50 ohm microstrip for heterogeneous conductors

[CNO345345]

New to the forum! I am designing a 50 ohm microstrip line for a sintered signal line of heterogeneous material. All the equations for characteristic impedance I am seeing are functions of the geometry and dielectric. This conductor has a conductivity ~20% of silver with a bottom plane of copper. Can I disregard these differences and choose my dimensions from the many online calculators? Or are those all assuming homogeneous copper conductors? Any help is much appreciated!

 

[FvM]

Transmission line calculators don't regard the conductor material, it's simply considered as massive metal.

 

[vfone]

Looks like your conductor is copper plated with silver. In this case, Skin Effect behavior may apply:

Skin effect - Wikipedia

en.wikipedia.org

 

[CNO345345]

Thanks. Skin effect will definitely be in play but will these increased conductor losses require significant deviation in design of microstrip for matching characteristic impedance of 50 ohms?

 

[KlausST]

Hi,

Characteristic impedance does not depend (much) on core resistance.
It mainly depend on inductance and capacitance. Both are independent of characteristic resistance of the material.

Klaus

 

[volker@muehlhaus]

Skin effect has a little effect on inductance also, but microstrip calculators like ADS LineCalc ignore that small effect. They only use conductivity for loss calculation.

But for your case with two good conductors, the material mix has almost no effect.