The disclosure relates to a circuit board and a manufacturing method thereof.

As the frequency of signal transmission and the number of input/output interfaces increase, higher requirements are placed on the signal transmission loss of the circuit board and the reliability of the circuit layer. In the traditional circuit layer manufacturing method, the subtractive method and the improved semi-additive method have poor ability to produce fine circuit layers, and the cost of the semi-additive method is high.

In view of the above, it is necessary to provide a circuit board and a manufacturing method thereof to solve the above problems.

A circuit board manufacturing method includes the following steps:

(1) Provide a substrate, and make a hole in the substrate to form a through hole;

(2) Fill the through hole with a conductor to form a conductive hole;

(3) Provide a peelable film to cover one side of the substrate;

(4) Form a groove in the peelable film and the substrate by laser ablation, the groove includes a concave portion, the concave portion is located at the conductive hole, and the diameter of the concave portion is larger than the diameter of the conductive hole to expose a portion of the conductor;

(5) Perform a surface treatment on a side wall and bottom wall of the groove to improve roughness;

(6) Remove the peelable film;

(7) Form a seed layer on the side wall and bottom wall of the groove;