Study of curing mechanism of epoxy/phenolic system for underfill applications

Underfill technology has been adopted for high reliability in flip-chip on organic board. The epoxy/phenolic resin system is a potential candidate underfill. The curing mechanism of the epoxy/phenolic system is studied using the differential scanning calorimeter and temperature controlled Fourier transform infrared spectrometer. The effect of hardener and catalyst type and the catalyst concentration on the curing mechanism is investigated. It is found that 1,8-diazabicyclo[5.4.0]undec-7-ene has the tendency to catalyze condensation reaction within hydroxyl groups at high temperature during curing. It can be a potential concern in no-flow underfill applications when the resin undergoes high temperature reflow.