Effect of temperature on joint quality in wave soldering of Sn-9Zn-2.5Bi-1.5In lead-free solder alloy

IF 2.6 4区工程技术 Q2 ENGINEERING, ELECTRICAL & ELECTRONIC

Microelectronic Engineering Pub Date : 2024-06-25 DOI:10.1016/j.mee.2024.112229

Vichea Duk, Anshi Ren, Gong Zhang

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引用次数: 0

Abstract

SnZn (tin‑zinc) solder has been regarded as a promising lead-free solder material with a low melting point of 198 °C, serving as a suitable alternative to both SnPb solder due to its lack of hazardous substances and Sn-Ag-Cu solder because of the high cost associated with silver. Nonetheless, its susceptibility to oxidation hinders solderability and increases soldering defects such as bridging, insufficient fillings, and voids, limiting its use in commercial production. Devices designed with through-hole technology, in contrast to surface-mounted ones, continue to exhibit superior interconnection reliability in such applications. In this investigation on wave soldering, a newly developed lead-free solder, composed of 87% tin, 9% zinc, 2.5% bismuth, and 1.5% indium by weight, was employed under two conditions related to nitrogen content: 1) Ensuring that static oxygen content remained below 3000 ppm. 2) Maintaining soldering section oxygen content below 600 ppm at a conveyor speed of 1200 mm/min. The soldering results were examined at various temperatures of preheating and soldering. It proves that the measured peak temperature of liquid solder T_pL over 230 °C makes the bridging defect rate lower than 0.30%. Additionally, setting the peak temperature of solder joint T_pZ above 220 °C, along with specific preheating temperatures (105/115/135/145 °C), archives 100% vertical filling without significant voids in the solder joints. Moreover, optimizing wave soldering settings, specifically adjusting the wave soldering setting temperature T_s to 235 °C, conveyor speed v_c to 1000 mm/min, resolves soldering defects associated with Sn-9Zn-2.5Bi-1.5In alloy in wave process.

Relevance summary

1.
T_pL surpasses 230 °C, the total number of bridging defects per board decreases to fewer than 6, approximately 0.30%. T_pZ values of 220 °C or higher results in 100% vertical fill and no significant large voids, demonstrating optimal filling effects
2.
Under the conditions of T_S = 235 °C and v_c = 1000 mm/min yield T_pL > 230 °C and T_pZ > 210.9 °C, it leads to a reduction in bridging defects.
3.
To maintain flux efficiency and minimize internal voids, an optimal selection of preheating temperatures (105/115/135/145 °C) is demonstrated.
4.
An integrated nitrogen content-controlled system is utilized to eliminate oxygen from the solder pot, aiming to prevent oxidation.

Abstract Image

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温度对锡-9Zn-2.5Bi-1.5In 无铅焊料合金波峰焊接质量的影响

锡锌（SnZn）焊料的熔点低至 198 °C，被认为是一种很有前途的无铅焊料，因其不含有害物质，可作为锡铅焊料和锡银铜焊料的合适替代品，因为与银相关的成本很高。然而，它的易氧化性妨碍了可焊性，并增加了桥接、填充不足和空洞等焊接缺陷，限制了其在商业生产中的使用。与表面贴装器件相比，采用通孔技术设计的器件在此类应用中继续表现出卓越的互连可靠性。在这项波峰焊调查中，采用了一种新开发的无铅焊料，其成分为 87% 锡、9% 锌、2.5% 铋和 1.5% 铟（按重量计），在两种与氮含量有关的条件下进行焊接：1) 确保静态氧含量保持在 3000 ppm 以下。2) 以 1200 毫米/分钟的传送带速度将焊接部分的氧含量保持在 600 ppm 以下。在不同的预热和焊接温度下对焊接结果进行了检验。结果表明，测量到的液态焊料峰值温度 TpL 超过 230 ℃ 时，桥接缺陷率低于 0.30%。此外，将焊点 TpZ 的峰值温度设定在 220 ℃ 以上，再配合特定的预热温度（105/115/135/145 ℃），可实现 100% 垂直填充，焊点中无明显空隙。此外，优化波峰焊设置，特别是将波峰焊设置温度 Ts 调至 235 °C，传送带速度 vc 调至 1000 mm/min，可解决波峰焊工艺中与 Sn-9Zn-2.5Bi-1.5In 合金相关的焊接缺陷。在 TS = 235 °C 和 vc = 1000 mm/min 的条件下，TpL > 230 °C 和 TpZ > 210.9 °C，桥接缺陷会减少。为保持助焊剂的效率并尽量减少内部空隙，对预热温度（105/115/135/145 °C）进行了最佳选择。

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来源期刊

Microelectronic Engineering 工程技术-工程：电子与电气

CiteScore

5.30

自引率

4.30%

发文量

131

审稿时长

29 days

期刊介绍： Microelectronic Engineering is the premier nanoprocessing, and nanotechnology journal focusing on fabrication of electronic, photonic, bioelectronic, electromechanic and fluidic devices and systems, and their applications in the broad areas of electronics, photonics, energy, life sciences, and environment. It covers also the expanding interdisciplinary field of "more than Moore" and "beyond Moore" integrated nanoelectronics / photonics and micro-/nano-/bio-systems. Through its unique mixture of peer-reviewed articles, reviews, accelerated publications, short and Technical notes, and the latest research news on key developments, Microelectronic Engineering provides comprehensive coverage of this exciting, interdisciplinary and dynamic new field for researchers in academia and professionals in industry.