DF40HC(3.0)-100DS-0.4V(58) from Hirose Electric Co Ltd is a fine-pitch board-to-board rectangular connector designed for compact electronic assemblies that need high contact density in a low-profile format. As a 100-position, 0.40 mm pitch receptacle in the DF40 series, it is well suited for portable devices, industrial control boards, embedded modules, medical electronics, and other space-constrained designs where reliable mezzanine interconnection is important. Engineers typically select this style of connector for stacking PCBs while maintaining signal routing efficiency and compact mechanical height. The specified 3 mm mated stacking height and SMT mounting support dense automated assembly workflows. Lifecycle status is currently listed as unknown, so design teams should confirm long-term availability directly with Hirose or an authorized channel before committing to new production. RoHS compliance information is not explicitly provided in the supplied data, so compliance should be verified against the official datasheet, manufacturer declarations, and current procurement documentation.