DF40HC(3.0)-100DS-0.4V(51) from Hirose Electric Co Ltd is a fine-pitch board-to-board rectangular connector designed for compact, high-density interconnect requirements in modern electronic assemblies. As a 100-position, 0.40 mm pitch receptacle in the DF40 series, it is well suited for portable devices, embedded control boards, industrial modules, medical electronics, and other space-constrained systems that need reliable mezzanine stacking at 3 mm. Engineers typically choose this type of connector when PCB real estate is limited and signal routing density is critical. The gold contact finish and SMT mounting format support automated assembly and dependable contact performance in production environments. Based on the provided data, lifecycle status is currently unknown, so teams should confirm ongoing manufacturer support before committing to new designs or long-term service builds. RoHS compliance information is not explicitly provided in the specifications, so compliance should be verified through the latest Hirose documentation or supplier compliance records before regulated-market deployment.