In a message dated 8/17/98 8:03:45 AM Pacific Daylight Time, [log in to unmask]
writes:

<< The IPC document IPC-SM-782 states that a fine pitch component must have
 local fiducials added at the component level.  I would like to know what
 deteremines "Fine Pitch".  Is it anything that is 25 Mil pitch and
 below, or is it anything below 25 Mil pitch...what is the true
 definition of "Fine Pitch"?

 Thank you >>

Good Day!

        I would consider fine pitch anything 25-mils or below, but does that
really require local fiducials? It's been my experience that nowadays local
fiducials really aren't required...at least not until you start getting down
around 15.7-mils or so, and I've always used them on BGA, just out of habit I
guess...but they probably don't need them either. The folks in the bare fab
business are just making the boards too good nowadays!

The requirement for locals came from back when the bare PCB quality wasn't
what it is today...I have yet to run across a board that has shrunk or
stretched to the point that reading globals wasn't sufficient to give me good
placement...maybe I've just been lucky and not run across any real flakey
boards.

-Steve Gregory-

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