On Sun, 12 May 2002, Drew Vassallo wrote:

>I noticed that the "absolute maximum storage temp" for many PICs (and other
>chips as well) is 150 deg. C.  But, if I check the reflow specs for SMD
>solder paste, the range goes up to 225 deg. C for at least 30 seconds or so.
>
>Anyone know if it's safe to hold this temperature for longer than 30
>seconds?  What does the "maximum storage temperature" really mean?

It means that at that temperature irreversible changes occur in the chip
and/or package, if it is maintained indefinitely (more than tens of
minutes at least).

>Will the chip get damaged if I put 250 deg. C on it for a minute?

Not likely. But you may have to preheat SMDs and other chips to avoid
cracking. Follow the soldering temperature profile given for that package
by the manufacturer as exactly as you can. If you do not have a profile,
request one. You can then tweak as necessary by a small amount. One minute
is a bit long. Dwell time at reflow temp. is at most 20 seconds in my
charts. However the part will spend a considerable time nearby (slightly
under that temp.).

Peter

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