Ultrasonic-assisted soldering of sapphire through metallic transition layers of Al and Zn using Sn-xZn-2Al solder alloys

Ultrasonic-assisted soldering has potential in the electrical industry especially for the joining of ceramics. The Al-activated Sn-based alloys are promising ultrasonic solders due to simple preparation, while the current approaches required long ultrasonic action. In order to increase the efficiency and reduce ultrasonic-induced damage, this study investigated the soldering of sapphire (monocrystalline α-Al₂O₃) performed under an ultrasonic action for 0.5 s by using Sn-xZn-2Al(x = 9, 25, 45) solder alloys. Microstructures of interfacial transition layers between the sapphire and solders were focused on. It has been found that at the interfaces no interfacial reaction phases formed and the interfacial bonding was realized via metallic transition layers. Three kinds of interfacial structures existed, that is, sapphire/Al atomic layer/β-Sn, sapphire/Al atomic layer/(Zn enrichment layer)/β-Sn and sapphire/Al atomic layer/Zn nanocrystalline clusters/β-Sn. The elements of Al and Zn in the solder alloys underwent a selective and asynchronous adsorption process during the ultrasonic action. An Al atomic layer formed on the sapphire surface by the stronger chemical adsorption and acted as a transition layer between sapphire and β-Sn. The Zn enrichment layer was distributed locally along the interface and as the Zn content increased in the solder alloys, more localized Zn nanocrystalline clusters formed. These Zn transition structures strengthened the interfacial bonding by transforming the Al atomic layer/β-Sn interface into the Al atomic layer/Zn transition structures/β-Sn interfaces. The joints possessed a shear strength of up to 28 MPa when soldering with Sn–45Zn–2Al at 350 °C.     

Automated X‐ray inspection method for fillet‐less mounted chip components

Chip components mounted on the printed circuit board are rapidly being miniaturized. Furthermore, the fillet‐less chip soldering technique, which does not use a solder fillet, is widely used in portable products such as mobile phones. However, there is no method to inspect the soldering of fillet‐less chip mounting. In this paper, we propose an automated X‐ray inspection technique for fillet‐less chip mounting. It extracts three inspection parameters from the X‐ray image. In the experiments, we evaluate the repeatability and inspecting ability of the technique and confirm that sufficient information for failure detection is obtained. An automated X‐ray inspection system using this technique is now in operation at some factories, so in conclusion our automated method would be useful in practice. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

快速凝固 Sn-Ag-Sb钎料提高钎焊接头致密性机理

通过试验方法研究了快速凝固Sn-Ag-Sb合金在紫铜板上的润湿性能、填缝性能和组织特点，以及与保温时间等工艺因素的关系。并探讨了该钎料提高钎焊接头致密性的原因。     

基于Boosting-MKELM的回流焊过程质量预测研究

通过建立基于钽电容仿真模型的代理模型，实现对其回流焊过程的质量预测。以锡膏尺寸中的最小末端连接宽度、最小侧面连接长度、最小填充高度和焊料填充厚度作为钽电容回流焊过程中的关键质量指标，运用Boosting-MKELM算法建立质量指标预测模型；并以E_RMS和R²作为模型性能评估指标，通过与传统代理模型算法对比，验证算法的有效性及性能。结果表明，相比PRS模型、SVM模型及RBF模型，Boosting-MKELM所预测的4个质量指标都拥有最小的E_RMS和R²,说明所建立的Boosting-MKELM预测模型具有更高的精度，可更好地表征输入变量与质量指标之间的映射关系。     

Liquid Metal based Stretchable Room Temperature Soldering Sticker Patch for Stretchable Electronics Integration (Adv. Funct. Mater. 36/2023)

Researchers are eagerly developing various stretchable conductors to fabricate devices for next-generation electronics. Most of the major problems in stretchable electronics happen at the connection between rigid and soft parts and the development of reliable soldering material is a major hurdle in stretchable electronics. Though there are attempts to devise new soldering processes for integrating chips and stretchable conductors, they still possess limitations such as mechanical stability, mass production, sophisticated processes, and restricted candidates for conductors and substrates. Here, this study presents a room-temperature universal stretchable sticker-like soldering process that can stretchably solder multiple spots at once and directly fabricates a stretchable device in an in situ manner while a target conductor is installed on one's body. The solder developed in this research possesses high conductivity with a unique freestanding feature enabling the process. It can be elongated when directly positioned between a rigid chip and a rigid conductor, demonstrating its extraordinary stretchability. It is expected that this simple but unique stretchable soldering technique utilizing the invented solder will allow the integration of functional stretchable conductors with highly advanced rigid chips for next-generation stretchable electronics.     

高强度ZA合金软钎料的研制

分析了高强度ZA合金的焊接性能，在大量试验的基础上，研制出了一种新型的适合高强度ZA合金钎焊的钎料CZ5＃。该钎料具有熔点低，对母材的润湿性好，钎焊接头组织中含有强度、硬度较高的呈弥散分布的固溶体，以主接头强度较等特点。