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I'm an electrical engineering and I hope you can give me some advice as I'm not much into chemistry. I'm trying to start making my PCB (Printed Circuit Board) at home but I'd like to have some advice concerning how to handle and where to store these (potentially dangerous) chemicals.

I need NaOH as a developer, hydrochloric acid + hydrogen peroxide as etchant (they should be a better alternative than Ferric Chloride) and isopropyl alcohol (to make soldering flux).

As far as I understood I need:

  • Glasses (to protect against vapors and splashes)
  • Gloves (to protect when mixing the chemicals)
  • Some kind of protective clothes (not sure if I need to, but obviously I'm not wearing nice clothes when doing etching)

I have a few questions though:

  • Do I need kind of mask / filter (to put on my nose) - are these vapors dangerous ?
  • I read gloves should be stored in quite cold locations and not be exposed to sunlight. Does that apply to the chemicals listed above too ? I'd like to store them outside but maybe it's not safe ...
  • Hydrochloric acid comes in 36% concentration but I think I'll need to dilute it to 1%-5% max. After it has been diluted it should be quite safe, isn't it ?
  • Is it safe to store them inside a house (as long as it's well ventilated) ?
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6 Answers 6

You probably don't need a mask - vapours from hydrochloric acid can be a little noxious, but if you're diluting it down and using it in a reasonably ventilated area, you shouldn't get much of that. Isopropyl alcohol vapour is toxic like most alcohols, but I don't think an ordinary mask will prevent that, and you'll be better off just making sure you have enough ventilation.

Standard white cotton labcoats are inexpensive and can be quickly removed if you spill a nontrivial quantity of something on them.

Hydrogen peroxide will probably come in an opaque container, but if not, it does break down in sunlight. Everything else is pretty stable to light, although you want to avoid storing the alcohol somewhere that's going to get too warm, because it evaporates readily and can pressurise the container more than is a good idea.

All these materials are pretty safe to store indoors in unspecialised storage, although for commercial purposes or quantities you may need to take regulatory precautions that will obviously vary by locale.

Edited to add: The copper chloride that comes out should be regenerated as many times as possible, but when you eventually end up with too much of it, you'll want to already have thought about what you're going to do with it - it's pretty toxic and you can't (or, well, shouldn't) just wash it down the sink.

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Thank you for your reply. For highly diluted chemicals (lots of water and a bit of chemical) there is almost no problem then. However - the non-diluted chemicals can be stored - with their container tightly closed - inside a closet or in a cellar? And what about the after-etching products (I know I should put them in a box similar to those of these chemicals and dispose of them properly, but do I need to keep this inside as well ?). Thank you. –  user51166 Jun 20 '12 at 18:46
Furthermore does any of these chemicals have a sort of "Expire date" after which they'll be no more useful or something ? I ask this because I'd get a quite big supply if I can. Small supplies costs a lot more per liter ... –  user51166 Jun 20 '12 at 18:51
Most substances have an expiration date printed on the container. You can also inquire about that when purchasing. –  Ben Norris Jun 20 '12 at 19:17
Also note that you should NEVER store strong acid and strong base next to one another. They create a lot of heat when they mix. If you are storing them on the litre scale you should get a proper fire resistant chemical storage cabinate, one for each acid and base. –  Canageek Jun 21 '12 at 4:35
@Canageek: even if they're in their container they cannot be stored one next to the other? What kind of fire resistant cabinet for instance (any recommendations)? –  user51166 Jun 21 '12 at 4:44

A few additions:

shelf life

  • $\ce{H2O2}$ won't last forever, not even in the dark and cool
    edit: if it is stored cool and dark, and does not get contaminated, it will last for some years. However, the degradation is catalyzed by metal ions (famous: $\ce{Mn^2+}$) and bases ($\ce{OH-}$), so the problem is that once it gets contaminated (there is stabilizer added, but that of course won't last forever and cannot prevent every type of degradation), it will degrade rather fast.

  • the isopropanol must be kept tightly closed to prevent evaporation (the container it comes in is usually good),

  • but $\ce{NaOH}$ (pellets in tightly closed plastic container) and $\ce{HCl}$ (glass bottle with plastic cap) can be kept for years without problems.

Storage of NaOH

  • $\ce{NaOH}$ is deliquescent (very much hygroscopic).
  • $\ce{NaOH}$ also reacts with $\ce{CO2}$ from air to $\ce{NaHCO3}$ and $\ce{Na2CO3}$. The corresponding reduction in base equivalents is not going to hurt you much, but the carbonate can form a crust at the lid of $\ce{NaOH}$ bottles. You should not store $\ce{NaOH}$ in glass stoppered glass bottles as opening them becomes very hard and finally impossible with the carbonate crust.
  • ($\ce{NaOH}$ is also directly corrosive for glass, but not much)
  • Overall, it is best to store the $\ce{NaOH}$ pellets in plastic bottles (they usually come stored this way) and prepare frequently small amounts of solution.
  • You can also store the $\ce{NaOH}$ solution for a while in a tightly closed plastic bottle.
  • How frequently you need to make fresh $\ce{NaOH}$ depends: If you use the $\ce{NaOH}$ in an open bath daily, it won't last as long as if you just need it every few weeks, and meanwhile it is stored away from fresh air. I believe your application is rather robust wrt. the real $\ce{NaOH}$ concentration, so you can probably reuse the $\ce{NaOH}$. On the other hand, preparing the solution is really fast & easy: take the water, count the needed number of $\ce{NaOH}$ pellets into it and let them dissolve.
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So the biggest problem would be hydrogen peroxyde. Any idea how long it should last about (like 1 year, or 1 month), as an order of magnitude ? And best pratices for storing HCl and NaOH in solution ? I don't think I can put them on my shelf in the living room though :D. –  user51166 Jun 21 '12 at 19:30
More accurate would be "NaOH is deliquescent" (so you'd better keep it in a watertight box or you'll be left with slush) –  ManishEarth Jun 22 '12 at 3:58
@Manishearth: thx, new English word learnt :-). Watertight usually isn't a problem if it has to be air tight, too. –  cbeleites Jun 22 '12 at 15:22

