Charles Barker@IO-US
10/16/97 08:39 AM

1. I would expect the paste to throw off the vision sytem in your PnP
equipment when it tries to zero in on a paste-covered fiducial that has
normally been taught when it is clean.
2. I can't see any useful purpose for solder on fiducials. Your SMT process
folks will probably want to take someone's life for saddling them with such
a problem!

Sounds like your board shop either has new people running the show, or they
have managed to lose the "recipe" for building usable boards.

Good luck,

Charlie B.



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Subject:  [TECHNET] SOLDER PASTE ON FIDUCIALS




     HI,
        WE HAVE AN ISSUE HERE THAT NEEDS SOME CLARIFICATION.  WE'VE BEEN
     BUILDING FIDUCIALS FOR 4 YEARS NOW THAT HAVE NOT HAD SOLDER PASTE ON
     THEM (NO RELIEFS IN THE PASTE MASK).  NOW OUR VENDORS, (YES THE SAME
     ONES WHO HAVE BEEN BUILDING THE BOARDS FOR 4 YEARS), ARE SAYING THAT
     THEY'VE ALWAYS PUT SOLDER PASTE ON THE FIDUCIALS.  THE FIDUCIALS IN
     QUESTION ARE GLOBAL BOARD FIDUCIALS.
        MY QUESTIONS ARE;
     1. WON'T THE SOLDER PASTE, (PRE-REFLOW), LACK CONTRAST/REFLECTIVITY?
     2. WHAT PURPOSE DOES SOLDER PASTE SERVE ON THE FIDUCIAL?

                                        THANKS,
                                                ROB

     ROBERT BUTTERWORTH
     CAD DESIGN ENGINEER<-----WHAT THE HELL IS THIS?
     ADC BROADBAND COMMUNICATIONS
     11 FAIRFIELD BLVD
     WALLINGFORD, CT 06492
     203-630-5755
     [log in to unmask]
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