Julien,
It is not clear whether your pick and place equipment works by moving the
circuit pack on a dynamic x-y table or whether the pick and place heads do
all the moving.  If your system is the former, then why not program it so
that your problem part is placed last so it is not subjected to any of the
sudden stops and starts of the table?  If the part is moving from just the
normal forward movement of the conveyor belt and its attendant slow stops,
then you have a more difficult problem to solve.  One company I know of
solved this sort of movement problem by getting its problem board made with
Precision Pad Technology (PPT) and sticking the part down with a tack flux.
The tack flux was sufficient to keep the part in place, unlike the solder
paste on ordinary boards.

regards,
Bev Christian
XLTEK

-----Original Message-----
From: Julien Bouchard [mailto:[log in to unmask]]
Sent: Monday, September 11, 2000 11:04 AM
To: [log in to unmask]
Subject: [TN] Displacement of PQFP with heat slug


Hi everybody,
        We currently have problems with some PQFP ( 208 and 240 pins ) that
have a
piece of metal mold inside the IC to enhance the thermal exchange. Because
of this metal, the IC is very heavy, in comparaison of other IC. After they
have been place by the pick and place machine, they often move from there
original position when the conveyor start or stop. It seem that the IC is so
heavy, and is inertia is taller than the retention force of the paste. We
try a lot of solution, but none of them give a good and constant result.
        We want to know if someone have similar problem and if a good
solutions
have been found. Thank you.

Julien Bouchard
Matrox - Process Engineer
Email : [log in to unmask]

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