Combined metallic bonding and molding for electronic assemblies including void-reduced underfill

Abstract

A method for forming electronic assemblies includes providing a plurality of IC die each having IC bonding conductors and a workpiece having workpiece bonding conductors. A curable dielectric film is applied to the IC bonding conductors or the workpiece surface. The plurality of IC die are placed on the workpiece surface so that the plurality of IC bonding conductors are aligned to and face the plurality of workpiece bonding conductors to provide a first bonding. The placing is performed at a vacuum level corresponding to a pressure <1 kPa, and at a temperature sufficient to provide tackiness to the curable dielectric film. The plurality of IC die are then pressed to provide a second bonding. A temperature during pressing cures the curable dielectric film to provide an underfill and forms metallic joints between the plurality of IC bonding conductors and the plurality of workpiece bonding conductors.