Mike,
        Your concerns that the device may be loaded and place incorrectly
are valid. If you can paint a small white triangle on the cut corner, the
optics of most machines will likely be able to see the contrast.

        However, the people in the trenches rarely use the orientation
option their machines are capable of.  Its just too much work to tinker with
it.  Invariably, when the option is activated, it will get de-activated at
the first sign of machine part rejection.  The end effect is other options
are used to ensure the orientation of the part is placed correctly. Meaning,
a human being looks at the part.  This decision is generally made by people
who can't personally tinker with the pick and place machines.  (That's a
wide ranging statement that covers 99.99% of the people in a plant).

        I like using all the neat bells and whistles a machine is capable
of.  The technicians don't.  Truth be known, there are many parts that can't
be checked for orientation, either because the pick and place machine is not
sophisticated enough, or, the part does not have any distinguishing
features.  The argument then becomes, if you have to manually check
orientation of one part, why not check them all.  Instructing people which
part are checked by the machine so they don't need to check, and which parts
are NOT checked by the machine so they must check them, becomes too
confusing for any shop with a high turn over of production personnel.
        The end result is it probably is not worth the fight.

Take Care

Ryan Grant
MCMS Inc.


> -----Original Message-----
> From: Michael Forrester [SMTP:[log in to unmask]]
> Sent: Wednesday, May 10, 2000 11:38 AM
> To:   [log in to unmask]
> Subject:      [TN] BGA Design and Pick-&-Place Optics
>
> We have designed a custom BGA device with a symmetrical ball design.  The
> substrate is a dark color and one corner of the device
> is cut off to show orientation.  My concern is that the optics in the
> pick-&-place may not pick up the cut corner due to contrast problems.
> In looking at a display of what the camera saw, looking at the part, the
> outside
> perimeter of the part was barely visible if at all.  I was using
> a MyData My19 machine.
>
> If the tray holding the parts is loaded incorrectly I feel the machine
> will
> incorrectly place the parts.  My suggestion was to add a ball to make
> the design non-symmetrical.  I am getting a strong opposition from R&D to
> add
> the extra ball because of the paperwork involved.  We are still
> in prototype stage of the design and want to correct any problems now
> before
> production starts.  This part needs to be placed using various
> manufacturers machines.  Are my concerns unfounded or should I be
> concerned and
> fight to have the ball added?
>
> Best Regards,
>
> Mike Forrester
> LeCroy Corp
>
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