Effect of Bi addition on the shear strength and failure mechanism of low-Ag lead-free solder joints

Chen, Yinbo; Meng, Zhichao; Gao, Li-Yin; Liu, Zhi-Quan

doi:10.1007/s10854-020-04982-4

Cited by 22 publications

(3 citation statements)

References 31 publications

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“…The transition of fracture surfaces from solder matrix to Cu 6 Sn 5 /solder interface shows that the thicker IMC became the weak point of the Sn– x Cu solder joint throughout the ageing process. In addition, there was no evidence of cleavage stages, river patterns or fishbone patterns, and it was concluded that Sn–0.3Cu and Sn–1.0Cu solder joints were examples of typical ductile fractures (Chen et al , 2021).…”

Section: Resultsmentioning

confidence: 99%

Role of Cu percentage in the Sn-xCu alloy on the mechanical performance at Sn-xCu/ENIG interface produced by laser soldering

Abdullah

Idris

2023

SSMT

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Purpose Pb-free solders have been developed to replace the standard Sn–Pb eutectic solder since the prohibition on Pb used in solders. The Sn–Ag–Cu series of lead-free solders is the most extensively used in the electronics industry. The Ag3Sn, which forms during isothermal ageing, can significantly degrade solder joint reliability. Sn–Ag–Cu solder’s high price further hindered its use in the electronics industry. This paper aims to investigate different copper percentages into Sn–xCu solder alloy to improve its microstructure and strength performance. Design/methodology/approach The solder alloys used in this work were Sn–xCu, where x = 0.0, 0.3, 0.5, 0.7, 1.0 Wt.%, which was soldered onto electroless nickel immersion gold (ENIG) substrate using carbon dioxide (CO2) gas laser. Then these samples were subjected to isothermal aging for 0, 200, 500, 1,000 and 2,000 h. The Sn–xCu solder alloy was fabricated through a powder metallurgy process. Findings Microstructure characterization showed that Cu addition resulted in fine and rounded shape of Cu–Sn–Ni particles. Shear strength of Sn–xCu solder joints was increased with increasing Cu content, but at aging duration of 1,000 h, it dropped slightly. It is believed that the strength improved due to the increment of diffusion rate during isothermal aging. Practical implications In a Cu–Sn solder, the recommended amount is 1.0 Wt.% of Cu. In extensive aging procedures, it was discovered that Sn1.0Cu solder improved the reliability of solder joints. The findings indicated that the innovative solder alloys might satisfy the needs of high-reliability applications. Originality/value The study shows that the right amount of Cu enhances the solidification of Sn–Cu solder, increasing the shear force of the Cu–Sn solder joint. The Sn1.0Cu exhibits a ductile fracture on the top microstructure, improving the joint’s average shear strength.

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Section: Resultsmentioning

confidence: 99%

Role of Cu percentage in the Sn-xCu alloy on the mechanical performance at Sn-xCu/ENIG interface produced by laser soldering

Abdullah

Idris

2023

SSMT

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“…Adding Sb could inhibit the formation of coarse β-Sn and also refine the precipitation of Ag 3 Sn, thus improving the mechanical and thermal resistant behavior of SAC solders [ 18 , 19 ]. Bismuth (Bi) is another important alloying element for solder alloy that shows a significant effect in improving the creep resistance and thermal fatigue resistance [ 13 , 20 , 21 , 22 ]. Adding Bi can also lower the melting point and improves the wettability of SAC alloys [ 23 ].…”

