varying levels of mismatch. For example, the top holes have a mismatch of about 0.6mm. Center holes are less than that. Top layer (first picture) are the holes I drilled exactly at center. Bottom layer (second picture) shows the mismatch.I had set the lamination machine to 250 degrees celsius. I'm suspecting that this was too hot and the PNP paper deformed as a result of the heat. That's why some holes match better than the others. All in all, I would say two sided PCB's are too fiddly to get right with the lamination method. Using UV light method with Positive 20 would probably be better for double sided PCB's.

author: ogden
author_rank: Super Contributor
timestamp: August 03, 2019, 11:23:53 am
content: Quote from: taydin on August 03, 2019, 10:57:31 amYour fills are riddled with holes. I would say that lamination method (toner transfer?) of such quality is hardly usable for anything but very crude PCB's. Try UV photoresist - film or PCB's with resist applied and you will not look back. You can use your laminator for UV resist film transfer, "nail UV lamp" is dirt cheap, developer and stripper are cheap as well, sold in most supermarkets.

author: janoc
author_rank: Super Contributor
timestamp: August 03, 2019, 11:49:06 am
content: Quote from: nctnico on March 25, 2019, 01:04:16 amFerric Chloride is corrosive only if you spill it on something. If you have it corrode stuff due to vapors, don't pour hydrochloric acid in it next time to regenerate it! (or buy liquid one where they sometimes add the acid in the factory already - buy crystals and dissolve them yourself).The acid fumes are what is causing the problem, not the ferric chloride. I have a bottle of the stuff in my bathroom for occasional board making for several years and no corrosion whatsoever (and it is a normal plastic bottle, certainly not gastight).

author: janoc
author_rank: Super Contributor
timestamp: August 03, 2019, 11:58:57 am
content: Quote from: coppercone2 on August 01, 2019, 01:19:12 amDepends on how concentrated it is (as with all chemicals) but yes, concentrated nitric acid can cause very bad burns and disfigurements. If you only had it turn you "yellow for a while", you had only a fairly weak concentration. Just google "nitric acid burns" if you really feel like you want to see some horrific injuries.Whether or not it is usable as a weapon is different debate but acids generally don't make very good weapons in themselves. Other acids than the nitric one are also much more readily accessible (hydrochloric is available as part of the pool and cleaning chemistry, sulphuric is for batteries and drain cleaning, etc) and if you throw them at someone they will cause pretty similar or worse damage.Nitric isn't readily sold to mere mortals because it can be easily abused for nefarious purposes (explosives, for ex.) and has little legitimate domestic use that cannot be achieved by other means.

