Printed circuit board

1. A printed circuit board (PCB) comprising:

a signal plane comprising a pad, a passive element mounted on the pad, and a signal transmission line electrically connected to the passive element via the pad; and

a reference plane to provide a return path for a signal transmitted through the passive element and the signal transmission line, wherein a void is defined in the reference plane corresponding to the passive element, to increase a length of the return path, a length of a first axis, perpendicular to the signal transmission line, of the void satisfies a following equation:

W

1

≈

8

⁢

Wpad

+

10

⁢

T

0.8

⁢

Wtrace

+

T

,

wherein Wpad is a width of the pad, Wtrace is a width of the signal transmission line, T is the height of the pad.

2. The PCB of claim 1 , wherein a length of a second axis, perpendicular to the first axis, of the void satisfies a following equation: W 2 =qW 1 , wherein q=0.5˜2.5.

3. The PCB of claim 2 , wherein the void is elliptic-shaped, the first axis is a minor axis of the void, the second axis is a major axis of the void, a center of the void corresponds to a center of the passive element.

4. The PCB of claim 1 , wherein the passive element is a resistor or a capacitor.

5. The PCB of claim 1 , wherein the signal transmission line is a high-speed serial signal trace, to transmit high-speed serial signals.