An interposer is provided which includes: a substrate having a first surface with a plurality of first conductive pads and a second surface opposite to the first surface, the second surface having a plurality of second conductive pads; a plurality of conductive through holes penetrating the first and second surfaces of the substrate and electrically connecting the first and second conductive pads; and a first removable electrical connection structure formed on the first surface and electrically connecting a portion of the first conductive pads so as to facilitate electrical testing of the interposer.