Syntheses and characterizations of thermally reworkable epoxy resins II

Flip-chip technology is a face-down attachment of the active side of the si licon device onto the substrate. It is the ultimate packaging solution to i ntegrated circuit devices used in 21st century electronic systems to meet t he requirements of small size, high performance, and low cost. Underfill te chnology enhances the flip chip on board cycle fatigue life and thus dramat ically extends the application of flip-chip technology in electronics from high-end to cost-sensitive commodity products. Reworkable underfill is the key to addressing the nonreworkability of the underfill, so it is very impo rtant to electronic packaging. To meet the need for reworkable epoxy resins , four cycloaliphatic epoxides containing thermally cleavable carbonate lin kages have been synthesized and characterized. These materials are shown to undergo curing reactions with cyclic anhydride similarly to a commercial c ycloaliphatic diepoxide. Furthermore, these cured epoxides start to decompo se at temperatures lower than 350 degrees C, the decomposition temperature for the cured sample of the commercial cycloaliphatic diepoxide. Two formul ations based on two carbonate-containing diepoxides start network breakdown around 220 degrees C, which is the targeted rework temperature. Moreover, these two formulations have similar properties, including the glass-transit ion temperature, coefficient of thermal expansion, storage modulus, viscosi ty, and adhesion, compared to the standard commercial diepoxide formulation . As such, these two formulations are potential candidates for a successful reworkable underfill. (C) 2000 John Wiley & Sons, Inc.