Effects of oxidation and particle shape on critical volume fractions of silver-coated copper powders in conductive adhesives for microelectronic applications

The effects of oxidation and particle shape on critical volume fractions of silver-coated copper powders in conductive adhesives are investigated. Silver-coated copper powders with spherical and flake-shaped particles were oxidized at temperatures of 30 degreesC, 175 degreesC and 240 degreesC for two hours and dispersed in an epoxy matrix. As silvercoated copper powders are oxidized at 30 degreesC and 175 degreesC, the critical volume fractions of the conductive adhesives are slightly affected by oxidation and particle shape at these temperatures. As the oxidation temperature approaches 240 degreesC, the critical volume fractions of the conductive adhesives are strongly affected by oxidation temperature and particle shape, owing to the formation of oxides such as Cu2O on the surd face of silver-coated copper powder-Cu diffuses from the interior to the surface of silver-coated copper powder and reacts with the oxygen in the air. Silver-coated copper powder with flake-shaped particles shows lower critical volume fractions in conductive adhesives than silver-coated copper powder with spherically shaped particles. (C) 2004 Society of Plastics Engineers.