In this example, the paddle card mates to a card-edge connector with 80 pins, split 18 pairs and 22 pairs. On the wire side of the paddle card, at one end there are four pairs of signals and grounds, while at the other end there are five pairs plus a sideband, plus two grounds. The ‘SPD08 High Speed Connector Intermediate Print Circuit Board Design Guide’, available from 3M, provides more information about the PCB layout.

