电子产品中元器件虚焊问题分析

电子产品元器件的焊接质量直接影响产品整机的运行性能。针对某些电子元器件虚焊的质量问题进行分析,总结焊点虚焊状态的可能原因,并提出相应的解决措施,从而提升电子产品的过程质量控制。     

无铅手工焊接及常见缺陷

软钎焊接是实现电子产品元器件装配与电气连接的主要生产工艺,软钎焊点的质量是决定电子产品质量和性能的重要因素。无铅焊料种类丰富,对应多种焊接温度,无铅焊接可以提供更大的焊接温度梯度,是解决高度集成的电气装焊问题的有效手段。为了在手工焊接过程中获得高质量的无铅焊点,研究了手工焊接的热能量传导方式,研究了手工焊接的基本步骤,研究了常见无铅焊料的组成及选用情况,得出了无铅焊接温度高、工艺窗口小等技术难点。分析了常见焊接缺陷特征及成因,在工艺参数、工具选用等方面提出了焊接质量提升的若干措施。对提高无铅手工焊接成品率,分析焊接质量原因,减少并消除使用无铅焊料进行手工焊接时出现的质量问题,具有指导作用和借鉴意义。     

80Au-20Sn钎料焊点可靠性研究现状与展望

共晶80Au-20Sn钎料在大功率电子及光电子器件封装中作为密封和芯片焊接材料特别具有吸引力,在这些应用中焊点的可靠性对于满足设备长期稳定运行至关重要。简要回顾了钎料焊点可靠性提出的背景,介绍了焊点可靠性的评价方法及当前不同工艺对80Au-20Sn钎料焊点的影响;指出今后其可靠性研究重点主要集中在复杂服役条件下焊接工艺优化、焊点可靠性测试方法、焊点寿命预测模型以及焊点本构模型等方面。     

微波组件模块组装焊点及其可靠性

介绍微波组件的应用及其组装焊接的重要性,提出组装焊接中焊点的特点,并对焊点失效进行详细机理分析,阐述机械应力和热应力对焊点失效的影响,在焊接工艺和焊点设计方面找到抗失效断裂的有效措施,从而保证焊点的质量,提高微波组件的可靠性。     

车门包边引出焊的设计研究

针对某车型汽车车门包边连接处焊接拼台,设计出了一种引出焊接机构,依据车门补焊点分布特征,拟定出此机构的设计流程与控制策略,同时借助AutoCAD平面分析设计与UG三维建模仿真装配,设计出此机构.该机构通过采用三维空间分布焊点转平面焊点、单次焊接单焊点、单次焊接双焊点等策略,实现了有限空间内多焊点的焊接自动化与通用型结构设计.     

基于PLC的钢筋笼焊点动态定位控制系统

为了提高钢筋笼焊点焊接过程中焊枪稳定性，进而提升焊点焊接质量，设计了一种基于PLC的钢筋笼焊点动态定位控制系统。根据钢筋笼动态焊点运动规律，制定了焊点动态定位原理，设计了钢筋笼焊点动态定位系统气动原理图，描述了焊点动态定位系统工作过程,在此基础上对PLC控制系统的硬件和软件进行了设计。该系统有自动控制和手动控制两种模式，自动控制模式下可实现对动态焊点的捕捉、跟随焊接、回原点等循环运动控制,焊接动作稳定；可根据钢筋笼形状、桩径大小，对焊点动态定位系统作出适当调整,灵活性好、适应性强。     

焊点密度对焊接板件模态影响的仿真分析

板件焊接中,焊点的密度决定了焊接后结构的静态和动态性能,而有限元模态分析是了解系统动态特性的方法之一。基于有限元方法,详细阐述了焊接板件有限元模型的建立方法以及模态分析方法。模态分析结果表明焊点密度对焊接板件模态频率、振型有一定影响,对板件焊接实际应用有一定的指导意义。     

汽车车身多机器人焊接路径规划和Tecnomatix虚拟仿真

多机器人协同工作在汽车车身焊装生产线广泛应用,简单的将多机器人情形看成单台机器人的组合,无法有效的解决汽车车身焊接生产线中的路径优化问题.以焊点合理分配、焊接路径最短为目标,建立基于凸优化理论的多机器人焊点分配模型,提出一种结合粒子群思想和遗传操作的改进蚁群算法解决分配后机器人的路径优化问题.在数字化虚拟仿真软件Tecnomatix中,搭建针对发动机舱总成的多机器人焊接虚拟仿真模型,对焊点可达性、机器人运动碰撞以及生产节拍等指标进行分析评估,仿真结果表明:在保障机器人可达性前提下,多机器人不存在干涉问题,基于凸优化理论建立的焊点分配模型可以达到合理地分配焊点的目的,改进蚁群算法可以有效缩短焊接路径,提高焊接效率.     

薄板构件点焊工艺优化

生产中要获得较好的焊点质量 ,除有最佳的焊接电流、焊接压力、焊接时间等焊接工艺参数外还须了解其它与焊接有关的参数对焊接质量的影响规律 ,并进行合理的优化与搭配 ,才能得到良好的焊接质量。　　一、焊点工艺设计的优化焊点工艺设计在相当程度上决定采用的工装和设备、焊点质量和成本。1.工艺设计时要充分考虑焊接设备的能力和本地区供电电网的品质 ,选择功率裕量足够的焊机和控制精度合适的焊接控制器 ,确保焊点质量及其稳定性。2 .焊点设计时尽量考虑使用双面点焊 ,特别是使用推挽双点技术。实践证明 ,双面点焊比单面点焊焊接质量更…     

台达行列式功能在副车架焊接中的应用

目前的点焊专机设备在实现多点焊接过程中,焊点坐标及动作程序编程较为复杂繁琐,本焊接系统采用台达新型的HMC的行列式清单功能,该功能配合焊钳焊点的定位、气动夹具的动作可以很好的解决焊接过程中多焊点的顺序控制。本文详细介绍了行列式表格中的焊点坐标及气动夹具动作的预设方法等,使系统PLC程序可根据该坐标自动顺序完成各个焊点的连续焊接,实现焊接系统利用行列式清单与PLC配合实现对整个焊接系统的顺序焊接控制。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

ANGULAR DISTORTION ALLOWABLE VALUE AND ASSESS METHOD OF WELD ON COKE TOWER

A graph as the new engineering method for estimate the safety of bulging deformation of coke tower is proposed. Through stresses analysis of circumferential weld of coke tower and comparing the stresses produced by pressure with heat stress of steady state, residual stress, bending stress produced by both itself weight and wind loads, it showed that the stresses produced by pressure on the angle distortion are the main factor of equivalent stress of the combined stress. After comparing four kinds of stress controlling conditions, the relation to stress with depth of angular distortion, grade of curvature of angular distortion and half of region of angular distortion has been inferred. Graph of deformation allowable value of coke tower for different condition by angular distortion and half of region of angular distortion has been plotted. The five steps for its engineering use have been explained. The lighter the grade of curvature is, the larger of bulge allowance, may be, and the bigger of depth of angular distortion may pose too. For the coke tower with a popular structure of Dg 5 400 mm×28 mm, the result by graph is nearly more than the result of two formulas formed by other research, the error is less than 7.0%. But, the graph can be easily applied to different size of angular distortion.