Don :

        What is the best shape of fudicials relative to size and
configuration?

        Normally I've seen circle with 1mm dia ( 40 mils )



        Also if the board has HASL on all of the pads, can the fudicials be
of different
material other than HASL?

    By the process I believe is not usual unless they mask the fiducial
before HASL but this can be cost add to the board.




        We are having a problem with reflective light causing a lot of
rejected boards. This is also causing down time. What is
        the industry using for this technolgy. We have DEK 265 printers and
Philips
        and Siemens placement machines.

            Normally fiducial are tought to machine using a gray scale
level. Up 255 levels are accepted by the vision system, there is a treshold
level that determines what is black and what is white. This value is keep
recorded with the machine like a reference for all other fiducials. When the
machines load the board and target the fiducial, basically it's compared the
image with the reference value, sometimes when you change a batch of boards
or use old boards from stock you start facing recognition problem. One
solution could be re-teach the fiducial using one board of the new batch in
this way you will keep one reference more compatible with this new batch.
Using eraser to clean fiducial sometimes is effective but requires more
labor.
           By the other side vision system has been upgraded to suport
better HASL fiducial, there is lightning conditions to avoid shadowing
effect caused by irregular surface. My Philips machines ( Topaz and Emerald
) are capable to reduce "noise" from fiducial image, using diferent light
spot ( they call inner and outer filters ), also you can see at monitor what
the vision system  is really "reading" from the fiducial and give you
information about center position, perimeter, etc...


        I hope this help .
Jorge Dourado de Santana
Maintenance / Process Engr
Microtec - Brazil












> -----Original Message-----
> From: Steffen, Don E [SMTP:[log in to unmask]]
> Sent: 24 de Setembro de 1999 16:09
> To:   [log in to unmask]
> Subject:      [TN] Fudicial Shape
>
> Technetters
>
> What is the best shape of fudicials relative to size and configuration?
> Also
> if the board has HASL on all of the pads, can the fudicials be of
> different
> material other than HASL? We are having a problem with reflective light
> causing a lot of rejected boards. This is also causing down time. What is
> the industry using for this technolgy. We have DEK 265 printers and
> Philips
> and Siemens placement machines.
>
> Donn E Steffen
> Senior Quality Engineer
> VDO Control Systems
> Auburn, IN 46706
> Phone (219)925-8887
> Fax (219)925-8710
> Email: [log in to unmask]
>
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