Microstructure Evolution and Shear Property of Cu-In Transient Liquid Phase Sintering Joints

Abstract

Transient liquid phase sintering (TLPS) is a promising joining technology that can achieve high temperature resistant solder joints at low temperature, showing excellent potential in power electronics. In this work, Cu/Cu-In/Cu solder joints were successfully prepared by TLPS process. The effects of bonding pressure and holding time on the microstructure and shear strength of Cu-In TLPS joints at 260 and 320°C were studied. The results showed that as bonding pressure increased from 0.1–0.6 MPa, the porosity decreased and shear strength increased significantly. No obvious change was found as bonding pressure continued to increase to 1 MPa. As holding time increased at 260°C, Cu11In9 was formed and gradually transformed to Cu2In that can withstand elevated temperature. Meanwhile, the porosity decreased while shear strength increased. It was calculated that volume expansion (12.74%) occurred during the phase transition from Cu11In9 to Cu2In. When bonding temperature increased to 320°C, only Cu2In was detected and then gradually transformed to Cu7In3 with the growing holding time. As holding time reached 120 min, their porosity increased and lead to weak shear strength due to volume shrinkage (15.43%) during the phase transition from Cu2In to Cu7In3.

High-Performance Skutterudite/Half-Heusler Cascaded Thermoelectric Module Using the Transient Liquid Phase Sintering Joining Technique

“…Both Pb-containing and Pb-free solders have been widely applied for power electronics. However, they have limitations such as being unreliable for repeated bonding reflow processes, complexity in precisely controlling the bonding positions, and compromised interconnect integrity due to the successive exposure at high reflow temperature. , Transient liquid phase sintering (TLPS) is one of the promising joining technologies that can be processed at low temperature than common solder-based interconnects and is capable of higher temperature performance. The principle of TLPS is that low melting point metals (e.g., Sn or Sn-alloy) melt at their bonding temperature and react with high melting point metals (e.g., Cu) to form high melting point intermetallic compounds with excellent electrical and thermal transport properties (Figure b).…”