PCB Etching and some chemistry - Page 1
Forum section: electronics / general

author: TheAmmoniacal
author_rank: Unknown
timestamp: May 25, 2014, 08:03:04 am
content: I just made my first PCB ever today, but also used all the hydrogen peroxide, so I need some help. Hydrogen peroxide has become difficult to acquire in the recent years, but that doesn't mean I can't get it or make it, I just need to know if it's worth it. I consider the usual ferric chloride a bit too messy to work work, as I have to do this in my room.So the next best option from googling around is persulfate/peroxymonopersulfate/oxone, but I haven't been able to find any videos or tutorials explaining how effective this compound is as an etchant, at which concentration is it the most 'active'? Does it require heating? Does it take a long time?Could anyone here give me an idea? The hardware store sell it in 1 kg bottles at $40 a piece.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 25, 2014, 08:08:57 am
content: Yes, give it a look. I recall it being popular in the magazines. More expensive, but way the hell cleaner. Anyone who thinks HCl + H2O2 is easier than FeCl3 is lying... it's stinky, highly acidic and corrosive, and almost as messy (copper doesn't stain quite as badly as iron).And your name is, rather smellyTim

author: SeanB
author_rank: Super Contributor
timestamp: May 25, 2014, 08:11:31 am
content: The persulphate requires heating to about 40C to get it to work effectively, and when cold it is a lot less reactive, so much easier to store. I used it years ago to etch in a tank, where it did a very good job pretty fast.

author: poorchava
author_rank: Super Contributor
timestamp: May 25, 2014, 08:12:46 am
content: You can use pharmacy grade 3% peroxide. Concentrated 30%+ peroxide is not needed (actually you need to dilute it in water or the reaction gets extremly violent)

author: TheAmmoniacal
author_rank: Unknown
timestamp: May 25, 2014, 08:49:59 am
content: Quote from: poorchava on May 25, 2014, 08:12:46 amThe pharmacy here charge $80/L for 3% hydrogen peroxide, which is something I wouldn't/couldn't pay. Chemistry was my primary hobby before I started doing electronics, where I used to make hydrogen peroxide by dissolving sodium percarbonate in water, precipitating the carbonate with calcium chloride and filter out a hydrogen peroxide/sodium chloride mixture. This way I could get 13% H2O2 (with ~7% NaCl), that works in 'all' acidic and basic solutions.

author: sleemanj
author_rank: Super Contributor
timestamp: May 25, 2014, 09:56:42 am
content: A quick check on ebay shows you can get 500ml of 35% H202 to your door in Norway from the UK for total 25 GBP, by what appears to be a business well versed in appropriate means of sending such chemicals around Europe.http://www.ebay.co.uk/itm/Food-Grade-Hydrogen-Peroxide-35-500ml-/130543355740Admittedly that's pretty pricey (at least here in NZ I can get a litre of 35% for nearly half that price), but it would last you a very long time - even given it's propensity to degrade, it's going to be plenty strong enough for a very long time, as long as you keep it cool and dark.Don't throw out the "used" etchant it becomes CuCl2 etchant, just add a little H202 each etching session to keep it bright green, and if etching is slower than you'd like a little more HCl.Since you have an interest and are experienced in chemistry, if you should want to get all technical, you can check out Adam Seychell's information which I've mirrored to a PDF here:http://sparks.gogo.co.nz/seychell.pdfBut, I just go by eye/feel, too dark = add a cap of H202, too slow = add a cap or two of HCl.

author: TheAmmoniacal
author_rank: Unknown
timestamp: May 25, 2014, 10:07:08 am
content: Quote from: sleemanj on May 25, 2014, 09:56:42 amThat eBay store is very much legit, and I have ordered from them before once for when I needed more concentrated solutions. At that time the shipping cost was lower aswell. But for reasons I won't go into I am not able/willing to import any such thing into the country again. (Breivik/EU Regulations)Thanks for the PDF, will have a read.

author: LukeW
author_rank: Frequent Contributor
timestamp: August 13, 2014, 07:12:32 am
content: Ammonium persulfate (or any of the persulfate salts really) work fine as etchants, but they do need to be heated up a bit, generally about 60 degrees C.Temperature regulation is not critical, you can just use just-boiled water from the kettle or stove when you initially dissolve the solution and then stick the board in, and let it etch as the solution cools.They don't stain everything like ferric chloride.

