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