HADCO advocates the removal of what is referred to as
          non-functional pads.  We have not really seen it add
          rigidity to the hole wall.  The reason why we ask for them
          to be removed is because they may detach and "float" during
          the inner layer fabrication process, ending up causing a
          short which would have to be removed when detected during
          the AOI (Automated Optical Inspection) process.  Another
          reason for advocating removal is because of an increase in
          layer counts.  Take a 14 layer with 1 oz. cu. inners and 1/2
          oz. outers.  If every layer had a pad, that would equate to
          drilling through almost .018" of copper!  The excessive wear
          and tear on the carbide drills might actually contribute to
          poorer hole wall quality without the proper checks in place.
          Less drill usage would also equate to a cost adder.  I am
          unaware of any returns from our customers which could be
          attributed to removal of non-functional pads (inner layer
          pads with no incoming traces).  I hope this helps.
          Tom Coyle
          Customer Services Engineer
          HADCO Corporation
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