Low-profile heat transfer apparatus for a surface-mounted semiconductor device employing a ball grid array (BGA) device package

摘要

A low-profile heat transfer apparatus is presented for a surface- mounted semiconductor device employing a ball grid array (BGA) device package having a chip mounted upon a substantially flat upper surface of a substrate. The semiconductor device is mounted upon a component side of a printed circuit board (PCB), and the heat transfer apparatus is used to transfer heat energy from the semiconductor device to an ambient. A thermally conductive cap structure is positioned between the semiconductor device and the ambient. The cap structure includes a bottom surface having a first cavity sized to receive the substrate and possibly any decoupling capacitors. During use, the substrate resides within the first cavity. In a first embodiment, the chip resides within a second cavity in an upper wall of the first cavity during use. The chip and substrate are thermally coupled to the cap structure by a first and second thermal interface layer, respectively. The use of two thermal interface layers achieves a relatively low value of &thgr;.sub.JS, allowing the cap structure to remain relatively small. In a second embodiment, the chip resides within a hole in the cap structure during use such that the upper surface of the chip is exposed to the ambient. The substrate is thermally coupled to the cap structure by a thermal interface layer. The achieved value of &thgr;.sub.JS is acceptably low for some applications, and the height of the cap structure relative to the component side of the PCB is substantially reduced.