High density plug connector unit

Claim 1

A plug connector unit comprising: at least two identical insulative housings each including a soldering face and a mating face, the soldering and the mating face defining a cavity therebetween, each of the at least two identical insulative housings including a central wall projecting upward from an inner surface of the cavity and two rows of passageways respectively defined in opposite side surfaces of the central wall; a plurality of contacts received in each row of the passageways wherein a portion of the contacts are defined as ground contacts while the remaining contacts are non-ground contacts, wherein the ground contacts are longer than the non-ground contacts and located at least at distal ends of each row of the passageways; and a metal shielding comprising a number of collars corresponding to the number of insulative housings so that the metal shielding covers the at least identical insulative housings so that the metal shielding covers the at least two identical insulative housings while each collar thereof is received and retained in the cavity of the corresponding housing, and the contacts received in each row of the passageways of the central wall are surrounded by a collar of the metal shielding; whereby when a complementary connector unit is engaged with/disengaged from the plug connector unit, a grounding engagement is firstly established and lastly released respective of other signaling engagements.