author: KL27x
author_rank: Super Contributor
timestamp: August 03, 2019, 08:17:03 pm
content: QuoteDon't give up yet. You barely started. You can't judge an encyclopedia by the first page.Your cupric looks a bit too transparent. Not enough cupric and probably too much acid.As for the holes lining up, yes, you are right. There will always be some slight misalignment due to distortion of the paper/transfer, but what you got there is way worse than what you can reasonably achieve with a bit of learning.I humbly suggest you try a couple of things.1. Pulsar transfer paper. Very minimal distortion due to heat2. Pre etch the board. Dip it in the tank, turn it around (don't even pause), dip the other end. Let it drip back into the tank for about 10-12 seconds. That time of drip-drying is all it takes to pre etch the board, sufficiently. Then rinse in a bucket of water and dry with a heat gun. Note you still have to clean the board BEFORE the pre etch.The reason for the pre etch is not to make the toner stick better at a lower temp. It's so that the textured surface sucks up the liquified toner without fattening/smearing when you get the board WAY hotter than what you're doing right now. I measure temp of the board at about 350C as it comes out the back of the rollers. I shoot the board with a heat gun as it is going into the laminator. Full power, 1200 watt heat gun. The pre-etch completely eliminates any adverse effect of using too much heat. And when you use that much heat, you completely eliminate any possibility of an incomplete transfer. And the extra icing on the cake is that you completely eliminate pores in your planes. And the toner will stay stuck. Theres an area of your board where it looks like the toner fell off, prematurely, because it wasn't stuck well. The toner sticks by mechanical adhesion. There's no chemical bond. So a textured surface will obviously hold it better throughout the etching, provided it has been liquified.Notice you cannot use this much heat with most other transfer papers. With a regular paper (and even magazine paper*), the toner will suck into the paper and you will get fibers stuck to the board. With PnP Blue, the vinyl sheet will melt. You must use a paper that can handle the heat. Aside from Pulsar, perhaps laser printer label backing sheet or the like may work. I don't know for sure.*Magazine paper also has a great amount of distortion, IME, when heated.Dunno how you are lining up your holes. I think the "envelope trick" is always going to allow more error, due to the thickness of the board. I transfer one side at a time.1. Take two reference holes in two corners of the transfer papers. Punch the center of each hole with a pointy scribe/needle and then drill with 74 gauge bit.2. Transfer that side. Leave the transfer paper on3. Drill through those holes/marks through the board, keeping as perpendicular as possible.4. Take the second side and line it up with light and/or put a small 30 awg wire through the holes to help get the second side on there. Remove the wires and tape it down with kapton tape, if you must. I just hold the second side on there while putting the board into the laminator. The first pass to get it to stick, then I shoot with the heat gun on the second pass.

author: coppercone2
author_rank: Super Contributor
timestamp: August 03, 2019, 08:48:11 pm
content: i found a new solution, you mix a drop of xenomorph blood into a beer, nice bubble etch process

author: Ian.M
author_rank: Super Contributor
timestamp: August 03, 2019, 11:28:20 pm
content: Quote from: taydin on August 03, 2019, 10:46:30 amAdam Seychell's paper "Etching with Air Regenerated Acid Cupric Chloride" which popularised hobby CuCl2 etching, can be found here:http://home.exetel.com.au/adam.seychell/PCB/etching_CuCl/index.html(there are other mirrors but many are missing important photos).Chemcut's Technical Bulletin 8 "Process Guidelines forCupric Chloride Etching", which covers commercial CuCl2 etching is here:http://www.chemcut.net/wp-content/uploads/2015/03/Chemcut_Bulletin_8_Cupri_Chloride_Proces_-Parameters.pdfSeychelle recommends starting with 120g Cu per litre, which puts your solution concentration to the left of the stable etch rate plateau documented by him & Chemcut, allowing for future increased copper concentration, but not right at the edge of it.Unfortunately Copper(II) chloride dihydrate is only 37% by mass copper atoms ( CuCl2(H20)2molar mass is 170.48 g/mol, Cu atomic mass is 63.546 u ), and you have approx 1.95 l of etchant, so your copper concentration is *way* low. I calculate it as 23.9 g/l, which is only 20% of what it should be.With the help of Sigma Aldrich's Acid & Base molarity calculator:https://www.sigmaaldrich.com/chemistry/stockroom-reagents/learning-center/technical-library/molarity-calculator.htmlusing 1.198 g/ml for the density of 40% Hydrochloric acid, it appears your HCl concentration in the etchant is about 2.36 molar. That's in the middle of Seychell's acceptable range.You need to add more copper, preferably as copper II chloride dihydrate, if you've got another 500g of it, or as 96g of scrap copper per litre or 120g of Copper(II) oxid per litre. Copper metal will require continuous aeration to dissolve.If you are using copper metal or copper oxide, you'll almost certainly need to add more acid which also will increase your etchant volume reducing the copper concentration slightly. How much acid to add depends on your target HCl concentration. There's enough acid to dissolve the suggested copper or copper oxide at the moment, but it will take your acid concentration down way below 1 molar so you'll need to titrate for acid, then check the density after adding acid to get back within Seychell's suggested bath parameter range (see table 1).

