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Abstract

A curable method useful for encapsulating solid state devices includes (A) an epoxy resin; (B) an effective amount of a cure catalyst comprising (B1) a first latent cationic cure catalyst comprising a diaryl iodonium hexafluoroantimonate salt; (B2) a second latent cationic cure catalyst comprising (B2a) a diaryl iodonium cation, and (B2b) an anion selected from perchlorate, imidodisulfurylfluoride anion, unsubstituted and substituted (C.sub.1-C.sub.12)-hydrocarbylsulfonates, (C.sub.2-C.sub.12)-perfluoroalkanoates, tetrafluoroborate, unsubstituted and substituted tetra-(C.sub.1-C.sub.12)-hydrocarbylborates, hexafluorophosphate, hexafluoroarsenate, tris(trifluoromethylsulfonyl)methyl anion, bis(trifluoromethylsulfonyl)methyl anion, bis(trifluoromethylsulfuryl)imide anion, and combinations thereof; and (B3) a cure co-catalyst selected from free-radical generating aromatic compounds, peroxy compounds, copper (II) salts of aliphatic carboxylic acids, copper (II) salts of aromatic carboxylic acids, copper (II) acetylacetonate, and combinations thereof; and (C) about 70 to about 95 weight percent of an inorganic filler, based on the total weight of the curable composition. The composition's cure catalyst allows the use of increased filler loadings, which in turn reduces moisture absorption and thermal expansion of the cured composition.

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