hole is formed vertical circuit paths or plated through holes pth 39 s can be utilized to connect circuits on different layers to components mounted on the board for instance dc voltage from the power plane 18 may be delivered to components by one pth and signal logic from circuit layer 14 may be delivered to components by another pth holes in printed circuit boards are typically on the order of 0 25 1 0 millimeters in diameter and may be utilized for electrical electrical mechanical or any other purpose required on the circuit board in fabricating a printed circuit board the layers are connected together typically with an epoxy resin or the like and then the necessary holes are drilled through the circuit board and then the holes are plated with copper it should be recognized that while this preferred embodiment is directed at printed circuit boards the invention can be applied or utilized in any operation where a substrate or bulk material is being drilled it should likewise be recognized that the term 34 drilling operation 34 is to be interpreted broadly as any hole boring operation including but not limited to laser drilling punching milling etc fig2 depicts the printed circuit board 10 of fig1 with a thermal sensitive film 22 placeable on the surface of the circuit board 10 pursuant to this invention thermal sensitive film 22 may be placed on either surface of the circuit board 10 or between any of.