Optimizing a Via Breakout using Parameters in Ansys HFSS 3D Layout

Printed Circuit Boards (PCBs) have multiple components that the signal travels through. No matter what components are on a PCB the signal will have to travel through a via breakout. If that area is not properly optimized, there will be poor signal integrity, which can cause issues.

Optimizing a via takes multiple iterations of geometry changes. Simulation speeds up this process so multiple spins of the board do not have to be manufactured and tested. Ansys HFSS 3D layout is one of the tools used to simulate PCBs. HFSS 3D layout also provides an additional tool called Optimetrics Setup that can speed up the process and make the optimization easier.

Optimetrics Setup allows for the parametrization of any variable, meaning that multiple dimensions for one variable will be simulated simultaneously, allowing the user to see an array of results. This saves time as the user does not have to run multiple simulations independently and can set this scan and let it do one simulation to provide results.

Let’s walk through a quick example of how to use the Optimetrics Setup:

1. Create or import the geometry of the PCB and via breakout region. Assign variables to any dimensions that you want to vary. In this case, the variables will be the radius of the via, the radius of the via pads, and the radius of the antipad.
   

2. Create the frequency sweep for the frequency range you want to analyze.

3. Create the Optimetrics Setup by choosing the start, stop, and step size for each variable.
   

4. After running Optimetrics Setup, you can see the s-parameters for all the different variable combinations. This allows a visual of which dimension combinations will be the closest to the desired results. The plot below pictures the TDR. The impedance should be as close to 50 ohms. The graph shows that the dimensions that are closest to 50 ohms are a via pad radius of 6 mils, a via radius of 4.5 mils, and an antipad radius of 12 mils.
   

Contact the Rand Simulation team if you're looking for guidance on your electronics engineering project. We can help by providing training, consulting or get you started with Ansys HFSS software.

About the Author

Anna Scovill is an Application Engineer for the Electronics team with a B.S in electrical engineering from University of Illinois at Chicago. She has been an Ansys user for 4 years and comes from a background of Signal Integrity and high frequency designs.

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