Apparatus including a chip substrate having a first chip surface facing away from a second chip surface; an array of microelectronic elements on the first chip surface; and an array of conductors each in communication with one of the microelectronic elements, the conductors passing through the chip substrate and fully spanning a distance between the first and second chip surfaces. Process including: providing an apparatus including a chip substrate having a first chip surface facing away from a second chip surface, an array of microelectronic elements being on the first chip surface, an array of conductors each being in communication with one of the microelectronic elements and partially spanning an average distance between the first and second chip surfaces; bonding a temporary support carrier onto the array of microelectronic elements; removing a portion of the chip substrate, thereby reducing the average distance between the first and second chip surfaces; and forming an under bump metallization pad at the second chip surface in electrical communication with a conductor.