A cold welded hermetic micro or nano package sealed in an inert atmosphere with optional force maintenance means for ensuring permanent closure. A package cap 410 coated with precursor weld material is sealed to a package base 405 containing integral device 445 then cold welded with an external force mechanism to compress and flow cold seal preform material 435 creating a hermetic peripheral seal in an inert or vacuum atmosphere. Arrays of devices can be sealed with individual caps or arrays of caps which are interconnected.