An embodiment of a printed circuit board includes a first insulating layer, a metal layer disposed above the first insulating layer, a second insulating layer disposed above the metal layer, and signal lines disposed above the second insulating layer, the signal lines extending in a first direction and having line widths in a second direction perpendicular to the first direction. The metal layer has open areas overlapping the signal lines in a third direction perpendicular to the first and second directions. In another embodiment, the open areas are replaced with metal meshes.