Electromigration Study of Cu Pillar Bumps Using Experimental and Numerical Methods

With the development of 2.5-dimensional (2.5D) and 3D packaging, high-density packaging technology and high reliability have become increasingly desirable. The Cu pillar bump is widely adopted for fine-pitch interconnects due to its excellent electrical conductivity and heat dissipation capability. However, the risk of electromigration (EM) failures, such as voids and cracks, is relatively high compared to conventional solder joints due to the high current density carried by the Cu pillar bumps. In this study, we investigate the failure mechanisms in the Cu pillar bump structure under high current and temperature stress, including the current crowding effect, the formation of intermetallic compounds (IMCs), and the distribution of vacancy concentration.