The Hirose DF12NC(3.0)-20DP-0.5V(51) is a 20-position header from the DF12 series, designed for board-to-board mezzanine stacking.
It drives the trace width and via keep-out on the PCB. Surface-mount termination keeps the bottom side of the board clear for additional components, but the fine pitch demands a solder paste stencil with good aperture alignment to avoid bridging between adjacent pads.
Mating and Stack Height — Confirming the Pair
The outer shroud contacts are the key alignment feature — they guide the receptacle into position and take the shear load during assembly, so the signal pins are not stressed. Confirm that your receptacle order code specifies the same 3 mm stack height to ensure the boards sit at the correct separation.