The Mechanical Properties and Elastic Anisotropy of η′-Cu6Sn5 and Cu3Sn Intermetallic Compounds

Chao Ding,Hongbo Qin,Jian Wang,Tianhan Liu,Daoguo Yang,Guoqi Zhang

doi:10.3390/cryst11121562

Abstract

Full intermetallic compound (IMC) solder joints present fascinating advantages in high-temperature applications. In this study, the mechanical properties and elastic anisotropy of η′-Cu6Sn5 and Cu3Sn intermetallic compounds were investigated using first-principles calculations. The values of single-crystal elastic constants, the elastic (E), shear (G), and bulk (B) moduli, and Poisson’s ratio (ν) were identified. In addition, the two values of G/B and ν indicated that the two IMCs were ductile materials. The elastic anisotropy of η′-Cu6Sn5 was found to be higher than Cu3Sn by calculating the universal anisotropic index. Furthermore, an interesting discovery was that the above two types of monocrystalline IMC exhibited mechanical anisotropic behavior. Specifically, the anisotropic degree of E and B complied with the following relationship: η′-Cu6Sn5 > Cu3Sn; however, the relationship was Cu3Sn > η′-Cu6Sn5 for the G. It is noted that the anisotropic degree of E and G was similar for the two IMCs. In addition, the anisotropy of the B was higher than the G and E, respectively, for η′-Cu6Sn5; however, in the case of Cu3Sn, the anisotropic degree of B, G, and E was similar.

Highlights

The application of high-powered electronic equipment and third-generation semiconductor power devices is currently widespread and requires high service temperatures (>250 ◦ C) for solder joints [1,2]
The volume and mass of these solder joints are reduced due to high-density packaging, which enables increasing the proportion of intermetallic compound (IMC) in solder joints and creating a full IMC solder matrix
Several studies have shown that the tensile and shear strength of solder joints will be influenced by the thickness of the IMC layer [6,7,8]

Summary

Introduction

The application of high-powered electronic equipment and third-generation semiconductor power devices is currently widespread and requires high service temperatures (>250 ◦ C) for solder joints [1,2]. Full IMC solder joints have fascinating advantages in high-temperature application fields. Several studies have shown that the tensile and shear strength of solder joints will be influenced by the thickness of the IMC layer [6,7,8]. Hundred-micron solder joints only include a small number of grains; this will cause the solder joints to exhibit obvious anisotropic mechanical properties [9]. It follows that the mechanical properties of materials, based on large-scale specimens, will not accurately characterize the mechanical behavior of microscale solder joints.

Methods

Results

Conclusion