Pcb Board Vias Studies, High-speed Signal Characteristics

With the increase of clock frequency and edge rates in high-speed digital systems, high-speedsignal experience delay, reflection, attenuation, crosstalk, dispersion in high-speed interconnect, which get more critical and become domain in signal integrity design. The signal integrity problems are electromagnetic(EM)problems in nature. In order to take complex electromagnetic effects into account, full-wave EM analysis based on EM theory must be resorted.As the high-density layout and larger number of via holes in the high-speed circuit, electromagnetic environment in the PCB is extremely complicated. The interconnect via holes have two negative aspects:on the one hand, because of the discontinuity of via hole as the transmission line will result in the refection:on the other hand, the via hole has open geometry, which leads to radiating the electromagnetic wave in the open space and exciting the radiative wave between the metal plane. Although the radiation influence could be cared at the lower frequency, the radiative effect would be put much attention at high frequency. For example, the via holes of connector and BGA have discontinuous transmitted characteristic, resulting in the crosstalk and simultaneous switching noise of power delivery network.Around the topic of EM modeling and simulation, high-speed interconnects and 500Mbps high-speed system have been analyzed for signal integrity issues in frequency and time domain, which incorporated circuit and system analysis methods and experiment measures. They mostly study how the transmission of high-speed signal is effected in interconnects circuit. Then design guidelines for improved signal integrity are derived from the results obtained. Thereby, the design of high-speed circuits can be guided to solve signal integrity issues. The goal of signal integrity analysis is to ensure reliable high-speed data transmission. It is the research of via holes in designing high-speed circuit is very meaningful and necessary that this paper focus on the via hole.This paper focus on the discontinuous impedance of via holes, discussing the impedance optimization and the importance of impedance in the high-speed series channel, the contents of dissertation are mainly listed as follows.1. Illustrating the essence of impedance, importantly analyzing the reflect coefficient and lattice diagram is intuitionistic to illustrate the reflect theory. The essential physical concept of capacitance and inductance is to analyze the capacitance and inductance characteristic in impedance test.2. Analyzing four ways to optimize the impedance of via hole:pad anti-pad drill size backdrilling. And discussing the influence of relative position of signal and ground via holes inside differential pair, in addition, the affect of stagger arrangement of row signals on the crosstalk.3. Concluding the challenges and primary problems and optimizing functional parts in the high-speed series channel:BGA and DC cap. Moreover, contrasting the optimization before and after in the overall series channel, which is to show the importance of via hole impedance in the high-speed series channel signal transmission.In this dissertation, the researching the via hole impedance and series channel simulation evolves from the practical engineering, hence, the results can be used in the practical design.