耐高温插装元件通孔回流焊接工艺优化

介绍了印制板组件上耐高温插装元件的通孔回流焊接工艺技术。通过焊膏印刷模板开口设计优化、焊膏印刷模板厚度设计优化、焊膏印刷参数优化、预成型焊片的焊膏量补偿工艺以及回流焊接工艺参数优化,在厚度较厚的印制板组件上形成的插装元件焊点形态良好,焊料润湿所有焊接面,形成良好的锡焊轮廓线,孔内焊料结晶组织均匀,填充率达到100%,焊接质量良好。     

常用表面安装技术英文缩写译文

SM尸fSMCSMDSMASOSOICSOTSOJLCCCPLCCDIPQFPPQFPPCBPWAPWB表面安装技术表面安装元件(无源)表面安装器件(有源)表面安装组件小外型小外型集成电路小外型品体管带“J”引线小外型器件无引线陶瓷芯片载体塑料有引线芯片载休双列直插式封装象限扁平封装塑料象限扁平封装印制电路板印制引线组件印制引线(电路)板THMAMELFCOBTABUVVPSIRRMARARSAOASACFCATESIRDFM通孔插装组件金属电极无引线面(圆筒式)器件板上芯片自动带焊紫外线光汽相回流焊红外回流焊轻度活化松香简单活化松香超活化松香有机焊剂合成活化…     

大电流高热容量电源汇流板焊接工艺研究

电源汇流板是雷达产品供电系统的重要组件,需要较高的可靠性,其中焊接质量的保障尤为关键。某雷达产品中应用的电源汇流板采用内部加厚的覆铜板设计,同时又采用铝板作为安装底板,大电流、高热容量的设计给电源汇流板的焊接带来了很大的困难。文中主要针对大电流、高热容量的电源汇流板,分析焊孔透锡率的影响要素并提出工艺解决方案,经过工艺试验验证,将电连接器引脚的透锡率从20% 逐渐提高到85%,解决了焊接难题,对软钎焊焊接工艺具有一定的参考价值。     

射频器件超细引线键合工艺及性能研究

作为有源相控阵雷达的关键组成部分,T/R （Transmitter and receiver）组件的尺寸与性能决定着装备的重量和功能。引线键合是T/R组件中常用的互连技术之一,随着组件集成度的提高势必也要开发相应的高密度引线键合技术,这使得键合线的尺寸越来越小,而超细的引线会使焊点力学性能降低,造成可靠性下降等问题。采用超声热压楔形键合的方法实现了的超细金丝与金焊盘的连接,并对工艺进行优化。结果表明,随键合压力、键合时间和超声功率的增大,键合后引线形变量逐渐增大,而键合后金丝的拉力先增加后减小,且工艺参数对金带形变量的影响小于金丝;由于第二焊点作用力过大会导致引线形变量较大、最大拉力小于第一焊点,需增加题焊点数量;最后,通过正交试验方法获得了金线和金带的最佳键合工艺参数,实现了超细尺寸引线的键合,对T/R组件的小型化具有重要意义。     

微波密封器件无腐蚀感应钎焊工艺研究

通过对铝合金微波器件接头进行局部镀镍铜,选用双面有铜层的聚四氟覆铜板,实现了微波器件接头和聚四氟材料封盖的可钎焊性。采用优化的漏印网板添加焊膏,有效地控制了焊膏预置量,保证了钎焊缝的一致性。通过优化设计感应加热线圈,解决了矩形接头的感应加热温度场均匀一致性问题;通过对微波器件感应钎焊的工艺过程研究,获得了稳定的工艺参数。利用感应加热的快速、局部的优点,实现了微波密封器件局部快速钎焊。     

SMT生产工艺和质量控制

三、焊膏的漏印工艺随着SMD种类和规格的日益增多以及SMT的发展,采用再流焊组装工艺的电子厂商不断增加。而爆膏的定量涂布,是再流焊组装工艺的第一道工序,其涂有质量的好坏直接影响到SMA的组装质量及正常的生产,据文献介绍,SMT组装中64％的缺陷是由于焊膏漏印不当而造成的。因此,对涂布工艺业、须严格控制。目前,用于焊膏定量涂布的方法主要有三种,即丝网印刷法（ScreenPrinting）、漏板印刷法（StencilPrinting）和气压计涂法（Dispensins）。丝网印刷法,早已在混合电路和印制权行业上应用,由于丝网漏报价格低、交货决,…     

微波毫米波T/R组件内键合引线熔断机理研究

键合引线的耐电流水平是影响键合可靠性的重要因素之一,直接决定了雷达微波毫米波T/R组件的使用寿命。文中结合雷达微波组件的实际应用需求,开展键合引线耐电流水平研究,并深入分析了引线熔断机理,探讨引线熔断的微观过程,为电讯设计提供数据和理论参考。研究发现,键合引线熔断过程是焦耳热作用下的原子热迁移过程。熔断电流水平受外部气氛影响,大气气氛下的熔断电流水平略高于真空气氛下,可为航天产品设计提供参考。     

集成固相焊接方法在液冷板制造中的应用

为了提高6063铝合金翅片式大宽度流道液冷板的散热性能和焊接可靠性,满足雷达系统功放组件高集成、大型化带来的热耗快速增加的散热需求,文中提出采用2种固相焊接方法(扩散焊和搅拌摩擦焊)集成完成液冷板的制造方案,明确了集成焊接方法的工艺性结构设计要求,验证了工艺制造路径,仿真分析了集成焊接方法对结构刚性的影响。结果表明,集成焊接方法能够实现液冷板的高质量焊接,焊后结构刚性得到大幅提高。某功放组件采用集成固相焊接方法成功成型了液冷流道,其焊接质量满足设计要求,在1.5 MPa服役压力下的流道表面变形量仅为0.015 mm。     

MSR管子管板封口焊

通过对MSR管子管板封口焊的研究,介绍了焊接工艺设计与试验过程。自动钨极氩弧焊在管子管板封口焊缝的成功运用,改善了焊接质量,提高了工作效率。     

CO_2气体保护焊在工字轮上的应用

某钢厂拉丝机上的工字轮,材质为45钢。原工艺是采用挤压翻边进行总装,但因两侧板不能承受外力p的作用,工作不久即破坏。为解决这个问题,我们就改用CO_2焊来代替挤压翻边工艺,使焊接质量和接头强度均达到设计要求。现将CO_2焊焊接工艺和工艺装备介绍如下。一、焊前准备焊接设备:NBC-250CO_2焊半自动焊机一台;     

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.