An assembly includes an expansion card, an enclosure, a mounting bracket, and a sliding member. The expansion card includes a first terminal and a second terminal. The mounting bracket secures the first terminal of the expansion card. The securing bracket is mounted on the enclosure. The securing bracket includes a main body. The second terminal of the expansion card is placed on the main body. A positioning piece is located on the main body. The positioning piece comprising a free end on which a first protrusion is located. The sliding member is slidably mounted on the main body. The sliding member includes a pressing piece. A second protrusion is located on the pressing piece. The sliding member is adapted to slide on the main body between a first position and a second position. At the first position, the pressing piece presses the second terminal on the main body, and the first protrusion blocks the second protrusion to prevent the sliding member sliding from the first position. At the second position, the second protrusion slides over the first protrusion, and the pressing piece is disengaged from the second terminal.