Interfacial IMC Growth and Nanomechanical Characterizations of Solder in Sn-16Sb/Cu Joints during Solid-state Aging

Abstract

The effects of aging time and temperature on the formation and growth behavior of interfacial intermetallic compound (IMC) of Sn-16Sb/Cu(wt%) solder joints prepared by using dip soldering were investigated. The results show that the major IMCs between Sn-16Sb solder and Cu substrate after thermal aging are Cu₃Sn and Cu₆Sn₅. The thickness of the interfacial IMC in Sn-16Sb/Cu is linearly against the square root of aging time, which indicates that the growth of IMC is mainly controlled by diffusion between Cu and Sn atoms. By using linear regression method, the growth rate constants of interfacial IMC layers are 1.254×10^-18, 8.821×10^-18 and 1.22×10^-17 m²s^-1 for Sn-16Sb/Cu joints aged at 120, 150 and 170 °C, respectively. Besides, the activation energy of the interfacial IMC growth was also calculated to be 68.27 kJ/mol. The IMC grain diameters after aging treatment increase with the increasing aging time, with i e, d = 0.492t ^0.106, d = 0.543t ^0.143 and d = 0.290t ^0.263 for aging temperatures of 120, 150 and 170 °C, respectively. Besides, by using nanoindentation, the softening of Sn-16Sb solder was found during aging treatment. Moreover, the U-shape evolution of the values in hardness and Young's moduli was found in this work.

Keywords

lead-free solder / aging treatment / intermetallic compound / interfacial reaction / nanoindentation

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