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Li, L.; Qin, W.; Mai, B.; Qi, D.; Yang, W.; Feng, J.; Zhan, Y. Effect of Carbon Nanotubes on Tin-Based Lead-Free Solders. Encyclopedia. Available online: https://encyclopedia.pub/entry/44821 (accessed on 27 August 2024).
Li L, Qin W, Mai B, Qi D, Yang W, Feng J, et al. Effect of Carbon Nanotubes on Tin-Based Lead-Free Solders. Encyclopedia. Available at: https://encyclopedia.pub/entry/44821. Accessed August 27, 2024.
Li, Liangwei, Weiou Qin, Baohua Mai, Da Qi, Wenchao Yang, Junli Feng, Yongzhong Zhan. "Effect of Carbon Nanotubes on Tin-Based Lead-Free Solders" Encyclopedia, https://encyclopedia.pub/entry/44821 (accessed August 27, 2024).
Li, L., Qin, W., Mai, B., Qi, D., Yang, W., Feng, J., & Zhan, Y. (2023, May 25). Effect of Carbon Nanotubes on Tin-Based Lead-Free Solders. In Encyclopedia. https://encyclopedia.pub/entry/44821
Li, Liangwei, et al. "Effect of Carbon Nanotubes on Tin-Based Lead-Free Solders." Encyclopedia. Web. 25 May, 2023.
Effect of Carbon Nanotubes on Tin-Based Lead-Free Solders
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This entry is adapted from the peer-reviewed paper 10.3390/cryst13050789

Carbon nanotubes (CNTs) are being applied with increasing frequency for advanced soldering. They have excellent mechanical, electrical, and thermal properties and are primarily used to reinforce lead-free solders. The addition of CNTs can effectively improve the ultimate tensile strength, microhardness, shear strength, and creep resistance of the solder. However, the practical application of CNT composite solders has been a challenge for researchers for decades. The most significant issue is uniform dispersion due to the large density and surface differences between CNTs and solders. Other concerns are the structural integrity of CNTs and their limited addition amount, solder wettability, and interfacial bonding. CNT composite solders can only be widely used in a real sense when these challenges are properly addressed and overcome.

CNTs lead-free solder strengthening mechanism preparation method

1. Introduction

Carbon nanotubes (CNTs) are promising nanomaterials that are attractive components in composite solder applications due to their excellent mechanical, electrical, and thermal properties [1][2]. The mechanical properties of composite solders have been significantly improved by using CNTs [3][4]. In CNT-based composite solders, CNTs can be roughly divided into unmodified CNTs and metal-modified CNTs [5][6]. The following main processing methods have been widely used to combine CNTs and solders: mechanical mixing, powder metallurgy (P/M), and electrochemical deposition [7][8][9]. The former two are to mix CNTs directly with solder by physical means, and the latter is to deposit and embed CNTs in the solder matrix by chemical means.

