Molecular dynamics simulation of copper paste sintering for chip interconnection

Micron or nano-scale copper particles paste as a new generation of packaging materials, with low temperature sintering and high temperature service characteristics. The interconnect layer structure formed using copper paste after sintering is capable achieve unique high temperature resistance characteristics, excellent electrical conductivity, suitable for SiC chips, GaN chips and other chips using for power electronics devices. Unfortunately, the diffusion mechanism of adjacent copper particles in copper paste during sintering process in copper paste is still unclear. In this paper, we use the kinetic simulation software Lammps for different sintering processes of copper particles with different sizes, as well as the growth behavior and mean-square displacement(MSD) of the sintering neck was used, to analyze the atomic stacking condition, the distance between the centres during different sintering periods, and the atomic ordering of copper atoms with temperature. The trend of the local crystal structure changes around the copper atoms and the crystal defects during the different sintering periods were analysed using crystal structure. The result indicated that the melting point decreased with the size of the sintered copper particles decreased, so does the sintering temperature, the radius distribution function(RDF) is relative to the size of copper particle, during the sintering process, the copper particles tend to produce an amorphous structure and accelerate the densification of the voids. The growth pattern of the sintered neck is generally similar at different periods of sintering, but depend on the different sizes of copper particles. This study provides a theoretical basis for the development of copper paste sintering interconnection.