I'm talking about USB ports and charging ports for laptops and phones. I want to use a cotton swab or a microfiber cloth dampened with alcohol to clean the inside. Compressed air won't do it.
They're connected to a battery but shut off, are these devices safe to have their electrical contacts cleaned with alcohol as long as they are shut off and it won't cause any short circuits or issues? Can I also clean the inside of USB connectors?
are these devices safe to have their electrical contacts cleaned with alcohol as long as they are shut off and it won't cause any short circuits or issues?
Broadly speaking yes. Use care, do not use too much, clean up excess and do not leave undue residue. Practice on an old board. Any cleaning should be done with a large surplus of care.
Wet a soft rag with alcohol and make sure not too wet. Clean with the rag.
I clean connection contacts, potentiometers, oscilloscope contacts and parts, other electric equipment and parts, charger contacts, outside of USB connectors, outside of BNC connectors and so on. Cleaning inside a USB plug needs to be done delicately with Alcohol and a thin cloth.
I have been using Isopropyl Alcohol 70% USP for many years and keep it handy in my electronics shop.
I also use top quality electronic contact cleaner (electronic parts stores) for some contacts (not delicate contacts), model train rails, and so on. I use this on a cloth to clean BNC connectors and USB connectors that I use in my shop (Raspberry PI, chargers and like).
Use care, safe to use, clean up residue, do not apply too much. All equipment OFF when cleaning.
Quote from the instruction manual for a Tektronix 7A29 Amplifier plugin from a 7000 series oscilloscope:
"Avoid the use of chemical cleaners which might damage the plastics. Use a non-residue cleaner preferably isopropyl alcohol, totally denatured alcohol, or a flourinated solvent (trifluoroltrichorolethane)"
It is actually safe to clean circuit boards with plain water. However, before you re-power the board, all water and residue must be removed with no dampness at all.
Alcohol is actually much safer than water because it evaporates faster and leaves less residue. Usually it does not matter if it is 70% or 90% alcohol as long as it is completely dry before it is powered up.
Some older manuals recommend isopropyl alcohol especially for things like magnetic recording heads, as it does a better job of dissolving relevant residues and less chance of rusting the steel surfaces. In this case, 90% or higher isopropyl alcohol should be used.
The only reason to avoid water is if iron or steel is present, in which case there is a chance of rusting, and water should be quickly dried off, but even then, rust is not likely unless the device is soaked or some drops are left behind.
It would actually be OK to power up a board if it had pure deionized water on it as pure deionized water will not conduct. However, water does not stay deionized, and tap water frequently contains enough contaminants to be a conductive electrolyte. In these conditions, water can short out the circuit board in unexpected ways that can damage the board, and even if that is not an issue, its electrolytic properties combined with current between contacts can cause corrosion which can very quickly damage surface mount components. If it is dry when powered, this is not an issue.
Some devices (besides the circuit board itself) could be damaged by water, especially if they are water soluble or there is a chance they could absorb water in a way that it can't be dried. Immersing a board or using excessive liquid (water or alcohol) is not a good idea as many components (like electrolytic capacitors and speakers) can be damaged by any liquid.
For some surfaces (like computer screens), water is actually the recommended method of cleaning, as things like window cleaner can damage the anti-reflective AR coating on the screen. But then, some care must be taken to not allow drips to drain into the bezel where it could collect and not be wiped off.
Chemicals like professional contact cleaner are designed to remove nonconductive tarnish and oxide layers while leaving behind a protective residue on metal surfaces that is still conductive.
