Preferably, {HEAD ~ the larger diameter} of {TAIL ~ the via opening edge portion} at an upper portion of the via includes at most, an upper one third of the via opening depth 
of
Preferably , { HEAD ~ the larger diameter } of { TAIL ~ the via opening edge portion } at an upper portion of the via includes at most , an upper one third of the via opening depth
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH