Novel fast cure and reworkable underfill materials

Abstract

A novel fast flow, fast cure and reworkable underfill material has been developed. This non-epoxy material satisfies all the basic requirements for underfill materials, such as high glass transition temperature, low viscosity and low thermal expansion coefficient. During laboratory testing, this underfill exhibits excellent flow behavior (about 10 seconds for a quarter inch die), and fast curability (less than 5 minutes at 150/spl deg/C). A distinct feature of this underfill material is its reworkability. The rework was achieved by thermal removal of the silicon die, followed by solvent cleaning of the underfill. Laboratory work demonstrates that the chip removal and underfill cleanup process can be completed within 5 minutes.