Simulation of morphology evolution and pore segregation of Ag sinter joint at high temperature

Sintered silver, characterized by high thermal conductivity, excellent mechanical properties, and high-temperature reliability, holds great potential as a material for the bonding of high-power dissipation device chips. Silver with micron or nanometer size can be sintered at low temperatures while maintaining good mechanical and thermal properties, owing to its high surface energy. However, the powder sintering process can bring a mesoscopic structure with numerous pores. The porous structure of sintered silver undergoes continuous evolution in high-temperature environments, and such mesoscale morphological changes can significantly impact the performance of the interconnection layer. Therefore, it is imperative to investigate the mesoscale morphology evolution of sintered silver under high-temperature conditions. This paper employs the phase field theory to establish a simulation method that describes the pore growth and segregation caused by thermal mismatch stress in sintered silver joint. The coarsening of pores in sintered silver is driven by the reduction of surface energy. The segregation behavior of pores under stress gradients is simulated using a temperature-displacement-phase-field coupled simulation method. To illustrate and validate the proposed approach, a structure of Si-sintered Ag-Cu joint is constructed. The results indicate that, at high temperatures, concurrent with the coarsening of pores, there is an enrichment of pores on the Si side with a higher mismatch of coefficients of thermal expansion.