Board-to-Board Mezzanine Header, 0.40mm Pitch
The Hirose BM20B(0.8)-20DP-0.4V(51) is a 20-position, dual-row header from the BM20 series, designed for board-to-board mezzanine stacking. Mated stacking height is 0.8mm, which sets the board spacing for the mezzanine pair.
0.8mm Stacking Height and SMT Fit
The 0.8mm mated stack height is the dimension that decides the board-to-board gap — design the mezzanine around that number. The 0.026" (0.65mm) height above board means the connector sits low, leaving room for components on the underside of the top board. Against the 16-position BM20B(0.8)-16DP-0.4V(51) at the same pitch and stack height, this 20-position version adds four circuits for a wider I/O count without changing the board footprint or the z-height budget.