Polyethersulfone-epoxy terminated materials as thermosetting resins for microelectronic devices

A totally arom. polyether/sulfone resin (PES-E) was synthesized and tested as an insulating glue in the construction of a Chip-on-Chip (CoC) device. PES-E, essentially constituted of open-chain macromols. of low mol. mass (Mn of about 3000 Da) with hydroxy and/or epoxy end-groups, has a glass transition temp. of about 150° and is subject to crosslinking at temps. higher than 320°. A CoC device was assembled using a five-step process by interposing a layer of PES-E between two chips. After curing, SEM cross section images showed a homogeneous crosslinked resin layer well stuck (flick and shear tests) to both chips. The chem. structure of the chains and the hydroxy/epoxy end-groups ratio were optimized to obtain a crosslinked material with good adhesion and sufficient flexibility to avoid cracking during assembly and use.