Structure and method of making a board having plating though hole (PTH) core layer substrate and stacked multiple layers of blind vias. More stacking layers of blind vias than conventional methods can be achieved. The fabrication method of the board having high-density core layer includes the following: after the making of the PTH, the filling material filled inside the PTH of the core layer is partially removed until the PTH has reached an appropriate flattened depression using etching; then image transfer and pattern plating are performed to fill and to level the depression portion up to a desired thickness to form a copper pad (overplating) as the core layer substrate is forming a circuit layer; finally using electroless copper deposition and the pattern plating to make the product.