Patent ID: 7004375

Claim:
A pressure sensitive fluxable underfill encapsulant material comprising a) at least one epoxy resin; b) a solid anhydride curing agent, and c) at least one catalyst, wherein the catalyst is an imidazole-anhydride adduct comprising an adduct of imidazole and anhydride selected from the group comprising pyromellitic dianhydride, methylhexa-hydro phthalic anhydride. hexa-hydro phthalic anhydride, tetra-hydro phthalic anhydride, phthalic anhydride, bisphenyl dianhydride, benzophenone tetracarboxylic dianhydride, 1-cyanoethyl-2-ethyl-4-methyl-imidazole, alkyl-substituted imidazole, triphenylphosphine, onium borate, non-N-substituted imidazoles, 2-phenyl-4-methyl imidazole, 2-phenyl imidazole, imidazole, N-substituted imidazole and mixtures thereof and wherein the imidazole-anhydride adduct comprises in the range of about 0.01 wt % to about 10 wt % of the encapsulant.