author: con-f-use
author_rank: Unknown
timestamp: August 13, 2014, 07:36:23 am
content: You can "regenerate" (actually it's a different reaction) your spent H202 + HCl etchant by bubbling air into it. See Etching withAir Regenerated Cupric Chloride.Actually it doesn't even needthat much attentionto chemistry .

author: poorchava
author_rank: Super Contributor
timestamp: August 13, 2014, 08:29:27 am
content: If one has space to make a special "etching lab", then solutions which require heating and strong agitation (persulfate, cupric chloride) may be fine. If (like me) you do not have space to do that, then peroxide + hydrochloric acid is the way to go. Mix 50ml of the solution, etch the board in 5-10 minutes and flush in the toilet. Job done. Quick and clean. Plus the reaction is exotermic, so the solution heats up itself (just don't overdo it - at higher concentrations of peroxide and bigger acid contents this gets REALLY violent). The very minor amount of copper introduced into sewers won't hurt nobody (if anything, it may slown down scale build up by a bit)

author: con-f-use
author_rank: Unknown
timestamp: August 13, 2014, 09:17:25 am
content: Quote from: poorchava on August 13, 2014, 08:29:27 amThe toilet? Really? You don't eat fish, do you

author: SeanB
author_rank: Super Contributor
timestamp: August 13, 2014, 05:13:59 pm
content: Flushing it down the toilet here would be an improvement. A small amount will be rapidly diluted, and in any case the water supply has copper in it anyway from piping, and the other chemicals are used in water treatment planys in large amounts. At present the beaches are not classed as a place to swim, unless you like to swim in a septic tank. Ecoli pretty much off the scale and other stuff high enough that you can measure with your nose at 500m.

author: rob77
author_rank: Super Contributor
timestamp: August 13, 2014, 09:37:58 pm
content: Quote from: con-f-use on August 13, 2014, 09:17:25 amare you feeding some fish-farms with water from the sewers in Austria ? I would be more worried about the industrial waste water than a 50ml of etchant with 1gram of copper in iti personally use the official waste collecting places to dispose all suspicious waste (we have those in every town), but i know very well what amount of industrial shit is disposed into the rivers. ecology is one thing... but corporate cost savings is another which always wins unfortunatelyit's like that even in your ecological country (otherwise the Danube would be crystal clear when entering my country right ?)don't get me wrong.. .i like the way your country is trying to be more green - big thumbs up for thatand even bigger thumbs up for the ecological consciousness of the citizens of Austria !but let's not ignore the corporate and industrial realitythe industrial waste is killing the nature, not the minor waste which comes from a misbehavior of individuals.

author: PepeK
author_rank: Regular Contributor
timestamp: August 13, 2014, 09:52:35 pm
content: Is it really so complicated and expensive to buy a peroxide ? In my country, absolute no problem, every big shop selling paints, thinners etc. have 500ml bottle of 30% for approx 1 euro. The same for a hydrochloric acid, 32%, 500 ml ...I mix 20 ml of acid + 10 ml of peroxide + 70 ml of water. Works nice, very little smell, can be done inside in a bathroom.

author: poorchava
author_rank: Super Contributor
timestamp: August 13, 2014, 10:09:17 pm
content: Here in poland Peroxide used to be stocked in any hardware store like Obi or Leroy Merlin, but people are stupid. Any container with peroxide must have a tiny hole in order to let the oxygen gas out and prevent pressure buildup. There is a HUGE sign to keep the bottle vertical, but people are dumb and they were tipping the bottle over anyway, they've burnt their clothes and such and stores resigned from selling it. Hydrochloric can still be bought as a strong flux for soldering galvanized gutters. You can also get it from chemical wholesaler (like I did) but since it's a dangerous substance, I has to give them my personal data and purpose for purchasing the chemical ("metal etching" worked just fine).I'm buying my 30% peroxide from professional haircut supplier for about 4€/liter

