高速PCB单端过孔研究

在高速数字电路设计中，过孔的寄生电容、电感的影响不能忽略，过孔在传输路径上表现为阻抗不连续的断点，会产生信号的反射、延时、衰减等信号完整性问题。文章采用矢量网络分析仪研究了过孔长度、过孔孔径、焊盘/反焊盘直径对过孔阻抗的影响。通过在信号孔旁增加接地孔，为过孔电流提供回路方法，提高过孔阻抗的连续性，并有效降低过孔损耗。此外，文章还探讨了过孔多余短柱对过孔阻抗及损耗的影响。本研究可为高速数字电路过孔设计和优化提供依据。

Study on single-ended vias in high speed PCB

In high-speed digital board designs, parasite capacity and inductance on vias have to be considered carefully. Vias can lead to impedance discontinuities resulting in signal relfections and hence deterioration of signal integrity. This paper carried out a comprehensive study of the impacts of various via design parameters on impedance discontinuities of vias by vector network analyzer. The design parameters under study were via diameter, via height, pad diameter and anti-pad diameter. By adding ground vias near the signal vias to provide return current path for signal in vias, impedance of vias can be accurately controlled, and insertion loss of vias can be greatly decreased. Furthermore, impact of excess via-hole stub on vias’ impedance and insertion loss were studied. This paper allows high-speed digital designers to have a more in-depth assessment of via holes design and optimization.