DF40HC(3.0)-90DS-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 high contact density and reliable mating are important. With 90 positions, gold-contact construction, and tape-and-reel packaging for automated assembly, it is well suited for space-constrained industrial electronics, embedded systems, communication hardware, portable devices, and other dense PCB designs. Engineers typically select parts in this category for signal routing between stacked boards where consistent mechanical alignment and assembly efficiency matter. From a sourcing perspective, the provided data indicates limited supply status and an estimated production lead time of 25 weeks, so forward planning is recommended for new builds and ongoing production. Lifecycle status is listed as unknown, so design teams should confirm current manufacturer status before committing. RoHS compliance information is not available in the provided specifications; engineers should verify environmental compliance directly with Hirose documentation or authorized distribution channels.