| 主权项 |
1. A printed circuit board, comprising:
a substrate; a first conductive layer on a top surface of the substrate; a second conductive layer on a bottom surface of the substrate; and a hole passing through a top surface of the first conductive layer and a bottom surface of the second conductive layer, wherein the hole includes
a first opening part passing through the first conductive layer;a second opening part passing through the second conductive layer;and a through part disposed between the first opening part and the second opening part,and the through part passing through the substrate,wherein a width between an arbitrary point having a maximum width of the through part and the first opening part or the second opening part decreases gradually from the arbitrary point to the first opening part or to the second opening part,wherein a width of the first opening part gradually decreases from the bottom surface of the first conductive layer to the top surface of the first conductive layer,wherein a width of the second opening part gradually decreases from a top surface of the second conductive layer to a bottom surface of the second conductive layer,wherein an internal surface of the first opening part has a curvature extending along an internal surface of the through part,and wherein an internal surface of the second opening part has a curvature extending along an internal surface of the through part,wherein the maximum width of the through part is larger than each width of the first opening part and the second opening part,wherein the internal surface of the through part has a curvature,wherein an imaginary extension line extending along the curvature formed by the internal surface of the through part forms a circular or elliptical shape,wherein the maximum width of the through part is larger than a thickness of the substrate and is formed to be increased up to 5 to 15% compared to the thickness of the substrate. |
