25 Jul
2012
25 Jul
'12
1:40 a.m.
On Wed, 25 Jul 2012, Dave McGuire wrote:
In this case it didn't turn to goo (or it has passed that stage by the
time I got them). When I went to remove the components from the foam, the
foam crumbled away and with it went the badly corroded IC leads. If I can
find where I stuck those ICs away I should see about getting a photo.
Luckily none of those parts were all that "rare" or uncommon.
On 07/25/2012 04:06 AM, Tothwolf wrote:
It isn't 100% ESD safe because it isn't shielded. This is why many
electronic component distributors will still put parts that are in foam
inside an anti-static bag.
So you mean the lack of the Faraday effect?
Right.
Being *too* conductive is not ESD safe. The idea is to
let the charge
drain away slowly. If a charge drains too quickly, it can induce a
charge nearby that might not be protected, like something internal to
a component.
So that black (carbon-impregnated) foam used for ICs isn't ESD-safe
becasue the resistance is only a hundred ohms or so per square inch? A word of
caution with black ESD foam... In the late 1990s I obtained a
bunch of 1960s logic chips stuck in black foam that had begun to break
down and it attacked (and literally corroded away) the IC leads. For
this very reason I prefer to store ICs in tubes vs conductive foam for
long term storage.
I've had this happen too. It makes quite a nasty mess, and whatever
ooze the foam turns into is very corrosive.