Plug connector and connector assembly

The plug connector for a substrate-to-substrate connector includes: a connector body including a pair of first side walls extending in a first direction and facing each other and a pair of second side walls extending in a second direction perpendicular to the first direction and facing each other; a pair of mounting pins overmolded in the plug connector; and a plurality of plug terminals overmolded on the pair of second side walls. Each of the pair of mounting pins includes: an upper surface contacting an upper end of the first sidewall; a central reinforcement bent downward from the upper surface to contact at least a portion of an outer surface of the first sidewall; a pair of side reinforcing portions extending from the upper surface and bent downward to contact at least a portion of an outer surface of each of the pair of second side walls; and a pair of arm parts which are bent from the left and right ends of the central reinforcing part, are spaced toward the interiors of the pair of side reinforcing pa