The Hirose DF12B(3.5)-20DP-0.5V(86) is a 20-position, 2-row header with outer shroud contacts from the DF12 series, designed for parallel board-to-board stacking at a 3.5mm mated height. Gold plating at 8.00µin on the contacts gives a solid mating cycle count for production assembly and field service, though it's not rated for the high-cycle duty of a gold-flash connector.
What the 3.5mm Stack Height and 0.50mm Pitch Mean for Your Board
The 0.50mm pitch is tight — it routes well between BGA pads on a standard PCB but demands careful trace width and spacing to avoid crosstalk on the inner rows. That z-height budget is fixed, so the mating receptacle must also be a 3.5mm stack variant from the DF12 series. The outer shroud contacts mean the signal pins are recessed inside a plastic shell — this protects them during handling and prevents bent pins before mating, but it also means the footprint has a keep-out zone around the shroud that the PCB layout must respect.