The Hirose DF40TC(4.0)-20DS-0.4V(58) is a 20-position receptacle from the DF40T series, designed for board-to-board mezzanine stacking. It uses a 0.40mm pitch and a center strip contact arrangement across two rows, giving you a compact signal interconnect for tight PCB layouts. The 4mm mated stacking height is fixed by the (4.0) designation in the order code — this part mates with a matching DF40T header to create a precise 4mm gap between boards.
Footprint and Assembly — What the 0.40mm Pitch Means
At 0.40mm pitch, the footprint is dense — each contact sits on a 0.40mm centerline, which drives the trace-and-space capability of your PCB. You need a fabricator comfortable with fine-pitch SMT routing; the solder pads are small and the keep-out zone between rows is tight. The connector includes pick-and-place features and solder retention aids, so it handles reflow soldering without tombstoning. Surface mount termination means no through-holes, which frees up routing channels on inner layers directly under the connector.
The DF40T series has no official cross-reference or second-source; the mating header must be a Hirose DF40T series part with the matching (4.0) stack height code.