Don,
I don't know of any standard regarding the shape of the fiducials. What I
know is that the vast majority of the machine manufacturers recommend round
ones. For global fids, you may want to have a diameter of 0.060". 0.050" may
be OK, but stay away from the 0.040", since they are approximately the size
of VIA pads, which may confuse the machine if VIAs are close to the fid.
Whereas HASL, it's a hassle. I never worked with your machines, but I sure
did with a many not so high end ones. My experience says that solder on the
fids is a problem, but, if the programmer is willing to spend some time
adjusting the lighting level, he could always come up with a good setting.
Spending a few hours experimenting with the vision can give a general rule,
a setting that would make a relaible reading no matter any bump or hole in
the solder deposit.
A bigger problem is the inconsistency of the solder mask between different
batches. This gives funny reflections, so you may want to make sure you have
the same solder mask, once the programming is finished.
Hope this helps, Ioan
> -----Original Message-----
> From: Steffen, Don E [SMTP:[log in to unmask]]
> Sent: Friday, September 24, 1999 3:09 PM
> 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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