Effects of Ni Addition to Sn–5Sb High-Temperature Lead-Free Solder on Its Microstructure and Mechanical Properties

Abstract

The purpose of the present study is to investigate the melting properties, microstructures, tensile properties and fatigue properties of Sn 5Sb(0.050.50)Ni (mass%) high-temperature lead-free solders. The solidus temperature and liquidus temperature of the Sn5SbNi solders are approximately equal to those of the Sn5Sb alloy. From the result of EPMA mapping analysis and the SnSbNi ternary phase diagram, the Sn 5SbNi solders are found to consist of ¢-Sn, SbSn and NiSb phases. As the amount of Ni in the Sn5SbNi solder increases, the number of NiSb phases increases and the phases are coarsened so that the 0.1% proof stress and tensile strength increase, and the elongation decreases at 25°C. In contrast, the effects of the Ni content on the tensile properties are negligible at 150°C and 200°C. The fatigue ductility exponent ¡ of the Sn 5SbNi solders is smaller than that of the Sn5Sb solder at 25°C. At 150°C and 200°C, the ¡ values of Sn5Sb0.05Ni and Sn5Sb0.10Ni remain small, whereas those of Sn5Sb0.25Ni and Sn5Sb0.50Ni increase. This means that the Sn5SbNi solders with 0.050.10 mass% Ni have superior fatigue properties to the Sn5Sb solder in the temperature range from 25°C to 200°C.

Evaluation of Microstructures and Mechanical Properties of Sn-10Sb-Ni Lead-Free Solder Alloys with Small Amount of Ni Using Miniature Size Specimens

“…The α values of the Sn-10Sb-0.05Ni and Sn-10Sb were almost the same at 25 • C. At 150 • C and 200 • C, the absolute values of α values of the Sn-10Sb-Ni solder alloys except for the Sn-10Sb-0.05Ni tended to increase. This result has the same tendency as the fatigue properties of Sn-5Sb-Ni solder alloys that tested previously [16]. In particular, the absolute values of α of the Sn-10Sb-0.50Ni which has the most Ni addition was largest among all of the solder alloys in this study.…”

“…Therefore, we focused on the Sn-Sb with Ni minor addition to further improve these properties. We have already reported that Sn-5Sb-Ni with 0.05-0.10 mass% Ni have superior fatigue properties to Sn-5Sb (mass%) in the temperature range from 25 • C to 200 • C [16]. In addition, it has been reported that the high concentration of Sb in the Sn-Sb solder alloys can increase mechanical strength [17][18][19].…”

“…shows the OM images of the cross-sectional views of the miniature size specimens of Sn-10Sb and Sn-10Sb-Ni with 0.05-0.50 mass%, and included that of Sn-5Sb[16] for comparison. As can be seen in the images, increasing the amount of Sb in the solder alloy coarsens Sn-Sb compounds.…”

“…It was found that the specimen of Sn-10Sb consists of a single grain or a few grains, and specimens of Sn-10Sb-Ni consist of several grains. Sn-Sb-Ni ternary equilibrium phase diagram at 25 • C, reprinted with permission from[16], copyright The Japan Institute of Metals and Materials.…”

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

“…scribed in Section 3.1, the addition of Ni into Sn-Sb alloys causes the formation of SbNi phases in the matrix [24][25][26]. Such SbNi phases became the origin of recrystallization, and continuous dynamic recrystallization with dynamic recovery occurred easily in Sn-6.4Sb-3.9Ag-0.4Ni.…”