Hi Mark,

HASL and fiducial recognition turned out to be very proplematic in my past. 
It´s hard to get a proper vision file for all that different appearances. We
typically had to change or optimize the file according to changing light
conditions and board conditions. Maintenance of lightsources and regular
cleaning of lenses are necessary. 
The best and most preferable surface for the fiducials would be a flat and
even surface with good contrast with the surrounding area. With others than
HASL finishes the fiducial recognition is fine.
Does it give you to much trouble leaving the fiducials in bare copper with
your HASL process ?
Ask your customer if he can live with that ....  and ask what in his opinion
the differenceis between your boards and the boards that work fine actually
are, ...are they HASL too ?
Cleaning those fiducials during assembly  with "brushes" or erasers or
whatever isn´t good at all, .... stops the process, requires additional
handling with the risk of contaminations and disturbing your fine printed
paste deposits.

Having the choice of a light scanner for fiducial recognition like we had as
an option made HASL less problematic but sure not without problems.

Wolfgang





-----Ursprüngliche Nachricht-----
Von: Mark Hargreaves [mailto:[log in to unmask]]
Gesendet am: Dienstag, 21. August 2001 13:57
An: [log in to unmask]
Betreff: [TN] P&P can't locate fiducials

Hi All,
We've made boards for a customer for a few years.  They've  been very
satisfied with HASL finish.  Last month they started rejecting approx 40% of
boards received (3 lots) because their P&P camera couldn't locate the
fiducials.  The coating looks typical to us (thickness & smoothness).
Customer can't see any difference between good & bad boards until they're on
the P&P machine.  They say they haven't changed equipment, processes or
operators.  We say the same.  No HASL hassles from other customers in this
time period.  We tried reworking by wicking solder from the fiducials.
Customer rejected approx. 20% for the same reason.  They also say that
boards from another vendor are working fine.
Any comments/ ideas?


Mark

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