过孔阻抗控制及其对信号完整性的影响

传输线的连续性问题是高速数字电路设计的重点,尤其是高速多层PCB中的过孔结构。随频率的增加和上升时间的缩短,过孔阻抗不连续、寄生电容和电感会引起信号反射和衰减,并导致信号完整性问题。本研究采用矢量网络分析仪研究了单端微带线上过孔孔径、焊盘、反焊盘大小对阻抗连续性的影响,并通过为过孔信号提供返回路径,提高了过孔阻抗连续性与信号完整性。

Impedance control of Vias and its impact on signal integrity

In high-speed digital board designs,every slightest discontinuity on the board has to be considered carefully,especially via holes,which are abundantly used in high-speed multilayer PCB.As frequency increases and signal rise time reduces,via holes cause impedance discontinuities,parasite capacity and inductance which result in signal reflection and attenuation,and hence deterioration of signal integrity(SI).The paper carries out a comprehensive study of the impacts of various via design parameters on impedance discontinuities of single-ended vias by vector network analyzer.The design parameters under study are via diameter,pad diameter and antipad diameter.Furthermore,impedance continuities and SI for via holes were greatly improved by providing return current path for signal in vias.