Cube 630 was a Borg cube that was in service in the late 24th century. In 2377, this cube had a crew complement of 64,000 drones, and three of those drones had disengaged from the Collective.
While Cube 630 was patrolling Grid 94, the Borg Queen noticed that the voices of those three drones had become silent. Fearing a possible resistance from drones affected by Unimatrix Zero, the Queen initiated the cube's self-destruct mechanism, thus silencing all 64,000 voices. (VOY: "Unimatrix Zero, Part II")