Determining the impact resistance of electrically conductive adhesives using a falling wedge test

This study was conducted to determine the impact resistance of electrically conductive adhesives (ECAs). A novel falling wedge test that was used to quantitatively characterize the impact resistance of conductive adhesives at a material level has been described, and some important findings obtained from the falling wedge test are presented. This unique impact resistance testing method is not only a substitution of the conventional drop test which has several severe drawbacks, but also provides some useful information for screening adhesives at the materials level and helping formulate new conductive adhesives with improved impact performance. Three model conductive adhesives were studied in this work and the impact fracture energies of the adhesive materials were measured utilizing the falling wedge test. The effect of test temperature on the fracture behavior of ECAs was examined and the correlation between the impact resistance and damping property of the conductive adhesive was also investigated. This study suggests that 1) the falling wedge test is able to discriminate between adhesives and this technique is capable of screening adhesives for bonding purposes; 2) the viscoelastic energy has played an important role in the fracture behavior of the conductive adhesives. As a measure of the internal friction, the loss factor tanδ is found to be a good indicator of a conductive adhesive´s ability to withstand impact loading.