author: taydin
author_rank: Frequent Contributor
timestamp: August 04, 2019, 08:44:49 am
content: Quote from: KL27x on August 03, 2019, 08:17:03 pmUnfortunately Pulsar is not avaiable here in Turkey and ordering from outside means at least $100 customs fee, so not an option for meI have used PNP blue, which is still very expensive here (about $5 per sheet). I really had to put as many specimen on the sheet as possible to get the most out of itRegarding pre-etch, I have actually done pre-etch on these boards (I had read your posts where you describe it). After pre-etch, the copper had a nice, uniform pink texture. I think the pre-etch didn't yield any benefits because my temperature is WAY LOWER than what you have. With 250 celsius, the PNP blue was undergoing quite some deformation, so I really need to bring the temperature down, not up ... Or I can try the laser printer label backing.Quote from: KL27x on August 03, 2019, 08:17:03 pmAfter punching and drilling the first side, do you just hold the transfer paper in place? If not, how do you have it stay put?To line up, I'm using a small LED hand torch. When shining the lignt from underneath, I line up the left and right side and then staple the PNP blue at that point. Then I slide in the PCB (I pre-heat it with a hot air gun, but it really cools down very quickly). And then I slide the package through the laminator for about 7 times. I finally remove the package and massage the PNP blue on both sides until it is cool, after which I peel off the PNP blue. There are always spots to touch up.I have laser printer labels available. I will try with those and see if it makes a difference.

author: taydin
author_rank: Frequent Contributor
timestamp: August 04, 2019, 09:05:05 am
content: Quote from: Ian.M on August 03, 2019, 11:28:20 pmI had gone through those documents, but having consistently and repeately failed chemistry at school, I wasn't able to deduce the amount of CuCl2 dihydrate I have to mix in from that information.Quote from: Ian.M on August 03, 2019, 11:28:20 pmThanks a lot for this information! I will order more CuCl2 + 2H2O. But I'm glad that my HCL concentration was right at the mark. I know that going forward, the role of H2O2 will be to regenerate the Cl2+ ions, but what is the role of HCL in this mix? How do I know it's time to add more?Indeed, after etching the first board (100 x 100 mm), the solution got quite dark. I added a little H2O2 which made it green again. I etched two more boards (same size) and it took about 30 minutes each.But I suppose, just like high concentration causes overetching because of the aggresiveness, low concentration also causes overetching because of the extra time that the acid has to attack the copper. My initial target was an etch time of about 5 minutes.

author: Ian.M
author_rank: Super Contributor
timestamp: August 04, 2019, 10:55:48 am
content: Apologies: the Copper (II) chloride dihydrate formula above got garbled when I was copy/pasting the2subscripts.The HCL provides the acidity and Cl-ions required to get Cu1+ions to dissolve (Copper (1) chloride is nearly insoluble in water at pH 7) and is used up providing the H+ions when Cu1+ions are regenerated to Cu2+, and also the Cl-ions to balance the chemistry. See Seychell section 3 (Chemistry) equation 4.As I said you need four times more copper ions in solution, and the easiest way to get there quickly without messing up other etchant bath parameters would be to add 500g more of Copper (II) chloride dihydrate. The cheapest would be to etch scrap copper till you get there, but as that uses up acid, and adding more acid increases the volume, you'd need to titrate for acid and check density to hit the target bath parameters.Regenerating with H2O2is generally counter-productive. In most countries its very difficult for hobbyists to get high concentration Hydrogen peroxide (a good thing as its extremely dangerous), and even if you can get it, you probably don't want to unless you want to get on the same watch lists as the terrorists mucking about with chapati flour! Low concentration hydrogen peroxide dilutes the etchant too much, making it difficult or impossible to keep the copper concentration in the desired range. Also the H2O2+ HCl etchant system is extremely aggressive, with a lot of under-cutting which makes it very difficult to produce fine traces, and increases foul-biting as the peroxide is aggressive enough to gradually attack organic resists. If you want good quality results you need to regenerate with oxygen from an air bubbler, continuously during etching, then afterwards till the bath stays bright green, not hydrogen peroxide.Commercially, PCB houses that regenerate with peroxide rather than elemental chlorine get away with using it without adverse effects on the etching accuracy by very careful metering to only add the minimum required to regenerate the etchant so there is minimal free peroxide at the surface of the board being etched. Hobbyists don't have the continuous process control required to use peroxide successfully for finer pitch boards.

