Role of intermetallics for both tin-lead and lead-free solder structures and its solder pad combination.

摘要

It is attempted to quantify the role of intermetallics for the electromigration in flip chip solder interconnects (C4). Intermetallics are formed at the interface of solder and metallic pad where they serve as metallic bonding agent. For the transition to the Pb-free solder interconnects, electromigration is one of the prime reliability concerns. It is observed that some flip chip solder interconnect fails earlier than the estimated time to failure. It is explained by the effect of intermetallics formed by solder and different matching pad metallurgies. This paper quantifies the role of the intermetallics in the time to failure for a system. A series of experiments are being conducted to determine the current exponent and activation energies of the Black's equation for different solder and pad metallurgy combinations. Two test structures are proposed. The first test structure was made to study the role of the intermetallics and the second structure was made to characterize the pure solder's electromigration.