Static is [not] your friend - vacuuming PC?

" In terms of static, how safe is it to clean inside a home PC by using a vacuum cleaner? "

IMO it's still not safe at all. Buy a can of compressed-air from an electrical hardware store.

Static can be caused by the brush bristles. Use compressed air instead.

Using a vacuum cleaner in a PC, or any electronics devices using CMOS technology is not safe at all. It does not matter how well everything is grounded. The fact of having a motion contact using device that uses an insulating material can cause a static build-up. You can read up on static electricity generation for details.

Even handling the circuit boards under some conditions are at risk for damage from static electricity. Most of the appliances of today, such as TV's, radios, VCR's, DVD's, and many other types of devices are using CMOS devices. Great care should be taken when handling these devices. I have seen units damaged from improper handling.

The proper way to clean any electronics equipment is to use filtered compressed air. The unit and the operator of the compressed air must be in contact to each other in reference to the unit's ground plain (metal case for example), to prevent any potential difference between them.

The compressed air blown from a distance of at least 6 to 10 inches will give no effect to build up static charges, and cause any problems with the device being cleaned.

DON'T DO IT

By leaving the PC grounded you are giving static a perfect path from the vacuum, through your parts, to ground... GREATLY increasing the risk of damage.

Use compressed air!

The web page descriptions are indeed fairly funny, if you know what they are talking about. But I highly suspect anyone with a limited background in Electro Static Discharge will be more confused than not.

Yep. Quite a lot.

*Moving* *dry* *air* around is a great way to build up a static charge on any component that is an insulator.

Hence *compressed* *dry* *air* and *vacuum* *cleaners* are not good ideas. In fact, compressed air might be worse because it can forcefully blast dust into places it wouldn't otherwise go.

If you get enough charge (a few thousand volts, for example, is common), it will then break down the insulation between the charge and the next nearest object that is either also holding a charge or is able to dissipate the charge (e.g., a conductor). The current flow when that happens is what kills your computer. And it isn't just that specific current, but also any current induced into other conductors as a result of that current.

The way to get the dust out of a computer case safely is to use a damp rag to manually pick up dust. It shouldn't be so wet that it drips moisture (though that isn't necessarily bad either, see below), but needs to be damp enough that dust will stick to it and static cannot build up on it. I personally prefer to have a large bowl of water mixed with a little household cleaner (such as 409 or Mr. Clean), in which the dust rag (a well worn bathroom wash cloth or a thin dish towel, is nice) is washed as it get dirty. The soapy water in the bowl should be changed somewhat regularly too, i.e. when it gets so dirty that as much dirt moves from the water to the rag as from the rag to the water!

Which type of soap to use does make a difference. The idea is something that will dissolve any grease film or other coating that might be present, but even more important is that it be a good water dispersant. Automatic dishwater soap is perhaps the best in that respect.

Note that there aren't many things which can actually be damaged by water itself. Disk drives or CRDOM/DVD drives (things with moving parts) can be damage by water. But keyboards and motherboards can be totally immersed in water without damage. Any time that a system is *really* dirty, or is taken apart for other reasons, it makes sense to literally wash the device in a kitchen sink with a solution of soapy water, and then rinse it off with a water spray if you have one of those handy spray hoses meant for cleaning dishes.

If the water supply is very hard (filled with minerals) and will leave a residue, use a final bath of rubbing alcohol. Otherwise a very dilute solution of automatic dishwater soap is probably best. (It will leave a very thin film of water dispersant, loaded with water, on everything. That will help protect against static and it will also reduce dust build up because of reduced static build up.)

After such a dunking it takes considerable time to be sure that the water has dried completely. In places where the humidity is low that will happen in a day or two anyway, so just put it on the shelf and wait. Otherwise one method is to use a kitchen oven on warm, leave the door partially open and put the device inside the oven for several hours.

