Electrical property improvement of electrically conductive adhesives through in-situ replacement by short-chain difunctional acids

To improve the electrical properties of electrically conductive adhesives (ECAs), short-chain difunctional acids, such as malonic acid (acid M), adipic acid (acid A), and terephthalic acid (acid T) were introduced into a typical isotropic conductive adhesive formulation. By in-situ replacement of the commonly used surfactant-stearic acid in silver(Ag) flakes, such difunctional acids can increase the conductivity of ECAs. With the addition of malonic acid and adipic acid, which only have short chain single-bond hydrocarbon between the dicarboxylic groups, the conductivity of the typical conductive adhesives was improved significantly. Terephthalic acid, however, deteriorates the conductivity due to the rigid aromatic structure in the molecule. Dynamic mechanical analysis and thermomechanical study indicated the improved electrical properties with malonic and adipic acids were achieved without negatively affecting the mechanical and physical properties of ECAs.