Package substrate and fabricating method thereof

A method of fabricating a package substrate, the method comprising:

• forming a first circuit layer on a carrier;
• forming a first insulating layer and a core board body sequentially on the carrier, wherein the first insulating layer is bonded with the carrier to cover the first circuit layer, and the first circuit layer is embedded in the first insulating layer, wherein the core board body has a first side and a second side opposing the first side, the first side of the core board body is bonded with the first insulating layer, and the core board body has a first inner circuit layer and a second inner circuit layer protruding from the first side and the second side respectively, and a plurality of conductive vias electrically connecting the first inner circuit layer and the second inner circuit layer;
• wherein a surface of the first insulating layer is flush with a surface of the first circuit layer;
• forming a second circuit structure on the second side of the core board body, wherein the second circuit structure has a plurality of second insulating layers and a plurality of second circuit layers bonded with the second insulating layer, and the second circuit layer is electrically connected to the second inner circuit layer;
• wherein the plurality of second circuit layers protrudes from the plurality of second insulating layers;
• the core board body, the first insulating layer and the second insulating layer are formed on the carrier in a press-fit manner;
• removing the carrier to expose the first circuit layer and the first insulating layer;
• forming a first circuit structure electrically connected to the first inner circuit layer by the first insulating layer and the first circuit layer, wherein a line width and a line pitch of the first circuit layer is the same as a line width and a line pitch of the second circuit layer, and a number of wiring layers of the first circuit layer is less than a number of wiring layers of the second circuit layer;
• and
• forming a wiring structure on the first circuit structure, wherein the wiring structure has at least one dielectric layer, a redistribution layer bonded with the dielectric layer and a plurality of blind-via conductors disposed in the dielectric layer and electrically connecting the redistribution layer and the first circuit layer, and a line width and a line pitch of the redistribution layer is different from the line width and the line pitch of the first circuit layer;
• wherein
• a coefficient of thermal expansion of the second circuit structure is equal to a coefficient of thermal expansion of the first circuit structure with the wiring structure as a whole.