But *don't* use compressed air, vacuum cleaners, plastic brushes, or synthetic cloth to clean a computer. And don't do it on a day when the relative humidity is 10% either.

Aaaakkk! No! Dishwasher machine soap (Cascade) is one of the nastiest cleaners I know. Full of trisodium phosphate, silicates and calcium hypochlorite. Perhaps you mean dishwasher anti-spot filming agent (JetDry). This stuff should be very benign when diluted.

Anybody have any good experiences cleaning IBM Model "M" keyboards in a (soapless) dishwasher?

Well, I guess in AK you have to worry about the latter :)

I'm less worried about compressed air than I am about vaccuum because compressed air nozzles are easier to ground and less likely to contact parts. Static can build up from moving gas past parts, but the parts should drain that small amount away. It's bigger (perhaps still invisible) discharges that cause trouble.

-- Robert

Yep, that's a bad one. Another good wetting agent is Photo Flo, sold by the gallon for darkroom use (or in smaller quantities at exorbitant prices).

Depends on where. E.g., humidity in Arizona, New Mexico, and west Texas is low. It is in the Alaskan interior too.

The current relative humidity here is 70%, and that is typical.

"Moving gas" is probably one of the *worst* offenders (next to cats and walking on carpets), and is exactly what is wrong with using a vacuum cleaner. There is no difference between that and compressed air, as far as static goes. Grounding the nozzle is not useful, other than to prevent a direct discharge from buildup on the nozzle itself. And it is *not* reasonable to expect either small or large charges to drain harmlessly away from components.

The whole concept of using moving air is a disaster plan!

Of course, if the relative humidity is 50% or above... the chances are fair that no damage will be done. If it is more like 6%, either use full protection or you *will* get bit. (I lived in Fairbanks for a couple decades, where at -40F in the winter you can almost be assured that the relative humidity inside any building that does not have a humidifier will be well below 10%. You don't need a carpet! Just the wrong shoes or shirt will be enough...)

Avoid all static problems by using a grounded wire brush .

EXACTLY, though I usually get away with using a dry paint brush when compressed air isn't handy. There is slight potential for static but I've never had any damage result.

What do you consider "nasty" about Dishwasher Detergent?

I mean, what harm do you expect?

I have cleaned a LOT of boards in a tub of warm water and detergent (dishwasher or whatever was handy) with a paintbrush, it does a great job and the boards worked fine afterwards, still do. Two important things to do though, are removing the battery and EPROM first. Of course it's also necessary to _completely_ dry the boards, including water wicked under chips and in sockets, which can take a few days or gentle heating.

Machine detergent. The pH is around 12 and there's chlorine. This will cause corrosion of copper and perhaps solder.

Hand dishwashing detergent is much less corrosive than the automatic machine variety.

-- Robert

Yeah-there's no real reason you need to vacuum your PC.Long before you have damage from dust, you will be upgrading to a new PC (say 5 years, which is a moderate life span for an ordinary PC0luck or unluck this can be up to 7 years).Before dust will reach dangerous levels, critical components should fail first.It's not a good idea to open your PC just for cleaning, though.My vendor told me these things.

-- Dimitris Tzortzakakis,Iraklion Crete,Greece major in electrical engineering-freelance electrician FH von Iraklion-Kreta, freiberuflicher Elektriker dimtzort AT otenet DOT gr Ï "Sammo" Ýãñáøå óôï ìÞíõìá news:958F7E6A631A81A7D4@204.153.244.156...

For what it's worth... Bob Pease, a respected designer at National Semiconductor and author of a number of very useful books including "Troubleshooting Analog Circuits", swears by the use of a dishwasher for cleaning PC boards especially for high-impedance, low-leakage circuits. He mentioned the use of a "standard load of Calgonite" as the cleaning agent... run 'em though the wash cycle, take out after the rinse, shake off excess water, and allow to air-dry.

Pease comments that after this sort of treatment, leakage currents across the board surface were often lower than could be achieved using an expensive commercial solvent-based PC-board-washing system.

