DF40HC(3.0)-30DS-0.4V(51) from Hirose Electric Co Ltd is a surface-mount rectangular connector receptacle in the DF40 family, designed for compact board-to-board interconnect applications where space efficiency, signal integrity, and reliable mating are important. With 30 positions and gold-plated contacts noted in the provided specifications, it fits well in portable electronics, industrial control modules, embedded systems, communication equipment, and other high-density assemblies. Engineers typically choose this type of connector when they need a low-profile interconnect solution from a well-known connector manufacturer with strong adoption in space-constrained designs. From a sourcing standpoint, this part should be treated with some caution because the listed supply-and-demand status is limited and the lifecycle status is currently unknown, so procurement teams should verify long-term availability before locking it into new programs. RoHS compliance information is not available in the provided specifications, so engineers should confirm current RoHS and related material declarations directly through the official Hirose documentation or manufacturer-authorized channels.