A method and apparatus for mounting microelectronic chips to a thermal heat sink. The chips are arranged in a desired configuration with their active faces all facing a common direction and with their active faces defining a common planar surface for all of said chips. A metallic material is applied to the chip, preferably by electroplating to backsides of the chips, the metallic material being electro-formed thereon and making void-free contact with the backsides of the chips.