DF40HC(3.5)-30DS-0.4V(51) from Hirose Electric Co Ltd is a fine-pitch rectangular board-to-board receptacle designed for compact electronic assemblies that need reliable interconnect density in limited PCB space. With a 0.40 mm pitch, 30 positions, dual-row layout, and 3.5 mm mating stack height, it fits well in portable devices, industrial control modules, communication hardware, and other miniaturized embedded systems. Engineers typically select this series when balancing profile, contact reliability, and SMT-friendly assembly. The listed status is Active, which supports ongoing design consideration, although the provided lifecycle field is otherwise marked unknown, so long-term program teams should still confirm current manufacturer guidance. RoHS compliance information is not explicitly provided in the supplied specifications, so compliance should be treated as information not available pending official Hirose documentation or distributor confirmation. For procurement, supply is listed as sufficient, but open-market counterfeit risk is notable, making authorized sourcing and traceability especially important.