Low-Profile Mezzanine Receptacle for Dense Board Stacks
The Hirose DF40C-90DS-0.4V(51) is a 90-position receptacle with center strip contacts on a 0.016" (0.40mm) pitch, arranged in two rows. The mated stack height lands at 1.5mm, with the receptacle itself sitting 0.057" (1.45mm) above the board — a profile that fits between closely spaced PCBs in handheld or portable electronics. The contacts are finished with gold, plated to 2.00µin (0.051µm). Surface-mount termination keeps the footprint clean for automated pick-and-place assembly, and the narrow 0.40mm pitch packs 90 circuits into a board edge that a 0.50mm pitch part would need 45% more width to cover. The center strip contact arrangement — contacts in the middle of the connector body — simplifies routing by keeping the signal traces on inner layers of the PCB.
The receptacle height above board is 0.057" (1.45mm), meaning the header side contributes the remaining 0.05mm to reach the 1.5mm total. When laying out the board, the keep-out zone under the receptacle is minimal, but the solder pads for the 0.40mm pitch need tight registration — the pad width and spacing must match the Hirose recommended footprint to avoid opens or shorts.