[sdiy] Storing ICs (and static sensitivity) - how much to worry?

[Mike I]

Aluminum foil not ideal ( and  solid aluminum antistatic tubes were once
used  ), but a bit of resistivity  is supposed to help... by limiting
discharge currents into IC pins when they are put into the rail or
antistatic bag, if the pins and the bag / rail are at different potentials..
M.



----- Original Message -----
From: Needham, Alan <Alan.Needham at centrica.com>
To: Tristan <tu at alphalink.com.au>; <synth-diy at dropmix.xs4all.nl>
Sent: Thursday, May 29, 2008 9:05 AM
Subject: RE: [sdiy] Storing ICs (and static sensitivity) - how much to
worry?


>
> I have a big problem with this explanation, even after inserting the
> supplied correction.
>
> An antistatic bag may measure a few hundred kOhms from corner to corner,
> I do not believe that this is enough to slow down any charge front, and
> if it did, it would result in the very thing you are trying to avoid -
> pins at significantly different voltages.
> As I understand it, the packaging attempts to provide some form of
> Faraday cage around the device; no matter what static voltage is
> applied, all the pins need to be maintained at the same potential, even
> if that is 1000's of volts above ground. Aluminium foil would be ideal
> IF you could guarantee a connection to every pin.
>
> ~~~Snip~~
> The materials used in antistatic bags and foam etc are conductive but
> have a relatively low conductivity. If you touch the antistatic
> material when you are statically charged the charge spreads through
> the material slowly, thus only producing a small local differential
> between pins on ICs.
> ~~Snip~~
> It is the high voltages typically involved in static discharge, combined
> with a path of HIGH conductivity, that leads to high currents between
> the IC pins and damage to the circuit inside.
> ~~Snip~~
>
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