A printed circuit board includes a top conducting layer, an escaping layer, one or more first reference layers interposed between the top conducting layer and the escaping layer, and a second reference layer disposed under the escaping layer. The top conducting layer includes two connecting pads for receiving a pair of differential signals. A pair of vias are provided to extend vertically to penetrate the one or more first reference layers, the escaping layer, and the second reference layer. The vias connects the top conducting layer with the escaping layer. Each of the one or more first reference layers includes a continuous via void surrounding the pair of vias. The second reference layer includes two round via voids each surrounding one of the vias. The second reference layer includes a conductive film disposed between the two round via voids.