A method of manufacturing at least a portion of a printed circuit board, the method comprising: attaching a plurality of sub-assemblies (100, 100') with each other after processing at least one of the plurality of sub-assemblies (100, 100'), wherein each of the plurality of sub-assemblies (100, 100') comprises a plurality of circuit layers, and the processing of the at least one of the plurality of sub-assemblies (100, 100') comprises: forming at least one hole (110, 310) having a first diameter and a first depth from a first side of the at least one of the plurality of sub-assemblies (100, 100') and into the at least one of the plurality of sub-assemblies (100, 100'); metalizing the at least one hole (110, 310); applying a lamination adhesive on the first side of the at least one of the plurality of sub-assemblies (100, 100'); applying a protective film on the lamination adhesive; and removing the protective film to expose the lamination adhesive on the at least one of the plurality of sub-assemblies (100, 100') for attachment with the other plurality of sub-assemblies (100, 100'); characterized in that the method further comprises: forming at least one countersink (130, 330) having a second diameter larger than the first diameter and a second depth shorter than the first depth from the first side of the at least one of the plurality of sub-assemblies (100, 100') and into the at least one of the plurality of sub-assemblies (100, 100') at the at least one hole (110, 310); metalizing the at least one countersink (130, 330); forming at least one via into the lamination adhesive to expose a metalized portion of the at least one countersink (130, 330); and filling at least one conductive paste into the at least one via formed in the lamination adhesive. attaching a plurality of sub-assemblies (100, 100') with each other after processing at least one of the plurality of sub-assemblies (100, 100'), wherein each of the plurality of sub-assemblies (100, 100') comprises a plurality of circuit layers, and the processing of the at least one of the plurality of sub-assemblies (100, 100') comprises: forming at least one hole (110, 310) having a first diameter and a first depth from a first side of the at least one of the plurality of sub-assemblies (100, 100') and into the at least one of the plurality of sub-assemblies (100, 100'); metalizing the at least one hole (110, 310); applying a lamination adhesive on the first side of the at least one of the plurality of sub-assemblies (100, 100'); applying a protective film on the lamination adhesive; and removing the protective film to expose the lamination adhesive on the at least one of the plurality of sub-assemblies (100, 100') for attachment with the other plurality of sub-assemblies (100, 100'); characterized in that the method further comprises: forming at least one countersink (130, 330) having a second diameter larger than the first diameter and a second depth shorter than the first depth from the first side of the at least one of the plurality of sub-assemblies (100, 100') and into the at least one of the plurality of sub-assemblies (100, 100') at the at least one hole (110, 310); metalizing the at least one countersink (130, 330); forming at least one via into the lamination adhesive to expose a metalized portion of the at least one countersink (130, 330); and filling at least one conductive paste into the at least one via formed in the lamination adhesive. forming at least one hole (110, 310) having a first diameter and a first depth from a first side of the at least one of the plurality of sub-assemblies (100, 100') and into the at least one of the plurality of sub-assemblies (100, 100'); metalizing the at least one hole (110, 310); applying a lamination adhesive on the first side of the at least one of the plurality of sub-assemblies (100, 100'); applying a protective film on the lamination adhesive; and removing the protective film to expose the lamination adhesive on the at least one of the plurality of sub-assemblies (100, 100') for attachment with the other plurality of sub-assemblies (100, 100'); characterized in that the method further comprises: forming at least one countersink (130, 330) having a second diameter larger than the first diameter and a second depth shorter than the first depth from the first side of the at least one of the plurality of sub-assemblies (100, 100') and into the at least one of the plurality of sub-assemblies (100, 100') at the at least one hole (110, 310); metalizing the at least one countersink (130, 330); forming at least one via into the lamination adhesive to expose a metalized portion of the at least one countersink (130, 330); and filling at least one conductive paste into the at least one via formed in the lamination adhesive. forming at least one countersink (130, 330) having a second diameter larger than the first diameter and a second depth shorter than the first depth from the first side of the at least one of the plurality of sub-assemblies (100, 100') and into the at least one of the plurality of sub-assemblies (100, 100') at the at least one hole (110, 310); metalizing the at least one countersink (130, 330); forming at least one via into the lamination adhesive to expose a metalized portion of the at least one countersink (130, 330); and filling at least one conductive paste into the at least one via formed in the lamination adhesive.