A Review of Recent Research Trends of Forming of Metallic Bondlines Using Core-Shell Particles and Bonding Properties According to Particle Type

Abstract

With the increasing numbers of electric vehicles and the prevalence of high heat generating devices, recent studies have attempted to address the limitations of conventional solder materials, including their low durability at temperatures exceeding 200 ℃, insufficient mechanical properties in a joint, and low thermal conductivity. Transient liquid-phase (TLP) partial bonding using solders or Sn, and sinter bonding using Ag particles, are alternative bonding methods which involve a modification or change of the material. Advanced alternatives can significantly reduce bonding time or material cost. Various additional studies have investigated various core-cell particles that can be used to form an all-metallic bondline. This review summarizes reports of bonding studies using different core-cell particles. The particles were not only applied as a form of paste but also preform. In the TLP bonding using X(Cu, Ag, Ni)@Sn particles, the degree of voids generated in the formed bondline was dependent on the type of intermetallic compound formed. The preforms consisting of X@Sn particles provided relatively uniform microstructure and void distribution, compared to the pastes containing identical X@Sn particles, resulting in better long-term mechanical reliability. The addition of Zn@Sn particles contributed to the more practical control of microstructure and mechanical properties in the joint formed by pure Sn and Sn-58Bi solder alloys. Cu@Ag particles can be considered a promising low-cost material for compression-assisted sinter bonding, replacing pure Ag particles. The application of core-cell particles is expected to improve the processes used for forming metallic bondlines.