Aspect Ratio and Loading Effects of Multiwall Carbon Nanotubes in Epoxy for Electrically Conductive Adhesives

摘要

Isotropic conductive adhesives (ICAs) filled with metal particles are commercially available as alternatives to solder joining in electronic packaging. Replacing metal fillers with multiwall carbon nanotubes (MWCNTs) offers the potential benefits of being corrosion resistant, high strength and lightweight. Traditional metal filled ICAs require high metal loading to ensure electrical conductivity, which may cause problems with respect to reliability and strength to weight ratio. The ultra-high aspect ratio and surface area of multiwall carbon nanotubes induce a low percolation threshold of less than 0.25 wt% in epoxy. MWCNTs dispersed in epoxy increase the thermal diffusivity of the polymer by a factor of 2 to 3 and decrease the volume resitivity to less than 10 Ω cm for loadings up to 12 wt%. Lap shear strength decreases with increased MWCNT loading. The dependences of electrical, thermal and mechanical properties on loading and aspect ratio of MWCNTs are reported, and the electrical conduction mechanism is discussed.