Andre,
At my former company, I did quite a bit of testing on the feasibility of
32 mil pitch QFPs and some 25 mil pitch QFPs.  The source that I began
with was a Philips Semiconductors IC Package Databook 1995 that provided
the starting point for the solder thieves.  The critical aspect of the
thieves is the spacing from the trailing land pattern.  My suggestion is
that you work with your CAD layout folks and create a test board with
multiple patterns that are different from one another.  On the topic of
wave parameters, dual wave is preferred and you should experiment with
the wave(s) heights to determine the optimum settings.  One other point
of note is to pay close attention to the adhesive and the dot pattern.
 The dots should be balanced about the centroid of the device land
patterns else skewing may occur during cure and will give you false
indications that your wave parameters are providing shorts.

Steve Sauer
Senior Manufacturing Engineer
Xetron Corporation
Cincinnati, OH
513-881-3368

 ----------
From:  Andre Bisson[SMTP:[log in to unmask]]
Sent:  Wednesday, July 08, 1998 7:45 AM
To:  [log in to unmask]
Subject:  [TN] Qfp's in wave

Hello All,

I will like to know if some people ever did some test with qfp's on
solder
side going in the wave.

We have to do some test with 20 and 25 mils pitch at wave. I already did
some test, placing the component at 45degres with solder thief, but the
result were questionable. I saw some short. For now I did some test on
just
few boards so the wave profile and parameter are not realy define. My
question will be more on faisability and shape of solder thief and also
some guideline for wave parameter.

If some people can help me I will be greatfull.

Thank you.

________________________________

Andre Bisson
Process Engineering
Matrox Electronic Systems
Tel.: (514) 969-6000 Ext: 2462
E-mail: [log in to unmask]
________________________________

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