An electrical connector assembly includes a seat unit and a cover unit. The seat unit defines a receiving cavity for receiving the CPU. The cover unit is pivotably mounted upon one end of the seat unit. The cover unit includes a first cover and a second cover surrounding the first cover. The first cover includes a first frame equipped with therein a floating heat sink which is located above and aligned with the receiving cavity. The heat sink forms a pair of side extensions sandwiched between a pair of pressing blocks and the first frame in a vertical direction and essentially downwardly pressed by the pair of pressing blocks of the first cover in a resilient manner. Resilient mechanism is provided between the pressing block and the heat sink to result in a downward force constantly urge the heat sink downwardly against the first frame.