Numerical Investigation on Microfluidic Electroless Deposition for Uniform Copper Pillar Microbumps Interconnection

The conventional thermo-compression bonding method in either solder-based or solder-less approaches for the 3D chip integration lead to reliability issues including warpage, delamination and die crack due to high temperature and pressure. To eliminate the issues, an approach of microfluidic electroless interconnection featured with low temperature and pressure has been reported. In this work, the multi-physical field model was firstly developed to understand the deposition mechanism of the microfluidic electroless interconnection method based on a simulation framework considering electrochemistry, fluid flow and mass transfer, and experimental validation was conducted. The results of the numerical work manifest good agreement with the experimental data, and the dominant limitation of the technology is insufficient mass transfer in the microchannel introducing deposition thickness non-uniformity reaching 90%. To eliminate the non-uniformity, the effects of flow velocity and reverse flow are investigated demonstrating remarkable enhancement. The theoretical simulation model shows good feasibility and accuracy providing insight and understanding in the process and mechanism of the technology.