2. Structure of CNT Composite Solder

In general, it is difficult to directly observe the structure of CNTs in composite solders due to the small amount of CNTs added. Most studies reported the structure before CNTs were added to the solder, as shown in Figure 1 [10], while few studies reported the structure after CNTs were added to the solder. Considering that agglomeration is easy to cause crack initiation, theoretically, the structure of CNTs in solder can be indirectly observed on the fracture surface.
Figure 1. (a) Scanning electron microscopy image and (b) transmission electron microscope image of Ni-decorated multi-walled carbon nanotubes (Ni-MWCNTs) before solder addition [10]. Copyright 2022 by Liu, X.; Lu, G.; Ji, Z.; Wei, F.; Yao, C.; Wang, J. Copyright under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/, acccessed on 3 April 2023).
Figure 2 [11] depicts the fracture morphology of Sn-3.0Ag-0.5Cu (SAC305) composite solder joints containing 0.5 wt.% Ni-modified carbon nanotubes (Ni-CNTs) aged for 96 h. Enlarge the dimple circled by the purple ellipse on the right side of Figure 2a and perform energy-dispersive X-ray spectroscopy analysis, as shown in Figure 2b. The presence of Ni-CNTs was observed. The selected area is further enlarged, and the morphology of Ni-CNTs is shown in Figure 2c, where it can be seen that although the Ni-CNTs have been fractured, one end is still embedded in the solder matrix. There are also some Ni-CNTs that still serve as bridges to connect the separated parts into a whole after the composite solder joint breaks, as shown in Figure 2d. It can be seen from Figure 2e that the structure of Ni-CNTs in the composite solder has not changed significantly. However, the Ni-CNTs are entangled haphazardly, which indicates that fractures tend to occur where there are agglomerates. The above is because CNTs are embedded in the solder matrix, so CNTs may be observed at the fracture surface. If, as shown in Figure 3 [12], a large number of multi-walled carbon nanotubes (MWCNTs) are discharged to the solder surface due to their low density during the reflow process, it is not necessarily possible to find the presence of MWCNTs on the fracture surface.
Figure 2. Fracture surface of Sn-3.0Ag-0.5Cu (SAC305) composite solder joints containing 0.5 wt.% Ni-modified carbon nanotubes (Ni-CNTs) aged at 170 °C for 96 h: (a) macroscopic photo, (b) magnification of the circle in (a), and (c–e) micrographs of different types of CNTs appearing in the magnified rectangle of (b) [11]. Copyright Springer Nature BV Publisher, 2022.
Figure 3. Micrographs of (a) SAC305 without layer formation and (b) SAC305-0.04MWCNTs covered by MWCNT layer formation on top of the solder bump [12]. Copyright 2021 by Ismail, N.; Jalar, A.; Afdzaluddin, A.; Bakar, M.A. Copyright under the terms of the Creative Commons Attribution 4.0 License (https://creativecommons.org/licenses/by/4.0/, acccessed on 3 April 2023).

3. Strengthening Mechanism of CNT Composite Solder

The use of CNTs to enhance solder has become a research hotspot. It is essential to understand their strengthening mechanisms to facilitate the development of CNT composite solders. So far, many strengthening mechanisms of CNTs have been reported, and the widely accepted ones mainly include the following four [13][14][15]: (1) load transfer strengthening; (2) dislocation interference strengthening (Orowan strengthening); (3) mismatch strengthening; and (4) fine grain strengthening. These mechanisms synergistically reinforce the matrix [16].
First, load transfer means that when the composite solder is loaded, the interfacial stress will be transferred to the CNTs dispersed in the matrix. Due to the excellent mechanical properties of CNTs, they can bear most of the stress. Ismail et al. [17] explained this mechanism through experimental results, showing that adding CNTs prevents sudden changes in the deformation mechanism in solder under shock waves. Compared with the SAC305 solder joints of the explosion test samples and the control samples, the indentation depth displacements of the SAC305-CNTs solder joints of the explosion test samples and the control samples were reduced by about 42% and 56%, respectively. The load transfer effect of CNTs was also reflected in the finite element simulation results, as the location of maximum stress intensity was shifted from the solder at the interface edge to the CNTs [18]. Additionally, the interfacial bonding strength between CNTs and the solder matrix is crucial to load transfer strengthening. Literature studies have shown that the load cannot be transferred from the Sn-3.5Ag-0.7Cu (SAC357) solder matrix to Ni-modified multi-walled carbon nanotubes (Ni-MWCNTs) when the interfacial bonding strength is insufficient [19].
Second, CNTs are inert materials that do not react with elements in the solder matrix and have a melting point much higher than the soldering temperature [20][21]. Thus, CNTs can function as pinning sites. It has been reported that the yield strength of the composite solder was increased by 17.52% compared with the original Sn-0.7Cu solder when Ni-CNTs were added in an amount of 0.075 wt.% [22]. This is because when the addition amount is less than 0.075 wt.%, Ni-CNTs are dispersed in the solder as the second phase, effectively hindering the movement of dislocations.
Third, the thermal modulus, elastic modulus, or geometric mismatch between the solder matrix and the reinforcement CNTs can induce plastic deformation, making dislocations multiply. Nai et al. [23] showed that the high dislocation density in the matrix could be attributed to the significant difference in thermal expansion coefficient between SAC357 solder and MWCNTs. They also expressed similar views in other research results, arguing that the geometrically necessary dislocations are generated to accommodate the thermal elastic modulus mismatch between solder and MWCNTs [24].
Finally, CNTs are usually dispersed at grain boundaries in the solder matrix, inhibiting grain growth. As a result, the number of grains per unit volume increases, the stress concentration decreases when a force is applied, and the grain boundary area increases, hindering the movement of dislocations [25]. According to the study by Zhu et al. [26], MWCNTs refine the microstructure of the composite solder and increase the grain boundary density. Therefore, the movement of dislocations is hindered microscopically, and the shear strength and hardness are improved macroscopically. However, due to the limitation of the amount of addition, the degree of grain refinement is limited. Compared with the initial solder, the average grain size of the SAC357 composite solder decreased by 6% under the influence of 0.1 wt.% Ni-MWCNTs and only 4.6% under the influence of 0.1 wt.% unmodified MWCNTs [27].

