The Hirose DF40B-50DS-0.4V(51) is a 50-position receptacle with center strip contacts from the DF40 series, a family of fine-pitch board-to-board connectors designed for compact, parallel-stacked PCBs. The 0.40mm pitch and 1.5mm mated stacking height place it squarely in the mezzanine interconnect space for handheld devices, camera modules, and other dense electronics where every millimeter of z-height is budgeted. It is the receptacle half — the board-mount side that receives the mating header — and carries gold-plated contacts on two rows.
At 0.40mm pitch, this is a fine-pitch part that demands a controlled SMT process — no hand-soldering, no rework without a hot-air station and a steady hand. If your assembly has a 1.6mm board pair, the total stack with this connector lands at about 4.7mm, which fits inside a typical 5mm housing gap.
The gold contact finish is 2.00µin (0.051µm) thick — a light flash. If your application requires dozens of mate-unmate cycles, look for a heavier gold option in the DF40 family. For a one-time board stack that stays mated, this plating is perfectly fine and keeps the cost down.
It is in normal production and available through the independent distribution channel.