Microstructure and mechanical properties of electroplated Ni-Sn TLP bonded joints with different bonding and aging times

Abstract

Much attention has been drawn to the Ni Sn transient liquid phase (TLP) bonded joints for high-temperature electronic packaging applications since their inception. A comparative study of Ni Sn TLP bonded joints with different interlayers was conducted. The evolution of microstructure and mechanical properties of joints with different bonding times was also investigated. In addition, the high-temperature (300 °C) thermal reliability of the Ni Sn TLP bonding joints was explored with aging times from 0 h to 100 h. The results show that the electroplated Ni Sn TLP bonding joint exhibited a slightly higher average shear strength than when using a Sn foil and Sn 96.5 Ag 3.5 paste. Also, the average shear strength of the electroplated Ni Sn TLP bonded joints was greatly improved as the bonding time increased from 0.5 h to 5 h, while there was a continuous decrease in the average shear strength with the aging time from 4 h to 100 h. During the aging, the Ni/Ni 3 Sn 2 interface was the preferential site for the nucleation of the newly formed Ni 3 Sn 2 intermetallic compounds (IMCs). Furthermore, the cross-sectional microstructure of the shear fractured joints after aging from 4 h to 100 h indicates that the shear fractures propagated through both the Ni 3 Sn 4 IMCs and the Ni 3 Sn 2 /Ni 3 Sn 4 interface. • Joints using electroplated Sn were stronger than that using Sn foil or solder paste. • The average shear strength of joints increased with bonding time from 0.5 h to 5 h. • Prolonged aging time (from 4 h to 100 h) deteriorated the shear strength of joints. • Ni/Ni 3 Sn 2 interface was the preferential site for nucleation of Ni 3 Sn 2 during aging. • Aged joints shear fractured through both Ni 3 Sn 4 IMCs and Ni 3 Sn 2 /Ni 3 Sn 4 interface.