Thermal expansion of a composite of single-walled carbon nanotubes and nanocrystalline aluminum

With the rapid development of microelectronics, materials used in electronic packaging are undergoing a revolution. Electronic devices such as multichip modules demand packaging materials with a low coefficient of thermal expansion (CTE), high thermal conductivity and excellent mechanical properties [1]. With outstanding mechanical properties, extraordinarily low thermal expansion (CTE � 0), and high thermal conductivity [2–4], carbon nanotubes (CNTs) are an attractive reinforcing agent to lower the CTE of Al packaging material. The CTE of Al is so high compared to those of semiconductor materials that thermal stress and strain may occur at the boundary between them. The fabrication and properties of CNT reinforced composites reported recently [5–7] have mainly focused on the mechanical properties, while their thermal properties were rarely investigated. Based on the successful fabrication of nanocrystalline aluminum (nano-Al) based composites reinforced by single-walled carbon nanotubes (SWNTs) [7], the ther