Characterisation of curing shrinkage for isotropic conductive adhesives containing silver coated polymer spheres

This study investigates the volume shrinkage of isotropically conductive adhesives (ICAs), including those filled with silver coated/metallised polymer spheres (Ag-MPS), and the effect of factors such as Ag-MPS volume fraction, adhesive matrix type, and curing process conditions on their overall volume change during cure. This study also investigates flake filled adhesives, including one that is commercially available, and compares it with the Ag-MPS filled adhesives. The results show volume expansion occurred for the majority of Ag-MPS filled adhesives in contrast with the shrinkage observed for all flake filled adhesives. For flake filled adhesives the results showed a significant effect of adhesive matrix type on shrinkage. However, for Ag-MPS filled adhesive the results showed absence of any consistent trend for the dependence of shrinkage on filler volume fraction, curing conditions and epoxy matrix. A detailed analysis, along with discussion of the likely mechanisms for the results observed, is presented in this paper.