采用轴对称二维有限元法提取过孔分布电容

采用简便的两维轴对称有限元法分析了四层印制电路板的过孔电容。将极坐标形式的拉普拉斯方程变换成直角坐标形式,避免了复杂的椭圆积分。将过孔的电容分层处理,分析了过孔的高度、半径、焊盘半径等参数对过孔电容的影响。与有限元分析软件ANSYS进行了对比,计算结果基本一致。此方法可用于任意层复杂印制电路板过孔电容的提取,所得结论有助于过孔的等效电路建模以及高速PCB的信号完整性分析。

Extracting Via Capacitance of PCB Using Axially Symmetric Two-Dimensional FEM Method

The capacitance of via in four-layer printed circuit board(PCB) was calculated using a convenient axially symmetric two-dimensional finite-element method(FEM).The Laplace equation in polar coordinate form was converted into Cartesian coordinate form,so the complicated ellipse integral was avoided.The via capacitance was divided into several partial capacitances by the layers of PCB,and the effects of the parameters including the height and diameter of via and the diameter of pad on the capacitance was analyzed.The calculated results agreed very well with those by FEM software ANSYS.The method suggested in this paper can be widely used in extracting the capacitance of complicated multilayer PCB,and the obtained results are contributive to model the equivalent circuit of via and the signal integrity analysis of high speed PCB.