STRUCTURE AND METHOD FOR STRESS REDUCTION IN FLIP CHIP MICROELECTRONIC PACKAGES USING UNDERFILL MATERIALS WITH SPATIALLY VARYING PROPERTIES

摘要

A structure for a flip chip package assembly includes: a flip chip die with solder attach bumps; a substrate for receiving and solder attaching the flip chip die; an underfill material with spatially varying curing properties applied to fill voids between the flip chip die and the substrate, and for forming a fillet around the perimeter of the flip chip die and extending to the surface of the substrate; and wherein the portion of the underfill material forming the fillets is cured prior to curing the portion of the underfill material that fills the voids between the flip chip die and the substrate.