| Summary: | 碩士 === 國立成功大學 === 機械工程學系碩博士班 === 94 === The goal of this research is to evaluate the effects of adding 1, 5, 10wt.% Indium into Sn-Ag-Sb lead-free solders on melting point, microstructure, wettability, microhardness and the interfacial reaction with Cu substrate. Furthermore, the single lap specimens and high temperature storage were used to evaluate the shear strength and heat-resistance of Sn-Ag-Sb-xIn solder joints.
Experimental results show the melting point of Sn-Ag-Sb-xIn solders are decreased with greater indium additions. The gap between solidus and liqiudus temperature (Mushy zone) will expand with the addition of Indium into Sn-Ag-Sb solder
The formation of Ag3(Sn,In) is suppressed by the presence of indium in Sn-rich solder matrix and Ag2(In,Sn) appears in the solder matrix through the substitutional reaction between Sn atoms and In atoms. Moreover, the area of β-Sn in solder matrix also increase.
When Sn-Ag-Sb-xIn solder combine with Cu substrate, Ag-Sn-In-Cu and Cu-Sn-In IMC compounds were observed on the interfacial microstructure. The greater Indium additions and thermal storage time, the coarser of Ag-Sn-In-Cu compounds. After the 150℃ thermal storage, thickness of IMC layer will be raised as the Indium addition increasing.
The spreading ratio (Sr) tend to increase with presence of Indium, contact angle decreases with the greater Indium content. The hardness of Sn-Ag-Sb-xIn solders will increase as the addition of indium and degradation occurred after thermal storage.Shear strength of as-soldered joints is increased with higher Indium additions. The shear strength of whole solder joint decrease distinctly after 150℃ thermal storage.
Fractographic analysis showed that most of the solder joints failure in solder (Solder mode) at the as-soldered condition. The greater additions of Indium and thermal storage time lead to transform the fracture mode to be IMC mode which fracture occurred at IMC layer.
With compare of melting point, microstructure, wettability, shear strength and interfacial behavior of Sn-Ag-Sb-xIn solder. The solder contains 5wt.% Indium has better behaviors.
Keywords : Lead-free solder joint, melting point, Ag2(In,Sn) compounds, wettability, hardness, shear strength.
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