There are three simulation models available for via objects in Momentum-GX in ADS 2006A:
2D Distributed Model
Lumped Model
3D Distributed
The Lumped Model can be used to more efficiently simulate contact via’s (the main purpose of which is to provide electrical or mechanical contact). The 3D Distributed Model yields a full 3D modeling of all the components of the via currents (including the horizontal via currents) and can be used to more accurately simulate the electrical behaviour of signal via’s.
The default via model (available in prior releases).
A distributed model for the via object is created by meshing the surface with rectangular cells
Only the vertical component of the via current is modeled, using vertical oriented rooftop functions. Hence, the modeled current distribution of the vertical component varies both in the cross-section and in the vertical direction (2D current distribution).
Each via object contributes two unknown currents per rectangular cell to the matrix equation
The via resistance and skin effect are included using the sheet surface impedance formulation
The via self and mutual inductances (vertical currents only) and capacitances are included in the simulation
The via objects are extracted from the structure and replaced by a lumped model.
All branches in the distributed via network topology are removed and replaced by a single lumped branch, connecting the center bottom and top cell of the via object.
Each via object contributes only one extra unknown to the matrix equation, the lumped via current, which has only a vertical component with a constant amplitude.
A lumped series R, L impedance is used as electrical model in the simulation of the via.
The resistance R and inductance L of the via are automatically calculated from the geometry and the material parameters.
The mutual inductances are NOT included.
The self and mutual capacitances are NOT included.
The via cells do NOT contribute to the matrix equation load process.
The internal impedance (resistance and internal inductance) of the via follow from the application of the surface impedance concept for a uniform vertical current distribution on the via. That is, we have:
For via mask layers specificed by a conductivity, the surface impedance Z_{s} is calculated using the single-sided skin effect formula. Hence, the frequency dependent skin effects (yielding a higher resistance and a lower internal inductance as frequency increases) are included in the lumped via model. For via mask layers specified by an impedance, the frequency dependent skin effects are NOT included.
A distributed model for the via object is created by meshing the surface with rectangular cells.
Both the horizontal and vertical components of the via current are modeled, using horizontal and vertical oriented rooftop functions. This yields a complete 3D current modelling of the via objects.
Each via object contributes four unknown currents per rectangular cell to the matrix equation.
The via resistance and skin effect are included using the surface impedance formulation.
All the via self and mutual inductances and capacitances are included in the simulation.
Selection of Via Model
Default via model is defined in the Momentum Analysis dialog “Simulation Options” page (the default for the analysis is the planar “2D-model”).
The model
may be defined for each substrate (dielectric) layer in Layout properties
dialog window, “Layer page”, “Via Model” column, defined for dielectric layers (see
Layer page).
Default in the page means using
Momentum Analysis model.