High Thermal Conductivity Metal Matrix Composites

Abstract

Metal matrix composites (MMCs) are composed of a metal matrix and a reinforcement, which confers excellent thermally conductive and mechanical performance. High thermal conductivity MMCs have special advantages for particular electronic packaging and thermal management applications because of their combination of excellent thermal conductivity, relatively low density, and tailorable coefficient of thermal expansion (CTE) to match the CTE of semiconductor materials such as silicon, gallium arsenide, or alumina. The optimal design of MMC components is based on appropriate selection of matrix materials, reinforcements, and layer orientations to tailor the properties of a component to meet the needs of a specific design. The specific factors that influence the characteristics of MMCs include reinforcement properties, shape of the dispersed phase inclusions (particles, flakes, fibers, laminates), and orientation arrangement of the dispersed phase inclusions, such as random or preferred; reinforcement volume fraction; matrix properties, including effects of porosity; reinforcement-matrix interface properties; residual stresses arising from the thermal and mechanical history of the composite; and possible degradation of the reinforcement resulting from chemical reactions at high temperatures, and mechanical damage from processing, impact, etc. In the absence of ductility to reduce stress concentrations, joint design becomes a critical design consideration. Numerous methods of joining MMCs have been developed, including metallurgical and polymeric bonding and mechanical fasteners. This chapter will give a brief review about the processing of these composites and their performance and applications in the thermal management of electronic packaging. The contents will include typical processing methods for MMCs, the principal high conductivity for MMCs such as aluminum, copper, and their alloy-based MMCs, and to a lesser extent, other MMCs based on beryllium and silver, etc., as well as low CTE composite solders and advanced multifunctional laminates.