A socket connector assembly (10) comprises an insulative housing (10) comprising a bottom conductive section (201) defining a plurality of contact-receiving slots and four sidewalls (202) extending upwardly from edges of the conductive section, and a pick-up cap (30) assembled to the insulative housing and comprising a smooth top surface (301) adapted for being sucked by a vacuum device and opposite contacting surface (302). At least one of the sidewalls of the insulative housing and the pick-up cap defines at least a pair of aligning posts (303) at opposite corners thereof, and at least one of the pick-up cap and the sidewalls of the insulative housing defines a pair of aligning slots (203) at opposite corners thereof to interferentially receive the aligning posts to assemble the pick-up cap to the insulative housing.