An interposer for establishing a vertical connection between semiconductor packages includes an electrically insulating substrate having a first main side and a second main side opposite the first main side, a plurality of first electrical conductors at the first main side of the substrate, a plurality of second electrical conductors at the second main side of the substrate, and a programmable connection matrix at one or both main sides of the substrate. The programmable connection matrix includes programmable junctions configured to open or close electrical connections between different ones of the first electrical conductors and different ones of the second electrical conductors upon programming of the junctions.