Method of making high density interconnected printed circuit boards with micro-vias filled with copper

The present invention relates to a method of preparing a high density interconnect printed circuit board (HDI PCB) containing micro-vias filled with copper. The method comprises the steps of: a1) providing a multi-layer substrate comprising (i) a stacked assembly of conductive interlayers embedded between two insulating layers having a peripheral surface, (ii) a capping layer covering the peripheral surface of the multi-layer substrate, and (iii) a micro-via, a conductive interlayer extending from the peripheral surface of the multilayer substrate through the capping layer and terminating on the conductive interlayer; b1) depositing a conductive layer on the covering layer and the inner surface of the micro through hole; or a2) providing a multilayer substrate comprising (i) a stacked assembly of conductive interlayers embedded between two insulating layers having a peripheral surface, (ii) micro-vias extending from the peripheral surface of the multilayer substrate and terminating on the conductive interlaye