Xitao Wang

Experimental and theoretical characterization of electrical contact in anisotropically conductive adhesive

Electrical conduction through anisotropically conductive adhesive (ACA) is caused by deformation of metal fillers under pressure and heat. In this work, the hardness of the electrical particles under various deformation degrees was determined by nano-indentor measurements and the electrical resistance of the electrical contacts was measured under various deformation degrees. Theoretical model and simulation have been developed for the microscopic mechanism of the electrical conduction through metal fillers in the anisotropically conductive adhesive. By comparing with experimental data it is concluded that the deformation of the metal filler in our ACA is plastic even at rather low external load. Further theoretical simulation reveals two important aspects of the conductance characteristics. The conductance is improved by increasing the external load but the dependence of the conductance on the spatial position of the metal filler becomes stronger. Design and optimization of the ACA with respect to the absolute value of the electric conductance and its dependence on the spatial position of the metal filler are of essential importance for the electronics packaging application of the anisotropically conductive adhesives.

Quantitative estimate of the characteristics of conductive particles in ACA by using nano indenter

The characteristics of conductive particles in anisotropically conductive adhesives (ACA) were studied by optical microscopy observation and nano indenter measurements. The indentation measurement was performed at the particles in ACA joints using different bonding forces. The load-displacement curves and microhardness values are obtained, which indicate that the nano indenter could be used for quantitative estimation of the electrical and mechanical characteristics of conductive particles in ACAs.