Electromigration Behavior of Cu Core Solder Joints Under High Current Density

Cu core solder ball (CCSB) is formed by a Cu core surrounded by solder alloy and is used as an interconnection material for 3D packaging. Herein, the electromigration behavior of CCSBs with an organic solderability preservative surface finish is compared with that of Sn–3.0Ag–0.5Cu (SAC) solder joint. The current density and temperature for electromigration test are 0.9 × 104 A/cm2 and 100 °C, which are in compliance with JEP154. The current density of the solder joint is analyzed using finite element method analysis and maximum current density of the SAC solder joint is 1.1 times higher than the CCSB solder joint. The CCSB solder joint is less affected by the current crowding effect because electrons move through the Cu core located at the center of the solder. A void form in the Cu electrode of the cathode that coincides with the simulated maximum current area of the solder joint. The electromigration reliability of the CCSB solder joint is superior to that of the SAC solder joint.