ETCHANT Question - Page 1
Forum section: electronics / projects

author: innkeeper
author_rank: Unknown
timestamp: July 24, 2018, 12:55:01 am
content: OK its been years, ok maybe decades since I etched my own PC boards.. last time I did it I used ferric chloride and either those radioshack transfers or a sharpie.so now I plan to move on to laser transfer as it just seems like a good method. but. now the real question is what etchant.Radio Shack being closed, I can't exactly run around the corner and buy etchant so i will need to either order some or make my own.also, my recollection of ferric chloride were not exactly the best experiences, where it stains anything it gets on if its accidentally spilled...basically so if there are better options I am open.My need to etch will be occasional at best, but likely when I do etch it will be a few in a row.what are the recommendations for etchant, I see a lot of options out there on eBay, some of which i can't even find info on..also, I've read about some DIY formulas using muriatic (hcl) acid and hydrogen peroxide.also seems various formulas are available in liquid and powder. it would be great if I could store used etchant for reuse later for extended periods of time., but not a deal killer if it is not the best option.so I am looking for advice from others that do this more than me. I'm sure there are things I haven't thought of. So please fill me in.Thanks

author: Fred27
author_rank: Unknown
timestamp: July 24, 2018, 08:52:02 am
content: Ferric chloride is still the best etchant in my opinion. A lot of people will say to use HCl and peroxide instead but that is far nastier. It may not stain things, but the fumes can cause all your expensive tools to rust.Of course, if you just need some boards (rather than enjoying the process of making then yourself) then getting PCBs made is always getting cheaper.

author: wraper
author_rank: Unknown
timestamp: July 24, 2018, 09:45:03 am
content: Quote from: Fred27 on July 24, 2018, 08:52:02 amFerric chloride causes rust as well.

author: Siwastaja
author_rank: Super Contributor
timestamp: July 24, 2018, 09:48:12 am
content: If you are going to etch regularly, consider cupric chloride:http://jimlaurwilliams.org/projects/seychellePaper/index.htmlIn a nutshell, this starts with your typical HCl+H2O2 method, but instead of throwing it away, you just keep accumulating the "waste", and the "waste" itself slowly starts becoming useful! You add less and less H2O2, until the cupric chloride concentration in your solution is high enough to work on its own, and no H2O2 is needed anymore. What's left is adding a tiny little bit of HCl every now and then; the consumption is down to maybe 1/20 to 1/50 what it is on a single-use HCl+H2O2 method.You still need to consider the fume handling.Strong bubbling is very much recommended - not only to speed up etching, and not only for the self-regeneration process; but also to increase the etching resolution.In H2O2 single use non-bubbled quick etching, I always found practical line width limit at around 10 mils on 1oz clad, whereas a strongly bubbled bath can do 8 mils on 1oz clad very easily and robustly, and 6 mils on 0.5oz.Strong bubbling, though, generates even more acid mist, so I'd do it outdoors or design a proper fume hood.We have used this process since... 2012? .. in a club enviroment where a lot of PCBs get done. About a litre of HCl needs to be added only about once a year, which is great because someone needs to get the acid and maintain the process, and this is the only process that runs almost unmaintained! At some point, no one added any HCl for about two years, and the process slowed down from the usual 12 minutes to about 25 minutes, but was still usable.We built our tank out of PVC (by gluing, using specific PVC glue designed to build tanks), which holds about 6-8 liters of etchant, with a big bubbler on the bottom (also made of PVC sheets, with small holes drilled all over). We run the bubbler out of compressed air line through a pressure regulator valve. The PCB is held in the lid construction: the lid has a piece of PVC sheet with a bit-less-than 1.6mm gap in it; the PCB sits firmly in the gap, and is held vertically. (Air bubbling tries to force the PCB one way or another, so mounting it firmly is important.)

author: HB9EVI
author_rank: Frequent Contributor
timestamp: July 24, 2018, 09:48:33 am
content: what about sodium persulfate? not only it doesn't have the nasty sideeffects of ferric chloride, it also has better etching properties.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: July 24, 2018, 11:40:22 am
content: I've used ammonium persulfate and it's very clean working and IMO better than ferric chloride.

author: sleemanj
author_rank: Super Contributor
timestamp: July 24, 2018, 12:03:04 pm
content: For convenience I think nothing much beats out HCl+H2O2 (or the resulting cupric chloride after a bit of copper is in the mix), HCl is fairly easily obtained I think in most places from hardware stores, pool supplies, or concrete places (under the names HCl, Muriatic or occasionally "Spirits of Salts"), and H2O2 can be found in some way or another, in the US you can of course get 3% in bulk easily I think, stronger probably online, or hair developer is not uncommon if you really get stuck.Just don't store your HCl / CuCl2 in an open container around your steel tools is all, and don't mix it up so it's so aggressive, you don't need the acid to be fuming, and it shouldn't be going off like Vesuvius when etching, with 3% peroxide that's not too likely of course, but if you use 30% like I do, a little goes a long way. As above I don't throw it away, just reuse it, add a cap of peroxide every time I break it out and some HCl now and then in a pretty haphazard manner.Ferric, if you can get it, is ok, but so messy and really does like to be warm.I think the "blue green" etchant sold by China is one of the persulfates, they don't stain like Ferric and you can watch the process going on, but they do need heating and have a limited life. I see there is only one Aliexpress seller of it oddly, have never bought it intentionally but I think I do have a bag around here that some China vendor threw in as a freebie without telling me... thankfully customs didn't seem to notice the bag of white powder with Chinese writing on it since the package wasn't even opened.

author: madires
author_rank: Super Contributor
timestamp: July 24, 2018, 12:05:38 pm
content: Quote from: HB9EVI on July 24, 2018, 09:48:33 amAnd it should be heated up to 45°C for best performance.

author: KL27x
author_rank: Super Contributor
timestamp: July 24, 2018, 05:35:14 pm
content: I use cupric. You need a bubbler/aeration or high concentration peroxide to use it efficiently.QuoteI suggest if you can't source cheap, high concentration H2O2, don't expect to reuse muriatic and peroxide over and over. If all you have is 3% from the drugstore, you will overdilute the acid and your etchant is not reusable. It will never turn into cupric chloride. (Once mixed, the H2O2 breaks down spontaneously, releasing O2 into the atmosphere. This means you are diluting the acid with a lot of water every time you add 3% peroxide. Use it within an hour or two of mixing it or you lose it). With 3% peroxide, you would have to be very careful to mix up only as much as needed to barely etch your board, then you might end up with high enough concentration to eventual turn into usable cupric. But it will be a crap shoot.If you want to use cupric (and you don't have 30% peroxide), it's better to saturate with as much copper as possible the first time you mix the muriatic and peroxide. All you need is a few feet of power cord off some broken lamp or tool per liter. Drop it in your freshly mixed muriatic and peroxide with a bubbler. Let it run for several hours or overnight. It has enough copper when it turns dark, opaque green like pureed spinach. Then when fully oxidized, it will turn bright green. You can't add too much copper. So you can just put the whole cord in there and remove what's leftover. Then when you use it, just add a little acid and water to dilute it down. (Which you periodically have to do, as maintenance). It's really not that hard or exacting.

author: innkeeper
author_rank: Unknown
timestamp: July 24, 2018, 05:53:47 pm
content: lots of good info.the cupric chloride method sounds interesting...and relatively cheap to try, though requires a bit more maintenance and knowledge than just using a throwaway etchant.I might give that a go to learn about the process.

author: KL27x
author_rank: Super Contributor
timestamp: July 24, 2018, 06:09:48 pm
content: If you ever end up back to ferric, reusing ferric over and over is possible. When it stops working, dilute it with about 1/3 33% muriatic to water AND add aeration or high concentration peroxide. This is because the by product of ferric is cupric chloride. It will stain like ferric for near infinity and beyond, though. So if you like it, you will eventually mix up some pure cupric.

author: Siwastaja
author_rank: Super Contributor
timestamp: July 24, 2018, 06:32:18 pm
content: Quote from: innkeeper on July 24, 2018, 05:53:47 pmNope, it requires much less - almost no - maintenance. The process is so robust against variations that you don't need much control at all.Throwaway HCl+H2O2 is more tricky to get right and actually requires measuring all three liquids (including water) to get it right. We often saw people being too lazy get totally unpredictable results - such as destructive 30-second etching volcono, or etching that never seems to finish, until you pour in some more H2O2, get a bit too much and then it's a volcano again... One of the reasons it's so tricky is because it's a single-use, we naturally want to save on chemicals (cost & environmental reasons), and measuring small amounts makes measurement errors more serious, as well as can even cause a situation where one of the reagents runs out before the etching is complete. This happened to me a few times while etching large boards in minimal amount of single-use etchant.Cupric chloride allows you to work with a tank of several litres. If you do hundred boards per year, expect adding HCl once a year and ditching half of the tank to reduce cupric chloride concentration maybe once or twice adecade. We haven't done that yet after five years of active use, just added acid (and water due to evaporation).

