DF40C-90DS-0.4V(58) from Hirose Electric Co Ltd is a fine-pitch board-to-board mezzanine receptacle designed for compact electronic assemblies where space, signal density, and reliable interconnect performance matter. As part of the rectangular board-to-board connector family, it is well suited for portable devices, industrial control modules, embedded systems, display assemblies, and other high-density PCB designs that require a 0.40 mm pitch and surface-mount implementation. Engineers typically choose this style of connector for stacked board architectures that need low profile construction and gold-finished contact interfaces for dependable mating performance. Based on the provided data, this part is currently associated with a shortage condition, which can affect procurement planning for ongoing production or new designs. Lifecycle status is listed as unknown, so design teams should verify current manufacturer status before committing to long-term programs. RoHS compliance information is not available in the provided specifications, and compliance should be confirmed directly through official Hirose documentation or supplier certification before release to regulated markets.