[time-nuts] Anti-Static conductive foam warning

Joseph M Gwinn gwinn at raytheon.com
Thu Jul 24 14:43:28 EDT 2008

The turning into goo is called "reversion", and is a property of some 
kinds of polyurethane.  There is a good explanation in US patent 4040991, 
and in www.wolaa.org/files/Spring_2007_OHS_-_WOL_In-house_Expertise.pdf . 
It can be difficult to find a solvent for the goo.

As for corrosion causing unsolderability, there is a draconian solution. 
It was a classic story from the 1970s.  We were getting a demo ready for a 
show, and it turned out that the leads on the Nixie tubes had corroded 
enough that they would not take solder.  This is Sunday afternoon.  What 
to do?  I dipped them in dilute sulfuric acid (battery acid cut 3:1), 
rinsed them off in hot water, and then had no problem soldering.  The acid 
dip did not cause subsequent problems, although one could have also used 
dilute bicarbonate of soda to neutralize any traces of acid that survived 
the hot rinse.

Joe Gwinn

time-nuts-bounces at febo.com wrote on 07/24/2008 01:38:45 PM:

> Hi Nigel
> I've seen this happen in some other circumstances too, and one of the 
> ones was for VNA Cal kits.  It really makes a mess, and it's 
> pretty hard to clean up.
> I'm wondering if anyone else who's seen this problem has some advice on 
> good way to restore the items. 
> It does seem that there are several types of foam (and rubber for that
> matter)
> Daun
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of GandalfG8 at aol.com
> Sent: Thursday, July 24, 2008 1:12 PM
> To: time-nuts at febo.com
> Subject: [time-nuts] Anti-Static conductive foam warning
> Apologies to those who might see this on more than one group or list and
> apologies again if it's old news to everyone but me, but I did think it
> important enough to share.
> I've just retrieved a pair of ICs that have been dry stored as 
> spares in a
> component storage rack since 1979, a long time I know but probably not
> unusual for those of us using and maintaining older equipment.
> These, as I thought anyway, were correctly stored with the pins pressed
> into black anti-static foam, the usual stuff that's been used for this
> purpose for years.
> Unfortunately the foam has broken down into a sticky crumble and the
> plating on the IC pins is quite badly corroded, probably to the
> point  where
> they won't take solder. A metal canned crystal lying against the foam 
> also corroded at the pont of contact.
> I've seen this stuff turn into a gooey mess inside some instrument cases
> but hadn't previously even thought about the same thing  happening where
> it's used used for component storage.
> I've checked other trays and whilst not too many used this 
> stuff but  where
> they did there's evidence of similar problems.
> I've even got a later large component rack, all ok so far but for how
> long?, where it was fitted from new to every drawer:-(
> That's all, just offered as a word of warning to anyone else with
> components similarly stored.
> regards
> Nigel
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