author: KL27x
author_rank: Super Contributor
timestamp: July 24, 2018, 06:49:24 pm
content: I use a very small vertical tank. About 10" x 7" x 3/4". Even with this, there's not much care involved. I probably have to dilute it every 2-3 6"x9" boards in the minimum, but there's nothing to measure. It's as simple as diluting the stuff when it slows down. If unused, it will be ready to go a year later.The thing about corrosiveness is true. Ferric and cupric need very little to no free acid to work, properly. They are generally a lot less corrosive than muriatic and peroxide. But when you add a bubbler, it is definitely a problem. While it is common to etch with ferric, indoors, I would not recommend you do this with a cupric bubbler tank.The other thing with HCl and peroxide that is less well known is that it's a very innaccurate etchant. It is easy to chew up or break traces, and the thicker the copper pour, the worse the problem. It is generally sufficient for up to 1 oz pour of smaller boards. When you try to go larger board or use thicker copper, you start having to pay more attention and actively rotating the board to manage hot and cold spots.HCl and peroxide also eats up sharpie quite fast. If you use sharpie, even to repair small defect in your resist, ferric or cupric are a lot kinder. I've found you need to apply the sharpie to bright shiny copper for it to hold up in cupric; I pre etch my boards before the transfer, and it works great for the toner transfer. But if I want to add any sharpie anywhere, I have to scrape to bright copper, first. I very rarely would ever have a repair to make in a transfer; I've got that down. But I try to make a board singlel sided if at all possible. Sometimes I need to add just a few fat traces to the bottom, and it is often easier to just add those in with sharpie or tape, rather than align and transfer two sides.There is a hierarchy of accuracy in etchants, with the basic etchants like persulfide being the best. Then ferric. Then cupric. Pure muriatic and peroxide is many times less accurate than cupric. If you start getting into really fine pitch and tight traces, you cannot achieve the same results with acid peroxide without throwing out a lot of boards and making repairs. This may be difficult to understand. The way I picture it is that HCl and peroxide is able to diffuse into small cracks very quickly and is almost as likely to etch the side of a trace as anywhere else, but more "accurate" etchants need more room to work. It's not that the persulfate doesn't undercut the resist layer at all, it's just that the stars have to line up a little better for this to occur. So unprotected copper will etch away at a much faster rate than the sidewall of the protected copper. I have read the lateral etch rate of persulfate is described as 1:8 (w/e thickness of copper pour they use in this scale, who knows? Probably 1 oz pour?) Ferric 1:5, Cupric 1:4. The more excess free HCl you add to the ferric/cupric the less accurate it gets.

author: janoc
author_rank: Super Contributor
timestamp: July 24, 2018, 07:45:30 pm
content: Persulfate is a good etchant but a terrible idea if the goal is to to use it only every once in a while. The solution degrades very quickly and you will be making a fresh batch every time. Gets expensive fast unless you are making a lot of boards at once.Ferric chloride lasts essentially forever without much maintenance. Also, ferric chloridedoes not make things rust, unlike hydrochloric acid! (unless you spill it on something, obviously). If someone has ferric chloride fumes causing corrosion, thendo not pour acid in itto regenerate it (or to produce cupric chloride) next time! That's a very common reason why this happens - the hydrochloric acid fumes are the culprit, not the ferric chloride (which normally doesn't release any fumes). I have a bottle of it in my bathroom for 8 years now and nothing has ever corroded. However, when I had a bottle of hydrochloric acid around, with factory original stopper and everything, I had everything metallic nearby starting to corrode in as short time as a few weeks.Also some ready-made ferric chloride solutions have acid added from the factory, but that is far less concentrated and usually not a problem. If you want to be sure, buy ferric chloride crystals and dissolve it in distilled water yourself.Apart from the corrosion issues, hydrochloric acid and peroxide are a terrible etchant - undercutting of traces is common because the reaction is so rapid and violent. There is a serious splash hazard if you need to add peroxide during etching - acid should go into water, never water into acid (peroxide is essentially water in this regard). Furthermore, the solution releases horrible fumes while etching - pretty much necessitates working outdoors unless one has a proper fume hood on hand. Also disposal is "fun" because the solution cannot be reused and must be neutralized before disposing of it. Basically the only thing going for this combo is price and availability (any drugstore). Do yourself a favor and skip this thing.

author: KL27x
author_rank: Super Contributor
timestamp: July 24, 2018, 07:58:28 pm
content: ^I wonder, now. Maybe the corrosion is due to the bottle of muriatic I keep by the tank. Any unpainted steel within a few feet is toast. I often used ferric indoors without any problem.Any rate, if you did want to buy ferric, you can still buy it in most countries very easily. You can do it in two ways.1. buy "dry" ferric chloride "powder" and mix it with water. I use quotations, because it's super hygroscopic and is a sticky brown staining mess that will be one solid clump after the first time you use it. Try search term "anhydrous ferric chloride," I think. This is an exothermic reaction, so take proper precautions. It is super slow to dissolve until the water gets hot, then it goes really fast... and gets hotter. Don't do it in one of those disposable "red cups." The powder is so hard to work with, I suggest to mix up "all of it" at once, if you can, and just store the liquid ferric chloride in appropriate bottles. Quotes, again, because half of it will be a brown goo stuck to the inside of the bag, lol. It won't go bad until you use it.2. buy iron oxide, red rust powder. This is harder to source, but they sell it in farm supply stores. It is used to stain concrete, among other things. You mix this with about 10% muriatic acid, and you have instant ferric chloride without the mess.

author: sleemanj
author_rank: Super Contributor
timestamp: July 24, 2018, 09:14:17 pm
content: Quote from: KL27x on July 24, 2018, 07:58:28 pmA quick google and I see that it's available from local hardware stores (in NZ and AU, Bunnings) cheaply in 1Kg pots as various pigment shades from black through red, given the increasing cost (Black < Marigold < Light Brown < Dark Brown < Red) I'd guess that equates directly to the amount of time in a furnace it takes to make it out of Fe3O4https://www.bunnings.co.nz/search/products?q=Cemix%20oxide&redirectFrom=AnyThe black MSDS states that it is Fe3O4with 90% Fe2O3So that might be an easy alternative if H2O2 isn't available in much good concentration (here in NZ, you won't even find bulk 3% in pharmacies like you do in the states, you might get a tiny bottle with 30mL or something, but you can at least buy it online cheaply up to about 30%).I'll note for any compatriots that Bunnings also sell HCl (about 15% if memory serves), it's next to the meths, turps and such.

author: sleemanj
author_rank: Super Contributor
timestamp: July 24, 2018, 10:18:06 pm
content: Quote from: blueskull on July 24, 2018, 09:23:34 pmIf I need a one-off for testing an idea, a prototype, or a personal project, I could take it from finished gerber to ready to solder in an hour, for a couple dollars in raw materials.

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 24, 2018, 11:02:50 pm
content: Quote from: blueskull on July 24, 2018, 09:23:34 pm$2500 is hardly low cost for a hobbyist. Maybe compared to the setups AvE and Aussie50 have...Big Clive has done quite a few PCBs with the well known laser printer resist process.

author: KL27x
author_rank: Super Contributor
timestamp: July 25, 2018, 02:07:23 am
content: QuoteI have a true low cost Sherline CNC. I have never once considered making a PCB with it. If you figure out the process and work out the logistics (I have an outdoor bench where the tank sits, ready to etch 24/7), it's simply too easy to do toner transfer. I do 8 mil all day with my eyes closed. Only reason I can't do 6 with deadnuts reliability is because my printer can't actually make a solid line at 6 mil thickness.* Setup and watch CNC mill a PCB for no gain and to chew through and replace engraving/V bits? To get a board that is all chewed up?If I had the CNC, first, I'd probably think same as you. There is no really easy path to figuring out toner transfer. There is a lot of info out there which is dated or suboptimal. All of it, really. Never did see info/tutorial which shows the easiest way. Whenever I come across the latest and greatest "easy toner transfer" tutorial I read it and chuckle. Most tutorials are written by people who are excited because they just discovered something new. They don't realize if there's a better way... or if the other stuff they're doing can be improved. I'm guilty of that, too. I did a tutorial, once, and I have learned many improvements since then. If you take ALL the info out there and you try everything, with an open mind and scientific approach, it's all out there. Just not in one tidy place.I order PCBs every few months. I still do toner transfer every now and again. Esp if the board can be done on a single side (or mostly single side), it's fast and easy, and you can make as few or as many as you want without spending time fiddling with gerber settings required by the cheapo prototype place of the week and zipping them, and going through registration and payment and all that jazz. Some days I just don't want to click through folders or fill out online quote forms etc. Last time I used it, I made up 18 tiny EEPROM board for my PicKit2 programmer. Too many for a prototype bottom dollar special. Too little and simple to bother paying actual money. Done, v grooved on my tilting router table, ready to populate and snap off, before the parts arrived. Honestly, every time I order a new board, it's a headache making sure I crossed all the t's and dotted all the i's.*When viewed under the microscope, I will see a microscopic break in the printed 6 mil traces every several inches. So on a small board, there might be 2 or 3 breaks. I don't know if this is due to raster or just slop, because I didn't bother to verify if it is consistent or not; I just know it doesn't work. The etched board will have the same number of microscopic breaks in the traces, but the rest will look great. So I assume they are corresponding.

author: innkeeper
author_rank: Unknown
timestamp: July 25, 2018, 02:58:11 am
content: Quote from: blueskull on July 24, 2018, 09:23:34 pmgood question..I do get PCB's made, and get a quick turnaround cheap.but I am mostly a hobbyist, and don't want to shell out money if i don't have to or its a one-off that you just don't need a professional pcb for..When your experimenting, and want to do a quick proof of concept. there's nothing like being able to each a PCB, drill it, solder on parts and have it operational in an hour.no cnc, nothing fancy and nothing expensive.when your ready to have boards made, then I can go do that. it basically fills that gap between breadboarding, and PCB manufacturing, or when dealing with some RF circuitry where breadboards just won't do.

