An electrical connector for connecting a daughter board to a mother board, includes an insulating housing; contact terminals disposed in the insulating housing; an open mouth provided in the insulating housing for receiving the daughter board; terminal receiving slots provided in the open mouth; each of the contact terminals being made by stamping and forming a spring conductive sheet so as to have a fixing section to be fitted in the terminal receiving slot, a reverse U-shaped section extending upwardly from the fixing section and then downwardly into the open mouth to provide a lower contact point, a J-shaped section extending upwardly from the lower contact point and toward the rear wall and then upward to provide a stopper section, and a C-shaped section extending upwardly from the J-shaped section and into the open mouth to provide an upper contact point; the reverse U-shaped section, the J-shaped section, and the C-shaped section constituting a spring unit; shoulders provided on the rear wall of the open mouth for engagement with the stopper section to hold the contact terminal in the terminal receiving slot with the spring unit under a preload condition so that when the daughter board is turned to the latch position to flex the spring section, the upper contact points are brought into contact with the pads on the edge portion with a predetermined contact force.