Effect of Small Amount of Ni Addition on Microstructure and Fatigue Properties of Sn-Sb-Ag Lead-Free Solder.

Mizuki Yamamoto,Kohei Mitsui,Ikuo Shohji,Hirohiko Watanabe,Tatsuya Kobayashi

doi:10.3390/ma14143799

Mizuki Yamamoto, Kohei Mitsui + Show 3 more

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https://doi.org/10.3390/ma14143799

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Journal: Materials	Publication Date: Jul 7, 2021
Citations: 14	License type: CC BY 4.0

Affiliation: Kiryu University, Gunma University, Fuji Electric (Japan)

Abstract

The effect of the addition volume of Ni on the microstructures and tensile and fatigue properties of Sn-6.4Sb-3.9Ag (mass%) was investigated using micro-size specimens. The addition of Ni into Sn-6.4Sb-3.9Ag tends to increase the number of grains formed in the solidification process and produce a high-angle grain boundary. An amount of 0.1% proof stress of Sn-6.4Sb-3.9Ag decreases with an increase in the Ni addition volume at a strain rate of 2.0 × 10−1 s−1. The effect of the addition of Ni into Sn-6.4Sb-3.9Ag on tensile strength is negligible at both 25 °C and 175 °C. The elongation of Sn-6.4Sb-3.9Ag decreases with an increase in the Ni addition volume at 25 °C according to the fracture mode change from ductile chisel point fracture to shear fracture. The effect of the addition of Ni into Sn-6.4Sb-3.9Ag on the elongation is negligible at 175 °C. The low cycle fatigue test result shows that the fatigue life does not degrade even at 175 °C in all alloys investigated. The fatigue life of Sn-6.4Sb-3.9Ag-0.4Ni (mass%) is superior to those of Sn-6.4Sb-3.9Ag and Sn-6.4Sb-3.9Ag-0.03Ni (mass%) in the high cycle fatigue area. The electron back scattering diffraction (EBSD) analysis result shows that fine recrystallized grains are generated at the cracked area in Sn-6.4Sb-3.9Ag-0.4Ni in the fatigue test at 175 °C, and the crack progresses in a complex manner at the grain boundaries.

Highlights

Since the restriction of hazardous substances (RoHS) directive was enforced in the European Union (EU) in 2006, the use of lead-containing solder in electrical and electric equipment has been regulated and lead-free solder such as Sn-Ag-Cu, Sn-Cu, and Sn-Bi alloys has been used [1]
We focused on Sn-Sb system alloys as high-temperature lead-free solder and investigated their mechanical properties and microstructures [24,25,26]
The result shows that the fatigue life does not degrade at 175 ◦C in all alloys investigated, and they have excellent thermal fatigue resistance

Summary

Introduction

Since the restriction of hazardous substances (RoHS) directive was enforced in the European Union (EU) in 2006, the use of lead-containing solder in electrical and electric equipment has been regulated and lead-free solder such as Sn-Ag-Cu, Sn-Cu, and Sn-Bi alloys has been used [1]. As the reliability of the soldered joint, the thermal fatigue resistance, the heat resistance and ion migration resistance are very important. There are many studies for fatigue [7,8], thermal fatigue [9,10,11], interfacial reaction (growth of intermetallic compounds) [12,13,14], creep [15,16] and ion migration [17,18] of various lead-free solder. Finite element analysis of the electronics products is usually conducted to design the joint and predict its reliability. Various mechanical properties of the solder are required to conduct finite element analysis, and many studies on the mechanical properties of various lead-free solder have been conducted [19,20,21]

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