印制电路板及元器件引脚振动分析

航天产品发射升空过程中,会发生不可避免的振动,振动分析与振动控制是电子设备结构设计中必不可少的一部分,而印制电路板及其元器件是电子设备的关键部件。根据某航天产品内部的印制电路板结构及元器件分布,利用MSC.Patran建造有限元模型,为精确计算电路板及元器件响应,使用梁单元对FPGA元器件的引脚进行建模,再模拟引脚与焊盘的连接。使用MSC.Patran/Nastran有限元软件,分析了印制电路板的基频以及正弦振动与随机振动时的加速度和应力响应。结果表明电路板和FPGA元器件引脚可以承受火箭发射阶段的力学载荷。     

电子机柜中印制电路板的模态分析及抗振设计

针对在机箱中因振动而损坏的印制电路板进行模态分析,通过ANSYS有限元软件建立印制板的有限元模型,计算出其模态参数。根据模态分析结果,从提高印制板的动刚度和固有频率出发,对该印制板进行抗振设计。     

基于RADIOSS模态分析的电路板抗振设计的研究

通过对电路板结构的简化,建立了有限元仿真分析模型。借助于RADIOSS/Hyper Mesh模态分析平台,分析了电路板的厚度、固定方式、元器件布局和加强筋对电路板固有频率的影响,并得出相应的结论,从而为电路板抗振可靠性设计提供理论依据。     

面向元器件重用的印制电路板拆解试验

研究面向元器件重用的废旧印制电路板拆解工艺和拆解设备,需要分析评价不同拆解参数对印制电路板元器件拆解效率和已拆解元器件的重用性的影响。以废旧计算机主板为例,进行三种拆解施力方法和四种不同加热参数下的印制电路板拆解试验,在自制的印制电路板拆解试验样机及试验设备上测试并分析了印制电路板上元器件的分离率和已拆解元器件的可重用合格率。试验表明,采用接触式冲击、非接触式冲击和振动三种拆解施力方式对于贴片元器件和直引脚插装元器件均有良好的拆解效果;为了提高废旧印制电路板元器件的分离率,应重点提高接插件的分离率;为了提高元器件的可重用合格率,应主要考虑提高100脚以上贴片元器件的可重用合格率;在试验条件下以元器件分离率为试验指标时,得到了拆解元器件加热参数最佳水平的分布范围。试验还表明,较小的冲击势能有利于保证元器件较高的可重用合格率。以上试验结果为确定面向元器件重用的印制电路板拆解工艺提供了依据,也为研制废旧印制电路板拆解设备奠定了试验基础。     

印制电路板与元器件的抗振动冲击分析

针对电路板中元器件易损现象,运用ANSYS有限元分析软件,主要从瞬间冲击和优化设计两方面方面进行了详细分析,得出了电路板在振动和冲击条件下的变形量,依据分析结果,对原电路板中元器件进行重新布局、优化,并进行了试验验证,试验验证表明,优化后的电路板抗振动冲击能力提高,设计可靠性大大提高。     

基于Marc的风力发电机主轴动力学特性研究

本文根据振动理论建立了某型风力发电机主轴的振动方程。针对轴承弹性支撑对主轴固有频率影响的问题,建立了两种有限元模型,运用Marc有限元软件进行模态分析,并对计算结果做了对比。通过对比得出,考虑轴承弹性支撑方案计算出来的各阶固有频率值均有降低,说明轴承的弹性支撑对主轴固有频率有着较大的影响。这为以后进行进一步动力学研究提供了依据。     

椭圆齿轮有限元模态分析

应用弹性力学有限元理论,采用有限元分析软件COSMOSWorks对椭圆齿轮进行模态分析,得到了椭圆齿轮的5个低阶固有振动频率和模态振型,并对椭圆齿轮偏心率对固有振动频率和模态振型的影响进行了对比分析.结果表明,偏心率的大小对椭圆齿轮固有频率的大小有较大影响.     