author: con-f-use
author_rank: Unknown
timestamp: August 14, 2014, 07:38:17 am
content: Quote from: rob77 on August 13, 2014, 09:37:58 pmVery much agreed. Likewise it is not really sensible to require light bulbs to have a certain efficiency when household lighting or even all lighting combined only makes a tiny fraction of the overall electricity consumption. Or to recycle, when industrial waste is the bigger problem. Or to make effort as a small developed country, when 90% of the world's population (especially China, India and Russia) don't give a shit. However, it's still NEVER okay to pollute or waste no matter the extent. Pointing that out serves to educate people. Its a culture thing. Shaming people who make a small mess, might prevent them from making a big mess later on in their lives, when they might the decision makers. A few 100 years ago it was okay in Europe to beat your children, burn people on stakes and shit on the sidewalk. Society can evolve, but it starts with education and a general consensus......or a big catastrophy.

author: Refrigerator
author_rank: Super Contributor
timestamp: August 14, 2014, 01:02:48 pm
content: You can use copper chloride, just take your hydrogen peroxide and hydrochloric acid mix and add a bunch of copper until it becomes a very deep green, then boil off some of the water and add some more hydrocloric acid.Here, watch this video, it should explain everything you should know.

author: Cside
author_rank: Regular Contributor
timestamp: August 15, 2014, 09:44:04 am
content: try base pirhana (NH4OH + H2O2) or the stronger piranha (HS204 + H202). Ive used piranha in chemistry research and I promise you it will etch oxidize anything that has electroncs to strip.It will also blow up in your face if you mix it too fast, or incorrectly.

author: westfw
author_rank: Super Contributor
timestamp: August 15, 2014, 11:03:03 am
content: In the US, it's petty difficult to find peroxide stronger than 6% (aka "20 volume"; be careful what the label says.) Normal peroxide is 3%.Fortunately, that's just fine for making Copper Chloride etchant.It's a FEATURE that copper chloride, ferric chloride, and persulphate, are "milder" than The "pirahna" (strong acid + strong peroxide) etchants. Pirahna etchants are famous for dissolving organic contamination as well as metal. You know, like skin and flesh! (And in contact with organics, they're also prone to forming organic peroxide explosives... Not at all a good thing!)

author: Cside
author_rank: Regular Contributor
timestamp: August 15, 2014, 11:39:25 am
content: Quote from: westfw on August 15, 2014, 11:03:03 ama little bit of dissolved flesh never hurt anyone!wear gloves and use a fume cupboard, use a pipette and thermometer so it doesn't runaway from you.Otherwise stick to sofcore 3% H2O2 and wait all day to complete the oxidation.The real question is whats wrong with getting your pcb fabricated by any of the many cheap fab-houses? Im sure even the dodgiest company will produce superior results to a home-made etch. if its purely for experience and chemistry then I understand but otherwise???

author: Refrigerator
author_rank: Super Contributor
timestamp: August 15, 2014, 12:23:10 pm
content: Quote from: Cside on August 15, 2014, 11:39:25 amThe time is the main factor, for me i can make a PCB in three hours from print to soldering the components, but it might take a couple weeks to get them from a fab-house, it's also somewhat cheaper.

author: Cside
author_rank: Regular Contributor
timestamp: August 15, 2014, 01:04:37 pm
content: Quote from: Refrigerator on August 15, 2014, 12:23:10 pmThat is a good reason actually.in that case dont take my chemistry suggestion seriously unless you know what your doing you will probably blow your fingers off.If you cannot source H.peroxide you can make it with ozone. Ozone can easily be made with high voltage so you should be able to construct a colum easy enough.I know of no other known oxidizing agents that have been well tested and readily available. These days anything stronger than table salt is difficult to obtain without signing countless forms and proving you are not walter white or osama.

author: Refrigerator
author_rank: Super Contributor
timestamp: August 16, 2014, 05:44:10 am
content: Quote from: Cside on August 15, 2014, 01:04:37 pmReally? Well, that sucks.Here in Lithuania you can get all kinds of chemicals and no one will ask a thing.

