Residual stresses in isotropic conductive adhesives with nano-Ag particles

Residual stresses that develop in a nano-Ag ICA interconnect during the assembly of a flip-chip pin grid array are investigated. A multiscale modeling framework is adopted to link the nano-sized particles to the interconnect level. This is achieved by the numerical analysis of the mechanical response during the curing process through the computational homogenization approach, in which two boundary value problems, one at each scale are formulated and solved in a concurrent, fully nested manner. The mechanical response of the interconnect is analyzed with respect to the particle volume fraction and distribution properties. It is shown that, although the overall residual stresses at the interconnect scale decrease with increasing filler fraction, at the particle scale local stress concentrations increase, indicating the possibility of damage and decohesion that might compromise mechanical integrity and interrupt the conductive path.