Mating backplane for high speed, high density electrical connector

A printed circuit board comprising:

• a plurality of layers including attachment layers and routing layers;
• signal vias extending through at least the attachment layers, the signal vias including signal conductors;
• ground vias extending through at least the attachment layers, the ground vias including ground conductors;
• and
• groups of blind plated vias extending through the attachment layers, the blind plated vias including conductors that interconnect ground planes of two or more of the attachment layers, wherein the signal vias and the ground vias are arranged in a plurality of via patterns and wherein respective groups of the groups of blind plated vias are located between adjacent via patterns.

A printed circuit board comprising:

• a plurality of layers including attachment layers and routing layers;
• and
• via patterns formed in the plurality of layers, each of the via patterns comprising:
• first and second signal vias forming a differential signal pair, the first and second signal vias extending through at least the attachment layers;
• ground vias extending through at least the attachment layers, the ground vias including ground conductors;
• and
• shadow vias located adjacent to each of the first and second signal vias, wherein the shadow vias are free of conductive material in the attachment layers.