100-Position Mezzanine Receptacle, 0.80 mm Pitch
The seated height above the PCB is 3.75 mm, and the connector is specified for mated stack heights of 5 mm, 6 mm, 7 mm, or 8 mm, giving the board designer flexibility in the z-axis gap between the two PCBs.
The 0.80 mm pitch determines the pad layout on both boards. The 100 positions in two rows sets the footprint length along the board edge.
This matters in applications where the board stack is occasionally reworked or where the connector pair sees thermal cycling that can cause micromotion at the contact interface. The gold thickness is consistent across all 100 positions, so the signal path resistance stays uniform across the connector.