基于HFSS的高速PCB信号完整性研究

发布时间：2018-06-07 17:11

本文选题：PCB + 信号完整性　；参考：《电子科技大学》2015年硕士论文

【摘要】：随着电子技术的飞跃发展,高速系统的时钟频率不断提高,上升时间不断变短,印制电路板中传输线的性能对电子系统的影响越来越严重,印制电路板中传输线的信号完整性问题变得越来越重要。在低速电路中主要起电气连接作用的互连线在高速电路中表现为传输线,并可能导致在信号在正确的电气连接情况下发生错误。在这样的情况下,通过使用仿真工具来研究信号完整性问题是一种非常行之有效的方法,利用精确可靠的三维电磁场仿真,可以模拟高速电路板上的三维结构电磁场效应。HFSS软件作为高频结构仿真求解器,提供了许多最先进的求解器技术,它们基于有限元、积分方程或高级混合算法,可解决非常广泛的信号完整性问题。传输线主要由铜箔和介质材料构成,对于铜箔,分别采用不同表面粗糙度的铜箔制作传输线,测出不同粗糙度传输线的损耗差异,与仿真的光滑传输线对比,得到粗糙度对信号传输的影响;对于介质材料,首先使用不同损耗因子的介质制作传输线获取其对损耗的影响,然后针对介质中的增强材料玻纤布,研究它在与传输线不同几何关系下对信号产生的影响;而介质材料本身的介电系数和损耗因子会随频率的改变而发生改变,通过测量不同频率的介电系数和损耗因子获取它们的变化趋势。在PCB中布线时,有两种不连续结构不可避免,也不能被替代,那就是拐角和过孔。在高速设计中,过大的拐角会产生容性突变,必须对拐角外侧做切角处理,减小反射,通过HFSS对不同处理方法做定量研究,确定最佳处理方式。过孔作为PCB中最常见的不连续结构,使用HFSS通过单因子变量法研究孔的焊盘、反焊盘、残桩和接地孔对阻抗的影响。最后,从PCB工艺管控入手,研究PCB制造时不可避免的缺陷对信号产生的影响。传输线的线宽和介质高度是一个管控要点,尤其是当线宽和介质厚度较小时,它们更容易引起传输线特性阻抗的改变。层间偏移在一定程度上影响信号,打靶时测出层偏量,钻孔时给一定的补偿。阻焊层厚度很小时,对阻抗产生很大影响,在设计时必须考虑清楚,如有需要需适当减小线宽。
[Abstract]:With the rapid development of electronic technology, the clock frequency and rising time of high speed system are increasing, and the performance of transmission line in printed circuit board has more and more serious influence on electronic system. The signal integrity of transmission lines in printed circuit boards (PCB) is becoming more and more important. The main function of electrical connection in low speed circuits is the transmission line, which may lead to the error of the signal in the correct electrical connection. In this case, using simulation tools to study signal integrity problems is a very effective method, using accurate and reliable three-dimensional electromagnetic field simulation, HFSS software can be used as a high-frequency structure simulation solver, which provides many advanced solver techniques, which are based on finite element, integral equation or advanced hybrid algorithm. Can solve a very wide range of signal integrity problems. The transmission line is mainly composed of copper foil and dielectric material. For copper foil, copper foil with different surface roughness is used to make transmission line, and the loss difference of transmission line with different roughness is measured. The effect of roughness on signal transmission is obtained. For dielectric materials, transmission lines with different loss factors are first used to obtain their effects on loss. The influence of the dielectric coefficient and the loss factor of the dielectric material on the signal under the different geometric relation with the transmission line is studied, and the dielectric coefficient and the loss factor of the dielectric material change with the change of the frequency. The variation trend of dielectric coefficient and loss factor are obtained by measuring the dielectric coefficient and loss factor of different frequencies. In PCB wiring, two discontinuous structures are inevitable and cannot be replaced, that is, corners and holes. In the design of high speed, too large corner will produce capacitive abrupt change, it is necessary to cut the corner outside to reduce the reflection, and make quantitative research on different processing methods through HFSS to determine the best treatment method. As the most common discontinuous structure in PCB, HFSS is used to study the influence of solder pad, reverse pad, residual pile and grounding hole on the impedance by single factor variable method. Finally, starting with PCB process control, the paper studies the influence of the inevitable defects in PCB manufacturing on the signal. The line width and medium height of transmission line are a key point of control, especially when the line width and medium thickness are small, they are more likely to cause the change of transmission line characteristic impedance. The interlayer offset affects the signal to some extent, the offset of the layer is measured when shooting, and the compensation is given when drilling. The thickness of the resistance welding layer is very small, which has a great influence on the impedance, so it must be considered clearly in the design, and the line width should be reduced appropriately if necessary.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN41

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