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Latent defects from electrostatic discharge,

Discussion in 'Electronic Components' started by N Cook, Oct 16, 2007.

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  1. N Cook

    N Cook Guest

    at or before pcb assembly.

    Does anyone have proven evidence of this and definitely this as cause of
    defect , ie not stress cracking of die, internal bond failures etc. Or is it
    just a convenient label ?
     
  2. Pieter

    Pieter Guest

    Hi, with an electronmicroscope you can check the die. If it was
    destroyed due to ESD, you can see this. A "before and after" foto can
    be found at: http://www.jrwhipple.com/sup_notequal.html

    Also read what they say about AMD.

    Without advanced equipment, it is very difficult to tell the cause.

    Pieter
     
  3. N Cook

    N Cook Guest

    What I fail to see is how the most extreme conditions in the original HV
    discharge can fail to produce any immediate defect but produce a latent
    defect that only becomes a full defect, at some later date, in normal
    service conditions of voltages and currents.
     
  4. Arfa Daily

    Arfa Daily Guest

    I would guess from the photos that I've seen of this damage, that only part
    of an internal structure is blown away such that the manufacturing tests
    don't pick it up as being out of spec in any way. Imagine if a particular
    transistor was designed into the chip to be part of say a clock oscillator,
    and one of the connections to it gets partly blown away due to an ESD on an
    external pin. The connection might now be so thin that under the constant
    stress of the oscillator current flowing in it, it might heat up more than
    it was designed to, until eventually, it fractures and voila ! no clock and
    the chip completely dies. As far as proof of this, I think it has been shown
    pretty conclusively by s.e.m. photos, as Pieter says, that it is a very real
    effect. I seem to remember that some years ago a plane crash, or maybe one
    that was shot down accidentally or something along those lines, was shown in
    the subsequent investigation, to have suffered some kind of navigation
    equipment anomaly, that was caused by an ESD damaged chip. I could be
    telling utter lies there, but I'm sure that something like this is in the
    back of my mind amongst the cobwebs that seem to settle there a little more
    every year ...

    Arfa
     
  5. Smitty Two

    Smitty Two Guest

    Personally, I'm extremely skeptical of the ESD goblin, particularly in
    latency. I think the horror stories have been greatly exaggerated, at a
    minimum. But, I have no scientific data on which to base my skepticism.
     
  6. Al

    Al Guest

    Yes, it really does happen. The leakage current on the input may be
    specified as 1 nanoamp or some other value relevent to the geometry or
    materials involved. An electrostatic dischange that doesn't distroy the
    device may cause the leakage current to jump in the hundreds of
    microamps. This current can be easily suppled in most cases by the
    driving device. However, in such small structures, a phenomenon called
    electromigration can take place. The many microamperes of leakage can
    cause metal migration to take place along the leakage path. Eventually
    it leads to a sufficiently low resistance that the driving source cannot
    supply the current to change the logic state. Then you have a failure.
    It may take days or years depending on many factors.

    Al
     
  7. hr(bob)

    hr(bob) Guest

    After 44 years at Bell Labs, and head of the Bell Labs EMC Committee
    for many years, there are ESD effects at the atom level that lead to
    failures in later times, due to disruption of the normal atomic
    crystalline (SP?) structure. I wish it wasn't so, but it is.

    H. R. (Bob) Hofmann
     
  8. N Cook

    N Cook Guest

    Any idea of failure ratio, due to ESD damage, causing immediate failure and
    proportion due to delayed latent failures ?
     
  9. Al

    Al Guest

    If you Google latent esd you will find about 75000 hits. It sorta hard
    to pick out the relevent ones. Good luck!

    Al
     
  10. Peter K

    Peter K Guest

    When I worked at a computer company,
    if ever a PC came in for Lightning Damage, and the Insurance company
    INSISTED only replacing the damaged parts (instead of replacing the whole
    machine), we put in a disclaimer saying that Latent damage resulting from
    that strike may cause other components to fail later. And Guess What,
    They usually always failed within 3 to 6 months.

    P
     
  11. Well how do you go about repairing a pc thats been hit by lightning??? Just
    replace everything except the case?
     
  12. Surely depends on how direct the hit was. A direct one would induce
    currents that would blow the case apart violently from magnetic repulsion.

    As for damaged parts, I guess the answer is to zap the lot afterwards just
    to keep the insurance company honest.
     
