Learning Forum

[jhyeon1008]

Hi, I'm trying to observe the variation in S-parameters with temperature. To account for temperature changes, I added thermal modifier equations for relative permittivity and dielectric loss tangent, but the results aren’t linear. I think the equations might be incorrect. I would like to know the correct thermal modifier equations for dielectrics like FR-4 and PTFE, thank you.

[dushyant.marathe]

Hi Jhyeon,

To set the correct thermal modifier equations for dielectrics like FR-4 and PTFE in SIwave, you can refer to the Ansys documentation which provides a formula for temperature-dependent dielectric loss tangent. You can select 'Expression' to define an equation for the thermal modifier in the Modifier field. Additionally, under the Basic Coefficient tab, you can edit fields for the TempRef and units, and fields for C1 and C2 for the following equation: P(Temp) = Pref[1+ C1(Temp - TempRef) + C2(Temp - TempRef)^2], where TempRef is 22°C by default and where the Pref is defined as the reference relative permittivity [ https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/Electronics/v232/en/home.htm%23../Subsystems/Mechanical/Content/Materials/SpecifyingThermalModifiers.htm?TocPath=Mechanical%257CMechanical%2520Help%257CAssigning%2520Materials%257CAdding%2520New%2520Materials%257C_____3

Please note that the coefficients, C1 and C2, should be negative to yield physical results. For more detailed methods of applying a thermal modifier, you can also look at the provided images and instructions in the SIWAVE documentation https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/Electronics/v232/en/Subsystems/SIwave/SIwave.htm%23AssigningThermalSpatialModifiers.htm?TocPath=SIwave%2520Help%257CLayers%2520and%2520Materials%257CMaterials%257CMaterial%2520Properties%257C_____6 

Hope this helps, Thanks.