Re: [CAD_CAM_EDM_DRO] Re: ESD phenomena

Hi Fitch:
That was a really interesting synopsis of ESD and the hidden damage it
causes.
I was totally unaware of this.
I really appreciate the time you took to comment on this; 'twas fascinating.
Cheers

Marcus

----- Original Message -----
From: "Fitch R. Williams" <frwillia@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Tuesday, January 22, 2002 6:03 AM
Subject: Re: [CAD_CAM_EDM_DRO] Re: help with g201 needed


> On Tue, 22 Jan 2002 07:15:13 +0000, Jon Elson <elson@...>
> wrote:
>
> >ESD is fairly rare, and since I live in humid St. Louis, it is
practically
> >nonexistant in the warmer months.
>
> In the sense that this list is in a significant way about building
> things using electronic parts (stepper drivers, servo drivers, signal
> conditioning, etc. for use in home built CAM, CAM upgrades, or DROs), it
> does pay to be careful about ESD, so a few thoughts are probably a good
> idea to provide an ESD framework for those who aren't electronics
> professionals.
>
> The nasty part about ESD damage is that it can cause a latent defect. A
> latent defect is one that is induced now, but doesn't actually have
> detectable symptoms until later when the part fails, possibly after
> being in service for weeks or months, or sometimes years. Most ESD
> failures resulting from a latent defect are never correctly diagnosed.
> The part is just replaced, after some frustration, loss of service on
> the equipment, etc., and life goes on.
>
> It often takes some real determination and a good detective with a
> scanning electron microscope to even identify and confirm ESD damage.
> In my experience real ESD damage, inside a piece of semiconductor
> silicone (buried in the layers of the chip) is not visible optically.
> At least none of what I have seen that is real ESD damage can be seen
> under an optical microscope. Because of where we send our stuff at
> work, and the insidiousness of latent defects which can't be tested out
> in any practical sense, we are really paranoid about ESD damage. And,
> because we investigate every single part failure to root cause (which
> sometimes takes months and thousands of man hours - we don't give up
> easy as some vendors have discovered - they learn a lot from us) we get
> to see it more often than most folks.
>
> Some place I have a lovely SEM picture of ESD damage embedded in the
> side of a cavity in a little diode. Its only a couple of microns in
> size, but it caused the part, and the equipment, to fail. John Devaney,
> a good friend, an SEM wizard (and my instructor on the SEM), took the
> picture at Hi-Rel labs in Spokane, WA. If Nedra could stand the snow,
> I'd probably retire and work there (Hi-Rel) just for fun. Boy do they
> have some fun toys.
>
> The bottom line here is to follow good ESD practice when building up
> your electronics - especially kits and boards not in assembled systems.
> Careful avoidance of ESD damage can avoid a lot of frustration and
> mysterious diseases in electronics such as this list is concerned with.
>
> Fitch