EMI performance of Stripline routing with PTH is better than Blind Via

[ankitasinha96]

Case I: A particular net I routed as stripline in inner layer 3 of 14 layer board with blind via.( Via imepdance is 30 ohms)

Case II: Same net I routed as stripline in inner layer 12 with Pth via. ( via impedance is 37 Ohms)

Please not:
** in both the cases the net is sandwiched between reference planes on adjacent layer.

** imp in inner layer is 57 ohms and ext layer is 52 ohms with a series termination of 33 ohms

Can someone explain why it happened. As I was expecting blind via to give better EMI compared to pth due to reduced inductance.

 

[D.A.(Tony)Stewart]

Grounded microvias surrounding PTH can give better control of impedance in via EMI.

Without all the critical design details with signals, drivers, decoupling ESR, layout and spectral EMI, how can we help?