The effects of pressure, temperature, and depth/diameter ratio on the microvia filling performance of Ag-coated Cu micro-nanoparticles for advanced electronic packaging
Guannan Yang, Shaogen Luo, Bo Luo, Yan Zuo, Shiwo Ta, Tingyu Lin, Zhaohui Zhao, Yu Zhang, Chengqiang Cui
Abstract
ABSTRACTConductive fillers made from metal nanoparticles offer many advantages for the fabrication of a variety of electronic devices, but when they have a porous structure, their poor conductivity limits their adoption in many applications. In this study, an Ag-coated Cu micro-nanoparticle paste is used to achieve compact filling of blind vias on flexible copper clad polyimide laminates through a multistep filling and sintering technique. The filled blind vias achieve a resistivity as low as 6.2 μΩ·cm, which is comparable that of electroplated blind vias. Higher sintering pressure and temperature promote the filling performance, while the conductivity deteriorates at a via depth/diameter ratio greater than 1:1. Finite element simulations reveal a stress inhomogeneity in vias with large depth/diameter ratios, which is the key to understanding the evolution of the conductive properties of a paste-filled via. This study provides an effective method for high-performance microvia filling as well as insights into the mechanism that influences its performance.