Low-melting and thermal-conducting Sn-Bi-Ag solder enhanced with SnO2 nanoparticles for reliable mini-LED microsystems

IF 2.8 4区工程技术 Q2 ENGINEERING, ELECTRICAL & ELECTRONIC

Journal of Materials Science: Materials in Electronics Pub Date : 2025-04-21 DOI:10.1007/s10854-025-14658-6

Jiwan Kang, Ashutosh Sharma, Jae Pil Jung

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引用次数: 0

Abstract

In this work, low-temperature Sn-57.6wt%Bi-0.4wt%Ag (Sn-Bi-Ag) solder alloy was enhanced with SnO₂ nanoparticles (NPs, 0 to 0.7wt%) using low energy milling and melting process. The developed solders were reflowed to join Cu/Ni pad of 1608 mini-light emitting diode (LED) chips at 238 °C. The morphology, melting temperature, thermal conductivity, and electrical properties of the developed alloys were evaluated. The findings revealed a depression in melting point of Sn-Bi-Ag/SnO₂ solder by 1.1 °C compared to the pristine Sn-Bi-Ag alloy. Microstructural analysis indicated a refinement in the β-Sn and Bi-rich phase in Sn-Bi-Ag alloy after the addition of SnO₂ NPs (≈0.5wt%), accompanied by a decrease in β-Sn area fraction (0.49) with a mild increase in Bi-rich area (0.46). Additionally, the thermal diffusivity and conductivity were significantly enhanced, with the values of 13.2 mm²/s and 14.2 J/K/g all of which outperformed the Sn -Bi -Ag alloy. The electrical resistivity of the developed samples was in the range of 5.0 × 10^–7 to 3 × 10^–7 Ω.cm. To further assess solder joint reliability, the SnO₂ NPs-modified solder was applied to a 1608 mini-LED chip and bonded onto the Cu/Ni pad of a fiber glass reinforced printed circuit board (FR4-PCB). The solder joint characteristics was evaluated by shear strength tests by examining the post fractured joint morphology of the specimens. The shear tests showed an increasing trend with the fraction of SnO₂ NPs in the Sn-Bi-Ag matrix. The shear strength was improved by ≈10–11%, respectively, over Sn-Bi-Ag alloy. The fracture morphology revealed a mixed ductile and brittle fracture at 0.5wt.%SnO₂ NPs in the matrix while brittle fracture dominates at a higher fraction of SnO₂ NPs (0.7wt.%) is added to the matrix alloy. It is inferred from this investigation that an optimum amount of 0.5wt.% is desired for realizing high thermal conductivity, low-melting, and reliable solder joints in future microelectronics mini-LED packaging.

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用SnO2纳米粒子增强的低熔点导热Sn-Bi-Ag焊料，用于可靠的微型led微系统

在本研究中，低温Sn-57.6wt%Bi-0.4wt%Ag （Sn-Bi-Ag）钎料合金中加入了SnO2纳米粒子（NPs, 0 ~ 0.7wt%），采用低能铣削和熔化工艺进行强化。将所制备的焊料在238℃下回流连接到1608微型发光二极管（LED）芯片的Cu/Ni焊盘上。对所制备合金的形貌、熔化温度、导热系数和电性能进行了评价。结果表明，与原始Sn-Bi-Ag合金相比，Sn-Bi-Ag/SnO2焊料的熔点降低了1.1°C。显微组织分析表明，加入SnO2 NPs（≈0.5wt%）后，Sn-Bi-Ag合金的β-Sn和富bi相得到细化，β-Sn区域分数（0.49）下降，富bi区域分数（0.46）略有增加。热扩散系数和导热系数均显著提高，分别达到13.2 mm2/s和14.2 J/K/g，均优于Sn -Bi -Ag合金。发育样品的电阻率范围为5.0 × 10-7 ~ 3 × 10-7 Ω.cm。为了进一步评估焊点的可靠性，将SnO2 nps改性焊料应用于1608 mini-LED芯片上，并将其粘合到玻璃纤维增强印刷电路板（FR4-PCB）的Cu/Ni焊盘上。通过检查试件断裂后的接头形态，通过剪切强度测试来评估焊点特性。剪切试验结果表明，随着Sn-Bi-Ag基体中SnO2纳米粒子含量的增加，SnO2纳米粒子的含量呈增加趋势。与Sn-Bi-Ag合金相比，其抗剪强度分别提高了≈10-11%。在0.5wt时，断口形貌为韧性和脆性混合断裂。在基体合金中加入较多的SnO2 NPs （0.7wt.%）时，脆性断裂占主导地位。从本研究推断，最佳用量为0.5wt。%是实现未来微电子微型led封装中高导热性、低熔点和可靠焊点所需要的。

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来源期刊

Journal of Materials Science: Materials in Electronics 工程技术-材料科学：综合

CiteScore

5.00

自引率

7.10%

发文量

1931

审稿时长

2 months

期刊介绍： The Journal of Materials Science: Materials in Electronics is an established refereed companion to the Journal of Materials Science. It publishes papers on materials and their applications in modern electronics, covering the ground between fundamental science, such as semiconductor physics, and work concerned specifically with applications. It explores the growth and preparation of new materials, as well as their processing, fabrication, bonding and encapsulation, together with the reliability, failure analysis, quality assurance and characterization related to the whole range of applications in electronics. The Journal presents papers in newly developing fields such as low dimensional structures and devices, optoelectronics including III-V compounds, glasses and linear/non-linear crystal materials and lasers, high Tc superconductors, conducting polymers, thick film materials and new contact technologies, as well as the established electronics device and circuit materials.