DF40C(2.0)-40DS-0.4V(51) from Hirose Electric Co Ltd is a fine-pitch DF40 series rectangular connector designed for compact board-to-board interconnection in space-constrained electronic assemblies. With 40 positions, 0.40 mm pitch, 2 rows, and a 2 mm mated stacking height, it is well suited for handheld devices, industrial modules, embedded control boards, and other high-density designs where reliable signal routing and low-profile packaging are important. Engineers typically select this style of connector for miniaturized systems that need precise alignment, surface-mount assembly, and proven interconnect performance from a well-known connector family. Lifecycle visibility should be treated carefully: the provided lifecycle status is unknown, while the supplied data indicates an estimated EOL date of 2025, so design teams should verify current manufacturer status before committing to new programs. RoHS compliance information is not available in the provided specifications; procurement and compliance teams should confirm RoHS and REACH documentation directly from Hirose or authorized sources.