Effect of Ni Content on the Microstructure Formation and Properties of Sn-0.7Cu- x Ni Solder Alloys
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JMEPEG https://doi.org/10.1007/s11665-020-04996-3
Effect of Ni Content on the Microstructure Formation and Properties of Sn-0.7Cu-xNi Solder Alloys Jianglei Fan
, Hengtao Zhai, Zhanyun Liu, Xiao Wang, Ying Li, Hongxia Gao, and Jianxiu Liu (Submitted October 6, 2019; in revised form June 26, 2020)
Sn-Cu based solders have been widely investigated due to their good mechanical properties, good fluidity, narrow melting range, environmental friendliness, and low price. In this paper, the effect of Ni content on the microstructure, mechanical properties, melting behavior, spreadability, and conductivity of Sn-0.7 CuxNi (0.5-2.0 mass%, mass fraction except when specified) lead-free solders was studied. The Sn-0.7Cu-xNi (x = 0.5, 1.0, 1.5, and 2.0) solder alloys consisted of a b-Sn solid solution, Ni3Sn4 phase, and Cu6Sn5 phase. The volume fraction of Ni3Sn4 increased with increasing Ni content. The addition of Ni increased the solidus and liquidus temperatures of the Sn-0.7Cu-xNi solder alloys. However, the melting range of the Sn-0.7Cu0.5Ni and Sn-0.7Cu-1.0Ni solder alloys is lower than that of the Sn-0.5Cu solder alloy. The spreading area of the Sn-0.7Cu-xNi solder alloy first increased and then decreased with increasing Ni content. Moreover, the ultimate tensile strength and hardness of the Sn-0.7Cu-xNi solder alloy increased gradually with increasing Ni content. The Sn-0.7Cu-2.0Ni alloy has maximum ultimate tensile strength and hardness values of 52.01 MPa and 16.45 Hv, respectively. However, the electrical conductivity of the Sn-0.7Cu-xNi solder alloy decreased with increasing Ni content. These changes in performance related to the formation of the intermetallic Ni3Sn4 phase. The Sn-0.7Cu-1.0Ni solder alloy had the best comprehensive performance in the present experiment. For the Sn-0.7Cu-1.0Ni solder alloy, the expanded area was 1.28 times that of the Sn-0.7Cu alloy, and the liquidus temperature, melting range, strength, hardness, and resistivity of the alloy solder were at the intermediate level among the Sn-0.7Cu-xNi solder alloys. Therefore, the Sn-0.7Cu-1.0Ni alloy is a relatively ideal solder alloy with a good comprehensive performance among the Sn-0.7Cu-xNi solder alloys. Keywords
lead-free solders, mechanical property, microhardness, microstructure, spreadability property
1. Introduction Traditional Sn-Pb solder is widely used in electronic packaging due to its good wettability, low melting point, and low cost (Ref 1-3). Due to an increased awareness of the need for environmental protection, the harm from Pb to human health and the environment is being recognized (Ref 4, 5). Many countries have restricted the use of lead-containing solders, so the research and development of new lead-free solders is an urgent and important task. Jianglei Fan and Jianxiu Liu, School of Mechanical and Electrical Engineering, Zhengzhou University of Light Industry, Zhengzhou 450002, PeopleÕs Republic of China; and Henan Key Laboratory of Intelligent Manufacturing of Mechanical Equipment, Zhengzhou University of Light Industry,
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