0.40mm Pitch, 40-Position Mezzanine Receptacle — Board-Layout Fit
The Hirose BM20B(0.8)-40DS-0.4V(53) is a 40-position receptacle from the BM20 series, designed for board-to-board mezzanine stacking at a mated height of 0.8mm. The 0.016" (0.40mm) pitch on a dual-row layout packs 40 circuits into a compact footprint — the tight pitch is the primary constraint for PCB trace escape and pad spacing. Gold-plated contacts on both rows handle signal-level duty in dense, low-profile interconnects typical of mobile devices, wearables, and compact embedded systems.
Position Count and Stack Height — What Drives the Fit
The 40 positions match a 40-circuit BOM line directly — the first check against the schematic is the count. The 0.40mm pitch forces a fine-pitch footprint — standard 0.5mm or 0.8mm pitch routing rules do not apply here, and the board house must support the trace/space for 0.40mm pad centers.