PCB Libraries, Inc. | https://www.pcblibraries.com/Forum/smallest-via-hole-that-can-use-a-3-mils_topic2497_post10288.html
0.15 mm (6 mils). The big issue is the pad annular ring. The fab shop will add 3 - 4 mils to the finished hole size. Then you must consider drill drift and layer to layer tolerance of 3 mil
ORION Industries | http://orionindustries.com/pdfs/kapton.pdf
® is certified to meet the requirements of the military specification MIL-P-46112 B and ASTM D-5213-95 in addition to the items covered by this specifications bulletin
