Characterization of silver flakes utilized for isotropic conductive adhesives

Silver (Ag) flakes are widely used as conductive fillers for isotropic conductive adhesives. Silver provides superior conductivity and has reasonable costs associated with it compared to other precious metals utilized in the electronics industry. As a result, production of silver flakes and powders has developed into an industry of its own. The silver fillers are typically fabricated into flakes and lubricated with certain organic compounds such as fatty acids. The organic lubricants on the surface of silver flakes play an important role in the performance of isotropic conductive adhesives. In particular, improvements in rheology and electrical conductivity have been observed. However, the exact nature of the lubricants on the silver flake surface and their impact on the adhesive rheology and conductivity have not been fully understood. This study identified the structure of the organic lubricants on the silver flake surface. The results using DSC (differential scanning calorimetry), XPS (X-ray photoelectron spectroscopy), SEM (scanning electron microscopy), Raman spectroscopy, and DRIFTS (diffuse reflectance infrared Fourier transform spectroscopy) techniques to characterize silver flakes are discussed in detail.