author: taydin
author_rank: Frequent Contributor
timestamp: August 04, 2019, 12:00:22 pm
content: I used 50% H2O2 to refresh the mix. I think I added much less than 50 ml of it and the solution immediately got green. And even though the initial solution (with no H2O2 added) got dark after etching one board, the refreshed solution stayed green after etching two extra boards. And also, I have noticed that bubbles have formed in the solution.Just to be safe, I loosened some of the clamps and there is no gas escaping.IIUC you are saying that the HCL + H2O2 combination is causing over etching. But if that were the case, shouldn't the exposed copper take a very short time to dissolve? It took about 30 minutes.My plan was to use aeriation to regenerate, that's why I have hose guides in the tank. I will try and see how long it will take to regenerate, but I'm expecting it to take several days according to the Seychell document.

author: Ian.M
author_rank: Super Contributor
timestamp: August 04, 2019, 12:59:56 pm
content: If it stays bright green during etching without aeration, you've got excess peroxide. It will decompose during storage (causing the bubbles) and the oxygen bubbles will be wasted if they get big enough to break free and rise to the surface.HCL + excess H2O2 is aggressive because it doesn't slow down significantly (compared to its action on a bare copper surface) in the microscopic pockets that form at the edge of the tracks under the edge of the resist. This increases undercutting. If you etch fast enough that Cu1+ion diffusion out of the pocket is the limiting factor, with air regeneration instead of peroxide, you can vastly reduce undercutting. A slow etch tends to undercut more.Once you've got the bath chemistry right, with enough volume that air regeneration isn't limited by a need to restrict the air supply to keep it in the tank, and an air stone or diffuser that generates fine bubbles, air regeneration can pretty much keep up with the etching rate, so you shouldn't need to run the bubbler for much more than a few times longer than the etch time after use.N.B. always disconnect the air pump hose from the tank when not in use. With no air flow, HCl fumes will diffuse back up the hose and eat the pump internals! If you *MUST* run the pump on a timer without disconnecting the hose, you need an air lock in the hose filled with strong sodium bicarbonate solution to neutralise the HCl fumes before they get to the pump.

author: magic
author_rank: Super Contributor
timestamp: August 06, 2019, 01:23:07 pm
content: Quote from: janoc on August 03, 2019, 11:58:57 amAFAIK fuming nitric is the only chemical that can nondestructively dissolve epoxy IC packages at reasonable temperature.And of course banning it doesn't preclude production of explosives in any way. Nitric acid can be easily produced from concentrated sulphuric plus just about any nitrate. Anders Breivik had a stockpile of that stuff when they busted him.And that's before we get to fun stuff like acetone peroxide, successfully employed by terrorists in the past, which is almost trivially* prepared from acetone and hydrogen peroxide, the latter being possible to concentrate from a 3% solution just by drying or freezing out the water.* if you know how not to blow yourself up in the process, like some wannabe ISIS bombers didThose restrictions are complete bullshit.