References

  1. Javid, N.S.; Sayyadi, R.; Khodabakhshi, F. Lead-free Sn-based/MW-CNTs nanocomposite soldering: Effects of reinforcing content, Ni-coating modification, and isothermal ageing treatment. J. Mater. Sci. Mater. Electron. 2019, 30, 4737–4752.
  2. Wang, J.; Xue, S.; Zhang, P.; Zhai, P.; Tao, Y. The reliability of lead-free solder joint subjected to special environment: A review. J. Mater. Sci. Mater. Electron. 2019, 30, 9065–9086.
  3. Li, M.L.; Zhang, L.; Jiang, N.; Zhang, L.; Zhong, S.J. Materials modification of the lead-free solders incorporated with micro/nano-sized particles: A review. Mater. Des. 2021, 197, 109224.
  4. Xu, K.K.; Zhang, L.; Gao, L.L.; Jiang, N.; Zhang, L.; Zhong, S.J. Review of microstructure and properties of low temperature lead-free solder in electronic packaging. Sci. Technol. Adv. Mater. 2020, 21, 689–711.
  5. Bharath Krupa Teja, M.; Sharma, A.; Das, S.; Das, K. A review on nanodispersed lead-free solders in electronics: Synthesis, microstructure and intermetallic growth characteristics. J. Mater. Sci. 2022, 57, 8597–8633.
  6. Zhai, X.; Chen, Y.; Li, Y.; Zou, J.; Shi, M.; Yang, B. Mechanical, photoelectric and thermal reliability of SAC307 solder joints with Ni-decorated MWCNTs for flip-chip LED package component during aging. Solder. Surf. Mount Technol. 2022, 34, 257–265.
  7. Lee, C.J.; Min, K.D.; Park, H.J.; Jung, S.B. Mechanical properties of Sn-58wt%Bi solder containing Ag-decorated MWCNT with thermal aging tests. J. Alloys Compd. 2020, 820, 153077.
  8. Mohd Salleh, M.A.A.; Hazizi, M.H.; Al Bakri Abdullah, M.M.; Noriman, N.; Mayapan, R.; Ahmad, Z.A. Research Advances of Composite Solder Material Fabricated via Powder Metallurgy Route. Adv. Mater. 2013, 626, 791–796.
  9. Zhang, S.; Chen, Q. Fabrication of MWCNT incorporated Sn-Bi composite. Fabrication of MWCNT incorporated Sn-Bi composite. Compos. Part B 2014, 58, 275–278.
  10. Liu, X.; Lu, G.; Ji, Z.; Wei, F.; Yao, C.; Wang, J. Effect of Ni-Coated Carbon Nanotubes Additions on the Eutectic Sn-0.7 Cu Lead-Free Composite Solder. Metals 2022, 12, 1196.
  11. Qu, M.; Gao, Z.; Chen, J.; Cui, Y. Effect of Ni-coated carbon nanotubes addition on the wettability, microhardness, and shear strength of Sn-3.0Ag-0.5Cu/Cu lead-free solder joints. J. Mater. Sci. Mater. Electron. 2022, 33, 10866–10879.
  12. Ismail, N.; Jalar, A.; Afdzaluddin, A.; Bakar, M.A. Electrical resistivity of Sn-3.0 Ag-0.5 Cu solder joint with the incorporation of carbon nanotubes. Nanomater. Nanotechnol. 2021, 11, 1847980421996539.
  13. Carneiro, Í.; Simões, S. Strengthening Mechanisms in Carbon Nanotubes Reinforced Metal Matrix Composites: A Review. Metals 2021, 11, 1613.
  14. Hawi, S.; Gharavian, S.; Burda, M.; Goel, S.; Lotfian, S.; Khaleque, T.; Nezhad, H.Y. Development of carbonaceous tin-based solder composite achieving unprecedented joint performance. Emergent Mater. 2021, 4, 1679–1696.