author: sleemanj
author_rank: Super Contributor
timestamp: July 25, 2018, 09:11:22 am
content: Quote from: sleemanj on July 24, 2018, 09:14:17 pmIt got me curious and it was only $9 NZ so I gave it a try. The oxide powder was found in the cement ailse at Bunnings (a local NZ and AU hardware store chain), NOT in the paint section (who didn't know what I was talking about). As previously mentioned HCl is in the paint section, but I already have a bottle of that of course.I mixed about 1/4 Cup of the powder with 1/4 cup HCl and 1/2 cup water, the resulting liquid was pitch black, and much like Ferric Chloride stains everything, indeed, the powder does a good job of staining everything, if you have ever had to handle printer toner, you know what this is like. The measuring cup is now black, the tray is black...Anyway, after this a test PCB was added (dry film resist, long cured since this already developed test pcb has been sitting in my drawer for maybe a year never etched) and the tray put into a warm water bath as was my previous experience with ferric chloride, namely gentle rocking and sponge action until the copper was gone.Before Etching:Etching proceeded fairly typically, but the pcb is somewhat stained, during etching it is impossible to see anything even if you pull the pcb out it's just a black blackness until you rinse it then it's a slightly less black blackness.I didn't time it, I suppose 20-30 minutes.After Etching, Stripped with Acetone:I think I used way too much iron oxide powder which probably contributed to the problem, I expect that an actual ratio could be determined given the molar weights of the oxide powder and acid etc, but I don't think I'm interested enough to try and resurrect my high school chemistry to figure that.After the etch was done, I was left with of course a problem of disposal, I elected to dig out my old bottle of used ferric chloride and add it to that, then just rinse out the left over iron oxide... ask no questions and I'll tell no lies on that.

author: KL27x
author_rank: Super Contributor
timestamp: July 25, 2018, 11:03:20 am
content: That was FAST. LOL.Unless you are etching some super thick copper where accuracy is critical, the exact ratio is not necessary, as you have seen. Just wing it and if it's too dark and/or any noticeable sludge in the bottom, dilute some more.Then, unless you are paranoid about a very mild amount of corrosive fumes, it is practical to add a little more water n acid on top of that. The first product of the ferric reaction is charged cupric chloride. The charged cupric also etches and produces excess of something else. And a bit o free acid will turn that back to uncharged cupric.. which will very slowly over time reoxidize and etch once again. I probably have a lot of that wrong, but the excess acid and water will make the ferric etch better/longer and it will get used up in the process. Whenever you get sludge, you can add a little more. Then toss it when it's too slow.... or add aeration and use it forever.The reason it is black is the 10% black rust in there, I reckon you will end up with what is like 10% spent ferric chloride (or 5% or something; w/e the stoichiometry is), but without any copper/cupric in it, yet. And unfortunately, the spent ferric does not recharge with aeration or peroxide. It's just along for the ride.

author: janoc
author_rank: Super Contributor
timestamp: July 25, 2018, 02:03:17 pm
content: Quote from: KL27x on July 24, 2018, 07:58:28 pmYep, that's 100% the reason. Hydrochloric acid fumes will escape even what you think is a well closed bottle. Unless the bottle is actually sealed gas-tight you will have problems. Even if you don't smell the acid fumes they are there, there doesn't need to be a high concentration of them to start the corrosion.

author: CopperCone
author_rank: Super Contributor
timestamp: July 27, 2018, 07:11:21 pm
content: don't forget how much the chinese government likes to steal designs.. good reason to make your own if you are doing prototyping prior to mass production where you can get a market following.

author: CopperCone
author_rank: Super Contributor
timestamp: July 27, 2018, 07:15:58 pm
content: Quote from: janoc on July 25, 2018, 02:03:17 pmI add a tad of HCl to my ferric chloride etching solutions.A recommendation is if you want to store muratic acid but you don't want the corrosion, is to buy the 'green' kind which is diluted some what.. it hardly fumes. The normal 35% one basically pours fumes out of it as soon as you open it.Its alot kinder to use on cleaning cement and shit too.

author: janoc
author_rank: Super Contributor
timestamp: July 27, 2018, 08:24:22 pm
content: Quote from: CopperCone on July 27, 2018, 07:11:21 pmYeah right. The Chinese have an army of people poring over and reverse engineering every prototype gerbers that get sent to their fabs. Especially the small orders from hobbyists, in case it was something worth stealing. Come on. Paranoid much?I guess you have no idea how many boards fabs like JLPCB and similar processdailyand how much work/time does it take to get the gerbers processed, without even trying to figure out what the board could be for. Naked PCB without matching schematics and firmware is pretty much worthless, not even the Chinese have so much free time and labor on their hands to try to copy your product idea just from that.If you order assembly service, that is a bit different (there have been cases where the assembler "ran away" with someone's product and started to make copies) but we are talking bare boards, not assembly where the factory has everything necessary to manufacture the product, including any firmware, BOM, etc. But then nobody forces you to do assembly in China and/or you should have a proper contract and means to enforce it (lawyer, etc.).There are many reasons why etching boards at home may be worth the time and effort but this would certainly not be one. Also, what would you do if your product needed a multilayer board or something denser than 8/8 which about the limit of what is doable at home?

author: nctnico
author_rank: Super Contributor
timestamp: July 27, 2018, 08:32:07 pm
content: Quote from: innkeeper on July 24, 2018, 05:53:47 pmYou can also start a cupric chloride process using ferric chloride. Once the ferric chloride is saturated it has turned into cupric chloride. Add a little bit of HCl (hydrochloric acid) from the farmacy or grocery store and you can continu etching. This way you can use the same etchant for decades (been there, done that). With FeCl/CuCl you will also want a spray etching machine. These work just brilliant (and fast).Still consider the use of cheap services like Seeedstudio etc because they can make much better boards than you can.

author: janoc
author_rank: Super Contributor
timestamp: July 27, 2018, 09:31:28 pm
content: Spray etcher is a bit of a luxury for a home gamer. They certainly do work well but are quite an overkill unless making a lot of boards.You can get the same result without, it just goes possibly a little slower. Make sure to agitate the solution every once in a while to get a fresh solution to the copper. Or buy an aquarium pump and pump air in it. Works just fine.Some people etch using a sponge full of the etchant and rubbing it over the board (the resist will survive it), that goes really quick but I don't like the idea of sticking my fingers into a rather aggressive chemical, gloves or no gloves (gloves tear easily).

author: CopperCone
author_rank: Super Contributor
timestamp: July 27, 2018, 10:31:39 pm
content: Quote from: janoc on July 27, 2018, 08:24:22 pmyea you can totally prevent someone from taking a picture or downloading a data file on a unique project that you might release 12 months from making a alpha prototype. Because you can't look at it at home on your own timeyou know, you might want to like make a alpha prototype that looks nice and shit to help gather investors and maybe work on software?what does throughput on a digital file matter? All it has to do is look interesting enough to investigate further. When things are labeled with a silkscreen its even easier to reverse engineer. Someone can easily figure out something they are looking at might be a profitable arduino shield or such.

author: james_s
author_rank: Super Contributor
timestamp: July 27, 2018, 10:55:10 pm
content: I used to use ferric chloride, but then I discovered HCl + Peroxide. It's cheaper and easier to get, works faster, it's transparent (at the start) and once it turns into cupric chloride you can keep on using it.Funny thing is I remember finding instructions to dissolve copper wire in the mixture to produce cupric chloride, but that's just silly since you can just etch some boards. When you finish it's easy to neutralize any excess with baking soda.

author: james_s
author_rank: Super Contributor
timestamp: July 27, 2018, 11:01:49 pm
content: Quote from: KL27x on July 24, 2018, 07:58:28 pmThat is a problem. I store my bottle of HCl outside next to the garage, sealed in a plastic bag. I do my etching out on the deck after laying down a garbage bag with a sheet of newspaper over it to catch any small spills. I keep a jug of water saturated with baking soda nearby.

author: KL27x
author_rank: Super Contributor
timestamp: July 28, 2018, 05:38:53 am
content: QuoteIt's funny that the reason half the world thinks this is due to a runaway popular Instructable by "the Real Elliot," about ten years ago. Especially since he clearly stated that he made his batch of cupric by deliberately dissolving copper wire. He stated you could just use muriatic and peroxide until it eventually turned into cupric, but he had never even done this.In fact, in many countries the cost of 30% peroxide is high enough to be a deal breaker. And with 3%, you will not make useable cupric simply by "just etching some boards."QuoteSo you discovered this muriatic and peroxide, and you're still using it. Why are not using cupric chloride which you have automatically made by now? Surely, you have "simply etched a few boards" by now? Are you repeating this recipe without ever having done it yourself? Just restating as fact, something someone else initially stated as fact? And with no experience anywhere to back this up as actually being a good idea?Funniest thing about it. A year or two after the Real Elliot's Instructable, someone made a giant industrial spray etcher. And they mixed up several gallons of muriatic and 3% peroxide, citing the same thing you have just said as fact.... this several gallons of etchant with mere days of shelf life at most... to etch a COUPLE TEST BOARDS. I'm sure he had fun trying to etch with his 0.1% cupric chloride in 10% muriatic solution the following week.(I hope he didn't burn his house down what from the O2 gas produced by all that peroxide wasting away.)The problem here, is that peroxide is inherently unstable. You know how it bubbles when you put it on a cut? Same thing happens when you mix it up with cupric chloride. When you mix it up with the straight acid, it doesn't bubble, noticeably, but as soon as you start etching, the peroxide degrades faster. In fact, when you add even 3% peroxide to proper cupric or ferric, it will bubble vigorously... So only a fraction of what you put in there even oxidizes/recharges the cuprous to cupric. The rest just releases into the air. After you put your used acid and peroxide etchant away, all your peroxide will be plain water by the next time you want to etch a board.

