NANOMECHANICS OF MICRON SIZED POLYMER PARTICLES

Micron sized polymer particles have recently been utilized in developing anisotropic conductive adhesives (ACA). The mechanical properties of polymer particles in these applications are extremely important. Due to the spherical geometry and limited volume of micron sized polymer particles, the characterization of mechanical properties possesses great challenges. A computational method to determine the elastic properties of polymer particles at deformation up to 20% is developed based on finite element analyses. The FEM solution has been compared with the analytical Hertz solution and the implicit Tatara solution. It has been shown that the Hertz solution works only for a very small deformation (less than 1%) and the Tatara solution works for a larger deformation level. The finite element results show that the compression stress-strain curves of polymer particles can be normalized by a function of Poisson’s ratio for the compression deformation less than 20%. Based on the finite element solutions a method is proposed for determining the Young’s modulus and Poisson’s ratio of polymer particles at large deformation. The proposed method has been applied to analyze the experimental results from a nanoindentation-based flat punch test.