author: janoc
author_rank: Super Contributor
timestamp: August 07, 2019, 10:56:34 am
content: Quote from: magic on August 06, 2019, 01:23:07 pmSounds like a perfectly common domestic use to me!Anyhow, I don't think fuming nitric acid is commonly sold anywhere (as opposed to just regular, diluted nitric which used to be available), you have to specifically order it and then the vendor is going to ask some questions on why exactly do you need this stuff. And possibly demand some paperwork as well.Quote from: magic on August 06, 2019, 01:23:07 pmYes, I agree - but that won't make them go away.If anything, they are going to get worse in the aftermath of the recent splashing attacks using corrosives. Heck, you can't even carry a kitchen knife without risking an arrest in some countries these days.If someone knows how to produce TATP without blowing themselves up in the process or have the equipment and lab skills to produce the acid themselves, they certainly won't be stopped by this. But that's beside the point - the idea of these restrictions is that a teenage OG Joe Hoodie Gangsta doesn't buy a liter of the stuff and toss it in the face of his ex-girlfriend. Or a random person that they decided to mug for their wallet or scooter today.It is certainly not perfect because a lot of common chemicals could be used like this but it makes it slightly more difficult. E.g. the US thugs don't bother with knives and acids - they have readily available guns. In the UK guns are (mostly) unavailable to low level gangsters, so they resort to things like chemicals instead. Once the chemicals stop being available (or too many questions start to be asked), the thugs will move on to something else as a weapon. But maybe it will stop a few people from being maimed and disfigured in the meantime.

author: SiliconWizard
author_rank: Super Contributor
timestamp: August 07, 2019, 02:34:10 pm
content: Quote from: janoc on August 07, 2019, 10:56:34 amWho said it was?Quote from: janoc on August 07, 2019, 10:56:34 amOf course. As I said, you won't find that in your local hardware store. It's relatively easy to get it if you're an established company. They won't sell that to an individual. Seems pretty logical to me.Even the shipping itself requires special paperwork. You can't have dangerous chemicals shipped to you with no particular precaution... That seems pretty reasonable.Quote from: janoc on August 07, 2019, 10:56:34 amCriminals can do very nasty stuff with pretty much anything they can find. And they can find pretty much anything when they really want to. Especially things that are illegal. It's unfortunately very easy to get ahold of a gun in most countries in the world. Thinking otherwise is completely delusional.Anyway, I don't know how it all went this off-topic. Let's stick to EE here please. Many chemicals are dangerous and it's good to say so (I did). But talking about making explosives or disfiguring people with it has no place in this forum IMO.So let's stick to talking about EE uses, and give appropriate safety warnings.

author: magic
author_rank: Super Contributor
timestamp: August 07, 2019, 03:52:48 pm
content: Quote from: janoc on August 07, 2019, 10:56:34 amYou said "legitimate", not "common"I suppose basic mineral acids have use in general hobby chemistry too but of course European kids these days will all be rock stars and youtubers so meh.Quote from: janoc on August 07, 2019, 10:56:34 amThat's why I sarcastically called it the EUSSRYeah, I guess we're getting offtopic, I will leave it at thatThere are solutions to petty criminals known for millennia which do not involve total government control over everything remotely dangerous.

author: janoc
author_rank: Super Contributor
timestamp: August 07, 2019, 05:18:26 pm
content: Quote from: magic on August 07, 2019, 03:52:48 pmPut the blame where it belongs (the UK government in this case) instead of bashing the EU there, shall we? The blanket knives/acid bans are very much an UK thing.

author: coppercone2
author_rank: Super Contributor
timestamp: August 08, 2019, 03:25:03 am
content: Quote from: magic on August 07, 2019, 03:52:48 pmhow will the youtube videos get views without smoke and fire?then indians or some other lax place will take over

author: coppercone2
author_rank: Super Contributor
timestamp: August 08, 2019, 03:29:26 am
content: it makes me sad because all the good industrial chemists and even research chemists of the past all messed with stuff thats a bit dangerous if you read their notes and musingshow are you going to get the whizz kid without him being fascinated by advanced rocketry or such?I have been looking at you stoichiometric equation for 22 years. When I get to start my PhD I will finally know what you actually smell like.and all us eastern europeans know how well goverment allocation of resources (in this case chemical experience and practical knowledge) will work, its practically a commune. We will license so many people this year to meet a employment quota determined by the 'intelligent' (basically depends on how much the chemical industry lobbies).

