PTH PCB holes for maximum COOLING Shipco Circuits Ltd 2013
Drill holes 0.5 mm (finished approx. 0.4 mm). Swap X&Y in example as required.
Drill first a row of holes in X with pitch 0.7 mm, not less to obtain minimum 0.2 mm substrate between holes.
Then drill 2nd row like the first but offset 0.6 mm in Y and offset half the X-pitch in X, and drill one hole less than first row.
Then repeat above with pitch 1.2 mm in Y as many times as required.
Copper plate holes 0.25 um min, more if feasible but not less!