A circuit structure and a fabrication method thereof are provided. The fabrication method of the circuit structure includes the following steps: providing a substrate; fabricating a test circuit component on the substrate; fabricating a solder pad on the test circuit component; fabricating an insulating layer; and fabricating a conductive pad on the insulating layer. A second surface of the insulating layer covers the test circuit component and the solder pad. The conductive pad is coupled to the solder pad. Through the fabrication method of the circuit structure provided by the disclosure, circuit quality of the circuit structure may be monitored, and that reliability of the circuit structure provided by the disclosure is improved.

A method for forming a thermal and electrical path in a PCB may include forming a first removable layer over a top surface of a PCB and a second removable layer over a bottom surface of the PCB. The method may also include milling or laser drilling the PCB from the top surface to form a first cavity extending into the PCB, plating the first side panel plating the first side with a second metal to partially fill the first cavity; and milling or laser drilling from the bottom surface to form a second cavity extending into the PCB, the first cavity in a thermal communication and/or an electrical communication with the second cavity. The method may also include panel plating the first side with a second metal to fill the first cavity and the second side with the second metal to fill the second cavity, and removing the first and second removable layers from the PCB to form the PCB with a thermal and/or an electrical path comprising the first cavity and the second cavity filled with the second metal.

A printed circuit board includes: an insulating material; a metal layer disposed on a first surface of the insulating material and including an opening; a pad disposed along a second surface of the insulating material; a via hole penetrating through the insulating material and extending from the pad to the opening; and a conductor disposed along the opening and the via hole. A diameter of a portion of the via hole adjacent to the opening is smaller than a diameter of a portion of the opening adjacent to the via hole.

A method for forming a thermal and electrical path in a PCB may include forming a first removable layer over a top surface of a PCB and a second removable layer over a bottom surface of the PCB. The method may also include milling or laser drilling the PCB from the top surface to form a first cavity extending into the PCB, plating the first side panel plating the first side with a second metal to partially fill the first cavity; and milling or laser drilling from the bottom surface to form a second cavity extending into the PCB, the first cavity in a thermal communication and/or an electrical communication with the second cavity. The method may also include panel plating the first side with a second metal to fill the first cavity and the second side with the second metal to fill the second cavity, and removing the first and second removable layers from the PCB to form the PCB with a thermal and/or an electrical path comprising the first cavity and the second cavity filled with the second metal.