0.50mm Pitch Mezzanine Header for 40-Position Board Stacks
The Hirose DF17(4.0)-40DP-0.5V(57) is a 40-position header from the DF17 series, built for parallel board-to-board stacking at a tight 0.020" (0.50mm) pitch.
7mm or 8mm Stacking Height — Pick Your Board Gap
This header supports mated stacking heights of 7mm and 8mm, depending on the mating receptacle used. The height above board is 0.248" (6.30mm), so the 7mm stack leaves about 0.7mm clearance between the header body and the opposing board — enough for component keep-outs on the underside. The 8mm stack gives a bit more room for taller passives on the bottom board. Both heights use the same footprint, so you can swap between them without a board respin.
The board guide aligns the header during placement so it doesn't skew on the paste; the solder retention pads anchor it to the board during reflow and add mechanical strength against shear forces from the mating cable or vibration. For a 40-position SMT part at 0.50mm pitch, those retention features are what keep the joints from cracking under thermal cycling.
It's a current-production part with no announced end-of-life. No direct manufacturer cross-reference exists; the part is specific to the Hirose DF17 series.