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1996

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Thu, 30 May 96 19:30:17 EST
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               I totally agree with all who responded to Lou Hart's
          question about legend ink on surface mount pads.  It should
          be unacceptable, and spec'ed out as such.  My company
          standardly clips (removes) any legend ink falling within
          .008" of a solderable feature, due to the tolerancing
          required for the screen print operation.
               I would like to take this conversation one step
          further, however.  Why are we still using silkscreens on our
          circuit boards (other than for hand assembly)?  When the
          board shops clip silkscreen alpha-numerics from solderable
          features, "R"s start looking like "P"s, "B"s like "3"s, etc.
          Board designs are getting tighter and tighter, and there's
          barely any room for this stuff anymore.  Folks are being
          charged an average of $0.50 a side for silkscreens, and now
          with double-sided surface mount, we're dealing with two
          silkscreens, or a buck a board!  It's amazing how most of my
          customers are looking for ways to save pennies on their
          boards, but don't seem to mind shelling out money for
          silkscreens which in many cases are becoming next to
          impossible to read.  I realize that not using silkscreens
          requires a culture change, but more and more of our astute
          customers are taking a second look at whether or not they
          are really needed, and some have taken the plunge and
          discontinued their use.
               I certainly don't want to disgruntle anyone (especially
          inspection folks!), but maybe it's time to evaluate whether
          silkscreens are really of any value, or simply a dinosaur
          from the past.  Thanks for letting me throw in my $0.50!
          Regards,
          Tom Coyle
          Field Services Engineer
          HADCO Corporation



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