The Hirose DF12NC-40DS-0.5V(51) is a 40-position receptacle from the DF12 series of board-to-board mezzanine connectors. This part is designed for parallel PCB stacking, where the mated stack height is determined by the header height chosen — this receptacle supports mated stacking heights of 3.5mm, 4mm, and 5mm when paired with the corresponding DF12 header.
At this pitch, the escape routing under the connector typically requires microvias or blind vias on inner layers. The mated stacking heights of 3.5mm, 4mm, and 5mm are set by the header, not the receptacle; this DF12NC receptacle remains the same, and you select the header part number to achieve the required z-height between boards. The 0.106" (2.70mm) height above board of the receptacle itself is a fixed dimension.
40 Positions vs 60 Positions in the Same Footprint Class
The DF12NC-60DS-0.5V(51) shares the same 0.50mm pitch, 2-row layout, and 2.70mm board height, but carries 60 positions instead of 40. The 20-position difference changes the connector body length and the board footprint length, but the row pitch and contact pitch remain identical. If the BOM calls for 40 signal lines, the 40-position DF12NC-40DS-0.5V(51) is the correct fit; the 60-position variant adds board space without a routing benefit.