Lightweight metal matrix composites with graphitic fillers showing high thermal conductivity and low thermal expansion.

Abstract

The development of high performance electronic components shows a trend towards miniaturization and higher electrical power. Apart from recent high energy efficiency applications for battery driven devices, an exponential growth in power density of microchips was recorded, which makes thermal dissipation challenging. Heat sinks with excellent thermal conductivity (TC) cannot be exploited to their maximum if the interface to the cooled electronic component is poor due to a thermal paste layer. Direct, solid-solid interfaces achieve a lower interfacial thermal resistance (or Kapitza resistance), but require matching coefficients of thermal expansion (CTE) to avoid mechanical failure. . While the semiconductors typically used in microprocessors have a CTE between 4.2 ppm K-1 for silicon and 5.9 ppm K-1 for gallium arsenide, the CTE of thermally conducting metals ranges from 17 ppm K-1 in copper to 24 ppm K-1 in aluminum. A reduction of this thermal mismatch is the main motivation for investigating materials combining a high TC and a low CTE. Besides the cooling of high performance electronics, which is the focus of this research work, materials with high TC and tunable CTE are of interest in several areas of engineering experiencing high thermal excursions, for instance in aerospace. Both for mobile electronic devices and for aerospace application, a third fundamental property is required: a possibly low density