The Hirose FX2-40P-1.27DSL(71) is a 40-position board-to-board plug from the FX2 series, built for parallel board stacking where you need a reliable right-angle interconnect. It uses center strip contacts in a 2-row layout on a 1.27 mm pitch — tight enough for dense routing but still forgiving for hand assembly and rework.
Board Lock — Not Just a Fancy Name
It does two things: it keeps the connector square during solder reflow so the contacts don't skew, and it transfers mechanical strain from the cable or mating board into the PCB rather than the solder joints. On a 40-position right-angle plug, that matters — the lever arm from the mated board can generate enough torque to crack a solder fillet over time. The lock takes that load.