A comparative study on direct Cu–Cu bonding methodologies for copper pillar bumped flip-chips

Abstract

Copper pillar micro bump is one of the platform technologies, which is essentially required for 2.5D/3D chip stacking and high-density electronic components. In this study, Cu–Cu direct thermo-compression bonding (TCB) and anisotropic conductive paste (ACP) bonding methods are proposed for Ø 100 µm Cu-pillar bumped flip-chips. The process parameters including bonding temperature, bonding pressure and time are verified by die shear test and SEM/EDX cross-sectional analysis. The optimal bonding condition for TCB with regards to bonding pressure was defined to be 0.5N/bump at 300 °C or 0.3N/bump at 360 °C. In the case of ACP bonding, the minimum bonding pressure was about 0.3N/bump for gaining a seamless bonding interface.