For what it's worth, the Calgonite MSDS lists sodium tripolyphosphate, sodium silicate, sodium carbonate, and sodium sulphate. No hypochlorites.

In my area (Mountain View, Silicon Valley, fairly hard water) I'd probably do a final rinse by hand using distilled or deionized water, to prevent mineral deposits from developing ("hard water" spots). An anti-spot sheeting/filming agent might eliminate this risk, or might not... haven't tried it.

Not significant for short-term exposure, in a dilluted bath. There should be minimum if any copper exposed on a board to begin with.

Perhaps but it also isn't as good at cleaning. Boards washed in dishwasher detergent came out looking BETTER than brand new, even new boards have some residue/flux/etc that the detergent removes. I don't recommend leaving a board to soak in it though, generally I submerge them and they're done within a few minutes or less.

It depends a lot on the environment. Too often we assume queries are only related to home PCs but these days almost any business has some too.

Your vendor likely told you not to open it to minimize risk of user-induced problems within the warranty period. They expect a system to keep running for that period and don't care as much about longer-term effects. It is a good idea to open and clean a PC at whatever interval is dictated by the environment. Often "cleaning" doesn't mean getting every little spec of dust out, simply checking the primary fans and heatsink(s) for buildup.

You might as well use a vacuum cleaner. It isn't any worse, and it is a whole lot easier.

Actually, a "dry paint brush" might be the *worst* thing I've heard of yet!

*Any* *dry* *insulator* is bad news. Two pieces of paper rubbed together are bad. One of the worst offenders is putting tape of any kind onto a static sensitive circuit board, and then removing it. The potential generated when a one inch strip of tape is peeled away is just horrendous.

Here's a chart that I found at

They say the data comes from "AT&T ESD Control Handbook-1989".

TYPICAL ELECTROSTATIC VOLTAGES

EVENT RELATIVE HUMIDITY 10% 40% 55%

Walking across carpet 35,000 15,000 7,500 Walking across vinyl floor 12,000 5,000 3,000 Motions of bench worker 6,000 800 400 Remove DIPs from plastic tubes 2,000 700 400 Remove DIPs from vinyl trays 11,500 4,000 2,000 Remove DIPs from Styrofoam 14,500 5,000 3,500 Remove bubble pack from PCBs 26,000 20,000 7,000 Pack PCBs in foam-lined box 21,000 11,000 5,500

The immediate point that comes to mind is how much difference relative humidity makes, and how something you've commonly been doing at 70% relative humidity might just blow away everything if you do it on a day when the humidity is only 10-20%. Look at "Motions of bench worker"!

Funnily enough, this is the correct answer!... You can get brushes, with conductive bristles, and a grounding 'tag', that attaches to the standard fittings used on electronic benches, for exactly this purpose. On a workbench, with a grounded surface, and filtered extraction, it allows you to 'de-dust' CMOS components before servicing, and is standard equipment on a lot of service benches.

Best Wishes

It may seem that way to you but I've noticed static buildup from vaccume but not from the brush.

Let's put that in context though... You have a DIP in a tray, or a PCB in a foam-lined box... are you supposed to just leave it in the box because removing it would generate static??? Of course not.

If you don't want to use a paintbrush, fine, but I've been doing so for years and NEVER had a problem. I am not recommending anything in particular though, there is no cleaning method that is foolproof but one suggestion you made to use a damp rag is about the worst thing imaginable, because it will leave a gross-looking mess everywhere, as if the board were left out in an alley during a thunderstorm and debris washed up all over it. If there is enough dust that it really needs cleaned, a damp rag is just going to make a huge mess... been there, done that, found a better way.

A static charge from the vacuum cleaner can STILL jump to the exposed computer circuitry, even with the computer turned off. The computer being grounded makes no difference. Don't do it. Use a can of compressed air to BLOW the dust outlike everyone in the business does.