Abstract: An interposer and a probe card assembly for electrical die sorting is provided. The assembly may include probes electrically contacting pads of dies on a substrate, a first wiring unit including a first wire on and electrically contacting the probes, an interposer unit including interposers on the first wiring unit and electrically contacting the first wire, and a second wiring unit including a second wire on the interposer unit and electrically contacting the interposers. At least one interposer includes a conductive member, a first connection member adjacent to a first end of the conductive member so as to electrically connect the conductive member to the first wire, a second connection member adjacent to a second end of the conductive member so as to electrically connect the conductive member to the second wire, and at least one protrusion member on an external surface of the conductive member between the first and second connection members.