焊膏工艺性要求及性能检测方法

焊膏是SMT工艺中不可缺少的钎焊材料,广泛应用于再流焊中;它是由一定的合金粉末和助焊剂均匀混合而成的膏状体。主要对SMT中焊膏的组成及焊膏性能检测方法进行了简要分析。     

提高焊膏印刷质量的工艺改进

焊膏印刷作为SMT工艺的第一步，其质量好坏对SMT工艺有着重要影响。文章通过对焊膏成分、特性的分析，讨论了印刷中各种工艺参数的正确选择；对焊膏印刷中容易出现的质量问题进行了详细分析，指出了产生问题的原因，提出了改进措施。     

Early detection of ageing in solder joints through laser probe thermal analysis of the peltier effect

We have recently developed an optical contactless method for testing the quality of solder joints during accelerated thermal cycling ageing processes.¹ The method was based upon the measurement of the dynamic thermal behaviour of the joint to short bursts of Joule heating. It has proved to be efficient in revealing the formation of cracks at the lead-solder interface. We present a method to evaluate ageing at a much earlier stage in the cycling process. We have observed in earlier work,¹ that before cracks appear, structural changes occur in the solder at the lead-solder interface. The thermal response of the solder joint is recorded over time to a Peltier heat perturbation produced by flowing a current pulse through the interface where structural changes occur. The key point in this method is to discriminate the Peltier effect from the Joule thermal response because both effects generate heat. The variation of the early Peltier response in the thermal cycling ageing tests is seen as a quantitative signature of the structural changes in the lead-solder interface.     

延长自组织InAs／GaAs量子点发光波长的研究进展

在近几年的InAs／GaAs自组织量子点的研究中，如何荻得1．3～1．55μm。长波长量子点材料是一个很热门的课题。本文综述了各种延长自组织InAs／GaAs量子点发光波长的方法，并提出了实用化的最佳途径。     

Kinetics of reactive diffusion between Au and Sn during annealing at solid-state temperatures

The reactive diffusion between Au and Sn was experimentally studied at solid-state temperatures using Sn/Au/Sn diffusion couples prepared by a diffusion bonding technique. The diffusion couples were annealed at temperatures of T = 393 and 473 K for various times in an oil bath with silicone oil. After annealing, compound layers composed of AuSn₄, AuSn₂ and AuSn were recognized to form at the Au/Sn interface. The thickness of the AuSn₄ layer is about six and four times greater than those of the AuSn₂ and AuSn layers at T = 393 and 473 K, respectively. The ratio of the thicknesses of the compound layers is kept constant independently of the annealing time. The total thickness l of the compound layers is described as a function of the annealing time t by the equation l = k(t/t₀)ⁿ, where t₀ is unit time, 1 s. The exponent n is nearly equal to 1/2 at T = 393 K but takes a value between 1/4 and 1/2 at T = 473 K. Such an intermediate value of n at T = 473 K indicates that the grain boundary diffusion contributes to the reactive diffusion and the grain growth occurs at certain rates. As the annealing temperature decreases, the contribution of the grain boundary diffusion should become more remarkable, but the grain growth will slow down. Consequently, n becomes close to 1/2 at T = 393 K. According to the constancy of the ratio of the thicknesses, it is concluded that the same rate-controlling process works in the AuSn₄, AuSn₂ and AuSn layers at a constant annealing temperature.     

分级分段印制插头工艺的研发与应用

介绍了一种采用特殊的设计方法制作分级分段印制插头的工艺生产的印制插头完全没有引线残留的踪迹,对分级分段印制插头的品质做到了有效的控制,可靠性实达到品质要求,通过了实际生产应用的验证,建立了工艺规范和品质管制计划,为批量生产奠定了坚实基础。     

3D打印在新能源汽车电机壳体预防粘模上的应用

针对新能源汽车电机壳体压铸件产生粘模缺陷的问题,从模具结构设计、3D打印嵌件平衡模具温度,防止高温铝液破坏模具表面致密层等方面,在生产过程中对新能源电机壳体压铸件粘模缺陷进行改善,提出了应用3D打印嵌件的解决方案。     

基于GhostNet-YOLOv4算法的印刷电路板缺陷检测

针对印刷电路板表面面积小而且上面电子器件焊点众多,传统检测方法很难进行有效检测的问题,提出了一种基于GhostNet-YOLOv4的印刷电路板表面焊点检测算法。首先,修改了YOLOv4算法的主干网络以增强特征提取能力,其次加入注意力机制使网络更注重缺陷特征,用GhostNet代替CSPDarknet53作为主干网络。此算法相比于传统的印刷电路板检测算法提高了检测精度和检测速度,可以实现对印刷电路板表面常见的断路、漏焊、短路等缺陷的精确检测和迅速分类。通过对印刷电路板数据集的检测结果分析表明,该改进算法具有较好的实用性,在测试集上的平均精度为86.68%,FPS达到了25.43,可以满足印刷电路板实际检测需求。     

圆片级封装的凸点制作技术

圆片级封装是一种先进的电子封装技术,近年来,圆片级封装技术的发展速度很快,主要应用于系统级芯片、光电器件和MEMS等.凸点制作是圆片级封装工艺的关键工序,目前凸点制作工艺方法有多种,重点介绍常用的电镀法、植球法和蒸发沉积法凸点工艺,分别介绍这三种凸点制作技术的工艺流程、关键技术.     

Comparison of in-situ measurement techniques of solder joint reliability under thermo-mechanical stresses

Thermo Mechanical Cycle Lifetime (TMCL) test is a widely used test methodology for evaluating the reliability of solder joints in the microelectronics industry. The commonly used measurement techniques to monitor solder joint failures during the TMCL test are either event detector or data logger. In this study, TMCL test has been carried out on the same devices in parallel with both measurement techniques. The pros and cons of both techniques are compared. It is observed that the solder joint reliability results on the investigated samples by both techniques are comparable. The event detector can catch short intermittent events, while the data logger is able to capture the details of the solder joint degradation process. In applications for which performance is dependent on the transmission of signals with a frequency of several hundred megahertz or more, the event detector technique shall be used. In such cases the data logger technique may overestimate product lifetime. On the other hand, for some applications where the performance is less susceptible to intermittent solder joint interconnect interruption but more to the increase of the solder joint resistance, the data logger shall be used. In such cases the event detector technique may underestimate product lifetime. In conclusion depending on the end application of the device, the most suitable technique can be selected.