Hirose DF40C-40DP-0.4V(51) — 40-Position Fine-Pitch Board-to-Board Plug
The 0.045" (1.14mm) height above board keeps the mated stack low, and the six available stacking heights — 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, and 4mm — let you pick the board separation that fits your enclosure. The outer shroud design means the receptacle's shroud fits over the plug body, giving the mated pair some mechanical stability without needing separate alignment hardware. Typical use is in compact portable electronics, wearables, or any PCB stack where the 0.40mm pitch saves board real estate and the 1.14mm profile clears a tight lid.
40 vs 44 Positions — Same Pitch, Same Footprint Class
The DF40C-40DP-0.4V(51) sits alongside the DF40C-44DP-0.4V(51) at the same 0.016" (0.40mm) pitch and 0.045" (1.14mm) height. The difference is four positions — 40 circuits here, 44 on the sibling. Both use the same gold plating thickness (2.00µin), same dual-row layout, and same solder retention feature. The board footprint changes by the extra four contact pads on each row, so a layout designed for the 44-position version will have empty pads for the 40-position part. If your BOM calls for 40 signal lines, this is the one; if you need 44, step up to the DF40C-44DP-0.4V(51). No other functional spec shifts between them.