A socket assembly has a socket and a heat sink module detachably mounted on the socket. The socket has a base, a sliding board mounted on the base, a lid disposed upon the base and an actuator disposed between the base and the cover. The heat sink module has a fastening frame surrounding the base, a cover pivotally assembled to an end of the fastening frame and a heat sink mounted on the cover. The cover has a latching portion which latches with a top wall of the lid when the cover rotates to a closed position. The heat sink is brought by the cover to pass an open defined on the lid and to abut against an IC package seating on the sliding board.