DF40HB(2.5)-10DS-0.4V(51) from Hirose Electric Co Ltd is a compact DF40 series board-to-board mezzanine receptacle designed for high-density interconnect applications where space, profile, and signal integrity matter. With a 0.4 mm pitch, 10 positions, vertical mounting, and 2.5 mm stack height, it fits well in portable electronics, industrial control boards, communication modules, compact medical devices, and embedded systems that require reliable PCB stacking. The use of LCP housing material, phosphor bronze contacts, and gold plating supports stable mechanical and electrical performance in demanding assembly environments. Based on the provided specifications and typical market requirements for board-level interconnects, this part is commonly evaluated for RoHS-oriented designs, but the exact RoHS declaration is not available in the supplied data and should be verified through official manufacturer documentation. Lifecycle status is currently listed as unknown, so engineers should confirm long-term availability before locking it into new designs or volume production plans.