Conductivity improvement of isotropically conductive adhesives

To further increase the conductivity of isotropically conductive adhesives, short-chain dicarboxylic acids, such as malonic acid (acid M), adipic acid (acid A) and terephthalic acid (acid T), were introduced in a typical ICA formulation. By partially removing or replacing the surfactant stearic acid in silver (Ag) flakes, such dicarboxylic acids have potential to increase the conductivity of ECAs. With the addition of malonic acid and adipic acid, which only have short single-bond chain hydrocarbon between the dicarboxylic groups, the conductivity of the typical conductive adhesives were 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.