author: coppercone2
author_rank: Super Contributor
timestamp: August 08, 2019, 03:39:50 am
content: And Imagine how much corruption this can bring. Imagine being the only weld shop in a city that can get the chemicals to do metal treatments or plastics work, analytical work etc. Just throw a kick back to the licensing committee to keep competition out. That's like fucking las vegas.

author: KL27x
author_rank: Super Contributor
timestamp: August 08, 2019, 03:54:30 am
content: Adam Seychell's paper is great, but it focuses only on speed and has no regard for accuracy.QuoteExactly. Don't bother to pre-etch if your paper can't handle the heat.QuoteOk, great. I see's a pic of your big tank still bright green and translucent, with the board finished etching in it, and I actually second-guessed myself. I have preached/predicted even tank this big will darken and slow before finishing even a modest board. So knowing you added peroxide to make that happen is a relief to my current understanding.QuoteThis part you are not being very clear. High concentration of acid and/or presence of peroxide increases undercutting. It's not because of the aggressiveness/speed. It's because you are now etching with a completely different process.I can etch perfect boards in winter with a cold tank. It just takes quite a lot longer. There is no extra propensity for undercutting because it is slower. If you slowed acid peroxide, by say lowering the temp and/or using a low acid concentration, it would take longer, but the undercutting would be just as bad. You cannot achieve the same etching accuracy/density/yield with acid peroxide at any speed, concentration, or temperature.That said, 5 minutes is an unreasonable expectation for (pure) cupric etching of a regular (1 oz) board. A half oz board would etch in my pure cupric tank in about 10-15 minutes, in the warmer seasons. A 1 oz board would take in the neighborhood of 25-35 minutes. It takes (a lot!) longer than acid peroxide, but if you leave the board in there for an extra hour, even, it will not be ruined. It will still be great. It will probably be better than the board you etched in peroxide and watched like a hawk. It saves effort/time of inspecting for shorts and broken traces and/or doing repairs or re-dos. The etch speed should not be such a major concern for hobbyist use.Now a real production level cupric tank could etch quite a bit faster than mine. Mine will reach a steady state that is somewhere between pureed spinach and dull emeralds, depending on how much exposed copper is in the tank. In a production type tank, the solution will be recharged in a separate tank with chlorine gas or peroxide, then cycled back to the etch tank (without any H2O2 left in it), to maintain a higher concentration of cupric vs cuprous.

author: KL27x
author_rank: Super Contributor
timestamp: August 08, 2019, 05:01:58 am
content: QuoteThe first side, I leave that transfer paper alone. After getting the second side lined up, I usually just keep it pinched to the board until I get it into the laminator. Then after the hot pass, I remove both papers.QuoteShould be no problem. Even a few holes poked into a piece of tubing and run overnight on a fish tank diaphragm pump will recharge the entire 3L tank. It's just the entire tank doesn't do all that much. It's like charging a small capacitor to run a motor. Then when you actually get in the boat, you hook up a much bigger and stronger motor running on an unlimited supply of kerosene (or should I say "peroxide?"), and then you fire them both up. The capacitor would have run out partway through the trip, on its own. And even though it's constantly being recharged, now, it is barely making a dimple of a difference, because the acid peroxide is doing the job faster. But worse. So's if this is fine to you, you didn't need to even try to make cupric or should have ever cared what it was. If you have strong peroxide, that's all that matters. You could have watered down the acid peroxide solution with koolaid, and it would have performed very similarly.You might have incorrectly assumed that by slowing down the etching rate, you must have made it more accurate. You slowed the rate by diluting the acid, yes. Now, remove the peroxide. When you try that, you will see how fast the rug falls out. Even after diluting the acid, acid peroxide is still the overwhelming etch agent whenever you add peroxide and for some hours/days after. Until you figure out a way to get the floor back (figuring out your gas exchange bottleneck) and etch purely with cupric, you really can't compare the two. It is on a different curve. And you can't control the acid peroxide path by dilution. If you get the acid too low, the cupric reaction also slows/stops. Adding peroxide is "supposed to" recharge the solution, but it can't do that without creating a new reaction pathway that supersedes it by so much that it makes the achievement of the original goal near completely superfluous. This is like refilling an empty oil lamp by pouring gasoline all over the room.Gas exchange is what drives this. And it's slow. And there's no great way to store that energy; the solution doesn't store it very densely. If you want to etch with a bubble-regenerated cupric tank, you need a lot of really small bubbles. If you attempt to etch without using peroxide, you may find it takes a lot more air than what you can get out of an aquarium pump.Don't let me discourage you, though. It will definitely help your etch accuracy to have the tank charged before use, so even an overnight trickle charge should be worth the effort, if the tank is big enough. Just prepare to be underwhelmed by the difference. After a few minutes of etching a decent sized board, the cupric will peter out and you will have to add peroxide. That first few minutes will etch like 1/10th of the board. So the cupric will not be doing much of the lifting, and that will show in the accuracy/fidelity of the etching.