author: Ian.M
author_rank: Super Contributor
timestamp: July 28, 2018, 06:44:45 am
content: If you live somewhere where you cant easily buy *any* peroxide, its possible to get going with acid copper chloride etching without peroxide, although its a real PITA and takes a few weeks. Even a 50ml bottle of 3% Hydrogen Peroxide will vastly speed this up if you feed the initial acid/peroxide mix as much fine copper wire as it will take.Without peroxide you need to oxidise the copper as much as possible - take fine copper wire and heat it witha reducingan oxidisinggas flame to get a layer of black copper oxide, ball it up (over your container to catch any copper oxide that flakes off) then wet it with conc. hydrochloric acid, and leave it outside, sheltered from the weather in a wide open container*, with a little pool of acid in the bottom, prodding it every few days to turn the ball of wire over in the pool of acid so it gets wetted again. Once it starts to go green, it speeds up quite quickly and the copper will start dissolving overnight. You can then feed it more copper and acid, and when it wont take any more copper without adding acid, add just enough acid to redissolve any white crystals that have precipitated out, check the density to estimate copper concentration, dilute to get it within the typical range for the etching process, then titrate for acid concentration so you can bring that into range.* Open containers of conc. acid are *DANGEROUS* - make sure its adequately secured against kids, pets etc, cant blow over or get knocked over, and that nothing can fall into it.Edit: thanks Kl27x for the flame correction.

author: KL27x
author_rank: Super Contributor
timestamp: July 28, 2018, 07:04:40 am
content: As a lay person who once stayed in a Holiday Inn, I would think you want an oxidizing flame?Anyhoo, it's very easy to make the cupric with just 3% and a bubbler in the bottom of a jar or bottle. Took me just a matter of 3-4 hours, maybe, but this is temp dependent, and I live in hell. I suspect your method would also be a bit speedier with a bubbler.BTW, I know the Real Elliot left out a few things because I followed his advice. And I ended up with a bottle of useless greenish piss water and had to start over.QuoteMy experience jives. There's a trip point of concentration where the stuff actually works as etchant and warp drive kicks in. If you don't reach that within hours of mixing up your acid peroxide, you will have a hard time to reach the end point with just 3% peroxide to add in order revive your already diluted acid mix. Unless you are ok with "etching boards" by leaving them in the tank for several days and getting unusable result.

author: Ian.M
author_rank: Super Contributor
timestamp: July 28, 2018, 07:19:31 am
content: My bad - yes a blue oxidising flame is correct as you *dont* want the copper contaminated with soot and un-burnt hydrocarbons that would be produced by a yellow reducing flame.When you are getting started without peroxide, you cant start off with enough acid to use a bubbler unless you can get copper oxide powder, as starting with oxidised fine wire, if you simply immerse it in acid, the cuprous ion concentration will be too low to dissolve copper metal at a useable rate. Also, due to the conc. acid, the fumes are too noxious if you use a bubbler.Without *any* peroxide, it takes a very long time to get enough copper chloride for the reaction to 'kick off'. Basically one is weathering the copper to get a chloride patina, then washing that down into the little acid, and repeating until the cupric ion concentration in the acid is high enough that the bottom of the ball of wire starts dissolving at a noticeable rate. The cuprous to cupric regeneration is purely depending on diffusion of atmospheric oxygen into the acid pool, which is why it needs to be shallow and in a wide open container to get started.Once you've got enough to run a bubbler and have got the concentrations into the acceptable range, you can feed it copper + diluted acid quite rapidly till you've got enough for your etch tank.I'd expect it to take weeks without peroxide to get 100ml of conc coper chloride to start off, then a few days to 'grow' that to enough litres to fill your etch tank.Its not something one should consider if one can buy peroxide, even in small quantities and low concentration, without getting on any terror watch lists.

author: sleemanj
author_rank: Super Contributor
timestamp: July 28, 2018, 07:29:36 am
content: If you are in a REAL bind, I have in the past, out of curiosity and with no records or for that matter much though in the process, successfully etched a test PCB with using HCl, water, and... sodium percabonate (laundry whitening powder, or it might have been sold as deck cleaner or something), percabonate (aka peroxyhydrate) plus water gets you hydrogen peroxide, and sodium carbonate, the problem of course is that the sodium carbonate will work to neutralise the hydrochloric, and gas and foam and the hydrogen peroxide you're producing is also killed pretty quickly, but, purely out of curiosity, I did get it to work once.I think I mixed up the percabonate and water until it was saturated, then basically added that to the HCl (which may have been 33% at the time come to think of it so that might have helped).

author: KL27x
author_rank: Super Contributor
timestamp: July 28, 2018, 07:44:39 am
content: QuoteYes, I totaly understand. But I figure using a bubbler will be advantageous, here. You want to make the copper "rust." And you want that rust to be dissolved in acid. The bursting bubbles at the surface will splash and wet the exposed copper, speeding up the rusting process and also dissolving any oxidized copper.Also, since it does take weeks, might as well put that little bit of copper in there to work, best as can. Fish tank bubbler is what I used back then. They are made to run for lots of weeks.QuoteNot like you oughtta?

author: janoc
author_rank: Super Contributor
timestamp: July 28, 2018, 07:45:58 am
content: Quote from: KL27x on July 28, 2018, 05:38:53 amYep, basically you end up only diluting your etchant with water (which is what peroxide degrades to). This type of etchant is not storable/reusable, it needs to be mixed fresh every time.Also, a 3% peroxide is not very useful for etching, you will need a lot of it like that because it gets used up rapidly. If your only source of peroxide is the pharmacy 3% one for disinfecting wounds, that will get expensive pretty quickly. And getting a 10% or 30% one is not always easy - especially the 30% one. It is a dangerous chemical and a precursor for making "cool" stuff like TATP (the European terrorist improvised explosive of choice - e.g. the London and Brussels bombings used that) and pervitin (methamphetamine - illegal drug) so the peroxide sales tend to be closely watched/regulated in a lot of countries.

author: AE7OO
author_rank: Regular Contributor
timestamp: July 28, 2018, 08:13:01 am
content: Throwaway HCl+H2O2 is more tricky to get rightIn a glass bread pan, I just pour in 3% H2O2 to a level of about 2 inches, and then add 4 caps of HCl, no water. No fumes, no fuss.I just swish my board(I have duct tape handle on it) right side up until it is etched. I then let it evap, then rinse with a little water into an old wine bottle next time I etch; If I ever decide to go the cupric route, I'll have a copper solution to get me started. I do all of my etching outside and I'm in Arizona so it evaporates fast.I buy the H2O2 at the dollar store in a big bottle, and the gallon of HCl I bought at Home Depot for about $10 ages ago.

author: sleemanj
author_rank: Super Contributor
timestamp: July 28, 2018, 08:25:56 am
content: Quote from: KL27x on July 28, 2018, 07:44:39 amWell, I was almost certainly in bare feet, possibly without gloves and likely working in a dimly lit garage with poor ventilation and everything precariously balanced on piles of junk, so adding acid to water wouldn't make a lot of difference to the chance of disaster ;-)

author: Siwastaja
author_rank: Super Contributor
timestamp: July 28, 2018, 08:52:13 am
content: Quote from: KL27x on July 28, 2018, 05:38:53 amThis is a good point and worth mentioning. When converting from HCl+H2O2 to cupric chloride "by etching a few boards" - which is exactly what we succcessfully did, although we also did put in some scrap copper -, you don't do it by adding the H2O2 to the massive tank. That would be hugely expensive, since you need to add fresh H2O2 every time and need a certain concentration.So, you do it by taking a bit out of your big tank, and then proceed like you did with single use - add H2O2 to this small single-use container. Then you pour the "waste" back to the big tank.As the time goes by, you can use less and less H2O2, and at some point, you can just start etching in the big tank. Although, you need a bubbler for effective etching speeds. Spray etching would be even better, but bubbling is easier.We get 1 hour etcing time without bubbling, around 10-15 minutes with bubbling, in a large tank.The bubbling also ensures the self-regeneration process to curpic chloride.The amount of etching required to get necessary cupric concentration in our 5-10 liter tank was surprisingly low. I think we were fully converted in about a month IIRC, and as said earlier, almost zero maintenance after that, for more than 5 years now. HCl has been added maybe about five times, and water to top off the surface level (due to evaporation).

author: nctnico
author_rank: Super Contributor
timestamp: July 28, 2018, 09:47:07 am
content: Quote from: janoc on July 27, 2018, 09:31:28 pmThey are also available in the hobbyist realm. I got mine second hand for a low price. They are not difficult to make either.https://www.instructables.com/id/The-Etchinator-low-cost-spray-etcher/

author: Psi
author_rank: Super Contributor
timestamp: July 28, 2018, 09:55:41 am
content: Quote from: Conrad Hoffman on July 24, 2018, 11:40:22 amI could never get that stuff to work unless it was over 80degCIt would always cool down too quick to use.Even if you put the container of it in a bucket and poured boiling water around it, it would still cool down and stop working before you had finished etching.I guess if you had direct heating of the solution while etching it might work.But it doesnt work cold at all.HCL peroxide or Ferric chloride will work at room temp, just not as quickly.ammonium persulfate doesnt work at all.

author: tautech
author_rank: Super Contributor
timestamp: July 28, 2018, 11:50:29 am
content: And yet I've never had a problem with a fresh mix of ammonium persulfate sourced from Jaycar.What put me off it was it couldn't be stored or rejuvenated to be used again.I used it hot but not so hot that it would scald and with a bubbler. ~5 minute etches.Because of its cost I built a thin upright etching tank so to use less solution however for even a medium size PCB I still needed a 500ml brew.HCL has worked out much cheaper however sleemanj's new experimental brew looks very interesting.Please keep us posted on further developments.

author: CopperCone
author_rank: Super Contributor
timestamp: July 28, 2018, 12:19:30 pm
content: How much better is a spray etcher then bubble etch?I have some problem doing thin packages like TDFN-10 with etching on large PCB's (like 6x10 inches).. but I think its more of an exposure problem then a etching problem.. I need a light box, I failed to get a perfect board in 4 attempts once.. finally managed it with only a single transistor being compromised. I think the nonlinear light distribution of the desk lamp I use is the cause.

