Underfill materials for fabricating electronic devices are described. One embodiment includes an underfill composition including an epoxy mixture, an amine hardener component, and a filler. The epoxy mixture may include a first epoxy comprising a bisphenol epoxy, a second epoxy comprising a multifunctional epoxy, and a third epoxy comprising an aliphatic epoxy, the aliphatic epoxy comprising a silicone epoxy. The first, second, and third epoxies each have a different chemical structure. Other embodiments are described and claimed.