Preparation and curing chemistry of ultra-low CTE epoxy composite based on the newly-designed triethoxysilyl-functionalized ortho-cresol novolac epoxy

Abstract

For the design of the semiconductor packaging material, one of the most important challenges is to overcome the higher thermal expansion property of 'organic' epoxy composite than that of the 'inorganic' IC chip. Therefore, in order to prepare the epoxy composite with the ultra-low coefficient of thermal expansion (CTE), the new material class of epoxy, i.e., alkoxysilyl-functionalized novolac epoxy (Si(OEt)(3)-EOCN) was synthesized using the ortho-cresol novolac epoxy (EOCN) as a starting material. The new epoxy composite with the 85wt% of silica showed the CTE1 (at T < Tg) of 8 ppm/degrees C and CTE2 (at T > Tg) of 11 ppm/degrees C. Note that before alkoxysilyl-modification, the CTE1 and CTE 2 of the EOCN composite were 13 ppm/degrees C and 44 ppm/degrees C, respectively. In addition, the alkoxysilyl-functionalized epoxy was observed to show the unique curing chemistry due to the participation of alkoxysilyl group in epoxy curing reaction. In order to understand the chemistry of alkoxysilyl-functionalized epoxy, the reaction mechanism was studied using the model compounds.