Hi Mike,

I know this is a one month old question, but finally I got to browse through
my e-mail. Easy thing, about 400 letters.

Since I didn't see any answer to your problem, I'll try to suggest
contacting Cyberoptics. They make a coplanarity checking tool. We have one
on our most recent Fuji IP3. It is mounted at the back of the table. The bad
part is that it only checks one side at the time, so the inspection goes
like: camera, coplanarity side 1, 2, 3, 4. It takes time! So it is not a
tool you can use to check 100% all your QFPs.

But maybe there's something more performant available.
And you're right about the cause. One important factor is also the operator.
If he drops the tray while setting it in the machine, the parts will jump
from their locations and the nozzle will force the leads.

Good luck,
Ioan

> -----Original Message-----
> From: Mike Lang [SMTP:[log in to unmask]]
> Sent: Monday, August 21, 2000 10:11 AM
> To:   [log in to unmask]
> Subject:      [TN] Coplanarity Screening and Root Cause
>
> Two items:
>
> 1) I recently found defects at test on one of my products which uses a
> 0.025" pitch PQFP.  The defect was one entire side of the device had all
> except the outer 4 leads (two per end) uniformly formed above the normal
> seating plane.  Knowing that this was not the work of a random human thumb
> I set out to find the cause.  I found that I could duplicate the effect if
> I took a part and instead of centering it in the pocket of the matrix tray
> (these parts are received in standard matrix tray) I had is slightly
> offset the part in the pocket and pressed the upper tray on top of the
> assembly.  This would bend the leads as In mentioned above.  My suspicion
> to date is that the part was slightly offset and then vacuum bagged in
> this condition, resulting in the damage.  This may have been attributable
> to the supplier, or to us if the tray was resealed.
>
> Another possibility is that the part got miscentered while it was being
> placed into into the placement equipment and bent when the nozzle came to
> pick, although In am not sure if the forces could be high enough.
>
> Has anyone been down this path before???
>
>
> 2) It has been touched upon in the past, but In would like to ask more
> directly.  Does anyone know of a currently available piece of equipment
> which In can put into my SMT lines (Fuji and Siemens) which will allow me
> to screen for co-planarity issues.  In want to eliminate the problem at
> the root, but this tool will give me a better chance of identifying the
> problems which is difficult since they tend to be low occurrences and
> random.
>
>
> Thanks!
>
> Lang

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