Thermomechanical Analysis of Electrically Conductive Adhesives

Abstract

Mechanical properties of isotropic electrically conductive adhesives (ICAs) are mainly influenced by their formulation and thermal processing. Thermomechanical analysis of ICAs was used with the goal to find influence of addition of two types of nanoparticles, silver nanoballs and carbon nanotubes, and two types of curing processes, on air and in vacuum, on the glass transition temperature and storage modulus of bisphenol epoxy adhesives filled with silver flakes (70 to 80 % by weight). Specimens were formed as blocks. Three groups of specimens were fabricated: specimens of adhesives used as received and cured according to the recommendation of a supplier in air; specimens of adhesives used as received and cured according to the recommendation of a supplier in vacuum, specimens of the same adhesives added with low fraction (0,3 to 10 % by weight) of silver nanoballs, colloidal dispersion of silver, or carbon nanotubes. There were found differences in the glass transition temperatures and storage and loss moduli in dependence on the type of particles added into adhesive. It was also found that the adhesive cured in vacuum had lower thermal expansion coefficient and higher the storage and loss modulus in comparison with adhesive cured in air.