Development of isotropic conductive adhesives with improved conductivity

To improve the conductivity of electrically conductive adhesives, three short-chain dicarboxylic acids, malonic acid (acid M), adipic acid (acid A) and terephthalic acid (acid T), were used in a typical ICA formulation. 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.