Section: Introductionmentioning

confidence: 99%

Effect of Bi, Sb, and Ti on Microstructure and Mechanical Properties of SAC105 Alloys

et al. 2022

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The Sn-Ag-Cu (SAC) solder alloys with a low Ag (Ag < 3 wt.%) content have attracted great attention owing to their low cost, increased ability in bulk compliance, and plastic energy dissipation. However, some of their mechanical properties are generally lower than the SAC alloys with a higher Ag content. Adding alloying elements is an effective approach for improving the mechanical properties of the SAC alloys. In this study, the effect of Bi, Sb, and Ti on Sn-1 wt.%Ag-0.5 wt.%Cu (SAC105) solder alloys was investigated. The SAC solders with four compositions: SAC105-1 wt.%Bi, SAC105-1 wt.%Sb, SAC105-1 wt.%Bi-1 wt.%Sb, SAC105-1 wt.%Bi-1 wt.%Sb-0.4 wt.%Ti were prepared. The microstructure and phase compositions were characterized using electron scanning microscopy, and X-ray diffraction. The thermal properties and wettability were also examined. Uniaxial tensile tests and nano-indentation tests were conducted to evaluate the mechanical properties. The results show that adding Bi or Sb could increase the strength of SAC105 alloys mainly due to the solid solution strengthening effect. The creep resistance of SAC105 alloys was also improved with the additions of Bi and Sb. The co-additions of Bi and Sb into SAC105 alloys exhibit an enhanced creep resistance than that calculated by the theoretical calculation. The further addition of Ti into SAC105-1Bi-1Sb alloys demonstrated a much-improved creep resistance, which could be attributed to the synergistic effects of both solid solution strengthening and the precipitation hardening effects.

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“…Traditional eutectic Sn42-Bi58 solder alloy has a melting point of 138 °C, and has been widely used in consumer electronic products compared with SAC305 solder due to its lower cost [1][2][3][4]. The wetting angle of Sn-Bi solder on Cu substrate is larger than that of Sn63-Pb37 alloy, indicating that Sn-Bi eutectic solder has a good wettability during reflow [5].…”

Section: Introductionmentioning

confidence: 99%

Microstructural evolution and failure analysis of Sn–Bi57–Ag0.7 solder joints during thermal cycling

Chen

Wang

Gao

et al. 2021

J Mater Sci: Mater Electron

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Although many studies have reported the behaviors of thermal cycling of Snbased solder joints, the corresponding mechanism is difficult to describe universally due to the complexity of different cases. In the present study, microstructural evolution and failure of Sn-Bi57-Ag0.7 solder joints caused by thermal cycling between -40 and 85 °C from 0 to 1000 cycles were systematically investigated. The results indicated that the Sn-Bi-Ag solder joint was composed of Sn-rich phase, Bi-rich phase, large numbers of Bi dispersed-particles, and Ag 3 Sn precipitate. With the extension of time during thermal cycling, the microstructure of Sn-Bi-Ag solder joint gradually coarsened and the IMC layer became thicker (from 0.82 to 2.38 lm). However, Sn-Bi-Ag solder joints failed after 3000 thermal cycles. Two different stages of failure were found and the mechanism, related to the increment of thermal mismatch stress, was illuminated. Furthermore, Electron Backscattered Diffraction was used to detailedly elucidate the grain characteristics of the failed Sn-Bi-Ag solder joints, and the effect of thermal stress on orientations of Sn and Bi grains was also revealed. Being different from the orientation change observed in traditional Sn-Bi eutectic solder joints in previous studies, the present results demonstrated that both Sn and Bi grains did not present any preferred orientations after thermal cycling. And the reason of this phenomenon might be attributed to the Ag 3 Sn, which could be regarded as second-phase particles. Our present work would provide theoretical guidance for the development of new Sn-Bi-X solders with high reliabilities.

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Effect of Bi addition on the shear strength and failure mechanism of low-Ag lead-free solder joints

Cited by 22 publications

References 31 publications

Role of Cu percentage in the Sn-xCu alloy on the mechanical performance at Sn-xCu/ENIG interface produced by laser soldering

Role of Cu percentage in the Sn-xCu alloy on the mechanical performance at Sn-xCu/ENIG interface produced by laser soldering

Effect of Bi, Sb, and Ti on Microstructure and Mechanical Properties of SAC105 Alloys

Microstructural evolution and failure analysis of Sn–Bi57–Ag0.7 solder joints during thermal cycling

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