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Thu, 16 Oct 1997 07:51:33 -0700 |
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On Thu, 16 Oct 1997, Robert Butterworth wrote:
> 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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Robert,
One of our customers has us put the fiducials on the paste mask layer also.
When I asked why, he said they do a half etch, (as Hal said) which allows the
alignment of the paste mask. The paste application equipment can locate the
fiducial even if its a half etch and align to the board, no paste is placed
on the board. I know this is a short answer but it works for them and me...
Scott Decker
Senior PCB Designer
AKA: PadMasterson
E-Mail: [log in to unmask]
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