author: akis
author_rank: Frequent Contributor
timestamp: August 17, 2014, 07:22:04 pm
content: Quote from: TheAmmoniacal on May 25, 2014, 08:03:04 amI use ammonium persulfatehttp://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=161014761335&ssPageName=ADME:L:OU:GB:3160Take 1lt of hot water (50C) add a couple of tablespoons of the white powder and you have an etching solution that lasts for a few PCBs. Etching takes place at 50C and is quite slow. Just add hot water and powder when the levels go down.

author: N2IXK
author_rank: Frequent Contributor
timestamp: August 17, 2014, 07:40:25 pm
content: TPTB seem to be making high strength H2O2 harder to find because of the "OMG!! Terrorism!!!" stuff. Useful for producing acetone peroxide, an easily made (but dangerously unstable) explosive compound that contains no nitrogen, and therefore can avoid detection by many explosive sniffers.

author: Refrigerator
author_rank: Super Contributor
timestamp: August 18, 2014, 06:04:02 am
content: Quote from: N2IXK on August 17, 2014, 07:40:25 pmYou mean TATP? I use that stuff to detonate my ANFO.

author: westfw
author_rank: Super Contributor
timestamp: August 18, 2014, 06:15:04 am
content: TPTB == "The Powers That Be"TATP == "Acetone Peroxide"

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 18, 2014, 06:35:48 am
content: TPTB don't like TATP ^

author: skyline_stu
author_rank: Newbie
timestamp: October 06, 2014, 07:29:47 am
content: Haven't used Ferric Chloride or the other persulfates for donkeys years. Why ?FeCl3 is too messy, expensive, hard to clean up, a bit slow sometimes.Persulfates are waaaaaaay too slow for my needs.6% H2O2 and conc. HCl works great in equal volumes (a little goes a long way).Fresh mix etches in about 2 minutes.Gentle agitation is suggested as the bubbles formed can attack your resist.I often do prototypes in 5 thou or less widths. (photographic process).Hardest part in these thin traces is waiting for the photoliths to arrive.Other etchants undercut or have poor edge definition when at this scale.The remaining green solution is a great etchant too, You can let it evaporate to a concentrated liquid or even crystalise it.Next time add a little fresh HCl and peroxide and etch in a few minutes again.If you need to neutralize it, add washing soda (sodium carbonate) or bi-carb soda until it stops fizzing. You end up with a solid copper salt that can be more easily disposed of and salt water.If your solution goes brown when adding the acid and peroxide together, don't worry. It's just iron contamination in the acid - and that acts a like a catalyst !!!Avoid doing this in your room, the fumes will attack you and ANYTHING metal.

author: akis
author_rank: Frequent Contributor
timestamp: October 06, 2014, 09:08:56 am
content: Ammonium Persulphate comes in as a white powder which you mix with tap water. £7 pounds (about $11 USD) for 1Kg of powder to make 10 lt of solution. eghttp://www.ebay.co.uk/itm/1Kg-Ammonium-Persulphate-98-PCB-etch-Etchant-/161014761335?pt=UK_BOI_Medical_Lab_Equipment_Lab_Supplies_ET&hash=item257d3a4777I typically use 700ml in a plastic tub to etch my boards. The plastic tub is stackable, and I place it inside another tub full of very hot water, that allows me to keep the etching solution at 50C more or less.eghttp://www.amazon.co.uk/Whitefurze-Ladies-Shoe-Storage-Pack/dp/B003M2XI84/ref=sr_1_1?ie=UTF8&qid=1412586333&sr=8-1&keywords=whitefurze+boxAmmonium Persulphate is quite safe to use compared to the other etching chemicals. You can stick your hands in the solution and it is fine, you can spill it on the floor, in the sink, just wash away with water, it does not stain. Very easy and safe to work with.Also it will not over-etch, and will not eat into the resists because it is slow, so even after it is done (visual inspection), you can leave it for another 30 minutes and nothing will happen.It is a bit slow (needs about 1 hour at 50C) and it can be even slower if at room temperature but that's the price to pay for the extra conveniences.

author: zagnut
author_rank: Newbie
timestamp: November 08, 2014, 02:31:42 pm
content: my favorite has always been 2 parts 3%peroxide to 1 part 32% hydrochloric acid. cheap, easy to find and works fast without any nasty surprises.i usually mix just enough to cover the board while laying flat and gently wipe the surface with a foam brush.