author: Ian.M
author_rank: Super Contributor
timestamp: August 08, 2019, 06:12:53 am
content: @KL27x,You commented that Seychell focussed on speed, but you prefer a slower etch, so what acid concentration and copper ion concentration (or density) do you run your tank at? Also, what are your typical summer and winter temperatures .

author: taydin
author_rank: Frequent Contributor
timestamp: August 08, 2019, 06:20:51 am
content: Thanks for all the info guys. I have bought some chemistry tools so that I can get the bath exactly right. I am now able to measure density, and I also will be able to measure the acid molarity (according to an experiment in Seychelle's page). Will update here.

author: KL27x
author_rank: Super Contributor
timestamp: August 08, 2019, 06:32:51 am
content: Re: IanM, I wouldn't say I prefer a slower etch. All else equal, faster would be preferable to slower. There's nothing wrong with what Seychell wrote. But if that were the only thing you ever read, you might get the impression that etch accuracy is a footnote, and that you titrate to increase speed of the etching. You might even get the impression that because etching accuracy and speed are inversely related in this case, that they are inseparable, and as long as your etchant is etching it is optimized. That it is somewhere between a tradeoff or compromise between the two things. You might think adding peroxide doesn't do anything but move you a bit to the right on this ideal curve. This is false, so don't let that get in your head. When you add peroxide, you have completely left the reservation.If you want to etch with cupric, it IS slow. That's just how it is. If you add peroxide, you're etching with acid peroxide. I suspect that Seychell never got sufficient regeneration to actually etch with cupric. He might have been etching with mostly acid peroxide, in practice. And I'm sure theRealElliot only ever etched with acid peroxide; and he most definitely taught our current generation of home chemists to do it this way. Even if you "only add a capful of peroxide when you're impatient," you're not getting it; there's no way you're etching with cupric without (massive) regeneration; you'd need gallons of charged cupric to get anything done. Your "cupric" looks like mountain dew while the board is etching, and the etching is being done mainly by acid peroxide. If you want to attempt to titrate your peroxide regen, I suggest you drip it in only enough to where the solution becomes a bit greener but still opaque. If it becomes translucent, you will have excess peroxide. Have fun with that, because you will need to very carefully drip the peroxide in, constantly, for a full half an hour or so, to etch a board, and how much you need to add will change with the area of exposed copper in the tank. That will not remain static.The truth of the matter is Taydin won't see much difference in either speed or accuracy, whether he achieves an ideal concentration of cupric or not. Because the acid peroxide will be doing too much of the etching, in practice. See the edit to my previous post, about recharging the tank overnight.Temp: In summer it hits triple digits. Winter will reach a frost for maybe a week. So just around freezing, I guess.