低翅片管振动特性的有限元分析及实验研究

应用有限元分析软件ANSYS对低翅片管进行振动特性分析,考虑翅片形状、翅根处过渡圆角、管子长径比三种主要影响因素,建立低翅片管有限元计算模型.模拟低翅片管在换热器中的工作状态,得到低翅片管在四种约束模态下固有频率的有限元计算值.采用共振法对低翅片管在上述四种约束模态下的固有频率进行实验测试.对有限元计算值与实测值进行比较,四种约束模态下一阶固有频率有限元计算值的误差均小于15%,符合工程许可范围.表明该有限元模型可用于工程设计时对低翅片管振动特性进行数值分析,也可为其他形状翅片管的振动特性分析提供参考.     

悬臂梁裂纹参数的识别方法

以梁振动理论作为基础 ,将含裂纹梁的振动问题转化为由弹性铰联接两个弹性梁系统的振动问题 ,得到理论计算含裂纹梁振动频率的特征方程。由此特征方程计算得到裂纹深度参数和位置参数变化时悬臂梁振动固有频率的变化规律。利用计算裂纹悬臂梁振动固有频率的特征方程 ,提出一种辩识裂纹深度和位置参数的数值计算方法。并通过对模拟悬臂梁裂纹的分析说明文中方法的有效性。     

高温度环境下大功率PCB板的设计

多层PCB在电子插件和设备中使用广泛。随着电子产品的轻薄小型化、高性能化,导致电路板级散热问题愈发严重,在高温度环境下,按以往粗放型设计方式无法满足设计要求。主要探讨了大功率印制板的设计方法,提出了一种新型的多层印制电路板(PCB)热设计方法。根据印制板上器件的功耗进行理论计算和仿真分析,有效降低印制电路板级温度,具有较好的实用性,使得元器件降额设计达到要求。     

电子设备的抗振动设计

通过对电路板、元器件的固有频率和模态的分析,讨论了电子设备的振动问题。通过结构的优化设计,提高设备的抗振动强度以及环境适应性和可靠性。     

基于SURF特征的PCB元件匹配研究

通过研究基于印刷线路板(printed circuit board,PCB)中芯片元件的特征,提出了一种利用SURF(speeded up robust features)特征与颜色信息进行PCB元件特征匹配的方法.在对PCB元件特征进行分析的基础上,计算SURF特征描述,并利用融合颜色信息的最近邻法则寻找元件之间的匹配点对,最终给出匹配判决.实验结果表明本方法误判率低、匹配精度高、鲁棒性强,可以用于PCB元件的配准检测中.     

电子元件焊接质量的自动光学检测系统研究

为满足表面贴装电子元件的高密度化、小型化、零缺陷等要求,设计一种电子元件焊接质量的自动光学检测系统,可将缺件、多锡、少锡、假焊等焊接缺陷检查出来。该系统首先通过图像采集系统获取电路板图像,并提取元件的检测窗口,通过图像处理得到相应的图像特征,对其特征进行尺寸的测量和识别,然后与标准数据进行比较,判断元件表面焊接质量是否合格,以达到检测元件的目的。系统具有运行平稳、操作方便、智能化和模块化等特点,满足实际生产的需要。     

Production preparation and numerical control in PCB assembly

In this article, we analyze numerical control problems arising in a component insertion line for printed circuit board mounting. Such a line consists of a number of fully automated placement machines, connected by an automated, carrierless conveyor system. At each machine, the placement device consists of an arm equipped with a number of placement heads. Each head may serve certain component types; there is some freedom in the choice of equipment for each head. Components are supplied to each machine by tape feeders (each containing components of only one type) which are placed at certain feeder positions along the machine. Before actually operating such a line, a careful production preparation phase has to be completed, specifying for each printed circuit board type the exact way in which such a board should be mounted. Problems arising in this production preparation phase include: the choice of heads to be mounted on the placement arm of each machine, the choice of components to be placed at each machine (workload balancing), an assignment of feeders to feeder positions on each machine, clustering of components to be placed in one pick-and-place move, and the sequencing of component insertions at one machine. Formulations and solutions for all these problems are given and numerical results for some industrial examples are given. The numerical control system developed has been tested and implemented and has resulted in software, which is in use at several sites of Philips' Electronics.     

