A method of making an interposer in which at least two dielectric layers are bonded to each other to sandwich a plurality of conductors there-between. The conductors each electrically couple a respective pair of opposed electrical contacts which are formed within and protrude from openings which are also formed within the dielectric layers as part of this method. The resulting interposer is ideally suited for use as part of a test apparatus to interconnect highly dense patterns of solder ball contacts of a semiconductor chip to lesser dense arrays of contacts on the apparatus's printed circuit board.