What this 100-position 0.40mm pitch receptacle does in a board stack
The Hirose DF40JC-100DS-0.4V(53) is a 100-position receptacle with center strip contacts, part of the DF40 series designed for high-density board-to-board mezzanine stacking. At a 0.016" (0.40mm) pitch across two rows, it packs 100 circuits into a footprint that would normally hold half that count at a 0.50mm pitch — the trade-off is tighter routing clearance on the PCB and a more precise solder-paste stencil. The mated stack height is 2mm, with the receptacle sitting 0.057" (1.45mm) above the board surface, which sets the z-height budget for the parallel board pair.
The gold finish is 2.00µin (0.051µm) thick.
Mating and termination — what connects to it
Both halves are surface-mount only — no through-hole option exists in this series at this pitch. The 2mm mated stack height is set by the combination of the receptacle height (1.45mm) and the plug height; the plug sits lower on its board.