A genetic-based algorithm for the operational sequence of a high speed chip placement machine

Surface mount component placement machines are widely used in electronic manufacturing industry for automated placement of components on printed circuit boards. In this paper, we propose a new approach to the component placement problem using high speed turret style chip shooter machine and investigate the case of one single machine and one board type case with the objective of minimizing the assembly (cycle) time per board. The proposed method first groups the component types that can be processed at the same machine speed. Then the minimum spanning tree technique is employed to perform feeder duplications, reducing the distance effect between components of each type. Finally, a genetic-based algorithm with 2-opt local search using feeder arrangement list as solution representation is applied to determine the component placement sequence. Our experimental results indicate that the algorithm produces satisfactory solutions when a lower bound on cycle time per board is used as the evaluation criterion. It is also shown that the overuse of feeder duplication will produce a negative effect on the cycle time. Finally, the algorithm can help management to make a production plan that takes both component inventory cost and cycle time into consideration.     

The development of the physical fundamentals of contact soldering as a factor for reducing the number of defects in electronic devices

Automated control systems employ electronic components that are connected with a printed circuit board (PCB) by soldered joints. At elevated temperatures and with high vibration levels, soldering defects may occur that are characterized by the deterioration or complete loss of contact with the PCB, which can lead to the failure of the system. In this work, an approach is proposed to considerably improve the reliability of soldered joints.     

Machine setup and component placement in printed circuit board assembly

Populating printed circuit boards is one of the most costly and time-consuming steps in electronics assembly. At the beginning of each work order, three decisions are required: (1) a sequence must be specified for placing the individual components on the board; (2) tape reels must be assigned to positions on the magazine rack; and (3) a retrieval plan must be determined should the same component type be assigned to more than one magazine slot. Collectively, these problems can be modeled as a nonlinear integer program. In this paper, we develop a series of algorithms for solving each using an iterative two step approach.Initially, a placement sequence is generated with a weighted, nearest neighbor traveling salesman problem (TSP) heuristic; the two remaining problems are then formulated as a quadratic integer program and solved with a Lagrangian relaxation scheme. As a final step, the current magazine assignments are used to update the placement sequence, and the entire process is repeated.Our ability to deal, at least in part, with simultaneous machine operations represents the major contribution of this work. The methodology was simulated for a set of boards obtained from Texas Instruments and theoretically compared with a heuristic currently in use.     

应用模型修正方法的印制电路板参数识别

基于模态试验数据和模型修正方法,研究了印制电路板物理参数识别方法.印制电路板的动态特性对电子设备可靠性有重要影响,即使铺层相同的印制电路板因电路分布不同,其弹性模量、泊松比差异也较大.因此,为了获得更加精确的有限元模型,需识别印制电路板的主要物理参数.以航天使用的某种印制电路板为例,分别采用基于灵敏度分析和基于响应面方法的模型修正方法对印制电路板的物理参数进行识别.两种方法识别的弹性模量、泊松比基本一致,计算和试验的振型相关系数接近1,且修正后有限元模型计算应变值与试验应变值在载荷较小时基本一致,表明识别结果比较准确.结果表明,基于模态试验数据和模型修正相结合的参数识别方法合理有效,可用于工程中印制电路板物理参数识别.     

A genetic algorithm to optimise the component placement process in PCB assembly

In printed circuit board (PCB) assembly, the efficiency of the component placement process is dependent on two interrelated issues: the sequence of component placement, that is, the component sequencing problem, and the assignment of component types to feeders of the placement machine, that is, the feeder arrangement problem. In cases where some components with the same type are assigned to more than one feeder, the component retrieval problem should also be considered. Due to their inseparable relationship, a hybrid genetic algorithm is adopted to solve these three problems simultaneously for a type of PCB placement machines called the sequential pick-and-place (PAP) machine in this paper. The objective is to minimise the total distance travelled by the placement head for assembling all components on a PCB. Besides, the algorithm is compared with the methods proposed by other researchers in order to examine its effectiveness and efficiency.     

车载电子设备的抗振设计

针对振动和冲击对车载设备的危害,分析了车载电子设备机箱、机柜、印制板等的抗振措施,及隔振系统的选型和合理布局。