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I have access to these

  • isopropyl alcohol
  • ethyl alcohol
  • vodka
  • rum
  • acetone

And would like to know which ones should be used to clean electronics, and (out of curiosity) why some are worse choices than others?

Brian Harris
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    Acetone may dissolve some plastics, but it's not going to melt them. Melt refers to a phase change from solid to liquid. No other substance need be envolved. Dissolve is when individual molecules of the substance (the solute) diffuse into a liquid (the solvent) such that the result is still a liquid. – Olin Lathrop Jan 01 '12 at 18:03
  • http://www.merriam-webster.com/dictionary/melt - Note "usually", not "necessarily" – JustJeff Jan 06 '12 at 13:15

4 Answers4

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I would start with clean (distilled or de-ionized) water over any of those. Most ordinary dirt can be cleaned off with water well enough. Make sure whatever you are cleaning is unpowered, and don't power it back up until you are sure it is dry again. Most electronics using VLSI components are safe to immerse in clean water, but SMT electronics especially with chipsets and things that have mechanical components are notable exceptions. The water will go under the chipsets because it is using the space between the pcb and the chipset as a capillary and gets stuck under it. The liquid will not dry and even if it does after some time it will leave a certain amount of corrosion under it which may lead to a change in resistance including a short.Some of these electronics include anything that is a bit smarter than your lightswitch like buzzers, relays, watches, microcontroller controlled electronics, and anything in a housing where water might get in but have a hard time getting out again.

While extra clean water is a good idea, even ordinary tap water is good enough for most cases. The advantage there is that it's cheap and available, so you can afford to have new water flow over whatever you are cleaning. Washing with tapwater and rinsing with clean water is fine too. That will rinse away any of the crud that tap water might leave behind as a thin residue.

Next I'd use isopropyl alchohol. In fact, I keep some of that around the office, along with some cotton swabs. It can dissolve some solder fluxes that plain water can't. Otherwise, observe the same precautions as with water. Remember that it's probably 30% or so water anyway.

Ethyl alcohol would probably work similarly, although I don't have personal experience with it.

I would stay away from vodka, rum, and any other ethanol with extra stuff in it. If you have to go that route, moonshine is probably better because it's basically ethanol and water with little else. Still I wouldn't trust any liquors due to them containing stuff that may not evaporate and therefore be left behind.

I wouldn't use acetone at all unless I was sure the specific component it comes in contact with is rated for that. Acetone can dissolve various things that could cause trouble.

More about dissolving:

I think what I've said is clear enough, but since it was accused of being misleading I'll get into it a little more.

Dissolving is a process where individual molecules of a substance (the solute) diffuse into a liquid (the solvent) such that the result is still a liquid. Salt dissolving in water is a example we've all encountered. This is different from a slurry where small particles of some substance are suspended in a liquid. The particles are still many many molecules in size and are generally large enough to settle out after a while, but this is a digression anyway.

Some types of plastic dissolve in acetone. Some electrical components are in part made of such plastic. Therefore washing boards with these components on them in acetone can cause harm.

If this plastic were submerged in acetone long enough, it would eventually all enter solution (dissolve) and be rinsed away with that solution. The act of dissolving (molecules leaving the solid plastic structure and diffusing thru the acetone) takes time. Obviously this can only happen at the boundary between the solid and the acetone. That boundary moves further into the solid as the outer layers are dissolved and swept away. In this case, the solid doesn't just suddenly go from pristine to dissolved immediately at the boundary layer. Some of the acetone diffuses into the solid a bit, which "loosens" it, which makes it easier for the loosened molecules to dissolve, which also makes it easier for more acetone to diffuse further into the solid.

If this process is not allowed to complete, then there will be some part of the solid that is diffused with acetone where the molecules have loosened, but are still somewhat linked to each other and therefore not truly dissolved. This part becomes much weaker mechanically so that it can easily deform, from light touches, moving acetone, or even just gravity. Acetone is quite volatile, so after it is removed the molecules in the transition region of the solid diffuse out and evaporate. The molecules of the solid can then link to each other more tightly, making it mechanically stronger again. This causes it to re-solidify in whatever shape it was deformed to when weak.

True dissolving is not really a chemical reaction. I don't know whether acetone also reacts chemically with some plastics or if it's just dissolving action. The fact that the plastic re-hardens after the acetone is removed suggests it is not chemically altered, but I don't know that for sure.

Nissim Nanach
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Olin Lathrop
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    From my experience with 70% ethanol, I must say that it isn't too good at removing flux residue. – AndrejaKo Jan 01 '12 at 21:30
  • Why the downvote? As I said, I didn't have experience with ethanol so how it would work was only a guess. I believe I can defend everything else I said. – Olin Lathrop Jan 02 '12 at 13:31
  • I didn't down-vote. – AndrejaKo Jan 02 '12 at 15:38
  • I've removed obsolete comments. – clabacchio Oct 07 '14 at 11:17
  • I just looked at the label for "70% Ethanol" in the local drugstore. Also contains acetone and other ketones. I'd suggest using it quickly or not at all (don't let boards soak in it...) – rdtsc Mar 12 '15 at 15:39
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    Note: do not use water on transformers unless they are dipped (and even then still remove them first.) Reason being, water will wick into the windings and take a very long time to evaporate, even if baked. I've seen transformers fail from being wet - don't do it. – rdtsc Jun 20 '19 at 14:58
  • The drugstore isopropyl alcohol I encountered was not close to pure. I think it was 70%. I presume the other 30% is water. Do makers in practice use distilled or deionized water? If not then is there any reason why it may not matter? I am aware that 99.9% purity is available but I would have to go to an electronics component retailer for that (less convenient). I want to clean a SO-DIMM memory that stopped working after a spill of bottled drinking water. – H2ONaCl Sep 27 '19 at 15:49
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I'm going to disagree with Olin on the use of water -- although it may be effective in removing dirt and water-soluble flux, it takes time for the water to evaporate and you shouldn't use the device until it does.

