The HIROSE BM28B0.6-34DP/2-0.35V(51) is a 34-position, dual-row header from the BM28 series, designed for board-to-board mezzanine stacking at a mated height of 0.6mm.
Stacking height and board layout
That 0.6mm is tight — it limits component height on the inner board faces and means the board stack-up itself needs to be thin. The 0.46mm height above the mounting board gives the connector a low profile on the PCB.
That is a thin flash — adequate for the limited mating cycles typical of a mezzanine connector that gets mated once at board assembly and stays there. It is not specced for repeated field disconnect cycles; the gold is there to keep contact resistance stable through the solder reflow and the single mate event.
The 34-position BM28B0.6-34DP/2-0.35V(51) sits between the 30-position BM28B0.6-30DP/2-0.35V(53) and the 36-position BM28B0.6-36DP/2-0.35V(53) at the same 0.35mm pitch and 0.6mm stacking height. The position count is the only difference — the footprint length scales with the circuit count, so the board layout changes by the number of signal lines needed.