Study on the effects of silicone-modified curing agent on the toughness of underfills

Andvanced packaging technology is improving rapidly in recent years, which raise great demand in underfill with higher toughness. However, the application of traditional additive-type flexibilizers in advanced packaging are limited due to the weak mechanical properties caused by their low compatibility with epoxy. In this work, a silicone-modified aniline curing agent (SAN) was prepared through condensation reaction of aniline and polymethyl hydrosiloxane to improve the toughness of underfill and solve the “ trade-off” between the toughness and weak compatibility of epoxy-based composites. The results of infrared spectroscopic analysis demonstrate that siloxane chain segment was successfully grafted with aniline through hydrosilylation reaction. The influence of SAN on the toughness of UF was investigated using fracture tests. The obtained results demonstrate that by adding 6 wt.% of SAN, the toughness of UF-2 was significantly higher than that of neat UF both at 25°C and -55°C. Furthermore, the toughness mechanisms of SAN were studied by scanning electron microscopy (SEM) and in-situ bending test. The results certified the toughness mechanism of SAN was attributed to the flexible silicone chain segment, absorbing energy and forms floccus, limiting the crack growth, which were known as crack deflection and in-situ homogeneous toughening mechanism.