A study of lubricants on silver flakes for microelectronics conductive adhesives

Conductive adhesives are composites of polymer matrixes and metal fillers ( conductive elements). Silver (Ag) flakes are widely used as fillers for ele ctrically conductive adhesives (ECA's), Generally, there is a thin layer of organic lubricant coated on the commercial Ag flake surface. This lubrican t layer is needed for eliminating the Ag particle agglomeration while dispe rsing the Ag filler into the polymeric resin. Therefore the lubricant influ ences rheology, conductivity, and other properties of ECA's. The nature of the lubricant on a Ag flake and the interaction between the lubricant and t he Ag flake surface were studied by diffuse reflectance infrared spectrosco py (DRIR), Thermal decomposition of the lubricant was studied by differenti al scanning calorimetry (DSC) and thermogravimetric analysis (TGA), In addi tion, the effects of some chemical compounds on lubricant removal and the e nhancement of conductivity of the ECA were also investigated. It was found that 1) a chemical bonding was formed on the Ag flake surface between the lubric ant and Ag; 2) the short chain acids replaced the long chain lubricants; 3) an ether and a poly(ethylene glycol) enhanced electrical conductivity by partially removing the Ag flake lubricants.