0.50 mm pitch, 40 positions, 4 mm stack — the mezzanine signal path
Gold plating on the outer shroud contacts gives the mating interface corrosion resistance across repeated engage cycles, which matters for modules that get swapped in the field or for test headers that see dozens of mates before the build ships.
What the 4 mm stack height and 0.50 mm pitch mean for the board layout
The 0.50 mm pitch forces the board designer into controlled-impedance routing for high-speed signals; the narrow trace-and-space geometry means the PCB fab needs a fine-line capability. Surface-mount termination with gold-plated contacts keeps the signal path clean — no solder tail to add parasitic inductance, and the gold interface avoids the fretting corrosion that tin contacts can develop under thermal cycling in a sealed enclosure.