Abstract: Composite interconnect structure forming methods using injection molded solder are disclosed. The methods provide a mold having at least one opening formed therein with each opening including a member of a material dissimilar to a solder to be used to fill the opening, and then fill the remainder of each opening with solder to form the composite interconnect structure. The resulting composite interconnect structure can be leveraged to achieve a much larger variety of composite structures than exhibited by the prior art. For example, the material may be chosen to be more electrically conductive than the solder portion, more electromigration-resistant than the solder portion and/or more fatigue-resistant than the solder portion. In one embodiment, the composite interconnect structure can include an optical structure, or plastic or ceramic material.

Abstract: 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.

Abstract: 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.