Re: Cleaning Circuit Boards and "Static" rant

--- In CAD_CAM_EDM_DRO@egroups.com, ballendo@y... wrote:

> Mariss,
>
> Not really sure I want to get into this :-)
>
> So are you saying that, based on your experience (of many thousands
> of parts handled vs. product problems) that static control measures
> are unnecessary? Or over-hyped? Or both?
>
> I am willing to learn here, but some of this just doesn't make

sense.

> Am I to believe that the days' conditions (humidity, etc.) which

let

> me "pull" a 1/2 inch spark to the doorknob is of no consequence to

my

> electronic parts?!? Because they have intrinsic protection diodes?!?
>
> Gotta be honest here. This one's hard to swallow!
>
> Surely the several thousand volts of static can impact a 50V

device.

> Even at the infinitismal current?!?
>
> Is this something you can "back up" with documentation. (not a
> challenge, I just would like to know for myself). I'm a science

kind

> of guy. You know, reproducible results, peer review, and all that :-

)

>
> Or is this just an observation, based on your own experience?

(which

> may include EXCELLENT static practice, without you "consciously"
> doing it) Seen THAT with "experts" ALL the time! (ability to make
> the "correct" decision without "thinking" about it.)
>
> Ballendo
>
> P.S. If what you are saying is true, it will really help me! I have
> often "put off" electronic assembly due to weather conditions...

Hi,

Ballendo, thousands of volts only have significance relative to what
is being discussed (gate oxide rupture) only if they work into a very
high impedance. Mentioned was infinitesimal current; gate protection
clamps shunt this current into a low impedance. What is required and
provided is a fast forward recovery response of the protection diodes
and rapid clamping action provided by intrinsic zener diodes. The
infinitesmal current at that point is just that; microamps across a
20V clamping zener. The power levels dissipated are in the microwatt
range, orders of magnitude below what is necessary to cause damage
thermally.

Static discharge sensitive circuits are almost exclusively FET or
MOSFET circuits, and it it those that have these protection circuits.
Bi-polar devices are immune in the sense that an overvoltage will
cause these devices to avelanche, i.e. zener. What matters then is
the joules of energy delivered be sufficient to cause damage
thermally. A 100pF capacitor charged to 30,000VDC having a source
impedance of 2K Ohm (human being) is orders of magnitude short of
that threshold.

Mariss
Geckodrive Inc.