author: james_s
author_rank: Super Contributor
timestamp: July 28, 2018, 06:36:56 pm
content: Quote from: KL27x on July 28, 2018, 05:38:53 amI've been using the same dark green liquid now for about 5 years. When I'm done etching, I pour it back into the storage bottle and dispose of any excess. I don't know precisely what the chemical composition is but it's dark green in the bottle and turns a very light green when I add a capful of 3% peroxide. As I etch a board it gets darker and darker green until it becomes almost brown, adding a capful of peroxide turns it light green again. It etches copper, what more could I ask of it?So is it a good idea? Well like I said, I've been using the same stuff for several years now, I've etched many dozens of boards, haven't had any trouble with it. Why wouldn't it be a good idea?

author: james_s
author_rank: Super Contributor
timestamp: July 28, 2018, 06:40:51 pm
content: Quote from: Psi on July 28, 2018, 09:55:41 amI use a $5 aquarium heater in my bubbler tank. I've never tried persulfate but I suspect it would work fine in the same tank.

author: janoc
author_rank: Super Contributor
timestamp: July 29, 2018, 09:23:24 am
content: Quote from: Psi on July 28, 2018, 09:55:41 amPersulfate works well and it is certainly less messy than the alternatives but you need a heated tank for it or at least a water bath. Normally around 40 degrees C should be enough but I have seen some vendor instruction sheets specifying up to 75 degrees.If you had to heat it more to get it going then your solution was likely stale/decomposed - keep in mind that persulfate is not chemically stable and decomposes over time releasing oxygen. Heating it will also speed the decomposition up. So you both must not keep it in an airtight bottle (it will burst or eject the stopper) and don't keep a solution around for long (beyond a few days) because it will go bad. Ideally you should make a fresh batch every time.This is the main reason why this is not a good/economical etchant if you only make one board every once in a while - it is really wasteful and gets expensive. OTOH, if you are etching a larger amount of boards or working for a hackerspace/club/etc. where people need to make boards all the time, this is a good option.

author: innkeeper
author_rank: Unknown
timestamp: July 29, 2018, 04:28:27 pm
content: I'm going to attempt to make Cupric Chloride - my tank is 1.5 gallons 6 liters but id likely never fill it up completely...though, I am going to target making 1.5 gallons of cupric chloride.I've read quite a bit. but, still, I would like some validation on what I am about to do.anyone who knows about this who can check my reverse engineering to see if this holds or not? i am far from benign a chemist and so i am just trying to back into Jim's and Adams notes.Also, anyone can comment on the approach, the levels I am trying to attain or anything else, please chime in.my target concentration will be 150g/l Cu++ that seems to be in the center rage of the recommended concentration of 125-175g/l CU++ ikn Adam Seychell's paper also the target used by Jim at his site jimlaurwilliams.orgthough I am wondering if I should target a lower concentration as over time the concentration will increase with use.I will start with 1 gallon / 4L of Muriatic acid at a concentration of about 30% 900g copper (6l * 150g)I will put this into a 5-gallon bucket for the conversion process and to that, I will add hydrogen peroxide (concentration dependent on what I can get) in small doses, just enough to get a reaction but not enough to start any kind of foaming or highly vigorous action. (the lower the concentration of hydrogen peroxide the more I can add)[WARNING: READ JIMS SITE, ADDING TO MUCH HYDROGEN PEROXIDE AT ONCE WILL LEAD TO A VIGOROUS REACTION, CREATING LOTS OF HEAT AND FOAM ETC..SO IF YOUR USING PLASTIC CONTAINERS, IT WILL BASICALLY MELTDOWN]if my hydrogen peroxide concentration isn't high enough to finish the reaction once I reach 6l I'll add a bubbler and let it finish over time.once the copper is dissolved, I will make up the remaining volume by adding water. to total out 6 liters.HOW MUCH H2O2well.. this was an interesting exercise in reverse engineering notes.2.4 moles of h202 for 2.4 mole of coper according to jim sobasicly 1 to 1 on weight at 100% concentrationwith 30% peroxide.. i need 3.33 times the weight to be equivelentso 900g * 3.33 = 2997 = 3kg = 3l4l muric acid plus 3l hydrogen peroxide is gonna lead to 7l too much. the specific gravity will be too low.doing some reverse math, the minimum concentration I can use is about 40%900 * 2.5 = 2.25 - 2.25lwhich gives 6.25l and would allow for some evaporation.So, in general, anything less than 40% hydrogen peroxide will need aeration to complete the conversion. and since I am doubtful I can get 40% hydrogen peroxide easily I will likely need to end the process with aeration unless i target a lower concentration of CU++at 125g /l i can get away with 30% hydrogen peroxide and hit my 6l goal.comments, questions or observations are highly appreciated.

author: james_s
author_rank: Super Contributor
timestamp: July 29, 2018, 04:36:25 pm
content: I would suggest experimenting with small quantities before you mix up a large batch.My observation was that the ratios are not at all critical. The best etchant was the raw HCl + peroxide, it would etch a board very quickly without causing any pinholes, fantastic results and fairly clear for the first couple uses. After using it some it starts to pick up copper from the boards you etch and turns into cupric chloride which works well but is much slower and requires a bubbler to work well. If I want a very good quality board I'll sometimes still mix up some single use HCl + peroxide, otherwise I use the batch of cupric chloride I've been using for years.

author: Siwastaja
author_rank: Super Contributor
timestamp: July 29, 2018, 05:41:11 pm
content: Quote from: james_s on July 29, 2018, 04:36:25 pmOur experience shows its only good trait is the quick action, and the simple "one-shot" nature where you "only" need a fume hood, but not a bubbler tank.However, what made us eventually switch was the horribly poor etching uniformity and edge effects. Because the etching reaction works as a local catalyst, the local activity is directly proportional to the amount of copper being etched near that location.This tends to cause highly uneven etching, to the point that minimum trace width typically becomes 12 mils on 1oz clad - and this is not the worst case value. If you have lone traces without copper fills nearby, I even had a 12-mil trace completely break down, needing minimum track width rule to 20 mils. If another area on the same board has almost 100% copper fill coverage with only small cutouts (such as an uninterrupted ground plane with small clearances to tracks), this area can be left unetched while other areas overetch.I had boards where part of it would have required 2-3 minutes of etching in HCl+H2O2, whereas another part etched fully in 30 seconds.The warm-up during etching also accelerates the etching; with certain style of boards this can cause almost catastrophic thermal runaway. Luckily no accidents or splashes, but several ruined boards. The process speed runs away exponentially; luckily, the amount of copper is never so much that it would really boil or cause an accident, since it stops when it runs out of copper to etch.I managed to sidestep the issue by carefully controlling the concentrations to make the process a bit slower (like 2-3 minutes, instead of the 30-second volcano), and pre-warming the solution in the water bath, to have more predictable etching speed, then using cool water bath during etching to keep it from accelerating, and applying vigorous manual agitation by shaking the etching tray. This way I managed a 10/10 mils process that worked in most cases.Of course, some people never had any issues, but they were doing boards smaller than 10x10 cm, with all or mostly through hole design, with large tracks. I was using mainly 0603's, with tracks taken between the pads, and some 0.5mm pitch QFPs, and these were hit-or-miss 50% yield cases, or "redo the board three times, waste full day".Cupric chloride in a vigorously bubbled tank was a huge improvement, and a huge simplification, since no process control was needed anymore. Just keep track of the time, so that you have an idea how long it takes, so that when you do the next board, you don't need to keep watching it but can set a timer and keep doing other things.But yeah, if your boards are fairly small, with non-dissimilar patterns of copper / clearance, and you are fine mixing a lot more chemicals than the reaction actually needs, single use HCl+H2O2 may work very well for you.As a side note, when we were actively developing these processes (at a club), high-quality cheap Chinese fabs didn't exist as they do today (or if they did, nobody knew about them like today). People basically paid around $100 for boards that cost around $20 today, with longer lead times, and the specifications were typically around 8/8 mils; we could do better! We added through hole plating, soldermask and chemical tinning to our process, but we never got the desired yield and easiness out of the hole plating process. We had yield of about 99% of the holes being successfully plated (which is not acceptable), and this required about half an hour of extra manual work, and about 1.5 hours of waiting time to achieve, so it never really took off.

author: IanB
author_rank: Super Contributor
timestamp: July 29, 2018, 05:52:09 pm
content: Quote from: innkeeper on July 29, 2018, 04:28:27 pmI think you are using far too large quantities to experiment with. "Bucket chemistry" doesn't literally mean you should do it in buckets...I would strongly advise you to work with much smaller quantities and test until you get the recipe right, then scale up appropriately. If you start and end up with a bucket load of stuff that doesn't work you will have a huge amount of waste and a disposal problem, not to mention that copper is expensive.To etch a small PCB you should only need a few cupfuls of etchant.

author: SeanB
author_rank: Super Contributor
timestamp: July 29, 2018, 05:58:57 pm
content: Light box is easy, just look for a dead flat screen TV set, and remove the LCD panel from it, replace with a sheet of glass, and put it back together. Do not disturb the diffuser layers and the backlights, and it will be evenly lit, or just use a monitor, and set it to display a bright white screen instead, using either an old PC to display a blank document, or some other white display.

