Advanced Layout Design - microvias and capacitance

[kevbot]

Hello,

I had a question about using microvias in layer two of the Advanced Layout course.

During fanout under the BGA, we use microvias to move to layer 2 and then use another microvia to layer 3. (It's necessary because we need a reference ground plane for layer 2.) My question is, why did we route the signal underneath the track on layer 1? I thought we would want to avoid going directly under this route since it adds undesirable capacitance - with the tracks being the plates of the capacitor.

I appreciate any thoughts on the matter.

Kevin

[robertferanec]

I didn't want to use VIAs in pad nor stacked VIAs - these would make the PCB more expensive.

[robertferanec]

I didn't want to use VIAs in pad nor stacked VIAs - these would make the PCB more expensive.