What this connector is
The Amphenol FCI 87901-118HLF is the 18-circuit member of the BERGSTIK II dual-row board-to-board header series. It mates two parallel PCBs at 0.100" (2.54 mm) pitch with all 18 positions loaded, carrying square male pins through 0.820" of engagement depth into the matching receptacle. The series uses a push-pull fastening style on an unshrouded header body — retention comes from the pin/socket interference fit, not a locking arm or screw. The contacts are phosphor bronze with either gold or Gold GXT plating at 30.0µin (0.76µm) on the mating side, which is the grade that separates higher-cycle members from tin-plated siblings in the same series.
Ratings that drive the fit decision
5 A per contact at up to 110 V — the current rating governs wire gauge and circuit duty; the voltage rating is well within range for signal and low-power interconnect on a 2.54 mm pitch header. At 5 A per circuit with 18 positions in a dual-row layout, the thermal margin at the board entry point depends on your trace width and the connector's own UL94 V-0 housing — verify against your derating curve if the application runs warm. Through-hole termination with 0.120" (3.05 mm) post length and 1.040" (26.42 mm) overall contact length means the header sits proud of the board surface; the mated engagement depth of 0.820" (20.83 mm) tells you how far the receptacle sits over the pin during mating — relevant for z-axis clearance in stacked board assemblies.
Where it is used
Board-to-board headers at 0.100" pitch are the standard interconnects in industrial control modules, test and measurement equipment, and telecommunications backplane cards — anywhere two parallel boards need to dock and undock for service. The push-pull unshrouded style keeps the connector low-profile and avoids the extra envelope a locking lever adds, which matters in dense card-cage layouts where every millimetre of z-height is budgeted.