Coupling Effect of Electromigration and Joule Heating Induced Failure in Advanced Packaging

The Ball Grid Array (BGA) packaging method has been extensively applied in electronic packaging industry. Electromigration reliability in BGA determines the performance of the whole device, and thus has been an important research topic for decades. In this article, we report a new failure mode induced by the coupling effect of electromigration and Joule heating in BGA structure. The sample consists of a roll of 500 μm-BGA, the upper and bottom Cu under bump metallization (UBM) with different thicknesses (16 μm and 68 μm). The open failure was observed at the cathodic thin Cu trace of the solder joint under a test condition of 3056 A/cm ² at 160 °C. The current density and temperature at thin Cu UBM were proved to be higher than those at solder joints or thick Cu UBM by infrared temperature measurement and finite element analysis simulation. Severe current crowding and Joule heating increased the nucleation rate of voids, which could further increase the current density and temperature in turn. Finally, there will be a positive feedback effect until open failure in the circuit. Our work shows a new failure mode induced by the coupling effect of electromigration and Joule heating in a BGA sample. The results provide the guidance of structure design for EM tests.