| With the rapaid development of electronic packaging technology and the promotion of“Green Manufacturing”, Sn-Ag-Cu solder is regarded as the most promising substitute forthe Sn-Pb solder. But the excess Ag causes high cost and makes intermetallic growthbehaviors fairly obvious, which degrades the anti-dropping capability and thermal fatiqueproperty of solder joint. Therefore, we should refine the internal intermetallic compound bysome technological means in order to improve the properties of lead-free solder. The Ag3Snand Cu6Sn5nanoparticles were added into lead-free solders by different ways to improveseveral properties of solders in this study.The result showed that Ag3Sn particles can significantly optimize internalmicrostructure of the solder alloy. With the increase of Ag3Sn nanoparticles amount, therefinement of grain and intermetallic compound significantly improved. The meltingtemperature of the solder alloy had little change with the increase of Ag3Sn nanoparticles,so the nano-composite solders had good processing compatibility with the solders widelyused, and the wettability improved. The appropriate addition of Ag3Sn nanoparticles canreduce the thickness of interfacial intermetallic compound and enhance the shear strengthof solder joint. The Sn-0.7Cu-2.0(Ag)Ag3Sn solder alloy had the thinnest interfacial layerand the largest shear strength. And both the interface morphology and shear strength ofnano-composite solder alloy were better compared with the micro-alloying solder that isidentical in alloy composition. The evolution of interfacial intermetallic compound wasstudied during the isothermal aging at150℃, and the growth coefficient decreased with theincrease of Ag3Sn nanoparticles amount, which can prevent the overgrowth of embrittledphases and improve the reliability of joints.Similarly, the addition of Cu6Sn5nanoparticles made the grain and intermetalliccompound of solder alloy significantly refined. The melting temperature of the solder alloyhad little change and the wettability improved with the increase of Cu6Sn5nanoparticles.The Sn-0.5Ag-0.7(Cu)Cu6Sn5solder alloy had the lowest melting temperature and the bestwettability. In addition, the Sn-0.5Ag-0.3(Cu)Cu6Sn5solder alloy had the thinnestinterfacial layer and the largest shear strength. And the growth coefficient decreased withthe increase of Cu6Sn5nanoparticles amount, which can prevent the overgrowth of embrittled phases and improve the reliability of joints during the isothermal aging.In addition, the melting property, wettability and shear strength of SAC0307lead-freesolder paste with various amounts of Ag3Sn nanoparticles were also investigated. With theappropriate addition of Ag3Sn nanoparticles, the nano-composite solder paste had goodprocessing compatibility owing to the tiny changes of melting temperature. Both wettabilityof solder and the shear strength of joint improved because of the increase of Ag3Snnanoparticles amount. |
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