A New Current Crowding Phenomenon for Flip-Chip-on-Leadframe (FCOL) Package and its Impact on Electromigration Reliability

Abstract

Electromigration (EM) is a critical problem for interconnect reliability of modern integrated circuits (ICs) packages. In flip-chip-on-leadframe (FCOL) package, a new current crowding phenomenon at the solder joints interface is observed that exacerbates the maximum current density. To address this recent phenomenon, in this work, we detail the mechanisms of the electric current paths that lead to a potential adjustment of the average current density parameter in the current Black’s mean time to failure (MTTF) mathematical model. An appropriate design-of-experiment (DOE) for the FCOL package is developed. Through extensive simulation via a 3D quasi-static solver, the potential impact of this new phenomenon is assessed and quantified. A 35% increase in maximum current density was observed under the worst-case condition. Implications of the findings for future high-density microelectronic is under investigation experimentally.