An electrical connector assembly (1) includes a mother board (10), a card edge connector (20) mounted on the mother board, a daughter card (30), and a pair of board hold downs (40) mounted on the mother board. The card edge connector includes a housing (21) defining a slot (22), and a number of contacts (23) disposed on opposite sides of the slot and exposed into the slot. The daughter card includes a mating edge (31) inserted into the slot of the housing, a number of conductive pads (33) on the mating edge for electrically connecting with the contacts of the card edge connector. The board hold downs are separated from the card edge connector and hold the daughter card in the card edge connector.