| Summary: | 碩士 === 國立成功大學 === 機械工程學系碩博士班 === 96 === This research are to evaluate the effects of 1~5wt.% Indium additions on microstructure, hardness and interfacial reaction with Cu substrate of Sn-2Ag-3Ag(SAS) lead-free Solder alloys. Tensile and thermal storage tests were used to estimate the adhesive strengths and thermal resistance of SASxIn solder joints.
Experimental results show that addition of indium into SAS solder results in formation of intermetallic compounds of Ag-Sn-In and InSb in matrix in addition to eutectic of Sn riched β phase and Ag3Sn. Sn atoms in Ag3Sn compound are substituted by In atoms in SASxIn solder system as indium content and/or thermal storage time is increased. A structural and morphological transformation of Ag3Sn to Ag3(Sn,In), Ag2(Sn,In)and finally Ag2(In,Sn) was occurred. Cu6Sn5 formed in IMC layer is transformed to Cu6(Sn,In)5 and thickens with the increases of thermal storage time.
Mechanical properties of SASxIn solder joints including low cycle fatigue life, adhesive and shear strength were increase with increasing In addition, but decrease during thermal storage. After 150℃ thermal storage, fatigue life will improve because of the softening of solder joint. So the fatigue life of SAS1In~SAS3In/Cu solder joints are higher than as-soldered. Solder joints with 4wt.% indium or above, the fracture modes form solder mode transited to mix mode even IMC mode by IMC layer grown. In the meanwhile, fatigue life would be decreased.
With compare of interfacial behavior, hardness, mechanical properties of SASxIn, The SAS3In solder alloy has better behaviors.
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