Hardware Verification of Via Crosstalk Cancellation for Differential BGA-to-BGA Links

Coupling in dense via pinfields is known as a major contributor to crosstalk. In this work we present and verify a novel wiring strategy for links with a symmetrical pinfield-to-pinfield topology that reduces crosstalk significantly and requires no extra shielding vias. By twisting the orientation of the $p$ and $n$ wires of the differential stripline pair, a cancellation of the crosstalk between the differential via pairs is achieved. It can be implemented without any additional space requirements. The proposed design is fabricated and the crosstalk is measured with a vector network analyzer. It is shown that small changes in the orientation of the wiring in the pinfield region can reduce far-end crosstalk significantly.