  13. A great way to scam a new HDD or monitor?


    Best regards,
    Spehro Pefhany
     
  14. Peter K

    Peter K Guest

    Insurance would only pay to replace the items that showed physical damage
    (normally modems, PSU's and monitors.
     
  15. Peter K

    Peter K Guest

    I managed to get myself several modems and monitors that were easy fixes
    (normally opto on modem, HOT on monitor, sometimes even fuses on monitors).
    Just cos the insurance didn't want them after the claim.

    P
     
  16. This is why I never pay for insurance.

    And I DO mean never, apart from a brief period a few years back paying for
    life and injury insurance. The whole point is meant to be trust, sharing of
    the load in cases of loss, but the entire industry is founded on profit and
    distrust.

    If a computer worked, then after a nearby lightning strike it does not, and
    can easily be shown as not able to pass a POST or show any other seign of
    life, the insurance company must either accept that they are liable if it
    was insured against lightning strikes, or accept that people are not wrong
    to refuse to accept their'services' and therefore not pay for them.

    I'd rather put my money steadily into small assets than can be easily
    reconverted to cash fairly quickly at a decent rate. I could lose them, or
    my life. So long as I did not lose both, either I, or someone else close
    enough to me, will benefit in some way. The worst case is very serious
    injury combined with loss of all assets. That's very unlikely, and even
    people who get everything 'right' can't immunise themselves against that if
    it happens.

    The whole problem with insurance comes from a situation where people want
    to believe they somehow cannot lose. That, coupled with the fact thet they
    are ALWAYS losing the moment they start paying premiums, is absurdity. It's
    bad enough that we are sometimes forced to do this by law if we want to
    drive or own a house, but there's no point in encouraging it.

    If someone knows electronics well enough to handle their computers and
    other tech stuff, where is the sense in trusting crucial decisions about
    that stuff to people who don't, and whos primary motive is profit, or at
    least retention of what they now see as their assets?

    It's all very well saying that the small amounts from many people cover the
    high cost of unlikely events, but what possible use is that if they won't
    pay out when the shit hits the fan?


    /rant.
     
  17. ehsjr

    ehsjr Guest

    Maybe. But that is not my experience from the early '80's,
    for whatever that is worth.

    We had a major thunderstorm that took out the phone company
    and cable TV company equipment at their offices, and wiped out
    most of the electronics in our neighborhood. I had an Apple II
    at the time, which was destroyed, but with no visible physical
    damage. A bunch of other stuff was killed in my house, too,
    including the cable box and a cordless phone, both of which
    had to be replaced. I fixed the rest, but the Apple was totaled.
    The insurance company required a repair estimate from a local
    repair place. They said it was not repairable, so the insurance
    paid for a replacement PC. I suppose they recognized that there
    was no way they could deny the claim, with all the damage in the
    neighborhood and at the phone company and cable TV offices.

    Ed
     
  18. Guest

    Besides the other causes mentioned in this thread, it's also possible
    (though
    I don't know how commonplace) that the initial strike destroys the
    protection
    diodes (shunts to power and ground) but not the IO transistor itself.
    So the
    circuit functions normally but has no more ESD protection; a
    subsequent
    (unnoticed) static event at lower voltage then takes out the
    transistor.

    TM
     
  19. Guest

    Gallagher on life insurance:
    You're betting that you're going to die - you lose either way!

    TM
     
  20. wrote in
    Nice. Another way of looking at it, the house always wins. Ok, it might not
    be exactly the same as a casino but the similarities are shocking. First
    duty is to preserve the house. Second duty is to honour the winnings of the
    ordinary punter. Third duty is to try to minimise the unusual demands
    especially those which conflict with the first law. Sounds almost as
    simple as Asimov's Laws of Robotics, and it is. Anyone who has really been
    hit hard by injury knows that the insurance people never pay enough to
    cover, the promise is always vastly outpaced by the reality. Most people
    with really severe needs are more likely to be funded directly by the heath
    services as the results of the unusual procedures directly benefit them as
    well as the patient. Agreements like that usually begin after the insurance
    payouts have long since failed to cover.

    It won't be easy in many cases to work out what is the best way to do what
    insurance promises to do, but with the growing problems with insurance
    (another instance made national news on the BBC this evening), people will
    start to keep their money more carefully instead of spending high and
    payting what's left to other people for what amount to promises that can't
    be kept.
     
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