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ESD damage and relative humidity

Discussion in 'Electronic Design' started by garyr, Jul 26, 2013.

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  1. garyr

    garyr Guest

    What is the likelihood of ESD damage occurring if the relative humidity is
    100%?
     
  2. Syd Rumpo

    Syd Rumpo Guest

    About 4.3%, or 100/(e^pi) as a first good approximation, although
    bilateral effects caused by Cauchy scattering have some effect in areas
    of significant frombulism.

    Cheers
     
  3. DaveC

    DaveC Guest

    What is the likelihood of ESD damage occurring if the relative humidity is
    Don't know about 100%, but:

    http://esdsystems.descoindustries.com/whitepapers/wp_humidity.html

    Remember that junction failure isn't the sole possible outcome of an ESD
    event. Weakening ("degrading" in ESD parlance) of junctions will shorten
    operational life, not evident immediately after an event.

    3M has a nice handbook:

    http://www.digikey.com/Web Export/Supplier Content/3M_19/PDF/3M_StaticCont
    rolMeasures.pdf?redirected=1

    I've not found a 100% RH voltage value anywhere.

    With polyester carpet, I think even underwater you could get a healthy shock!
    (c; <<<- note smiley

    Dave
     
  4. Guest

    Pretty low. Unless there is an electric eel nearby.

    Matt Roberds
     
  5. John S

    John S Guest

    So, it was the tepid water they objected to?
     

  6. Chilly water makes for more turgid nipples.
     
  7. Guest

    You should be able to model the situation with your circuit connected
    by a variable resistance to a charged capacitor. Some of the charge
    will bleed to nearby ground planes, while the rest goes to ESD
    sensitive parts.

    With a constant voltage source (say 10 kV) connected to the capacitor
    a few cm from the device, the maximum constant leakage current can be
    calculated.

    Alternatively, charge up the capacitor and let it discharge through
    the resistance and get the RC time constant for different distances.

    If a charged finger moves towards the device at constant speed, the
    resistance drops rapidly, discharging the human body model capacitor.
    How low does the voltage drop just before contact ?

    Some interesting data can be found with Google search expression like
    "moist air conductivity" (with quotes). It appears that the air
    conductivity will increase with at least two orders of magnitude, when
    going from dry to moist air.
     
  8. John S

    John S Guest

    They objected to the nipples or the turgidity? We need to get to the
    root of the problem. Or something.
     
  9. Guest

    Soldering, or mechanical assembly? There are places *I* never want to
    feel a drop of hot solder and I am sure ladies have similar concerns.

    Mechanical assembly might be OK as long as you don't mind occasionally
    losing washers and stuff down the tub drain, and having to replace rusty
    hand tools.
    They wanted naked old people instead?

    Matt Roberds
     

  10. Blame Milla Jovovich. OMG! They're full of milk!


    DAMNIT, Janet! *I* wanted to marry her!

    We'll never find out now! She'll probably never sport those torpedoes
    in a flick again. It is truly a sad day. :-(

    (just kidding)
     
  11. Jasen Betts

    Jasen Betts Guest

    That depends if you go out in the rain or not

    Raindrops are often electrostatically charged.
     
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