The Hirose DF12B(3.0)-20DS-0.5V(86) is a 20-position receptacle from the DF12 series, one of the more common fine-pitch board-to-board mezzanine families. It uses a 0.50 mm pitch, dual-row layout with center strip contacts — the mating half is the corresponding DF12 header. The gold-plated contacts and 3 mm mated stacking height make this part suited for compact parallel-board stacking in portable electronics, handheld instruments, and other space-constrained assemblies where the z-height budget is tight.
What the 0.50 mm pitch and 3 mm stacking height mean for the build
The 0.50 mm pitch is tight — it drives the PCB routing density and limits the current per contact to the low-signal range. The 3 mm mated stacking height is the z-height between the two parallel boards; it's a fixed dimension, so the enclosure and component clearance on the underside of the top board must account for it.