Fundamental study on adhesive strength of electrical conductive adhesives (ECAs)

Electrically conductive adhesives (ECAs) are perceived as the next generation interconnection materials for printed wiring boards (PWBs) and electronic packaging. Poor adhesive strength and weakness in terms of impact resistance obstruct the wide application of ECAs. For this reason, fundamental studies of ECAs are needed. In this paper, relationships between the orientation of silver flakes in epoxy ECAs and the adhesive strength were investigated. Two kinds of processes to randomize the silver flake orientation were proposed. The silver flake orientation randomization was found to be effective in improving adhesive strength. A novel nonAu/Pd sputtering SEM technique was proposed. By this technique, the ECA conductive path was easily identified. The edges of the silver flakes and small particles in the ECAs were found to be very effective for electrical contact, as illustrated by the nonAu/Pd sputtering SEM study