Effect of ultrasonic vibration time on the Cu/Sn-Ag-Cu/Cu joint soldered by low-power-high-frequency ultrasonic-assisted reflow soldering

Techniques to improve solder joint reliability have been the recent research focus in the electronic packaging industry. In this study, Cu/SAC305/Cu solder joints were fabricated using a low-power high-frequency ultrasonic-assisted reflow soldering approach where non-ultrasonic-treated samples were served as control sample. The effect of ultrasonic vibration (USV) time (within 6 s) on the solder joint properties was characterized systematically. Results showed that the solder matrix microstructure was refined at 1.5 s of USV, but coarsen when the USV time reached 3 s and above. The solder matrix hardness increased when the solder matrix was refined, but decreased when the solder matrix coarsened. The interfacial intermetallic compound (IMC) layer thickness was found to decrease with increasing USV time, except for the USV-treated sample with 1.5 s. This is attributed to the insufficient USV time during the reflow stage and consequently accelerated the Cu dissolution at the joint interface during the post-ultrasonic reflow stage. All the USV-treated samples possessed higher shear strength than the control sample due to the USV-induced-degassing effect. The shear strength of the USV-treated sample with 6 s was the lowest among the USV-treated samples due to the formation of plate-like Ag₃Sn that may act as the crack initiation site.     

进口水溶性助焊剂的分析

用化学法对进口水溶性助焊剂进行分离，并用ＩＲ、ＧＣ／ＭＳ、ＮＭＲ对其进行了鉴定。     

Real-time traceability of sorghum origin by soldering iron-based rapid evaporative ionization mass spectrometry and chemometrics

Sorghum is an important grain with a high economic value for liquor production. Tracing the geographical origin of sorghum is vital to guarantee the liquor flavor. Soldering iron-based rapid evaporative ionization mass spectrometry (REIMS) combined with chemometrics was developed for the real-time discrimination of the sorghum's geographical origin. The working conditions of soldering iron-based ionization were optimized, and then the obtained MS profiling data were processed using chemometrics analysis methods, including principal component analysis–linear discriminant analysis and orthogonal projection to latent structures discriminant analysis (OPLS-DA). A recognition model was established, and discriminations of sorghum samples from 10 provinces in China were achieved with a correct rate higher than 90%. On the basis of OPLS-DA, the specific ions of m/z 279.2327, 281.2479, and 283.2639 had relatively strong discrimination power for the geographical origins of sorghum. The developed method was successfully applied in the discrimination of sorghum origins. The results indicated that the soldering iron-based REIMS technique combined with chemometrics is a useful tool for direct, fast, and real-time ionization of poor conductivity samples and acquisition of metabolic profiling data.     

Characterization of a laser-soldered avionic component using lead-free paste

Electrical cable-connector sets used in airplanes have been laser soldered using a lead-free paste. These connections are usually crimped using a hand tool, which necessarily leads to variable mechanical and electrical properties in the connection. Calorimetric studies have shown that paste melting occurs within tenths of a second at laser intensities of 400 or 500 W cm⁻². However, when such laser intensities strike the connector surface, some boiling occurs. In order to avoid paste losses, a stepped heating curve is applied, which allows good weldability. It was verified that a reaction layer of 2 μm length exists between the wires and the solidified solder paste, and also that there is some diffusion of copper from the wires to the paste. The soldered joints are 38% more electrically conductible and have 113% more tensile strength resistance than crimped joints.     

基于mini-bar的二极管激光器焊接实验研究

半导体激光器封装工艺过程对于激光器的输出特性、寿命等性能有重要影响,其中焊料的选择和焊接工艺是最关键的因素。采用半自动焊接系统将mini-bar芯片通过In焊料直接焊接在Cu热沉上,并通过硬件改进、软件优化、放缓成像过程等措施实现了高精度、高可靠性的焊接。通过对激光器的性能测试发现,其焊接功率稳定,焊接精度均值可达20 m,smile效应值可以控制在0.5 m。     

高功率二极管激光器封装的多层焊接技术

对高功率二极管封装工艺中的焊接技术进行了研究,掌握了高真空下利用蒸发沉积制备铟（In）焊料的方法,在不加助焊剂的情况下进行了多层焊接实验,并对封装的连续、准连续激光器进行了性能检测。结果表明,利用In和In-Sn合金的多层焊接技术进行激光器封装的方法是切实可行的。