Effect of Joule heating on electromigration reliability of Pb-free interconnect

Temperature and current are two major parameters that impact electromigration reliability. Due to the large current used in the accelerated electromigration test, the Joule self-heating associated with the stress current can be significant. The paper presents a study of electromigration fails in Pb-free interconnect from the point of view of localized Joule heating. The Joule heating effect in two types of packages, a fully assembled flip chip module with standard C4s and a silicon to silicon assembly with microbumps, is considered. A thermal FEM model is used as a guide to interpret the experimental observations.