An electrical connector assembly includes a socket body defining a receiving cavity, a pick up cap attached detachably onto the socket body and a movable fixing mechanism surrounding the socket body. The fixing mechanism includes a rotatable cover defining an open position and a close position and having two pressing portions extending towards the receiving cavity of the socket body. The pick up cap covers all terminals in the socket body and includes a planar body having concaved portions for receiving the corresponding pressing portions to prevent the pressing portions from interfering with top surface of the planar body of the pick up cap.