What This Connector Is — BM20 Series Header, 24 Circuits, 0.40mm Pitch
The Hirose BM20B(0.8)-24DP-0.4V(53) is a 24-position header from the BM20 series, designed for board-to-board mezzanine stacking. Gold contact finish is standard across the series, which suits repeated mating cycles without corrosion concerns.
This low profile is typical for tight enclosures where every tenth of a millimetre counts. The 0.40mm pitch drives the board footprint: trace escape between pads at this density needs careful routing, especially if inner-layer vias are involved. The solder retention features on the header body anchor it during reflow, reducing the chance of misalignment from paste slump or board handling.