Bob Axtell wrote:
> I've been told by a vendor or two that semis can also absorb moisture thru
> their tiny cases. This makes a case for PCB coatings, which we used to do
> years ago frequently.


A couple of months ago, I ordered some samples from National.
I'v done this before, and I always got them in a sticks
in standard (soft) envelopes. This time *one* of the ICs
was sent in a sealed plastic bag, with one of these anti-
moist things "SIEVE PAK(tm)" together with a small
thing with three circles that would turn pink
at 5, 10 and 15% rel humidity. And there was a separate
document attached with instructions and recomendations
about "baking" the ICs before mounting/soldering
if the marks had turned pink. This was "ADC12138" in
normal "SOIC-WIDE" packing :
http://www.national.com/pf/AD/ADC12138.html.

So, for *some* reason, these chips seems much more
sensitive to humidity then all other chips *I* have
seen so far...

Jan-Erik.

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