US Patent 10039184 Circuit board structure and manufacturing method thereof

A circuit board structure includes an inner circuit structure and a first build-up circuit structure. The inner circuit structure includes a core layer having an upper surface and a lower surface opposite to each other, a first patterned circuit layer disposed on the upper surface, a second patterned circuit layer disposed on the lower surface and a conductive via connecting the first and the second patterned circuit layers. The first build-up circuit structure is disposed on the upper surface of the core layer and covers the first patterned circuit layer, wherein the first build-up circuit structure at least has a cavity, the cavity exposes a portion of the first patterned circuit layer and a cross-sectional profile of an edge of a top surface of the portion of the first patterned circuit layer exposed by the cavity is a curved surface.