IR oven and rework station are little different:
(1) enough said about IR oven
(2) rework station normally got heater (hot plate type with program for
example) to heat up 120 C and IR provide top surface localized heat at
the chip location to 180-200 C range.  Since IR is tranmitted by silicon
(in theory at least), you will do minimum damage to the part.  You can
remove the part (provide you heat up the solder joints properly) but
push off at the chip location.   The rest of the board will still remain
120 C.
Hopefully, nothing is encapsulated when you need to do the rework....
(you do need experience and hopefully, the layout is got enough area for
you to do so without damage the assembly)
Good luck.
                                                              jk

>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]] On Behalf Of Kathy Kuhlow
>Sent: Tuesday, January 07, 2003 5:51 PM
>To: [log in to unmask]
>Subject: Re: [TN] Rework Station
>
>
>Interesting that you bring up old IR ovens and how this is
>just like the first IR ovens.  Anyone still using theirs?
>What  caused most users to stop using IR to begin with?  Could
>these technology be coming back, could grainy joints be the
>norm again?
>
>I have seen and used both the Airvac and the Metcal stations.
>The biggest issue I had with the Airvac is the nozzle heights.
> Sure it was good enough for Surface Mount processing but
>forget it if you were replacing a BGA from a test failure.
>The adjacent part heights limited the use of the equipment in
>any rework/replacement situation after surface mount.  The
>Metcal is a good station vision system is easy to use.  Seems
>fairly user friendly.  I think the board handler/rails could
>be beefed up.  Nozzles seem to have a bit more height to them
>for later rework needs.
>
>Also I wouldn't blame the operator for ripped pads and traces,
>unless you have undisputable training evidence.
>
>Most operators look for reflow or attempt to lift the part to
>see if there is reflow.  Get a machine that has the ability to
>store programs and a vacuum pick up so the operators don't
>guess.  I have done large package rework for 15 + years, I
>have trained 30 some operators in rework and always damage
>comes from the operator wondering if the part is ready or not.
>
>Kat
>
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