Board-to-Board Stacking Header for Tight Z-Height Budgets
The Hirose DF17A(4.0)-40DP-0.5V(57) is a 40-position, dual-row header with outer shroud contacts, part of the DF17 series designed for parallel board-to-board stacking. It uses a 0.50mm pitch and surface-mount termination, with gold-plated contacts throughout. The connector supports two mated stacking heights — 7mm and 8mm — giving the board layout engineer flexibility to match the z-height budget without changing the header footprint.
Stacking Height and Footprint Fit
That 0.70mm to 1.70mm gap between header top and receptacle bottom is where the contact beams engage. For a 0.50mm pitch dual-row layout, the footprint is tight: each row of 20 contacts on 0.50mm centers means the outer rows span about 9.5mm across the body. The board guide adds about 0.5mm to each end of the keep-out zone, so account for that in the component clearance area.
What the 40-Position Count Tells You
40 positions at 0.50mm pitch in two rows means 20 contacts per row — a common count for parallel bus interfaces or display ribbon replacements. The outer shroud contacts wrap around the mating receptacle, providing mechanical alignment and some EMC containment by surrounding the signal interface. Gold plating on all contacts supports repeated mating cycles; this isn't a one-and-done connector.
Comparing the DF17A Variant to Its Siblings
The DF17A(4.0)-40DP-0.5V(57) shares the same 0.50mm pitch and 6.30mm height above board as the DF17(4.0)-40DP-0.5V(57), but the DF17A adds a board guide feature that the base DF17 version lacks — the base part uses solder retention instead. For a 50-position alternative at the same stacking height, the DF17(4.0)-50DP-0.5V(57) gives you 10 more signal lines in the same footprint length, but the pitch stays 0.50mm so the routing challenge scales with position count. The DF17A(2.0)-80DP-0.5V(57) drops the height to 4.30mm above board for a lower-profile stack, useful when the z-height budget is under 5mm.