DF40HC(3.5)-60DS-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 high-density interconnection. With 60 positions, 0.40 mm pitch, 2-row layout, SMT mounting, and a 3.5 mm mated stacking height, it fits space-constrained designs such as industrial controllers, portable equipment, embedded modules, communication hardware, and consumer electronics. Engineers typically select parts in this connector class when they need stable board stacking, precise alignment, and gold-finished contacts for signal integrity and mating reliability. The listed product status is Active, which is a positive indicator for ongoing design support, although formal lifecycle confirmation should still be verified through Hirose documentation because the provided lifecycle field is marked unknown. RoHS compliance information is not explicitly provided in the input data, so compliance status should be treated as information not available pending official manufacturer or distributor documentation.