Thermal Analysis and Mechanical Property Evaluation of Sn-1Ag-0.7Cu-5BixIn/Cu Solder Joints

Publication Date

1-1-2026

Document Type

Conference Proceeding

Publication Title

Minerals Metals and Materials Series

DOI

10.1007/978-3-032-13828-6_76

First Page

919

Last Page

927

Abstract

Using CALPHAD-assisted phase fraction calculations, Sn-1Ag-0.7Cu-5Bi-xIn (x = 4, 8, 15, 17 wt.%, denoted as xIn) alloys were designed to meet long-term high-temperatureTemperature service requirements in solder joints. Bi and In were added to offset performance losses from reducing Ag content. With Bi fixed at 5 wt.%, this study investigated the effects of varying In content on melting behavior, microstructureMicrostructure, and mechanical propertiesMechanical properties. Results showed that increasing In eliminated Bi-rich particles, and at ≥ 15 wt.% In, InSn₄ phases formed. The interfacial IMCIntermetallic Compounds (IMC) transformed from Cu₆Sn₅ to Cu₆(Sn,In)₅, with InSn₄ and secondary phases increasing with In content. During isothermal aging at 170 °C, 4In joints formed Cu-rich layers. In 8In joints, Cu and In diffusionDiffusion converted Cu₆(Sn,In)₅ to Cu₃(Sn,In). Higher In contents lowered melting points, accelerated diffusionDiffusion, and stabilized Cu₆(Sn,In)₅, improving joint reliability. These findings inform strategies for controlling interfacial IMCsIntermetallic Compounds (IMC) and designing high-reliability solder joints.

Keywords

IMC, In-doped low silver SAC joints, Mechanical properties, Microstructure

Department

Aviation and Technology

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