An electrical connector for mounting on a circuit board includes a longitudinal base and a plurality of contacts received therein. The longitudinal base includes a mating face, an assembling face opposite to the mating face for confronting with an edge of the circuit board. Each contact includes a contacting portion exploding to the mating face and a spring tail extending out of the assembling face for elastically pressing against the circuit board in a height direction perpendicular to the longitudinal direction. A retention pad is secured to the housing and comprises a pressing end for elastically pressing against the circuit board to balance prepressure of the spring tails to the circuit board.