US Patent 9871325 Circuit board having selective vias filled with lossy plugs

An interconnect system includes a circuit board including a substrate having a first surface and a second surface opposite the first surface, a plurality of signal conductors and a plurality of ground conductors including respective contact pads in a mating area of the substrate for engaging corresponding contacts of an electrical connector, and a plurality of ground vias extending at least partially through the substrate between the first and second surfaces. The ground vias are coupled to corresponding ground conductors. The ground vias include lossy plugs at least partially filling the ground vias. The lossy plugs are manufactured from lossy material capable of absorbing electrical resonance propagating through the substrate.