Effect of Co on microstructure evolution and thermal fatigue stability of lead-free solder alloys of SACBSN series

IF 1.6 4区工程技术 Q3 ENGINEERING, ELECTRICAL & ELECTRONIC Microelectronics Reliability Pub Date : 2024-04-24 DOI:10.1016/j.microrel.2024.115395

Zhendong Wang , Jiaojiao Yang , Jikang Yan , Biao Wang , Chongyan Leng , Linyan Zhao

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Abstract

The majority of studies on high-reliability solder alloys have focused on the six-element system of Sn, Ag, Cu, Bi, Sb, and Ni. However, there is limited research on the influence of Co element within this system. In this study, a Sn3.0Ag0.5CuBiSbNixCo (x = 0 wt%, 0.02 wt%, 0.05 wt%, 0.08 wt%, 0.1 wt%) alloy (referred to as SACBSN-xCo alloy) was prepared using a melting method. The mechanical properties of SACBSN-xCo alloy solder joints were evaluated through ultimate shear strength testing. The composition analysis of the alloy, phase composition examination, intermetallic compound (IMC) investigation and interfacial layer morphology analysis were conducted using ICP, XRD, SEM and EDS techniques respectively. Furthermore, the evolution process of solder structure and solder joint interface layer under different aging times was observed in detail. Results indicate that with the addition of Co element in the alloy solder system two heat release peaks appear during the solidification process; specifically when adding 0.05 wt% Co element content to the mixture it reduces supercooling degree by 15.17 °C to only 1.03 °C; Moreover wettability improvement can be achieved to some extent when adding either 0.02 wt% or 0.05 wt% Co content. The addition of trace Co can inhibit the excessive growth of IMC in the solder alloy matrix and refine the alloy structure. It can promote the growth of Cu₆Sn₅-based IMCs and inhibit the growth of Cu₃Sn layer in intermetallic compound layer (IMCs). In addition, the mechanical properties and thermal fatigue stability of the solder joints are steadily improved by Co element. After adding Co element, the shear strength of the alloy solder joint is increased by about 14.84 %. After aging at 150 °C for 25 days, the shear strength of SACBSN-xCo alloy solder joints is increased by about 20.4 %, which significantly improves the thermal fatigue stability of the solder joints after high temperature aging treatment. The results show that when Co content is 0.05 wt%, the alloy solder has better comprehensive properties.

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钴对 SACBSN 系列无铅焊料合金微观结构演变和热疲劳稳定性的影响

大多数有关高可靠性焊料合金的研究都集中在锡、银、铜、铋、锑和镍的六元素体系上。然而，有关该体系中 Co 元素影响的研究却很有限。本研究采用熔炼法制备了 Sn3.0Ag0.5CuBiSbNixCo（x = 0 wt%、0.02 wt%、0.05 wt%、0.08 wt%、0.1 wt%）合金（简称 SACBSN-xCo 合金）。通过极限剪切强度测试评估了 SACBSN-xCo 合金焊点的机械性能。使用 ICP、XRD、SEM 和 EDS 技术分别进行了合金成分分析、相组成检查、金属间化合物（IMC）调查和界面层形态分析。此外，还详细观察了不同老化时间下焊料结构和焊点界面层的演变过程。结果表明，在合金焊料体系中添加钴元素后，凝固过程中会出现两个放热峰；特别是在混合物中添加 0.05 wt% 的钴元素时，过冷度会从 15.17 °C降低到仅 1.03 °C；此外，添加 0.02 wt% 或 0.05 wt% 的钴元素时，润湿性会得到一定程度的改善。痕量 Co 的添加可抑制焊料合金基体中 IMC 的过度生长，并细化合金结构。它可以促进 Cu6Sn5 基 IMC 的生长，抑制金属间化合物层（IMC）中 Cu3Sn 层的生长。此外，Co 元素还能稳步提高焊点的机械性能和热疲劳稳定性。添加 Co 元素后，合金焊点的剪切强度提高了约 14.84%。在 150 °C 下老化 25 天后，SACBSN-xCo 合金焊点的剪切强度提高了约 20.4%，这显著改善了高温老化处理后焊点的热疲劳稳定性。结果表明，当 Co 含量为 0.05 wt% 时，合金焊料具有更好的综合性能。

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来源期刊

Microelectronics Reliability 工程技术-工程：电子与电气

CiteScore

3.30

自引率

12.50%

发文量

342

审稿时长

68 days

期刊介绍： Microelectronics Reliability, is dedicated to disseminating the latest research results and related information on the reliability of microelectronic devices, circuits and systems, from materials, process and manufacturing, to design, testing and operation. The coverage of the journal includes the following topics: measurement, understanding and analysis; evaluation and prediction; modelling and simulation; methodologies and mitigation. Papers which combine reliability with other important areas of microelectronics engineering, such as design, fabrication, integration, testing, and field operation will also be welcome, and practical papers reporting case studies in the field and specific application domains are particularly encouraged. Most accepted papers will be published as Research Papers, describing significant advances and completed work. Papers reviewing important developing topics of general interest may be accepted for publication as Review Papers. Urgent communications of a more preliminary nature and short reports on completed practical work of current interest may be considered for publication as Research Notes. All contributions are subject to peer review by leading experts in the field.