PCB Material Characterization


The dielectric substrate and conductor surface roughness (SR) characteristics of printed circuit boards (PCBs) are important in high-speed interconnect designs. The direct usage of these material property values from their respective manufacturers’ data sheets into simulation often results in poor match between measurement and simulation.

PLTS introduces the new PCB material characterization feature to address this issue. It employs a 2-D stripline simulator together with the wideband dielectric model and surface roughness (SR) models, tuning the model parameters until a good correlation between simulation and measurement is achieved. Then the material property values (DK, DF, SR) are extracted. The Svensson-Djordjevic model is used as the dielectric model. The surface roughness models are the Huray model and the Cannonball model. Users can also specify the conductor surface to be smooth so that the surface roughness estimation is skipped.

This feature requires PLTS option N19308B PCB Material Characterization and PLTS base option N19301B.

The PCB Material Characterization Pane

To use this new feature, click the PCB Material Characterization item under the Utilities menu in PLTS. The PCB Material Characterization pane shows up. There are many configurations on it. Please see the details below.

Click the Calculate button to start the material characterization calculation. It would take a while to finish. The Advanced button launches the PCB Material Characterization – Advanced dialog.

The PCB Material Characterization – Advanced Dialog

This dialog allows a user to edit the model parameters. PLTS supports the Svensson-Djordjevic model for the dielectric substrate and the Huray model for the conductor surface roughness. The Cannonball model, a variant of the Huray model, is also supported.

The Svensson-Djordjevic Model

The Huray Model

The Cannonball Model

Other Settings

The Svensson-Djordjevic Model

This model only needs four variables to describe the wide-band DK/DF: , ,, and

is the low frequency of interest

is the high frequency of interest

and are user-defined model parameters

From the equation (1), it’s easy to see that if DK and DF at certain reference frequency are known, and can be determined.

In PLTS, Low Frequency, High Frequency and Reference Frequency are user-defined model parameters. The Reference DK and Reference DF at the Reference Frequency are to be estimated by the software.

The Huray Model

The conductor surface is divided into hexagonal tiles, and each tile is piled into a pyramid shape with same number of equal-sized balls. The Huray correction factor is defined as:

N is the number of balls in area Atile

Atile is the area of ball count, which is the area of the tile

r is the effective ball radius

δ is the skin depth

In PLTS, the Effective Ball Radius and Area of Ball Count are user-defined model parameters. Num of Balls in Area is to be estimated. If User-Defined is checked, Num of Balls in Area will also be user-defined. The software will then use this user-defined value and doesn’t estimate it anymore.

The Cannonball Model

This is a special form of the Huray model. It assumes that the number of equal-sized balls is always 14. The area of ball count can be derived from the effective ball radius.

In PLTS, The Num of Balls in Area is fixed to be 14. The Effective Ball Radius and Area of Ball Count are to be estimated by the software.

Other Settings

On this dialog, there are some other useful settings. Please see the description below.

The PCB Material Characterization Result Display

Click the Export Data button: User can export the frequency-dependent DK/DF values and the SR values into a CSV file.


Last Modified:

9-Jan-2024

New topic.