The Hirose DF37C-40DP-0.4V(53) is a 40-position header from the DF37 series of fine-pitch board-to-board stacking connectors. The mated stack height lands at 0.98mm, and the header itself sits 0.75mm above the board surface. This is the kind of connector you specify when the z-height budget between two boards is tight and the board area is expensive — think compact handheld devices, camera modules, or internal mezzanine links in portable equipment.
What the 0.40mm Pitch Means for Your Board Layout
At 0.40mm pitch, the routing channels between pads are narrow — expect to use 0.2mm trace widths and 0.2mm clearances to get two traces between adjacent pads on a standard PCB. The footprint's keep-out zone is small, but the via density under the connector body is limited; you'll likely need micro-vias or blind vias in the escape pattern if you're routing all 40 signals out on a single layer. The outer shroud adds about 0.3mm to the overall footprint width beyond the last row of contacts — account for that in the component clearance polygon.
The 0.75mm header height plus the receptacle height sum to that stack height — both boards sit parallel with a 0.98mm gap between their facing surfaces. For applications with vibration, a staking pin or adhesive under the connector body is advisable.
The contacts carry 2.00µin of gold over the base metal. It is not specified for repeated field service or frequent reconnections.
The DF37C series is available in 40 and 50 positions at the same 0.40mm pitch and 0.75mm height. The DF37C-50DP-0.4V(53) carries 50 circuits in the same footprint width — the extra 10 positions extend the connector length by about 4mm along the board edge. If your BOM calls for 50 signals, the 40-position part won't fit; the 50-position variant is the direct swap at the same stack height and pitch.