Reactive chemicals should be stored in chemical storage cupboards to prevent fires. I've attached an example of the type of cupboard we use in my lab to give you an idea of what I am talking about. We use an under-fumehood model, but freestanding models are avalible. Acids and bases should not be stored together. MSDS sheets from the manufacture may specificity additional constraints on which chemicals can be stored alongside one another. Note that hydrogen peroxide is a strong oxidizing agent; Do not store with oxidizers is a common constraint. Consider contacting your local fire department or the chemistry department of a nearby university for advice on the safe storage of chemicals.

Note; While I'm not endorsing them, I know that Fisher Scientific provides a range of chemical storage cupboards of this type, and has information on which are good for acids, corrosive chemicals and flammable solvents.

Example chemical storage cupboard

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Thank you. I have to look if I can find some inexpensive and not too heavy containers for this purpose. I see Fisher Scientific's are >3000$ for a small one. I don't have that kind of budget at home. –  user51166 Jun 22 '12 at 5:42
  1. Meh, personally I'm not worried about the vapours. You'll be sane and be doing this in an at least somewhat ventilated space, right? Don't do anything outright stupid, but also don't fear the substances so much that your defences cause you to trip and break a toe. $\ce{HCl}$ and $\ce{NaOH}$ aren't exactly harmless, but they're not dimethyl mercury either. There are loads of each of those ions in your body, but as another answer mentioned, $\ce{NaOH}$ doesn't play nice with eyes. (It also turns the oils in your skin into soap, but that's generally not a lifetime liability.)
  2. Like others have said, hydrogen peroxide won't like light. It develops oxygen, so storing it in a gas-tight container in conditions where it's likely to decompose, could cause trouble. I'll get back to this later.
  3. You might want to keep your acid undiluted. If you dilute it, etching can become slow.

AFAICT, you want polyethylene containers throughout. I wouldn't go with glass as a dropped glass container doesn't simply harmlessly bounce off the tiled floor like a plastic container does. I guess a polypropylene ice cream box would work as an etching bath too, but IIRC polypropylene doesn't like the acid all that much (but I haven't tried, and it might well be good enough.)

By all accounts I can find, you really, really want to keep the used etchant - it'll become a cupric chloride solution (which you may have to regenerate occasionally either by aerating or adding hydrogen peroxide). That means you have yet another storage problem. This is no longer pure $\ce{H2O2}$, so you have to think about where the evolved oxygen goes. And if you let the evolved oxygen vent, hydrogen chloride will also vent, attacking any metal nearby. The electronics people have tales of ruined tools sharing a garage with etchant solution. I've resigned myself to keeping the etchant indoors (in my kitchen in fact! where the cost of damaged stuff is least) which is at least better-ventilated than my garage.

And whatever you do, don't pour the beautiful blue cupric chloride down the drain. It'll eat your sink and bring forth chemical armageddon. Don't water your garden with it either, as it's a herbicide. I guess that leaves the options of making it someone else's problem (pay someone to dispose of it for you), or use it to electroplate something with copper, using an inert (not just more copper) anode. Plate faster than the solution etches.

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Storage considerations for chemicals are often noted on their Material Safety Data Sheet, or MSDS. All suppliers that I know of include a MSDS in the packaging when they ship chemicals. You can find lots of good sources of free MSDSs online through Google. Just google "Hydrochloric acid MSDS". I would look for one that appears to come from a reputable source, such as a commercial supplier.

As an example, I have linked the MSDS for concentrated HCl from Fisher Scientific. Section 7 of this MSDS is titled "Handling and Storage".

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Thank you. I though these MSDS were quite "universal" (I saw on Google there was a large site containing all documentation about dangerous materials) - not specific to each fabricator. Would sodium persulfate be safer to store than hydrochloric acid by the way ? –  user51166 Jun 20 '12 at 19:31
Each manufacturer is required to provide them by law. They will almost always have the same information; I just use Sigma-Aldrich's sheets. –  Canageek Jun 21 '12 at 4:34

For handling $\ce{NaOH}$ always use goggles (I know myself a case of a student that lost some 15 years ago her vision in the accident with $\ce{NaOH}$. In case of acid you'll get burn but with a bit of luck it will pass). In the case of even a diluted solution of a strong base, your eyes are gone.

The other thing: check your gloves for the chemicals the cover. The usual latex gloves cannot protect against bases perfectly; nitrile gloves (usually bright blue) are much better in this case.

Karen Wetterhahn had gloves on her hands when she worked with dimethylmercury solution. However, she didn't know that this compound goes through a latex in the blink of an eye. Of course, none of the compounds you have mentioned are that dangerous, but it's your health.

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Thank you for your precious suggestions. Exactly what kind of goggles? Yeah I thought nitrile gloves are better (found a pack of 100 on farnell for a good price). –  user51166 Jun 22 '12 at 5:35
Different labs I've been in use different types of goggles. Standard lab safety glasses are fine for \$5 by most people's count, but for some things I do prefer my (less comfortable) \$15 goggles that fully seal my eyes in. –  Canageek Jun 22 '12 at 20:51
@user51166: (Standard lab safety glasses are made from polycarbonate, just so you know what to look for.) –  Aesin Jun 22 '12 at 21:05

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