0.50 mm Pitch Mezzanine Header, 4 mm Stack Height
The Hirose DF12NC(4.0)-20DP-0.5V(51) is a 20-position, dual-row header from the DF12 series, designed for board-to-board mezzanine stacking. Its defining dimensions are the 0.020" (0.50mm) pitch and the 0.130" (3.30mm) height above board, which together set the mated stack height at 4mm — a common clearance for sandwiching a PCB between two boards in compact electronics. The connector type is listed as Header, Outer Shroud Contacts, meaning the outer shell contacts engage before the signal pins, providing ESD bleed and alignment guidance during blind mating — useful when the boards are assembled without direct line of sight.
The gold layer prevents corrosion on the signal interface; the underlying nickel barrier keeps the base metal from migrating through the gold.
Position Count vs. Siblings
Within the DF12NC(4.0) subfamily, the only variable that changes the footprint is the position count. The 20-position DF12NC(4.0)-20DP-0.5V(51) shares the same 0.50mm pitch, 4mm stack height, and 8.00µin gold plating as the 30-position DF12NC(4.0)-30DP-0.5V(51) and the 40-position DF12NC(4.0)-40DP-0.5V(51). If your BOM calls for more circuits at the same stack height and pitch, those are direct drop-in alternatives — same footprint length per position, same mating receptacle. The 20-position variant is simply the shortest of the three.