Surface mount conductive adhesives with superior impact resistance

Abstract

Surface mount conductive adhesives (SMCAs) provide an environmentally friendly solution for interconnections in electronic applications. In addition, SMCAs offer other attractive technical advantages over conventional metal solders including low temperature processing, fine pitch capability, and enhanced thermal cycling performance. However, one key obstacle to general replacement of metal solders by SMCAs in electronic applications is the poor impact resistance of the adhesive interconnections, which is characterized by the industry standardized "drop test" A structure-property-performance study of SMCAs was undertaken with the goal of identifying the key material properties for improved "drop test" performance. This study identified energy dissipation as the key factor governing "drop test" performance and, accordingly, reduced modulus and increased loss factor to be the material properties of importance. The above findings are based on analysis of a physical model of the SMCA assembly used for the "drop test", and further verified by experimental results on a series of exploratory SMCA materials. This study not only led to a thorough understanding of the key performance requirements of the material, but also yielded novel adhesive materials with superior impact resistance capable of maintaining adhesive interconnections during "drop test".