Impedance-controlled conductors with Microvias 

Electromagnetic waves propagate at a finite speed. This propagation speed depends on the material used (ε dielectric constant) and can be determined approximately with the formula cSignal ≈ cLicht / √εr. 

For FR4: cSignal ≈ 150.000 km/s.

Due to the finite propagation speed, the following rule of thumb formula applies:

The spatial dependence of voltage and currents becomes significant for a conductor length > λ / 10. Impendence matching should be implemented to avoid transmission faults. Production-compatible conductor tracks can be realised for impedance-matched system through the use of microvias.

Field Solver 8.0 from Polar Instruments is used to calculate the impedances.

On request we can produce your circuit boards to include a test coupon for impedance measurement and subsequently evaluate it with the aid of a modern TDR (Time Domain Reflectometer) cable radar.

We would be pleased to help you with planning and implementing your impedance-controlled circuit board. Let´s talk about it !