Flexible underfill compositions for enhanced reliability

An underfill composition comprising:

• an epoxy mixture comprising 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 glycol epoxy;
• the first, second, and third epoxies each having a different chemical structure;
• an amine hardener component;
• and
• a filler.

An assembly comprising:

• a die;
• a substrate;
• the die electrically coupled to the substrate;
• a gap between the die and the substrate;
• an underfill material in the gap, the underfill material comprising first, second, and third epoxies, each having a different chemical structure, the first epoxy comprising a bisphenol epoxy, the second epoxy comprising a multifunctional epoxy, and the third epoxy comprising an aliphatic epoxy selected from the group consisting of silicone epoxies and glycol epoxies.