The Hirose DF40C-20DP-0.4V(51) is a 20-position plug with outer shroud contacts from the DF40 series, designed for board-to-board mezzanine stacking. The connector sits just 0.045" (1.14mm) above the board, which lets you squeeze the stack height budget in slim enclosures.
Mated Stacking Heights and Board Fit
This plug mates with the matching DF40 series receptacle to achieve a mated stacking height of 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, or 4mm — six discrete height options from the same connector pair. That range covers everything from ultra-slim phone-style builds at 1.5mm up to a standard mezzanine gap at 4mm where you can route passives between boards. The choice of receptacle height determines the final stack, so match the receptacle part number to your z-height requirement before locking the BOM.
The connector includes solder retention features — additional SMT pads on the sides that anchor the part to the board during reflow. At a 0.40mm pitch, the signal pads alone don't provide enough shear strength to resist the nozzle forces from a pick-and-place head or the thermal stress of a lead-free reflow profile. Those retention pads prevent the connector from shifting or tombstoning, and they also help absorb the shear load from a cable tug if the assembly is handled before potting.
The contacts are finished with 2.00µin (0.051µm) of gold over the base metal. For a production board that's mated once and then shipped, the gold flash keeps contact resistance low through the initial mate and the first few reconnections during test.
Regulatory and Lifecycle Status
The RoHS compliance covers EU Directive 2011/65/EU, which is the baseline for most global electronics manufacturing.