the drilling and plating of high aspect ratio blind via holes in a multilayer printed circuit board are disclosed . a via hole is drilled through a sub - composite structure . the walls of the via hole are plated with a conductive material , and the hole is filled with a conductive medium . the sub - composite structure proceeds through the remainder of the processing that is necessary to manufacture the printed circuit board up to the completion of the solder mask step . the conductive medium of the via hole is drilled out to achieve a hole size that is of the desired diameter as required by the printed circuit board design .