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

Bang Jiang,Li Liu,Zhiwen Chen,Yan Shi,Qiaoxin Zhang,Lin Shi,Chundong Zhu

doi:10.3389/fmats.2021.658464

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.

Highlights

With the miniaturization and integration of power electronics, the increasing operating temperature makes the package module withstand high temperature (Teo and Sun, 2008; Yoon et al, 2013; Chen et al, 2015; Yoon et al, 2019; Xu et al, 2020)
The existence of low temperature phase Cu11In9 will reduce high temperature resistance of solder joints, which can be avoided by increasing bonding temperature to 320°C
When bonding temperature was 260°C, the shear strength increased with the extension of holding time

Summary

INTRODUCTION

With the miniaturization and integration of power electronics, the increasing operating temperature makes the package module withstand high temperature (Teo and Sun, 2008; Yoon et al, 2013; Chen et al, 2015; Yoon et al, 2019; Xu et al, 2020). Transient liquid phase sintering (TLPS) has been developed for power electronic package for the advantages of low bonding temperature and pressure, excellent high temperature resistance and high yield strength (Kejanli et al, 2009; Lee et al, 2015; Min et al, 2020). According to Cu-In binary phase diagram (Bolcavage et al, 1993), the melting points of Cu7In3 (δ phase) and Cu2In (η phase) both exceed 630°C, showing excellent high temperature resistance potential. No works have been reported on the effects of these parameters on the microstructure and shear property of Cu-In TLPS joints. The effects of bonding pressure on the microstructure and shear strength of solder joints were investigated. The microstructure evolution and variation of shear strength under different holding times were studied

EXPERIMENT PROCEDURES

RESULTS AND DISCUSSION

CONCLUSION

DATA AVAILABILITY STATEMENT