Akkara Francy John, Hamasha Sa'd, Alahmer Ali, Evans John, Belhadi Mohamed El Amine, Wei Xin
Department of Industrial and Systems Engineering, Auburn University, Auburn, AL 36849, USA.
Department of Mechanical Engineering, Faculty of Engineering, Tafila Technical University, Tafila 66110, Jordan.
Materials (Basel). 2022 Sep 29;15(19):6759. doi: 10.3390/ma15196759.
The surface finish (SF) becomes a part of the solder joint during assembly and improves the component's reliability. Furthermore, the SF influences the solder joint's reliability by affecting the thickness of the intermetallic compound (IMC) layer at the solder interface and copper pads. In this experiment, five different alloys are used and compared with the SAC305 alloy, two of which, Innolot and SAC-Bi, are bi-based solder alloys. This study includes three common SFs: electroless nickel immersion gold (ENIG), immersion silver (ImAg), and organic solderability preserve (OSP). The performance of three surface finishes is examined in terms of component characteristic life. All of the boards were isothermally aged for twelve months at 125 °C. The boards were then exposed to 5000 cycles of thermal cycling at temperatures ranging from -40-+125 °C. Most of the current research considers only one or two factors affecting the reliability of the electronic package. This study combines the effect of multiple factors, including solder paste content, SF, isothermal aging, and thermal cycling, to ensure that the test conditions represent real-world applications. In addition, the electronics packages are assembled using commercialized alloys. The current study focuses on a high-performance alloy already present in the electronic market. The failure data were analyzed statistically using the Weibull distribution and design of experiments (DOE) analysis of variance (ANOVA) techniques. The findings reveal that the micro and uniformly distributed precipitates in solder microstructures are critical for high-reliability solder joints. Re-crystallization of the thermally cycled solder joints promotes the local formation of numerous new grains in stress-concentrated zones. As the fracture spreads along these grain boundaries and eventually fails, these new grains participate in crack propagation. Aging significantly worsens this situation. Finally, although the ENIG surface finish with its Ni layer outperforms other SFs, this does not imply that ENIG is more reliable in all solder paste/sphere/finish combinations.
在组装过程中，表面处理（SF）成为焊点的一部分，并提高了组件的可靠性。此外，表面处理通过影响焊料界面和铜焊盘处金属间化合物（IMC）层的厚度来影响焊点的可靠性。在本实验中，使用了五种不同的合金，并与SAC305合金进行比较，其中两种，即Innolot和SAC-Bi，是双基焊料合金。本研究包括三种常见的表面处理：化学镀镍浸金（ENIG）、浸银（ImAg）和有机可焊性保护剂（OSP）。从组件特征寿命的角度研究了三种表面处理的性能。所有电路板在125°C下等温老化12个月。然后将电路板在-40至+125°C的温度范围内进行5000次热循环。目前的大多数研究只考虑影响电子封装可靠性的一两个因素。本研究综合了多个因素的影响，包括焊膏含量、表面处理、等温老化和热循环，以确保测试条件代表实际应用。此外，电子封装使用商业化合金进行组装。当前的研究集中在电子市场上已有的一种高性能合金上。使用威布尔分布和实验设计（DOE）方差分析（ANOVA）技术对失效数据进行统计分析。研究结果表明，焊料微观结构中的微观且均匀分布的析出物对于高可靠性焊点至关重要。热循环焊点的再结晶促进了应力集中区域中大量新晶粒的局部形成。当裂纹沿着这些晶界扩展并最终失效时，这些新晶粒参与裂纹扩展。老化会显著恶化这种情况。最后，尽管带有镍层的ENIG表面处理优于其他表面处理，但这并不意味着ENIG在所有焊膏/焊球/表面处理组合中都更可靠。
