Removing surface-mounted ICs

From: Clint Wolff <vaxman_at_uswest.net>
Date: Sat Jun 10 10:42:40 2000

On Fri, 9 Jun 2000, Mark wrote:

> Hi,
>
> Thanks for the several helpful replies on this topic.
>
>
> On Wed, 7 Jun 2000 Clint Wolff wrote:
> > I would recommend against putting the board in an oven. This will
> > result in the entire IC getting too hot, and possibly breaking.
> > Modern plastic package absorb a small amount of water from the air.
> > Heating the part may result in a small steam explosion. ICs are
> > shipped from the factory in sealed bags with some desiccant inside.
> > The label on the outside says to solder them down within a fairly
> > short time after opening (couple days IIRC).
>
> Ah, I have read about that.
>
> IC manufacturers often specify a procedure to use when chips which may have
> absorbed water are to be used. This involves baking at low temperature for a
> while.
>
> Assuming that (for the purposes of removing absorbed water) one plastic IC
> package is the same as the next, at which temperature and for how long should
> this baking be done?
>
> The lowest setting on my oven is 70 degrees C. If that is low enough -- I
> guess it should be as most ICs are specified for operation to 75 C or so -- I
> may try putting the board in there for 12 or 24 hours, before turning the
> temperature up to melt the solder.
>
>
> -- Mark
>

Hi Mark,

I don't know. I would be concerned about heating the entire chip up
to a high enough temperature to melt the solder. You are almost
certainly going to damage it. Most ICs are specified with specific
temperature profiles to avoid damage, and they are only above the
melting point of solder for a few seconds, followed by a fairly
lengthy cooldown period. You need to quickly melt the solder,
remove the IC, and let it cool down slowly. I don't think this is
possibly in an oven.

clint

PS the offer stills stands to use the hot air equipment at my
workplace. I regularly remove 208 pin SQFPs and occasionally
reinstall them :)
Received on Sat Jun 10 2000 - 10:42:40 BST