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

[Tristan]

Hi Julian,

If you are concerned about static then you should always try to keep
ICs in their antistatic tubes, antistatic bags and/or in antistatic
foam (usually black or pink). Do not store them loose in plastic
drawers or in white polystyrene foam! Some people spray polystyrene
foam with a conductive coating or cover it with foil but these are not
a good solution as the high conductivity can be a problem if a static
charge is applied.

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. It is the high voltages typically involved in
static discharge, combined with a path of low conductivity, that leads
to high currents between the IC pins and damage to the circuit inside.

For best protection you should also use an antistatic bench mat where
you are working and an antistatic wrist strap. The antistatic mat
should be grounded to your electrical earth through at least several
Meg ohms and your wrist strap should be connected to the mat or ground
through several Meg ohms as well. Synthetic clothing and shoes can
also generate or allow the build up of static charge on your body, as
can walking across synthetic carpets etc.

In the electronics labs where I work all benches and flooring have
antistatic coatings and we are required to wear antistatic shoes or
heel straps while working in the lab. The benches and equipment racks
also have antistatic wrist straps to use when handling boards and ICs.
Despite all these precautions I have still seen boards destroyed by
careless people taking off synthetic clothing.

-- 
Best regards,
Tristan                            mailto:tu at alphalink.com.au

Thursday, May 29, 2008, 10:07:41 AM, you wrote:

J> Im having a bit of a tidy up at the moment, and have a load of ICs to deal with .

J> Most of my other components are stored in draw things, a bit like this -

J> http://www.toolspecial.com/images/550_3.jpg

J> but evrey time i order any ICs at all now, they seem to come in
J> anti-static bags as standard.... so thats got me to wondering
J> if i 
J> should worry too much about all this in storage?

J> Somthing ive also wondered - in a conductive bag, surely if theres
J> an issue with static, without proper grounding, the whole
J> lot get 
J> 'zapped' insted of just individuals?  As you may have gathered, i
J> dont know much about this... ! : )

J> Julian