On Fri, 23 May 2008 01:05:05 +0100, Eeyore
wrote:

....snip.....

Aluminium foil is a BAD idea. In the event that there is any appreciable charge
on a given pin, pushing it into aluminium foil will discharge it *quickly* and

And how would this occur?

Because the ali foil provides essentially a short circuit path.


the resulting current may kill it.

Always use high resistance material for storing ICs like the anyi-static black
foam material. This allows any charge to 'leak' away slowly and safely.

Aluminum foil is fine. The black stuff has a relatively low resistance
anyhow. Check it with an ohmmeter.


The safer practice nowadays is to use high resistance materials,
and NOT aluminum foil, or metal film covered plastics, or that black
conductive foam. The low resistance materials allow fast and high
charge/discharge currents that can vapourize small tracks or
microcircuitry. You should notice that a lot of packaging now uses
those pink bags, and if you check with an ohmmeter, they appear to
have an extremely high resistance. That allows voltages to dissipate
with low (less damaging) current.
The low resistance stuff is used to protect against external
electric fields. If you have both situations, then put the component
in a disipative bag (pink, high resistance), and then put that inside
a conductive pouch, say aluminum foil.
I'm told that you can effectively use the stuff that women commonly
use to control static on their dress clothes. It's a spray can, I
believe the active ingredient is sodium stearate (tallow?). It doesn't
last forever, but for weeks or months it's not bad. There are
commercial products that do a much better job, but you probably won't
find them at your supermarket. It provides a dissipative ilm, and will
not shield against electric fields.
Some of the little plastic boxes are quite evil when it comes to
voltage build up. You can flex one of those boxes, and easily build up
a charge of 200v-2Kv on the inside surface. That charge can induce a
a charge (and voltage) on a pin of a chip inside the box. I hade an
old analog voltmeter with a pastic face, I rubbed the face, and the
meter shifted about 10% because of the induced charge. One year later,
it was still off by 5%. By opening it up and breathing on the inside
plastic, I was able to eliminate the problem. I was really surprised
at how long that charge was held!
The statistics of ESD (Electro static discharge) suggest that the
probability is quite high that no apparent damage will show up right
away, but the component will be stressed, and will not live out its
normal design lifetime. ESD problems are one of the biggest cause of
poor reliability of microcircuitry.
Check this site: http://www.esda.org

-Paul