The DF40TC(3.0)-20DS-0.4V(51): This is a Hirose DF40T series receptacle with 20 positions arranged in two rows on a 0.40 mm pitch. It's designed for board-to-board mezzanine stacking with a mated height of 3 mm. The gold-plated contacts (1.97 µin thickness) and center strip contact design suit signal-level applications where repeated mating cycles and corrosion resistance matter. Pick-and-place compatible packaging and solder retention features streamline automated SMT assembly.
That's a tight envelope for compact handheld or portable electronics. Height above board for the receptacle alone is 0.114" (2.90 mm).
Supplied in tape and reel packaging for automated pick-and-place.