Effects of Graphene Nanosheets on the Wettability and Mechanical Properties of Sn-0.3Ag-0.7Cu Lead-Free Solder
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https://doi.org/10.1007/s11664-020-08537-5 Ó 2020 The Minerals, Metals & Materials Society
Effects of Graphene Nanosheets on the Wettability and Mechanical Properties of Sn-0.3Ag-0.7Cu Lead-Free Solder LIMENG YIN ,1,2,3 ZHONGWEN ZHANG,1 ZILONG SU,1 CUNGUO ZUO,1 ZONGXIANG YAO,1 GANG WANG,1 HEHE ZHANG,1 LONG ZHANG,1 and YUPENG ZHANG2 1.—School of Metallurgy and Materials Engineering, Chongqing University of Science and Technology, Chongqing 401331, China. 2.—Key Laboratory of Modern Welding Technology of Guangdong Province, Guangzhou 510650, China. 3.—e-mail: [email protected]
Low silver Sn-0.3Ag-0.7Cu (SAC0307) composite solder reinforced with graphene nanosheets (GNs) was prepared by powder metallurgy techniques, and the effects of GN content on the melting characteristics, wettability, microhardness and shear strength of the composite solder were investigated. The wettability and microhardness of the composite solder increased significantly, and the initial melting temperature decreased slightly with increasing doping content of GNs, the wettability and microhardness of the composite solder increased significantly, but the initial melting temperature decreased slightly. When the GN content reaches 0.01 wt.%, the wettability angle of the composite solder decreases by 29%. When the content of GNs reaches 0.09 wt.%, composite solder of microhardness is up to 15.3 HV, approximately 1.12 times larger than that of the un-doped SAC0307 solder. At the same time, it is also found that the shear strength of the composite solder increases with the increase of GN content. When reaching 0.05 wt.%, the shear strength is the highest (24.70 MPa) and then presents a downward trend. In addition, the fracture morphology of microscale solder joints exhibits a typical ductile fracture character to the brittle one with increasing GN content. Key words: Lead-free solder, graphene nanosheets (GNs), wettability, mechanical property
INTRODUCTION Traditional Sn-Pb solder has been used extensively in microelectronic packaging due to its advantages such as low melting point, abundant reserves, excellent performance and low price.1 However, it cannot meet the pollution-free requirements in the electronics industry, because of the high toxicity of lead.2 Among the lead-free solders, Sn-Ag-Cu (SAC) solders are now widely applied in the electronic packaging industry thanks to their excellent comprehensive mechanical properties,
(Received August 26, 2020; accepted September 26, 2020)
good solderability and wettability, and low environmental damage.3,4 To a certain extent, the addition of Cu in SAC solder inhibits Cu dissolution from the substrate to solder and improves the reliability of solder joints.5–8 In addition, excessive Ag worsens the mechanical properties of the solder joint owing to the formation of large-scale Ag3Sn platelets.9,10 At the same time, considering the manufacturing cost factor, reasonably decreasing the amount of expensive Ag used can improve the competitiveness of products.11 On the other hand, too low Ag content
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