author: Ian.M
author_rank: Super Contributor
timestamp: July 29, 2018, 07:49:40 pm
content: Quote from: innkeeper on July 29, 2018, 04:28:27 pmWhy not shoot for 130g/l Cu++? It puts you in the effective 'window' but saves 13% on copper, and peroxide or oxygenation.QuoteHigh concentration hydrogen peroxide is very nasty stuff - see:http://blogs.sciencemag.org/pipeline/archives/2014/10/10/things_i_wont_work_with_peroxide_peroxidesespecially the comments. Even commercial 30% H202 can be problematic - see the MSDS:http://www.sciencelab.com/msds.php?msdsId=9924299Also see this for general peroxide safety:https://www.bnl.gov/esh/cms/PDF/peroxides.pdfPersonally I would try to avoid the need to work with significant quantities of >30% H202, even if in your country, you can buy it over the counter for cash, no questions asked.There are at least three reasonably affordable routes to cupric chloride without conc. peroxides or weathering copper metal.Copper oxide + hydrochloric acid. Black cupric oxide (CuO) is sold as a pigment, as is red cuprous oxide (Cu2O), and are commonly used in ceramic glazes. If you use cuprous oxide, you'll need to further oxidise the result with a bubbler.Copper carbonate + hydrochloric acid. Basic copper carbonate (malachite, azurite and mixtures) are used as pigments, and may be used as an agricultural algicide.Copper sulphate + calcium chloride. The reaction of stoichiometric proportions forms cupric chloride which stays in solution and calcium sulphate which is only sparingly soluble so precipitates out. Copper sulphate pentahydrate (blue crystals) is readily available, and calcium chloride is used as a dessicant and deicer. The anhydrous form used for chemical dehumidifier refills is probably the most readily available. Due to its tendency to adsorb water and deliquesce, it can be a bit tricky to measure accurate quantities.

author: tautech
author_rank: Super Contributor
timestamp: July 29, 2018, 08:18:07 pm
content: Some notes from when I went down the HCL road.

author: innkeeper
author_rank: Unknown
timestamp: July 29, 2018, 10:06:53 pm
content: just going over some math, I think I need 4.5l of 30% muriatic acid to have the right balance of cupric chloride and hcl at the end.can anyone confirm this?if I am understanding right, I might re-calculate the batch so i can use an even gallon of muriatic acid for simplicity.

author: IanB
author_rank: Super Contributor
timestamp: July 29, 2018, 10:11:37 pm
content: If you're going to all the trouble of dissolving stuff in HCl, why don't you just dissolve iron in it and make ferric chloride? There is surely a reason why the whole history of board etching has used ferric chloride and not cupric chloride?I'm still puzzled why you are trying to make up such enormous quantities?

author: tautech
author_rank: Super Contributor
timestamp: July 29, 2018, 10:14:55 pm
content: Quote from: innkeeper on July 29, 2018, 10:06:53 pmFrom my etchant notes above a good starting ratio was: My mix was 200ml acid added to 100ml H2O2 and 150ml water.A new brew etched quite fast and details are in the link.

author: tautech
author_rank: Super Contributor
timestamp: July 29, 2018, 10:17:07 pm
content: Quote from: IanB on July 29, 2018, 10:11:37 pmSee here:https://www.eevblog.com/forum/chat/what-did-you-buy-today-post-your-latest-purchase!/msg1708112/#msg1708112Good score innkeeper, I would've grabbed it too.

author: innkeeper
author_rank: Unknown
timestamp: July 30, 2018, 12:45:00 am
content: Quote from: IanB on July 29, 2018, 10:11:37 pmcause it basically lasts forever, you never have to throw it out just regenerate it and keep using it over and over again.it is the reason it is used in commercial applications.Quote from: IanB on July 29, 2018, 10:11:37 pmbecause of my tank size.

author: innkeeper
author_rank: Unknown
timestamp: July 30, 2018, 01:03:20 am
content: Quote from: tautech on July 29, 2018, 10:17:07 pmkind of funny, I truly wasn't looking for it at all, ... I just count pass that up though.

author: innkeeper
author_rank: Unknown
timestamp: July 30, 2018, 01:36:23 am
content: Quote from: IanB on July 29, 2018, 05:52:09 pmI think you are using far too large quantities to experiment with. "Bucket chemistry" doesn't literally mean you should do it in buckets...I would strongly advise you to work with much smaller quantities and test until you get the recipe right, then scale up appropriately. If you start and end up with a bucket load of stuff that doesn't work you will have a huge amount of waste and a disposal problem, not to mention that copper is expensive.To etch a small PCB you should only need a few cupfuls of etchant.well, i guess your right if I was etching in a tray, but i am etching in a 1.5-gallon tank.a neutralized solution can be disposed of.the amount of copper is about 2 pounds at best, maybe 5 bucks from your local salvage location.1 gal muriatic acid, 6.88 and 6.30 for the hydrogen peroxide,so $18.80 call it 20 bucksso for 20 bucks i can have a solution that will last me the rest of my life, .. not bad.I'll actually use a glass small necked 5 gal container for the reactor that is monitored for the temperature. and that will be sitting within a 10 gal capacity 4'x4' PP tray in case of any issues.also, I will be prepared to neutralize it if it becomes an issue.i don't consider this an experiment, just a process.and although i am not a chemist, it is not my first rodeothough always open to things i should do. safety first.

author: Ian.M
author_rank: Super Contributor
timestamp: July 30, 2018, 02:15:52 am
content: Quote from: innkeeper on July 29, 2018, 10:06:53 pmIf you are working by volume, you need to know the temperature to get the density of the 30% hydrochloric acid before you can calculate its molarity. There's a table & calculator here:http://www.handymath.com/cgi-bin/hcltble3.cgi?submit=EntryAssuming I've done the maths right, at 20 deg C, the molarity of 30% hydrochloric acid is 9.46, and 1 l needs 300g of copper (as Cu2+ions) to form copper (II) chloride stoichiometrically.Without knowing your target copper concentration and residual HCl molarity your figures cant be checked. However to prepare 6 l of etchant with 1 mol residual HCl, you will need an additional 635 ml of Hydrochloric acid (conc. and temp. as above).4.5 l *may* be too much acid - as even if you are using 900 g of Cu (instead of shooting for the bottom of the recommended working concentration range), that leaves you with 1.5 l of 30% acid, which will bring the final residual acid molarity up to 2.46 once its diluted to 6 l of etchant.

author: innkeeper
author_rank: Unknown
timestamp: July 30, 2018, 03:46:49 am
content: thanks ian,i appreciate the sanity check.i was shooting for a final hcl molarity of 2.5 so. sounds about right. and a cu2+of 150g/Li've put this all into a spreadsheet so i could play with numbers..and have shifted what i plan to do a little bit.since muriatic acid comes in 1-gallon bottles, 1 gallon is 3.785 i have dropped the total volume down to 5L and lowering the cu target to 140g/LI'm being a bit cheap and calculating it out to use 1 gallon bottle of muriatic acid.new target and calculations :Target Cu2+: 140g/lTarget HCL mol: 2.5/Lmy calculations are as follows:CU: 650gMuriatic Acid 30%: 3.63LH2O2@ 40%: 1.37L (all there is room for...2.05 would give full conversion, so aeration will be needed to complete conversion the final 30% )still sourcing the H2O2so whatever I get I will work with, though I think I can get 40%. once there's sufficient cupric chloride in solution it will break down the rest of the copper and then I can aerate.One question on your calculations / notes you posted ... you said 300g of copper for 1 liter to get 150g/L i don't think that's right, or maybe i misunderstood.i thought...since its 1 atom of cu with 2 ions. the weight should be 1:1 .. right 150g of cu should create 150g cu2+cucl2if not little education is in order for me.. again its not my strong suit.i should have paid more attention in chemistry class

author: IanB
author_rank: Super Contributor
timestamp: July 30, 2018, 03:56:10 am
content: There's some good process chemistry information here, since you mentioned commercial applications:http://www.chemcut.net/wp-content/uploads/2015/03/Chemcut_Bulletin_8_Cupri_Chloride_Proces_-Parameters.pdf

author: IanB
author_rank: Super Contributor
timestamp: July 30, 2018, 04:00:51 am
content: Quote from: innkeeper on July 30, 2018, 03:46:49 amRemember there may be some dilution afterwards (addition of more acid/peroxide/water) to get to the final etch concentration.

author: Ian.M
author_rank: Super Contributor
timestamp: July 30, 2018, 08:24:44 am
content: Yes, IanB is right, the 300g per litre of acid does *NOT* include dilution to final target Cu2+concentration, whether that's by the peroxide or final adjustment with water.You haven't made any allowance for oxygen or HCl lost as gas and are going straight to final volume. That doesn't leave you any range for adjustment - adding any extra acid or peroxide will dilute it below 140 g/l of copper.Unless you get lucky and someone's just scrapped some welding cables, I think you may have difficulty finding enough reasonably clean finely divided copper at the scrapyard at a price you want to pay.Even 500g of black copper oxide powder would make your life a *lot* easier - that's 400g of copper as Cu2+that does not need *ANY* peroxide - leaving you with only 250g of copper (added as metallic copper) that needs oxidising, which would be 0.4 l of 30% hydrogen peroxide, giving you back your volume margin for final adjustment, even if you dilute the peroxide before addition to reduce loss of O2as gas.

author: Psi
author_rank: Super Contributor
timestamp: July 30, 2018, 12:27:02 pm
content: Quote from: IanB on July 29, 2018, 10:11:37 pmI don't think cupric chloride was known as a possible etchant back then.

author: Fred27
author_rank: Unknown
timestamp: July 30, 2018, 12:35:49 pm
content: Yes - that's the only reason why professional board houses don't use CuCl and toner transfer.

