Epoxy resin composition with sulfonium borate complex
A sulfonium borate complex that is capable of reducing the amount of fluorine ions generated during thermal cationic polymerization, and is capable of providing a thermal cationic polymerizable adhesive with low-temperature fast curing properties is represented by a structure represented by the formula (1). In the formula (1), R 1 is an aralkyl group, R 2 is a lower alkyl group, and R 3 is a lower alkoxycarbonyl group. X is a halogen atom, and n is an integer of from 1 to 3.
1. An epoxy resin composition comprising an epoxy resin and a thermal cationic polymerization initiator, wherein:
the thermal cationic polymerization initiator is a sulfonium borate complex represented by formula (1):
wherein R 1 is an unsubstituted benzyl group, R 2 is a methyl group, R 3 is bonded to the 4 position of the phenyl group and is a methoxycarbonyl group, X is a fluorine atom, and n is 1; and
the epoxy resin composition has an exothermic onset temperature of from 60° C. to 80° C. and an exothermic peak temperature of from 100° C. to 110° C.
2. A connection structure wherein an electronic part is joined to a wiring board with a thermosetting product of the epoxy resin composition according to claim 1 .