Circuit board, apparatus and method for forming via hole structure

An apparatus, comprising an apparatus-main-body and a circuit board, the circuit board being disposed on the apparatus-main-body, wherein

• the circuit board comprises a main body (10) with a multi-layer structure, and a via hole structure disposed in the main body (10), wherein the via hole structure comprises a hole (12) enclosed by a conductive layer in the main body (10), and the conductive layer constitutes a wall (11) of the hole (12);
• and the via hole structure further comprises a dielectric filling layer (13), which is disposed between at least a portion of the wall (11) and the main body (10), and has a dielectric constant smaller than a dielectric constant of the main body (10),
• wherein the multi-layer structure of the main body (10) comprises a target signal layer (101) corresponding to the via hole structure, and an end of the hole (12) located inside the main body (10) is a lower end, which extends in the main body (10) along a thickness direction of the main body (10), and extends to the corresponding target signal layer (101) in the main body (10);
• and a part of the wall (11) of the hole (12) is located inside the corresponding target signal layer (101), and at least a portion of the part of the wall (11) is in direct contact with the target signal layer (101).

A method for forming a via hole structure, comprising:

• forming a first hole in a main body (10) of a circuit board with a multi-layer structure;
• filling the first hole with a dielectric having a dielectric constant smaller than a dielectric constant of the main body (10);
• forming a second hole, which penetrates the dielectric and has a diameter smaller than a diameter of the first hole, in a region of the dielectric in the first hole, the dielectric having the second hole formed therein being a dielectric filling layer (13);
• and
• forming a conductive layer on a wall of the second hole to obtain a via hole structure, wherein a hole (12) is enclosed by the conductive layer, and the conductive layer constitutes a wall (11) of the hole (12),
• wherein the multi-layer structure of the main body (10) comprises a target signal layer (101) corresponding to the via hole structure, and an end of the hole (12) located inside the main body (10) is a lower end, which extends in the main body (10) along a thickness direction of the main body (10), and extends to the corresponding target signal layer (101) in the main body (10);
• and a part of the wall (11) of the hole (12) is located inside the corresponding target signal layer (101), and at least a portion of the part of the wall (11) is in direct contact with the target signal layer (101).