Method of forming BGA interconnections having mixed solder profiles

Abstract

A method of forming BGA interconnections having improved fatigue life is disclosed. In particular, a combination of mask-defined and pad-defined solder joints are selectively positioned within the BGA package. The mask-defined solder joints possess a high equilibrium height, which forces the pad-defined solder joints to elongate, thereby making the pad-defined solder joints more compliant. Further, the pad-defined solder joints posses a slightly longer fatigue life because the stress concentrations found in the mask-defined solder joints are not present in the pad-defined solder joints. Therefore, the fatigue life of BGA packages is increased by implementing a majority of mask-defined solder joints to maintain a high equilibrium height, and selectively placing pad-defined solder joints in high stress areas of the BGA package.

Dependencies are inferred from the claim text.