Transfer Molding Encapsulation of Flip Chip Array Packages

Epoxy molding compounds have been developed which can simultaneously underfill and overmold the Flip Chip die in a single transfer molding process. Transfer molding is a well-defined industry process; with suitable mold design, these materials can utilize the currently installed capital base. The ability to apply pressure during the molding process can reduce the void rate under the die as well as achieving production efficiencies which are typical of transfer molding processes. Transfer molding compounds offer enhancements in thermal expansion coefficients and moisture absorption levels relative to traditional liquid underfills as well as low levels of package deformation due to cure shrinkage and thermal mismatch effects. These improvements are achieved through the use of unique resin chemistries and filler package compositions. This paper will provide an overview of molding compounds which are useful as transfer molding underfill/ encapsulant materials.