Applications of Fine Metallic Powders for Electrically Conducting Materials

Recently, electrically conducting adhesive materials have been actively investigated for the possibility of substituting the Pb-containing solders in microelectronics applications. An electrically conducting adhesive material is made of fine metallic particles dispersed in the matrix of a polymer material. Silver-particle filled epoxy is the most common example of the electrically conducting adhesive materials in use. The silver particles usually in the shape of flakes provide electrical conduction by percolation mechanism, while the epoxy matrix provides the adhesive bond between the components and a substrate. In order to overcome several limitations of the silver-filled epoxy materials, a new class of conductive adhesive materials has been developed by replacing silver particles with other conducting particles, such as solder, powder, copper powder and others. In this paper, several new conducting filler particles are introduced for the electrically conducting adhesive applications; dendritic powder and copper powder with a coating layer of a low melting point metal or alloy. These conducting particles provide the metallurgical bond among the conducting particles as well as to the substrate. This leads to enhanced electrical and mechanical properties of the adhesive joints