Manufacturing method of circuit structure

A manufacturing method of a circuit board structure, comprising:

• providing an inner circuit structure, the inner circuit structure comprising a core layer having an upper surface and an opposite lower surface, a first patterned circuit layer disposed on the upper surface and a second patterned circuit layer disposed on the lower surface;
• forming an insulating material layer on a portion of the first patterned circuit layer, wherein the insulating material layer covers a portion of the upper surface;
• forming a laser resisting layer on at least a portion of the insulating material layer after forming the insulating material layer;
• adhering a release layer to the laser resisting layer;
• performing a build-up process so as to laminate a first build-up circuit structure and a second build-up circuit structure on the first patterned circuit layer and the second patterned circuit layer, respectively, wherein the first build-up circuit structure covers the release layer;
• and
• performing a laser ablation process on the first build-up circuit structure to irradiate a laser beam on the laser resisting layer so as to remove a portion of the first build-up circuit structure and the release layer, thereby forming a cavity at least exposing a portion of the upper surface of the core layer.