Method of using both a non-filled flux underfill and a filled flux underfill to manufacture a flip-chip

A method for applying underfill to a flip-chip package comprising an integrated circuit die and a substrate, the method comprising the steps of:

• placing a first non-filled no-flow flux-underfill on a plurality of solder bumps located on the integrated circuit die,
• placing the integrated circuit die on the substrate such that the plurality of solder bumps are aligned both with corresponding bond pads on the substrate and with corresponding bond pads on the integrated circuit die, thereby creating an assembly of the flip-chip package, and forming a gap between the integrated circuit die and the substrate,
• dispensing a second filler loaded no-flow flux-underfill on a side of the substrate such that the second filler loaded no-flow flux-underfill flows by capillary action between the integrated circuit die and the substrate to fill the gap therebetween, and
• heating the assembly such that both the first non-filled no flow flux-underfill and the second filler loaded no-flow flux-underfill are cured, and such that the solder bumps are reflowed.