An electrical card connector assembly (100) comprising: a first electrical card connector (1); a second electrical card connector (2) disposed below the first electrical card connector; a third electrical card connector (3); a fourth electrical card connector (4) arranged abreast with the third electrical card connector; a PCB (5) defining an upper surface (50) and a lower surface (51), the upper and lower surface having a plurality of traces, respectively; wherein the combined first and second card connector are disposed on the upper surface (50) of the PCB and electrically connected with the corresponding traces of the upper surface, and the third and fourth electrical card connector are arranged abreast on the lower surface of the PCB (5) and electrically connecting with the corresponding traces of the lower surface (51).