The Effects of Antimony Addition on the Microstructural, Mechanical, and Thermal Properties of Sn-3.0Ag-0.5Cu Solder All
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OVER the past several years, Sn-Pb alloys have been typically used in conventional soldering processes owing to the unique properties and low cost of the materials.[1] However, medical studies have shown that Pb is a heavy metal toxin that can damage the kidneys, liver, blood, and central nervous system.[2,3] Therefore, alternative Pb-free solder alloys with the right balance of thermal, mechanical, and soldering properties have attracted the interest of several research groups.[4] Recently, studies of high Ag-content Sn-Ag-Cu (SAC) solder alloys have increased exponentially since their generally superior mechanical properties and relatively good solderability
PHAIROTE SUNGKHAPHAITOON is with the Department of Materials Science and Technology, Faculty of Science, Prince of Songkla University, 90112 Hat Yai, Thailand. Contact e-mail: [email protected] THAWATCHAI PLOOKPHOL is with the Department of Mining and Materials Engineering, Faculty of Engineering, Prince of Songkla University, 90112 Hat Yai, Thailand. Manuscript submitted March 27, 2017.
METALLURGICAL AND MATERIALS TRANSACTIONS A
make these alloys the most promising candidates in microelectronics applications.[5] However, these alloys have some drawbacks, including short creep rupture lifetimes. In addition, the formation of Ag3Sn and Cu6Sn5 intermetallic compounds (IMCs) in the solder matrix impairs the mechanical performance of the solder joints leading to failure under stressed conditions in actual service.[6] For this reason, some metal additives, such as Bi, Sb, In, Co, Ge, Ni, Ga, and nanoparticles, have been introduced into SAC solder alloys in order to refine the microstructures and to inhibit the formation of IMCs.[7–10] Interestingly, it has also been reported that the addition of Sb improved mechanical properties of the alloys, mainly due to the solid-solution hardening and particle hardening effects of Sb. The formation of SnSb in the b-Sn matrix phase, and the presence of Sb could suppress the coarsening of the b-Sn and refine the IMCs, thus improving the mechanical and thermal properties of the Sn-based solder alloys.[11–15] Chen and Li reported that the addition of 1.0 wt pct Sb into Sn-3.5Ag-0.7Cu solders led to the formation of Ag3(Sn,Sb) IMC layers and decreases in the thickness and grain size of the IMCs. Greater than this amount,
the thickness of the IMCs increased slightly. Adding Sb into Sn-3.5Ag-0.7Cu solders increased the activation energy, reduced the atomic diffusion rate, and inhibited the excessive growth of the IMCs.[12,15] Mahmudi and Mahin-Shirazi reported that the addition of 1.5 wt pct Sb into Sn-3.5Ag binary solder alloys resulted in increases in both the ultimate tensile strength (UTS) and ductility of solder alloys. The increased strength of the alloy was attributed to the solid-solution hardening effects of Sb in the b-Sn matrix phase.[11] The thermal properties of solder alloys are also important in the soldering process, and binary phase diagrams were constructed to understand the melting behavior of solder alloys b
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