The Hirose DF12NB(4.0)-50DP-0.5V(51) is a 50-position header from the DF12 series, designed for parallel board-to-board mezzanine connections. Solder retention features on the body help keep the part seated during SMT reflow.
What the 4mm Stack Height and 0.50mm Pitch Mean for Your Layout
The 0.50mm pitch drives the PCB routing density: you'll need fine trace-and-space capability to fan out 50 signals from the footprint. The two-row arrangement gives 25 contacts per row, so the footprint is roughly 12.5mm long (25 positions × 0.50mm) plus the keep-out at each end. The outer shroud contacts add some width to the body but also provide mechanical alignment and pin protection during mating — useful for automated assembly where misalignment can damage fine-pitch pins.