author: magic
author_rank: Super Contributor
timestamp: August 08, 2019, 06:55:30 am
content: Quote from: janoc on August 07, 2019, 05:18:26 pmWe wouldn't even be talking about acid bans if they were a UK only thing, I don't care much what happens in the UK.I could buy nitric acid in Poland, no questions asked, before we joined the EU. I can't do it now, ditto many other things. I know whom to blame. UK will leave and nothing will change.

author: ogden
author_rank: Super Contributor
timestamp: August 08, 2019, 08:56:27 am
content: Quote from: magic on August 08, 2019, 06:55:30 amRight. Being bloc’s largest beneficiary of cohesion funds is fine (105 billion EUR received), yet when it is about solidarity, following common rules, solving common problems - not fine anymore. "Here in Poland, it’s we who decide who will come to Poland and who will not". (c) Mateusz Morawiecki. This is not even mentioning benefits of labor movement.

author: Ian.M
author_rank: Super Contributor
timestamp: August 08, 2019, 03:13:53 pm
content: Can we *PLEASE* keep the politics out of this topic except so far as they directly affect availability of chemicals for homePCB etching? It would be a pity if Simon or Dave felt they had to lock it.

author: ogden
author_rank: Super Contributor
timestamp: August 08, 2019, 03:52:33 pm
content: Quote from: Ian.M on August 08, 2019, 03:13:53 pmSure. In EU Sodium Persulfate is freely available, it works well and not that expensive for small hobby volume. Manufacturer: termopasty.plhttps://www.tme.eu/en/details/b327-500/materials-for-pcb-production/ag-termopasty/

author: terminus
author_rank: Contributor
timestamp: August 08, 2019, 04:31:18 pm
content: I use the same approach with a fish tank stone aerator but with a small ozone generator (from aliexpress) connected to a fish tank compressor. I do not have much statistics but it looks like it restores etchant faster than the normal air bubbling. I also noticed that when the solution is dirty after etching it doesn't have ozone smell at all but as long as the etchant becomes light green it smells more.I made my etchant from 20% HCl and 3% H2O23 years ago and use it since then. After that I added 20% HCl couple of times to compensate evaporation.I know that ozone is poisonous and do it in well ventilated space. The ozone generator was sold as a water purifier.Can it be that that ozone gives away O-more easily?

author: Ian.M
author_rank: Super Contributor
timestamp: August 08, 2019, 06:20:01 pm
content: Quote from: terminus on August 08, 2019, 04:31:18 pmYep. Ozone is an extremely powerful oxidant, both as gas and in solution, and can directly oxidize bare copper. Unfortunately it also oxidizes most organics so its probably degrading your tank and hoses every time you use it, and if you run the Ozone generator while etching, I would expect excessive under-cutting if it can keep up with the etch rate.It might be worth seeing if you can detect if there's a significant Cu1+ion concentration using a optical sensor and use the output to control the ozone generator so the tank gets ordinary air as soon as the solution has cleared.

author: terminus
author_rank: Contributor
timestamp: August 08, 2019, 06:36:33 pm
content: I didn't notice any pcb quality degradation compared with just air. I do 0.3mm successfully. It takes about 40 minutes at 19C for a pcb about 120x80mm.For the etching tank I use a food container with a snapping cover where I made a hole for the air hose.

author: SiliconWizard
author_rank: Super Contributor
timestamp: August 08, 2019, 07:35:41 pm
content: Quote from: Ian.M on August 08, 2019, 06:20:01 pmOzone is also pretty toxic. You should probably not play with it unless your setup is extremely well isolated and you can evacuate the ozone safely.

author: KL27x
author_rank: Super Contributor
timestamp: August 08, 2019, 10:38:54 pm
content: QuoteQuoteBased on either one of these two observations/results, I am convinced it works. My hunch says it should increase the direct etching of the copper by acid, but not as bad as having excess peroxide in the solution. And it should be fairly controllable as to how much you are streaming into the tank. Very interesting solution.If you have enough curiousity, you might try putting a board in 10-15% HCl and running the bubbler and ozone generator to see if it etches, significantly. Hopefully, it takes hours without the cupric in there.