The Hirose DF12NC(3.0)-32DS-0.5V(51) is a 32-position, 2-row receptacle with center strip contacts from the DF12 series, designed for parallel board-to-board mezzanine connections. The 0.020" (0.50mm) pitch packs 32 signal lines into a compact footprint, and the 3mm mated stacking height sets the z-axis gap between the two PCBs — a dimension you lock in during board stack-up planning.
The 3mm mated stacking height is the fixed gap between the two parallel boards when this receptacle is mated with its matching DF12 header.
