Board-to-Board Stacking Fit — 0.050" Pitch at 5.00 mm Mated Height
The Hirose FX4A1-20S-1.27SV(71) is a 20-position receptacle from the FX4 series of mezzanine board-to-board connectors. It uses a center strip contact arrangement in two rows on a 0.050" (1.27mm) pitch, with a mated stack height of 0.197" (5.00mm).
What the 5.00 mm Stack Height Means for Your Board Layout
The 0.197" (5.00mm) mated height is the dimension that sets the gap between the two PCBs in a mezzanine stack. The surface-mount tails reflow on the same side as other SMDs, so no through-hole solder wave is needed.
FX4A vs FX4B — When the Board Guide Matters
The FX4B1-20S-1.27SV(71) shares the same 20-position count, 0.050" (1.27mm) pitch, 5.00mm stack height, and gold plating as this FX4A part. The difference: the FX4B adds a board guide feature — molded alignment posts on the connector body that help register the two boards during assembly. For hand-placed or low-volume builds the FX4A works fine; for automated pick-and-place with tight stack alignment, the FX4B's board guide reduces the risk of skewed mating and bent contacts.