author: Siwastaja
author_rank: Super Contributor
timestamp: July 30, 2018, 01:10:27 pm
content: Professional board houses need to do 3/3 mil grade with maybe 99.9% yield, with low cost on large batches, day in day out. There's quite a bit of optimization going on to achieve the last 10-20% of the resolution while keeping cost down and yield high.A hobbyist, on the other hand, usually buys the "For Hobbyist" products, and does 12/12 mil grade with about 50% yield, using products that are possibly 10000x more expensive per board compared to what the fabs use.You see a gap that's not even a niche?I noticed this huge gap, because I was completely dissatisfied at the "hobby" level, and brought over some industrial things to our club process. The process went to 8/8 mil with at least 80-90% yield easily (on average; for me it was basically 100%), and the cost dropped dramatically to basically zero.Many tried toner transfer and talked about it as the greatest thing after sliced bread, but when I looked at the results (they were satisfied with), I never saw a satisfactory board to my standards. Some were fairly good. But still "hobby standard", great for small boards with 20 THD parts.For me, hobby standard was a reliable 0.5mm QFP, reliable 0402 footprints, reliable 8 mil tracks and 8 mil gaps, all on large (up to 20x20 cm) boards, at the same time. In a large board like this, I could accept reworking one or two broken traces sometimes, but not much more. Using the established "hobby standard" - which for us meant using a laser printer to print masks, "Positive 20" photoresist spray on copper clad, NaOH developer, HCl+H2O2 etchant -, the yield for this level was almost zero. I remember redoing a board at least 4-5 times. Others did simple, small boards succesfully.AFAIK cupric chloride has been used industrially in history, but don't quote me on that.Even for modern SMD hobby use, cupric chloride is great, and won't be the limiting factor, unlike HCl+H2O2 which is almost useless for more demanding hobby boards.The best modification we made was the dry film negative photoresist, and to start CNC drilling first, then using dry film photoresist to tent over the holes. This forced us to think about the registration in the earliest phase possible, meaning no more boards got completely messed up as the last process step (which was drilling).

author: james_s
author_rank: Super Contributor
timestamp: July 30, 2018, 03:31:36 pm
content: Maybe it depends on the resist used? With toner transfer, the nicest, most consistent boards I've ever etched were using HCL + peroxide. No pinholes, consistent trace widths, they turned out fantastic. Those weren't particularly fine pitch stuff, I think 10 mil traces but they sure came out nice. Cupric Chloride works well but I often get a few pinholes on copper pours. I've still managed to push the process to do a few 0.5mm pitch SMT ICs though. At that point the toner squishing out during transfer starts to become significant.

author: janoc
author_rank: Super Contributor
timestamp: July 30, 2018, 03:39:16 pm
content: Quote from: innkeeper on July 30, 2018, 01:36:23 amSeriously, you want to be sitting on a gallon of concentrated acid mixed with concentrated hydrogen peroxide? Stuff that will corrode everything metallic in sight? For a month or how long it will take to make your cupric chloride?Is it only me who finds this idea completely bonkers safety-wise?

author: james_s
author_rank: Super Contributor
timestamp: July 30, 2018, 04:17:35 pm
content: What's the downside of making a small batch until you get it right and then make gallons of it? If you're trying a new cocktail recipe you don't start by mixing up a whole vat of it to see if it's any good.

author: Raj
author_rank: Frequent Contributor
timestamp: July 30, 2018, 05:07:16 pm
content: Why not ferric chloride from China? I get it from there sometimes. And sometimes from electroncomponents.comMost of the times,I buy it from local school supply-chemistry shop

author: janoc
author_rank: Super Contributor
timestamp: July 30, 2018, 05:33:27 pm
content: Quote from: Raj on July 30, 2018, 05:07:16 pmNo need to buy it from China, I am pretty sure that in the US he can get it even from Amazon, Digikey or Mouser. But some people prefer to mix and keep around a gallon of fairly dangerous chemicals instead ...

author: IanB
author_rank: Super Contributor
timestamp: July 30, 2018, 05:37:52 pm
content: Quote from: Siwastaja on July 30, 2018, 01:10:27 pmThe reason copper chloride is used industrially is noted in the technical note I linked above. It is because they can arrange the process into a steady state with continuous process control on the etchant concentration and activity so that every board etches exactly the same without any variation. They can regenerate the etchant by directly injecting chlorine so they can produce a waste stream containing uncontaminated copper that can be recovered. Every process parameter on the production line can be controlled exactly without any deviation from hour to hour or day to day, which allows them to predict outcomes precisely.

author: innkeeper
author_rank: Unknown
timestamp: July 30, 2018, 06:22:40 pm
content: Quote from: janoc on July 30, 2018, 03:39:16 pmthe process is only long if you wanna go cheap.. the cheaper you go the longer it takes.you can buy cupric chloride in powder form. it's just cheaper to make your own and even within making your own, there are cheap and cheaper methods.but really, in the overall cost, since its a one time purchase, your not saving all that much more by making it from scratch over buying powdered form and adding water and hcl.but its a hell of a lot more fun .

author: KL27x
author_rank: Super Contributor
timestamp: July 30, 2018, 08:04:43 pm
content: Innkeeper, you are doing far too much math and your focus is a little bit off.If you keep in mind a couple things, you will see how easy it is to get where you want to be.1. You can instantly dilute cupric chloride with water and acid. So you don't have to make it all at once. And you don't have to worry about over-concentrating it. So you ought to be shooting for maybe 2/3 of the total volume you want to end up with, and just saturate the heck out of it. At that point, making more is as simple as plugging in your bubbler and dropping copper into your tank. Add water and acid when it gets too concentrated. The problem you will have is what to do with the excess.2. As far as concentration of peroxide, you do not need 30-40%, because you are starting with fuming HCl. The initial concentration of your acid being 33%, this is way higher than you need to make a saturated solution of cupric. Using 3% peroxide, you will have plenty of initial peroxide once you have diuted the acid a bit.If you started with about 10% HCl, you would be in the right ballpark in the end, but it may help to dilute it more slowly (so you can add more peroxide with that water, later). I started about 50:50 33% acid and 3% peroxide. Also you might as well put the bubbler in there from the start. It doesn't take that long. Will be done overnight for sure, if not much sooner. If you started with anywhere from 1:3 to 1:2 and bubbler, you can literally drop in more than enough copper and just come back 8 hours later, unless you live in cold climate. And obviously don't drop a big solid chunk of copper. Using wire, or whatnot, it has a much larger surface area. Just dilute the stuff to the appropriate concentration when you use it.

author: janoc
author_rank: Super Contributor
timestamp: July 30, 2018, 08:07:29 pm
content: Well, your pick. I would still go with the ferric chloride which has the same benefits and no need for messing with dangerous chemicals.If you really attempt to do what you were describing, at least read up on safe handling of concentrated acids and peroxide.E.g. if you accidentally mix concentrated hydrogen peroxide with acetone/paint thinner (common chemical used to degrease boards), you could end up blowing yourself up - that's how TATP is made. If that mix dries, run - it is extremely shock sensitive.Concentrated acid is no fun neither - even if you don't spill it, the fumes are extremely toxic and aggressive, especially the ones after you add the peroxide. Frankly, the thought of having a gallon of this stuff mixed somewhere gives me a cold sweat and I have some chemistry training ...

author: KL27x
author_rank: Super Contributor
timestamp: July 30, 2018, 08:19:08 pm
content: The acid requires precautions, for sure. Yes, you can burn your cornea or your lungs.Once you have dilute the acid a bit, it is much less obnoxious to handle. Or you can buy it at 15% to begin with. A bit of dilution is all it takes to eliminate almost all the fume/breathing hazard. Once you have made cupric, you will never actually need to handle peroxide or fuming HCl for maintenance. Just watered down acid.Even when I used ferric, I added ~10% HCl to it to stretch it. I can't imagine why you would want to use ferric for just a little while then buy more, when it will last twice as long and cleaner (no sludge to deal with) if you add cheap as dirt HCl. And you get to push back the disposal issue.

author: IanB
author_rank: Super Contributor
timestamp: July 30, 2018, 09:02:48 pm
content: Quote from: KL27x on July 30, 2018, 08:04:43 pmNote that if you use air to oxidize copper (I) ions to copper (II) ions it will produce copper oxide (CuO) as a reaction product. This will require adding more HCl to the solution to dissolve it, otherwise the CuO will neutralize and use up the existing excess acid.

author: KL27x
author_rank: Super Contributor
timestamp: July 30, 2018, 09:08:04 pm
content: ^You are also overcomplicating it with all them fancy words. See the next sentence I wrote after that.My thought process is pretty much "hey, stuff is precipitating out of solution. Ok, I'll add some acid and water." Once you achieve a suitable concentration, the rest is gravy. The only thing to avoid is overdiluting, because that is harder to fix.* So you run until it slows (and with my aeration setup, I can run it until there's half an inch of white sediment on the bottom of the tank, even), then you dilute it enough to dissolve the precipitate and some extra to where you don't have to do it again, too soon. Just avoid turning it into green tinted Koolaid.If you can make your tank clear, it makes maintenance a lot easier.*Well, not necessarily harder. It just takes longer. You can get it back by adding more copper and running the bubbler. And waiting. And after you've done this for awhile, you'll have a bottle of concentrated cupric which you decanted off (or maybe even crystals that you dried out), so even over-diluting won't be a big deal.As far as getting the acid/water concentration right, that is a bit like cooking. You just tweak it when you need to. If there's too much acid, it will smell like acid. And it will have a noticeably blacker color to it when spent/deoxidized (when charged up, emerald green, you can't really see a difference in color). You will have to make adjustments depending on evaporation of your setup. But even having too much acid, it'll still work. It will just will not etch quite as accurately. Still way better than HCl and peroxide. If you pour some water in there and you see the local area turn blue, temporarily, you are very low on acid; etching speed will be greatly reduced.I notice if I don't use my tank in a really long time, even if there is no significant evaporation (which there is not; the lid works great), the acid will be low. Even though it's not "fuming," the acid and chlorine seem to gas off faster than the water. I suppose it might be specific to my tank/lid.

author: sleemanj
author_rank: Super Contributor
timestamp: July 30, 2018, 10:54:48 pm
content: Adam Seychell wrote a lot on the creation, monitoring and maintenance of CuCl2, I have a PDF version of his old website info (gone) here:http://sparks.gogo.co.nz/seychell.pdfeven if like me you are not into doing things by the numbers but just adhoc bit-o-this-bit-o-that, the document does include some useful information.