  15. Baig, Z.; Mamat, O.; Mustapha, M. Recent Progress on the Dispersion and the Strengthening Effect of Carbon Nanotubes and Graphene-Reinforced Metal Nanocomposites: A Review. Crit. Rev. Solid State Mater. Sci. 2018, 43, 1–46.
  16. Chen, B.; Li, S.; Imai, H.; Jia, L.; Umeda, J.; Takahashi, M.; Kondoh, K. Load transfer strengthening in carbon nanotubes reinforced metal matrix composites via in-situ tensile tests. Compos. Sci. Technol. 2015, 113, 1–8.
  17. Ismail, N.; Jalar, A.; Yusoff, W.Y.W.; Safee, N.S.; Ismail, A. Effect of shock wave on constant load behaviour of Pb-Free/CNT solder joint. Sains Malays. 2020, 49, 3037–3044.
  18. Yang, L.; Zhou, W.; Liang, Y.; Cui, W.; Wu, P. Improved microstructure and mechanical properties for Sn58Bi solder alloy by addition of Ni-coated carbon nanotubes. Mater. Sci. Eng. A 2015, 642, 7–15.
  19. Han, Y.; Nai, S.; Jing, H.; Xu, L.; Tan, C.; Wei, J. Development of a Sn-Ag-Cu solder reinforced with Ni-coated carbon nanotubes. J. Mater. Sci. Mater. Electron. 2011, 22, 315–322.
  20. Billah, M.M. Carbon Nanotube (CNT) Metallic Composite with Focus on Processing and the Resultant Properties. PhD Thesis, University of Central Florida, Orlando, FL, USA, 2017.
  21. Zhang, K.; Stocks, G.M.; Zhong, J. Melting and premelting of carbon nanotubes. Nanotechnology 2007, 18, 285703.
  22. Mao, J.; Yang, W.; Song, Q.; Lv, Y.; Jiang, S.; Li, Y.; Zhan, Y. The effects of the addition of on the hardness, density, wettability and mechanical properties of Sn-0.7Cu lead-free solder. J. Mater. Sci. Mater. Electron. 2021, 32, 10843–10854.
  23. Nai, S.; Gupta, M.; Wei, J. Development of novel lead-free solder composites using carbon nanotube reinforcements. Int. J. Nanosci. 2005, 4, 423–429.
  24. Nai, S.; Wei, J.; Gupta, M. Interfacial intermetallic growth and shear strength of lead-free composite solder joints. J. Alloys Compd. 2009, 473, 100–106.
  25. He, P.; Lu, X.C.; Lin, T.S.; Li, H.X.; An, J.; Ma, X.; Feng, J.C.; Zhang, Y.; Li, Q.; Qian, Y.Y. Improvement of mechanical properties of Sn-58Bi alloy with multi-walled carbon nanotubes. Trans. Nonferrous Met. Soc. China 2012, 22, s692–s696.
  26. Zhu, Z.; Chan, Y.C.; Chen, Z.; Gan, C.L.; Wu, F. Effect of the size of carbon nanotubes (CNTs) on the microstructure and mechanical strength of CNTs-doped composite Sn0.3Ag0.7Cu-CNTs solder. Mater. Sci. Eng. A 2018, 727, 160–169.
  27. Khodabakhshi, F.; Zareghomsheh, M.; Khatibi, G. Nanoindentation creep properties of lead-free nanocomposite solders reinforced by modified carbon nanotubes. Mater. Sci. Eng., A 2020, 797, 140203.
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Subjects: Materials Science, Composites
Contributors MDPI registered users' name will be linked to their SciProfiles pages. To register with us, please refer to https://encyclopedia.pub/register :
Liangwei Li
,
Weiou Qin
,
Baohua Mai
,
Da Qi
,
Wenchao Yang
,
Junli Feng
,
Yongzhong Zhan
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Revisions: 2 times (View History)
Update Date: 26 May 2023
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