Circuit board structure and manufacturing method thereof

A circuit board structure, comprising:

• a first sub-circuit board having an upper surface and a lower surface opposite to each other, and comprising at least one first conductive through hole;
• a second sub-circuit board disposed on the upper surface of the first sub-circuit board, and the second sub-circuit board comprising:
• at least one second conductive through hole;
• a first substrate having a first surface and a second surface opposite to each other, wherein the at least one second conductive through hole penetrates the first substrate;
• a first circuit layer disposed on the first surface of the first substrate and exposing a portion of the first surface;
• and
• a second circuit layer disposed on the second surface of the first substrate and exposing a portion of the second surface, wherein the first circuit layer and the second circuit layer are electrically connected via the at least one second conductive through hole, and the second circuit layer is electrically connected to the at least one first conductive through hole of the first sub-circuit board;
• and
• a third sub-circuit board disposed on the lower surface of the first sub-circuit board, and the third sub-circuit board comprising:
• at least one third conductive through hole;
• a second substrate having a third surface and a fourth surface opposite to each other, wherein the at least one third conductive through hole penetrates the second substrate;
• a third circuit layer disposed on the third surface of the second substrate and exposing a portion of the third surface;
• a fourth circuit layer disposed on the fourth surface of the second substrate and exposing a portion of the fourth surface, wherein the third circuit layer and the fourth circuit layer are electrically connected via the at least one third conductive through hole, and the third circuit layer is electrically connected to the at least one first conductive through hole of the first sub-circuit board;
• a first solder mask disposed on the third surface exposed by the third circuit layer, and extended to cover a portion of the third circuit layer, wherein the first solder mask is directly connected to the first sub-circuit board;
• and
• a second solder mask disposed on the fourth surface exposed by the fourth circuit layer, and extended to cover a portion of the fourth circuit layer;
• wherein at least two of the at least one first conductive through hole, the at least one second conductive through hole, and the at least one third conductive through hole are alternately arranged in an axial direction perpendicular to an extending direction of the first sub-circuit board, and the first sub-circuit board, the second sub-circuit board, and the third sub-circuit board are electrically connected to one another.