author: innkeeper
author_rank: Unknown
timestamp: July 31, 2018, 05:17:57 am
content: adams docs / notes are great as is jim's

author: intabits
author_rank: Frequent Contributor
timestamp: July 31, 2018, 06:12:10 am
content: I used ferric chloride when I was a kid, but for the past 40 years I've been using ammonium persulphate. I've used cupric chloride in gold recovery, and would use it if I made many PCBs regularly. But for occasional use, (say every 3 o4 months) persulphate is pretty easy.Per 100cm^2 of PCB, I use 33g of APS in 100ml H2O.Put a large flat pan half filled with water on the stove, heated to 3/4 boiling (say about 80C).In the pan, float one of those disposable plastic trays that meat comes in at the supermarket, or a Chinese takeaway container.Put the etchant and PCB in the floating tray, gently sloshing the etchant over the PCB.Done in 10-15mins, and the APS will be mostly consumed, leaving copper sulphate solution (for the garden?).

author: Ian.M
author_rank: Super Contributor
timestamp: July 31, 2018, 09:46:13 am
content: Quote from: KL27x on July 30, 2018, 09:08:04 pmIf the solution isn't sufficiently acidified, (pH>2.43), copper (I) chloride is minimally soluable. Therefore the white precipitate is copper (I) chloride that has dropped out of solution instead of regenerating. As regeneration to copper (II) chloride uses up hydrochloric acid, etching scrap copper past the point where the excess acid is used up will actually reduce the copper concentration in solution.This *may* be a viable method of reducing the copper concentration if the etchant density was too high before precipitation started: Rather than immediately re-acidifying to redissolve the precipitate, remove the precipitate before reacidifying, then only add enough precipitate back to bring the copper concentration back up to the bottom of the working range.Its more trouble than simple dilution, but it avoids the need to either store excess liquid etchant or dispose of it, as the copper (I) chloride crystals can simply be washed, dried and stored, (without the excess acid fumes problem of simply evaporating excess etchant to dryness) then used to either correct over-dilution, or passed on to another hobbyist who wants to get into acid copper chloride etching: just add hydrochloric acid, dilute and regenerate with air to get a viable etchant solution.Of course, if you actually need to dispose of significant quantities of excess etchant, you'd be better off precipitating the copper out as copper oxide using alkali (NaOH or KOH), followed by washing. Then if you have no use for copper oxide, mix the wet precipitate with cement powder, and let it set in a mould to get a reasonably inert block as the copper oxide wont dissolve under alkaline conditions, and the cement keeps it alkaline.

author: Psi
author_rank: Super Contributor
timestamp: August 04, 2018, 10:37:28 am
content: The main reason to avoid Ferric Chloride is disposing of it.You really really should not pour it down the drain. Copper in solution is really bad for aquatic life

author: innkeeper
author_rank: Unknown
timestamp: August 04, 2018, 02:23:58 pm
content: I wonder what the best type of container to store it in when not in use.I am thinking a milk jug is probably not the right answer.

author: NiHaoMike
author_rank: Super Contributor
timestamp: August 04, 2018, 02:35:51 pm
content: Quote from: Psi on August 04, 2018, 10:37:28 amIsn't any etchant going to dissolve the copper into solution? I don't think copper down the drain in small enough quantities would matter when it's commonly used to prevent tree roots from growing into sewer lines.

author: innkeeper
author_rank: Unknown
timestamp: August 04, 2018, 02:47:13 pm
content: NiHaoMikeThe point is, you have no need to dispose of it at all, it will likely last you a lifetime.. and if your an avid hobbyist the worst that can happen is you just end up with more then you can use over time. ... but we're likely talking 1000's of not 10's of 1000's of boards later.

author: Ian.M
author_rank: Super Contributor
timestamp: August 04, 2018, 07:44:30 pm
content: Quote from: innkeeper on August 04, 2018, 02:23:58 pmOnce *ALL* the peroxide has been consumed, the plastic jug the Hydrochloric acid came in will do nicely. Otherwise stout plastic jugs made of HDPE (preferred) or possibly polypropylene or a glass carboy. The stoppers must be entirely non-metallic. Store brand thin bleach in the 2 L or 64 Oz sizes is commonly sold in suitable jugs, that can easily be washed out and relabelled.Make sure that its correctly labelled, with the applicable hazard symbols, and store the jugs in a secured well ventilated area, preferably outdoors, but sheltered from the weather and direct sunlight (a lockable plastic garden toolbox is ideal), in a plastic tub or bucket with enough limestone chips in the bottom to neutralise the maximum possible quantity of HCl that could be released by a split jug.Quote from: Psi on August 04, 2018, 10:37:28 amThe environmental regulations concerning the use of and discharging copper (II) compounds are becoming far more restrictive in several jurisdictions. OTOH with the rarity of hobbyist PCB etching, occasional disposal in the waste water system after high dilution is unlikely to be a significant issue if the waste goes to a reasonably sized municipal treatment works. However if you need to dispose of spent etchat commercially, or as a club or organisation, you need to do it in full compliance with local environmental regulations.There are various ways to precipitate out the copper (as metal or minimally soluble compounds) and render the remaining solution minimally hazardous, but its messier and more difficult to be certain that you've got it all if its in a spent ferric chloride solution rather than cupric chloride etchant.

author: tautech
author_rank: Super Contributor
timestamp: August 04, 2018, 08:19:44 pm
content: Quote from: innkeeper on August 04, 2018, 02:23:58 pmI use a sistema brand vegetable microwaveable container with a clip on lid and a popup steam vent. It's not the 'perfect' seal so allows the etchant to breathe just a little while in storage. It's quite small ~6x6x4" high and 1.4L which is enough for my small tank.

author: KL27x
author_rank: Super Contributor
timestamp: August 04, 2018, 09:57:55 pm
content: i use the thick plastic jugs that the acid came in. Every one of them is filled with concentrated etchant.The problem I have now is that my latest acid came in what looks like milk jugs.I also use thick beverage bottles, like what you buy some brands of orange juice or tea.I'll have to start drying out some excess. It turns into green crystals, and I just bag 'em and put them in a tupperware box.Technically, you can do the same thing with ferric. But the crystals are brown and sticky. I tried neutralizing ferric, once. I don't remember what I put in there. Baking powder or baking soda. I'm not a chemist. W/e I used, it was a bad idea. The result was a huge volume of gelatinous goop, worse than what it started. I will stick with dehydrating in the sun.QuoteYeah, I have thought of that. I figure I would have to run the bubbler to suspend the solids and immediately pour out all the etchant into a new container. Let it settle and pour it back in. Seems like too much work. And you have to work the etchant hard to get a lot of the white stuff. If you titrate your tank more closely, you would never get any. Short of finding some use for the chemical, I don't see where I would bother.And after the stuff dries, I bet it dries to the container hard as a rock. I think the green "kryptonite" crystals are the way to go. They will break up fairly easy and fall away in big pieces with a smooth side, shaped to the glass. Easy to store/handle.

author: westfw
author_rank: Super Contributor
timestamp: August 09, 2018, 06:59:29 am
content: Does anyone have an idea why the Cupric Chloride I made (or tried to make) would be a deep bluish-green instead of the bright green usually described and pictured? (Perhaps it's just too concentated?)I started with Pool Acid (~2parts) and 3% H2O2 (~1part), a bunch of copper wire scrap, and a bubbler, and let it go until it started to precipitate (Copper OxyChloride?) Then I added enough more acid to dissolve the precipitate.Do "commercial" PCB shops really use copper chloride that much? I read some articles (quite some time ago, actually) that led me to believe that Ammonia/Alkaline etching processes were quite popular (not the least because they can use the tin plating as resist?)

author: IanB
author_rank: Super Contributor
timestamp: August 09, 2018, 08:03:37 am
content: Quote from: westfw on August 09, 2018, 06:59:29 amAccording to the technical note I linked earlier in the thread, the advantage to commercial operations is that they can operate the copper chloride process in a continuous closed loop circulating system where they keep the properties of the etchant more or less constant (so that every board is etched exactly the same) and where the only waste stream is a recoverable copper solution.Combine this with the low cost of the etchant make-up materials and the argument makes a lot of sense to me (I am a chemical engineer).

author: KL27x
author_rank: Super Contributor
timestamp: August 09, 2018, 09:55:00 am
content: See my last post. If you have blue in there, your pH is too high. You need more acid. (But this doesn't make sense!) You can't turn the stuff blue by over-concentrating it.Check the MSDS of your pool acid. I've bought some Kemtek stuff that was marked where I thought it was 15% muriatic, but it actually wasn't. It was some kind of chlorinating agent that is supposed to be a substitute for 15% muriatic. It totally ruined my etchant. It turned bluish and formed a slimy precipitate.With the ratios you used, if you were using 33% fuming HCl, you should have a large excess of acid. The blue color doesn't make sense. And the only precipitate you should be seeing is very light green/white in color, AFAIK, with a consistency like fine sand or powder that settles at the bottom fairly quickly. You shouldn't even make much of this unless you have really good aeration... with just a fish tank bubbler, the etching will slow down before you can make much, if any, AFAIK.The pros all use alkaline etchants for the finest pitch stuff. They also have to use the more finicky negative resist (or positive; I'm dyslexic at this) for the really fine pitches. Some of them use copper chloride for larger pitches. This is one of the reasons that your boards cost more when the pitch gets finer than say 7 mil traces.

author: sleemanj
author_rank: Super Contributor
timestamp: August 09, 2018, 12:18:43 pm
content: Quote from: westfw on August 09, 2018, 06:59:29 amColour is pretty subjective to describe, but the higher concentration of Cu1+ the deeper/darker the colour, add oxygen (aerate, or cheat and use H2O2) to reduce the cooper ion concentration and that should make it greener and brighter.The lighter brighter green, the faster etch.