Patent ID: 8168513

Claim:
A method for fabricating a packaging substrate, comprising the steps of: providing a base including a release film having two opposite surfaces, two first auxiliary dielectric layers correspondingly disposed on the opposite surfaces of the release film and enclosing the release film, and two metal layers disposed on the two first auxiliary dielectric layers, respectively, therewith an effective area defined on each of the two metal layers; forming an inner wiring layer on each of the two metal layers; forming a built-up structure on each of the two first auxiliary dielectric layers and the inner wiring layers, wherein the outermost surfaces of the built-up structures have a plurality of first conductive pads for two initial substrates to be formed on the two opposite surfaces of the release film; removing whatever is otherwise lying outside the effective area; removing the release film; and forming a plurality of dielectric layer openings in the two first auxiliary dielectric layers so as for two substrate bodies to be formed from the initial substrates, wherein a portion of the inner wiring layers correspond in position to and are exposed from the dielectric layer openings, respectively, thereby to function as second conductive pads.