TOM,
        I USED TO WORK AT A COMPANY, (NOW DEFUNCT), IN WHICH WE DID NO 
     SILKSCREEN BOARDS.  IF YOU HAVE A CAPTIVE ASSEMBLY SHOP OR A CLOSE 
     WORKING RELATIONSHIP WITH AN ASSEMBLY HOUSE IT'S GREAT.  BUT..... IF 
     YOU GO TO THE CHEAPEST HOUSE OR RANDOM HOUSES, (WE NEVER KNOW WHICH 
     UNTIL AFTER THE FACT), YOU'LL BE RECEIVING HOURLY PHONE CALLS.  AS 
     OTHERS HAVE STATED A SILKSCREEN ON A PROTO BOARD IS PRETTY HELPFUL TO 
     THE TECHS, ESPECIALY IF YOU HAVE A LOT OF ODD FORM COMPONENTS SUCH AS 
     WIRE WOUND XFMRs, INDUCTERs ETC.  HOPE THIS HASN'T CLOUDED UP THE 
     ISSUE TO MUCH.
     
     ROB BUTTERWORTH
     SR PCB DESIGNER
     ADC VIDEO SYSTEMS,
     MERIDEN, CT
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______________________________ Reply Separator _________________________________
Subject: RE: FAB:    Silk-screen ink on surface mount pads
Author:  [log in to unmask] at internet-mail
Date:    5/30/96 8:16 PM


               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