The Hirose FX11LA-100P/10-SV(71) is a 100-position, 2-row header from the FX11 series, designed for board-to-board mezzanine stacking with a fixed mated stack height of 2 mm. Gold-plated contacts (4.00 µinch) on the mating side keep contact resistance low through the first few dozen matings — adequate for a one-time assembly or limited rework cycles, not for daily field reconnects. The outer shroud contacts and integrated ground plate help manage signal return paths and reduce EMI in high-frequency digital or mixed-signal designs.
This header mates with a corresponding FX11 receptacle to achieve a board-to-board spacing of exactly 2 mm. That height is fixed by the connector design — the board stack-up, component clearance on the underside, and any heat sink or shield must all fit within that envelope. The 0.50 mm pitch also means the PCB trace routing between the connector pads needs fine-line capability; a standard 0.5 mm pitch land pattern with via-in-pad or micro-via is typical for this density class.
Comparing the 100-position to the 80-position sibling
The FX11LA-80P/8-SV(71) carries 80 positions at the same 0.50 mm pitch and 2 mm stack height, so the footprint and mating receptacle are identical in pitch and height — the difference is purely the position count. If your BOM calls for 100 circuits, the 80-position part leaves 20 traces unconnected; if you only need 80, the 100-position header still works but wastes board area and adds cost. Match the position count to the circuit count — no reason to oversize.