Electrically and thermally enhanced package using a separate silicon

Abstract

An integrated-circuit package assembly includes a separate silicon substrate to which an integrated-circuit die is fixed. The separate silicon substrate serves as a heat spreader for the integrated-circuit die. The separate silicon substrate to which the integrated-circuit die is fixed is packaged in either a molded package body or a cavity-type package body. For the molded package body, the package body is molded around a leadframe, the integrated-circuit die, and the separate silicon substrate to which the integrated-circuit die is fixed. For a molded package body, the leadframe has bonding fingers formed at the inward ends thereof which are attached to the separate silicon substrate or the lead frame may have a die-attach pad to which is fixed the separate silicon substrate. For the cavity-type package, the package body includes a mounting surface formed adjacent to a cavity formed therein and the mounting surface has the separate silicon substrate fixed to the top surface thereof. The cavity-type body is formed of a ceramic material or as a multi-layer printed-circuit board. One or more interposer areas are formed on the top surface of the silicon substrate for attachment of connection wires from the integrated-circuit die or the leadframe. A portion of the interposer can extend between the integrated circuit die and the top surface of the silicon substrate to accommodate integrated-circuit dies of various sizes. The interposer includes a layer of oxide formed on the surface of the silicon substrate, which layer of oxide is covered with a layer of conductive material.