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looking for: extremely ESD senistive componets - for demonstrationg safe ESD practices

Discussion in 'Electronic Design' started by Jeff L, Mar 11, 2007.

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  1. Jeff L

    Jeff L Guest

    To help back up the trainings of my employees about the potential dangers of
    ESD, I'm looking for the most ESD sensitive components.

    To be of use, the components have to be:

    1) cheap (they will be destroyed in the demonstration)
    2) easy to obtain (MR heads don't count for this reason)
    3) easy to show some form of functionality (MR heads are also not good for
    this reason)

    The things that come to mind are old CMOS 4000 series logic IC's (the newer
    types seem to be much more robust), small signal MOSFET's (2N700x), or maybe
    a small signal RF MOSFET.


    The intent is to build something like a LED flasher / sequencer, remove the
    said ESD sensitive component, make sure the air ionization is turned off,
    people are not wearing the normal ESD protective stuff (smocks, foot straps
    and wrist straps), or using the conductive chairs or are on conductive
    paint, etc, and have the said component passed around the room. Hopefully
    someone will have a nice furry sweater on, and the humidity will be low. If
    necessary, mount the part on a piece of PCB designed to encourage one person
    to be touching the ground / power / source pins, while the other person
    would first grab the end with the gate or I/O pins / pins exposed.


    Any suggestions on what is the most sensitive component for this
    application?
     
  2. Uwe Bonnes

    Uwe Bonnes Guest


    Don't underestimate Murphy's Law:
    If someting is considered to fail, it will not fail.
     
  3. whit3rd

    whit3rd Guest

    [and demonstrate failure after handling]


    There's a gizmo used by shippers called a 'shockwatch' that
    does this kind of task. Various types are used, like a prestressed
    glass tube of dye, weight-trapped-by-springs, etc. If the
    package to which the shockwatch is attached takes a
    hard bump or fall, the dye stains a card, or the weight dislodges.

    So, I'd think in terms of a power MOSFET with gate floating,
    with a battery/diode to bias D-S to 5V or so, and a fuse in the
    drain (maybe 0.5 A). If the gate turns hard ON, the fuse blows.
    This all goes on a plug-in card with card-edge fingers that
    your testers will be touching or getting near to. Make sure some
    of the touchable metal connects to the battery +5V, if you
    don't want to trust in static.

    Your test circuit will operate from a higher voltage (like, 12V) and
    will
    pass only 100 mA of current in, say, an audio buffer amp application.
    When in-circuit, the diode reverse biases so the battery isn't part
    of the active circuit. When out of circuit, leakage keeps the gate
    turned off (mainly).

    Most modern MOSFETs are gate-protected (I well remember the
    screams from RF designers back in the 1970s when unprotected
    MOS got dropped from the product lines), but this approach doesn't
    require the voltage stress to be outside the normal device range,
    so shouldn't be subject to effective gate-voltage-protection built
    into the MOSFET. The fuses, though, are gonna need replacement.
     

  4. I suspect these are old enough to have static sensitivity issues...

    http://cgi.ebay.com/Lot-100-Motorol...yZ109456QQssPageNameZWDVWQQrdZ1QQcmdZViewItem


    url may need splicing.

    --
    Many thanks,

    Don Lancaster voice phone: (928)428-4073
    Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
    rss: http://www.tinaja.com/whtnu.xml email:

    Please visit my GURU's LAIR web site at http://www.tinaja.com
     
  5. Barry Lennox

    Barry Lennox Guest

    1N23s are very sensitive, but fail badly on points 1 and 2 above.
    I don't know how costly or available the 40673 and 3N140 DG Mosfets
    are these days, but they were pretty easy to damage.

    Failing that, old CMOS should do, the older and cheaper the better.

    I did a few demo/tutorials on ESD a while ago, and while I did not
    damage anything, an electrophorus was great fun and much appreciated.
    I just used it to fire a neon bulb.

    See the IEEE "EMC Education Manual" page 13 for details on it,
    although I did not need the Teflon sheet specified, polythene worked
    fine. You can download it from here:

    http://www.ewh.ieee.org/soc/emcs/pdf/EMCman.pdf


    Barry
     
  6. Genome

    Genome Guest

    Since it matters I would suggest you set up a door.....

    Then you get one of your Mum type employees to play tag with you.

    You go through the door and slam it.

    She says.....

    'Don't slam the door.'

    You go through the door and slam it.

    She says......

    'Don't slam the door.'

    You go through the door and slam it.

    She says in a slightly louder voice....

    'Don't slam the door.'

    You put on a 'pained' face.

    You go through the door and slam it.

    She cuffs you around the ear and says, in a menacing way.

    'Don't slam the door!'

    You say

    'Sorry Mum.'

    You go through the door three times without slamming it.

    Then you go through the door again and slam it.

    She smacks you about the head and screams.

    'Don't slam the fucking door you piece of fucking shit!!!!!!!!'

    Now, this could carry on through your indignant phase but sometime close,
    during or after that point you carry on to explain, properly like, the
    systems you have in place to avoid all that ESD stress in the first place.

    And then you keep on reminding the little fuckers.

    DNA
     
  7. Genome

    Genome Guest

    Sorry, and the other side of the deal is you make sure you give them the
    tools to do the job.

    DNA
     
  8. MassiveProng

    MassiveProng Guest

    You think newer discreet devices are less sensitive? What a loon you
    are.
     
  9. Terry Given

    Terry Given Guest

    laser diodes

    Cheers
    Terry
     
  10. Jeff L

    Jeff L Guest

    Thanks Everyone!

    A special thanks goes to Barry for the link to the "electrophorus" and some
    sensitive part numbers!

    Jeff
     
  11. Barry Lennox

    Barry Lennox Guest

    You will have a lot of fun fooling with it, and determining the best
    combinations of plastic sheet and cloth. Rabbit skin is supposed to be
    well up there, but it was hard to find.

    A few hardy souls in the class were prepared to take a little zap off
    it.!

    Barry
     
  12. Lionel

    Lionel Guest

    I've tried this, & it works fine. You don't even have to touch the
    gate pin to enable it, just waving your hand nearby can switch it on,
    which looks impressive as hell.
     
  13. Lionel

    Lionel Guest

    Oh man, that is one nifty document. I'm going to have to build a few
    of those experiments just for the fun of it.

    Thanks for the link, Barry.
     
  14. Barry Lennox

    Barry Lennox Guest

    I did one of John Howard's courses 4 years ago (He's on the IEEE EMC
    Society Education Committee) and he said they were in the process of
    updating and expanding that EMC manual. It hasn't happened yet, but it
    should be very good when it's done. You might want to check their site
    from time to time.

    Barry
     
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