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Effect of thermal aging on microstructure and mechanical properties of indium-doped Sn-Ag-Cu lead free solder alloys.

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Title: Effect of thermal aging on microstructure and mechanical properties of indium-doped Sn-Ag-Cu lead free solder alloys.
Authors: Hameed, Muhammad Sohail1 (AUTHOR) miansohail910@gmail.com, Wakeel, Aneela2 (AUTHOR) aneela.wakeel@uettaxila.edu.pk, Ullah, Barkat3 (AUTHOR) barkat@ciitwah.edu.pk, Channar, Hassan Raza4 (AUTHOR) hassanraza@usp.br, Zubair, Muhammad5 (AUTHOR) mzubair@sharjah.ac.ae
Source: Soldering & Surface Mount Technology. 2026, Vol. 38 Issue 3, p185-195. 11p.
Subjects: Lead-free solder, Indium alloys, Intermetallic compounds, Solution strengthening, Microstructure, Heat treatment, Copper-tin alloys, Mechanical behavior of materials
Abstract: Purpose: Lead (Pb)-free solder alloys are increasingly adopted in microelectronic packaging due to their environmental compliance and favorable mechanical performance. This study aims to investigate the effect of thermal aging on the mechanical behavior of Sn98.5-Ag1.0-Cu0.5 (SAC105) solder alloy doped with indium (1, 2 and 3 Wt.%) to enhance reliability in high-temperature electronic applications. Design/methodology/approach: Specimens were fabricated via die casting and thermally aged at 125°C and 180°C for 72 h. Mechanical properties, including yield strength (YS) and ultimate tensile strength (UTS), were evaluated using a universal testing machine. Microstructural evolution was examined through scanning electron microscopy (SEM), and elemental composition was confirmed via energy-dispersive X-ray spectroscopy. Findings: As-cast alloys with 1–3 Wt.% In exhibited progressive improvements in YS and UTS, with the 3 Wt.% In composition reaching 46 and 52.62 MPa, respectively – a 72% increase over base SAC105. This enhancement is attributed to solid solution strengthening and microstructural refinement. Although thermal aging led to strength degradation, indium-containing alloys retained superior integrity. Notably, the SAC105 + 3 Wt.% In alloy maintained a UTS of 44.75 MPa after aging at 180°C. SEM analysis revealed uniform indium distribution and formation of Cu6(Sn,In)5 and Ag3(Sn,In) intermetallic compounds. Practical implications: Indium doping offers a cost-effective strategy towards sustainable and high reliability solder materials for automotive and aerospace electronics, with potential to reduce lead dependence in compliance with RoHD directives. Originality/value: This work provides novel insights into indium's role in reinforcing SAC105 solder alloys, supporting the development of sustainable, high-performance lead-free solders for thermally demanding applications. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
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Abstract:Purpose: Lead (Pb)-free solder alloys are increasingly adopted in microelectronic packaging due to their environmental compliance and favorable mechanical performance. This study aims to investigate the effect of thermal aging on the mechanical behavior of Sn98.5-Ag1.0-Cu0.5 (SAC105) solder alloy doped with indium (1, 2 and 3 Wt.%) to enhance reliability in high-temperature electronic applications. Design/methodology/approach: Specimens were fabricated via die casting and thermally aged at 125°C and 180°C for 72 h. Mechanical properties, including yield strength (YS) and ultimate tensile strength (UTS), were evaluated using a universal testing machine. Microstructural evolution was examined through scanning electron microscopy (SEM), and elemental composition was confirmed via energy-dispersive X-ray spectroscopy. Findings: As-cast alloys with 1–3 Wt.% In exhibited progressive improvements in YS and UTS, with the 3 Wt.% In composition reaching 46 and 52.62 MPa, respectively – a 72% increase over base SAC105. This enhancement is attributed to solid solution strengthening and microstructural refinement. Although thermal aging led to strength degradation, indium-containing alloys retained superior integrity. Notably, the SAC105 + 3 Wt.% In alloy maintained a UTS of 44.75 MPa after aging at 180°C. SEM analysis revealed uniform indium distribution and formation of Cu6(Sn,In)5 and Ag3(Sn,In) intermetallic compounds. Practical implications: Indium doping offers a cost-effective strategy towards sustainable and high reliability solder materials for automotive and aerospace electronics, with potential to reduce lead dependence in compliance with RoHD directives. Originality/value: This work provides novel insights into indium's role in reinforcing SAC105 solder alloys, supporting the development of sustainable, high-performance lead-free solders for thermally demanding applications. [ABSTRACT FROM AUTHOR]
ISSN:09540911