0.40mm pitch, 50 positions, 3.5mm stack — mezzanine interconnect for tight board spacing
The Hirose DF40HC(3.5)-50DS-0.4V(51) is a 50-position receptacle from the DF40 series, designed for board-to-board mezzanine stacking. Its 0.016" (0.40mm) pitch and dual-row layout pack 50 circuits into a compact footprint, and the 3.5mm mated stacking height sets the gap between parallel PCBs — a dimension you lock in when you choose the header half. Gold-plated center strip contacts (2.00µin / 0.051µm) handle moderate mating cycles typical of internal device interconnects, not repeated field service. Surface-mount termination keeps the assembly reflow-compatible for automated lines.
3.5mm vs 2.9mm — picking the right stack height for the board gap
The DF40HC(3.5)-50DS-0.4V(51) mates to a 3.5mm stack height, while the DF40HC(3.0)-50DS-0.4V(51) gives you a 2.9mm gap. Both carry 50 positions at the same 0.40mm pitch with identical contact finish — the choice is purely the z-height budget between your boards. The 0.6mm difference matters when a component on the lower board or enclosure wall sets the clearance.