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Static is [not] your friend - vacuuming PC?

Discussion in 'Electronic Components' started by Sammo, Oct 27, 2004.

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  1. Sammo

    Sammo Guest

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

    Some people like this website suggest that it is unwise.
    http://www.dansdata.com/sbs3.htm

    If my PC is switched off but remains earthed (to the mains earth) and
    I am careful not to do physical damage to the PC with my home vacuum
    cleaner, then surely there is no problem with static?

    Am I overlooking something?

    Sammo

    --
     

  2. Electrostatic discharge can produce some intersting effects
    on semiconductors and the risk shouldn't be discounted.

    However I have cleaned out the interior of countless cases
    with no apparent ill effect- using a soft haired paintbrush
    in one hand whilst hovering over the area with the nozzle of
    a domestic vacuum cleaner in the other. Due to the nature of
    the job, one hand or both is in contact with the case most
    of the time and so there is little chance for static build
    up on the nozzle/your body/brush. Touching the case before
    introducing the brush is a good idea.

    Personally, I prefer to have the case sat on an esd mat to
    leaving it plugged in - not so much from the static point of
    view but a marked reluctance to work on anything with power
    on or connected, unless unavoidable (like, I don't have the
    mat with me).

    Not to be done to a laser printer, but for other reasons.
     
  3. Cuzman

    Cuzman Guest

    " 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.
     
  4. Static can be caused by the brush bristles. Use compressed air instead.
     
  5. Jerry G.

    Jerry G. Guest

    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.

    --

    Jerry G.
    ==========================


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

    Some people like this website suggest that it is unwise.
    http://www.dansdata.com/sbs3.htm

    If my PC is switched off but remains earthed (to the mains earth) and
    I am careful not to do physical damage to the PC with my home vacuum
    cleaner, then surely there is no problem with static?

    Am I overlooking something?

    Sammo

    --
     
  6. Noozer

    Noozer Guest

    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!
     
  7. 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.
     
  8. 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
     
  9. 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...)
     
  10. CBFalconer

    CBFalconer Guest

    <facetious>
    Avoid all static problems by using a grounded wire brush <g>.
    </facetious>
     
  11. kony

    kony Guest

    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.
     
  12. kony

    kony Guest


    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.
     
  13. 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
     
  14. 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.
     
  15. Dave Platt

    Dave Platt Guest


    What do you consider "nasty" about Dishwasher Detergent?

    I mean, what harm do you expect?[/QUOTE]

    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.
     
  16. kony

    kony Guest

    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.
     
  17. kony

    kony Guest

    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.
     
  18. 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

    http://www.esdsystems.com/training/staticgeneration.htm

    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"!
     
  19. 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
     
  20. kony

    kony Guest

    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.
     
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