Conductivity improvement of isotropic conductive adhesives with short-chain dicarboxylic acids

With the phasing out of lead-bearing solders, electrically conductive adhesives (ECAs) have been identified as an environmentally friendly alternative to tin/lead (Sn/Pb) solders in electronics packaging applications. Compared to Sn/Pb solders, conductive adhesive technology offers numerous advantages. However, as a new technology, conductive adhesive technology still has many concerns and limitations. In order for conductive adhesive technology to achieve universal acceptance, ECAs with better properties must be developed. The purpose of this study is to increase the conductivity of conductive adhesives by using short chain dicarboxylic acids, since such acids can partially remove or can completely replace the C-18 stearic acid which are commonly used as the surfactant in Ag flakes manufacturing process. Malonic acid and adipic acid, which only have single-bond short chain hydrocarbon between the dicarboxylic groups, increase the conductivity of conductive adhesives greatly. Terephthalic acid, however, deteriorates the conductivity due to the rigid aromatic structure in the molecule. The stabilized contact resistance has also been achieved with the introduction of dicarboxylic acids. Most importantly, the significant improvement of electrical properties is achieved without adversely affecting the physical and mechanical properties of the ICAs.