Layer misregistration in PCB and its effects on signal propagation
Layer misregistration is one of the common issues in PCB manufacturing processes. In addition to physical limitations of manufacturability (large via pad/anti-pad), it may also have impact on the electrical performance of signal lines running through via fields with anti-pad openings. In order to quantify its effects on signal propagation, comprehensive test vehicles were designed, measured, and analyzed. Significant increases in layer-to-layer crosstalk and common-to-differential mode conversion were observed, when corresponding layers were misaligned. The results helped understand the mechanisms, validate modeling methodology, and define design rules.
Constructing 3D package component broadband electrical models with correct DC values
Accurate channel simulations of package interconnections require passive and causal models that faithfully represent the full frequency response from tens of gigahertz to DC. In this paper, we propose and test a method to create accurate models extending to DC while retaining passivity and causality. The model derived by this method is suitable for transient simulations of packaging interconnect systems.
On characterizing the impedance of power/ground planes - including the effect of anti-pads
In this contribution, the impedance of a power/GND plane pair with the inclusion of the effect of anti-pads (voids) is computed by applying a hybrid finite difference time domain (FDTD)-field theory procedure. The power/GND plane is analyzed by dividing the entire structure into a grid of square segments. Then each segment is replaced by an equivalent circuit module. The topology and elements of these modules are extracted by an analytical procedure, using the solution of Helmholtz equation while applying the FDTD method for regular regions. Then, an equivalent circuit topology is constructed by superimposition of all pre-made segments. This method is extended to include the anti-pads. The analytical/simulation results are presented, and those results are compared to the data obtained from preliminary measurements.