I recommend isopropyl alcohol. It comes in bottles or cans at 99% concentration, evaporates very quickly and cleans the PCB nicely. You can either apply it and then remove it using a piece of fabric (cover the PCB with the fabric and use a brush to push the fabric onto less accessible spots), or you can rinse the PCB in it.

Ethanol works fine too, if you can't get your hands on isopropanol.

Acetone dissolves polystyrene, which is used on some components (usually connectors). Things that you solder onto the PCB and are therefore meant to be heated will usually resist acetone. I used to use acetone a lot in the past for PCB cleaning and had no problems (and I like the smell).

Vodka and rum will leave residue on the board. There are better uses for these substances.

avakar
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    I agree water takes longer to dry, which is why I said *"don't power it back up until you are sure it is dry"*. That doesn't make water unusable, just take longer. Washing with water, sometimes even with detergent in it, is a normal part of most board manufacturing operations. In fact, I've seen some shops use ordinary dish washers for this. A long time ago at HP, we used to spec boards had to be washed "with Calgonite or equivalent" dishwashing detergent. – Olin Lathrop Jan 02 '12 at 13:44
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    @OlinLathrop, I'm sure it makes sense in manufacturing (I guess it's much cheaper :) and also due to pipelining you don't waste time drying the boards), but for OP's purposes I'd say water is not the best fit. – avakar Jan 02 '12 at 14:14
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    You could rinse it with isopropyl alcohol after washing it with water. – Brad Gilbert Jan 06 '12 at 18:34
  • Or use an air compressor (or canned air). They both work very well. Canned air is completely dry, and air compressors certainly dehumidify the air somewhat, considering all the water that fills their pressure tanks on a regular basis. – Connor Wolf Jan 08 '12 at 11:10
  • I also wouldn't use water. Not on a PCB anyway. I cleaned a keyboard with water (the keys...not the electronics) and even though I put the wet keys in the Sun for hours, used compressed air, etc. I STILL found drops of water inside the keys. And the keys don't have tiny holes either. It takes a lot more work to use water. Cheaper...yes. But like most things..cheapness often means more work. – cbmeeks Jul 25 '16 at 20:48
  • @cbmeeks It sounds like you didn't use water properly. Drying in a 140 ℉ oven for 20 minutes will vaporize all remaining moisture and won't melt thermoplastics. Allow to cool to room temperature for another 20 minutes before use. – dhchdhd Aug 30 '17 at 16:23
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    @Barry I've since changed my mind on using water. In fact, I now prefer distilled water and dish soap to clean really dirty PCB's, keyboards, etc. I just make sure to allow enough time to dry and I typically put them in some type of airflow. Preferably outside. – cbmeeks Aug 30 '17 at 17:32
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    @cbmeeks, to be honest, I also started using water since the time I wrote the answer :) – avakar Aug 31 '17 at 12:07
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Are you trying to :

  • Clean dirty electronics

or

  • Clean the flux from newly-assembled electronics.

The answer will vary depending on which you are attempting to do.

If you are trying to clean electronics that are dirty in the common use of the term (e.g. they have dirt and/or dust on them, I'd reccomend a vacuum, before you start trying solvents.

If you really do need to wash the electronics, and you are cleaning dirt, or miscellaneous sediment, water is probably the best bet. Some gentle physical scrubbing (use a soft brush) and some soap will help tremendously.

A light solvent (like isopropyl alcohol) could be used, if water does not suffice.
Also, isopropyl alcohol can be used to rinse boards that are already wet with water. It will displace the water, and result in a faster drying time.

On the other hand, if you are trying to clean flux, that's an entirely different ball-o'-wax.

If this is in production, the best thing you could do would be to contact your solder manufacturer. They will be able to tell you exactly what you need to most efficently clean their flux.

On the other hand, if this is just for personal use, you have a lot more latitude.

Personally my favorite method for doing this is to try a bunch of commercial flux-removers, pick one I like best, and look up the MSDS. From that, you can generally make your own.

Personally, I find a ~50-50 mix of acetone and methanol works very well. The threat of acetone melting things seems to be very overblown. I wouldn't dunk a whole assembled product in acetone, but I haven't had any issues just scrubbing the assembled boards with it. The worst I've seen it do is discolour some connector a little.

If I were making thousands of boards it would be another story, but for prototyping, it works very well, particularly for some of the more aggressive fluxes.

Connor Wolf
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  • By contrast, properly mass-manufactured SMT PCBs need almost no cleaning because of flux stencils. OTOH old, water-damaged boards usually have corrosion, gunm and/or burns. – dhchdhd Aug 30 '17 at 16:28
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isopropyl alcohol - 100% isopropyl is a great circuit board cleaner not drinking

ethyl alcohol - just as good and isopropyl not drinking

vodka - good for drinking with juice

rum - good for drinking with coke

acetone - not good for circuit boards, nor drinking, it dissolves certain materials

Dakarai Jordan
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