Characterization of flip chip assembly utilizing wafer applied underfill

The Motorola Advanced Technology Center, Loctite Electronic Materials and Auburn University are engaged in a NIST-ATP sponsored Joint Venture partnership to develop wafer-applied underfill materials and processes that will ultimately circumvent the need for any type of underfill dispense and cure processes on the surface mount line. Of key importance for wafer-applied underfill technology is the ability to form solder joints while immersed in the pre-applied underfill, with the proper balance of buoyant solder forces and surface tension/wetting forces between the underfill and the printed circuit board materials (core material, solder mask, and trace metallization). The focus of the present work is on the performance of the underfill material during the reflow process.