Pad shape effects on high frequency signal transfer characteristics

As one of the interconnects between board to board, pads on the boards could have considerable effects on high frequency signal transfer characteristics. In this paper, pad shape effects on the signal integrity is analyzed using add-in card model by simulation, and a test fixture designed and fabricated to test to a serial-ATA cable is used to measure the effect of pad length on high frequency signal transfer characteristics. From the simulation and measurement, it is confirmed that the pads make a considerable effects on the signal transfer characteristics, especially in high frequency range, and we need to carefully design the characteristic impedance of the pads.