电子电路热分析研究

发布时间：2018-05-13 07:08

本文选题：热设计 + PCB布局　；参考：《南京大学》2015年硕士论文

【摘要】：电子设备在进行一段时间工作之后会产生功耗,温度也将保持在一定的范围值内。如果这些热量不能够及时有效的排出,则会使得电子电路板的温度持续保持很高的数值,有些元件对温度十分敏感,当温度超过元件的额定值,元器件将失效,这被称作热损。热损坏已经成为电子产品的重要因素之一,并且随温度的增加,电子产品的失效率表现出指数增长[1]。因此对PCB进行热设计研究具有重要意义。在电子电路热设计方面,很多研究大部分以控制工艺为主,本文主要以PCB板级进行布局研究,即对于元件在PCB板上的排列位置,并不涉及具体元器件的工艺参数、PCB参数等。此外,提出等功率密度思想进行合理的布局,同时对等间距和常用的模拟退火算法进行布局相比较,结果表明等功率密度得到的温度最大值最低。并最后对等功率密度的优化结果进行了分析。本论文以下述内容方式进行研究热设计。绪论重点部分进行了国内外在热设计研究现状方面分析,指出PCB温升主要原因是功耗密度增大,影响功率密度增大的原因大致分为：芯片尺寸变小、PCB集成度高、封装参数等。所以对PCB进行热设计的主要原则是降低功耗密度。在进行电路板热设计方面,涉及PCB板材料参数、芯片封装参数、工艺条件等,总结主要从板级、封装级和系统级三个方面进行设计。在热设计中应用的理论是热力学和流体力学,PCB上元件因其自身存在电阻而产生热耗,能量通过传导、对流、辐射等形式进行流动。元件热量传导给PCB板、对流到相邻元件和辐射到附近元件。理论得出的方程往往是高阶的,方程求解很难。本论文运用有限差分法将连续方程进行离散化处理求解方程。PCB设计中热问题主要因素是芯片封装参数、PCB板参数,论文系统阐述了芯片封装技术、封装热参数、PCB板、PCB热参数等关键因素,并给出在设计中散热器选择和元件设计应该遵循的原则。最后部分以面积为5cm×5cm的PCB板、元件的面积为1cm×1cm为对象,研究布局对元件温度的影响。首先PCB板上的元件等间距分布,以第二章的热设计理论基础进行建立数学模型,通过有限差分法首先分析每个电子元件在等间距分布状态下的温度。在此基础上应用等功率密度分布进行布局和常用的模拟退火算法进行布局优化,等功率密度度即每个元件功率除以元件所占的面积相等。经过求解以上两种布局,结果元件最高温度都明显得到了降低。其中等功耗密度布局使得最高温度降低的更大,这在理论上是优于模拟退火算法布局。两种优化区别在于,等功率密度改变了元件之间的距离,而后者仅仅是变换了位置,进而前者优化的结果更好些。
[Abstract]:After working for a period of time, the electronic device will produce power consumption, and the temperature will remain within a certain range. If these heat can not be discharged in time and effectively, the temperature of the electronic circuit board will remain high. Some components are sensitive to the temperature. When the temperature exceeds the rated value of the component, the components will fail, which is called heat loss. Thermal damage has become one of the important factors in electronic products, and with the increase of temperature, the failure rate of electronic products increases exponentially [1]. Therefore, it is of great significance to study the thermal design of PCB. In the thermal design of electronic circuits, most of the research is mainly on the control technology. This paper mainly studies the layout of the components at the PCB board level, that is, the arrangement position of the components on the PCB board is not related to the process parameters of the specific components, such as PCB parameters. In addition, the idea of equal power density is put forward for reasonable layout, and the equal spacing is compared with the common simulated annealing algorithm. The results show that the maximum temperature obtained by equal power density is the lowest. Finally, the optimization results of equal power density are analyzed. In this paper, thermal design is studied in the following ways. In the introduction part, the current research situation of thermal design is analyzed at home and abroad. It is pointed out that the main reason of PCB temperature rise is the increase of power density. The reasons that affect the increase of power density can be divided into three parts: the chip size is smaller, the integration degree of PCB is high, and the package parameters are also discussed. Therefore, the main principle of thermal design for PCB is to reduce the power density. In the aspect of circuit board thermal design, it involves material parameters of PCB board, chip packaging parameters, process conditions and so on. It summarizes the design from three aspects: board level, package level and system level. The theory applied in thermal design is that thermodynamics and hydrodynamics PCB components generate heat consumption due to their own resistance, and energy flows through conduction, convection, radiation and so on. Element heat conduction to the PCB plate, convection to adjacent elements and radiation to nearby elements. The equation obtained by theory is usually high order, so it is difficult to solve the equation. In this paper, the finite difference method is used to discretize the continuous equation to solve the equation. The main factor of the thermal problem in PCB design is the chip packaging parameters and PCB board parameters, and the chip packaging technology is systematically described in this paper. The key factors, such as the thermal parameters of PCB board and PCB board, are given, and the principles to be followed in the design of radiator selection and component design are given. In the last part, the effect of layout on the temperature of 5cm 脳 5cm is studied by taking the PCB board with the area of 5cm 脳 5cm and the area of the element as 1cm 脳 1cm. Based on the thermal design theory of chapter 2, the mathematical model is established. The temperature of each electronic component under the condition of equidistant distribution is analyzed by the finite difference method. On this basis, the distribution of equal power density and the common simulated annealing algorithm are used to optimize the layout. The equal power density is equal to the power divided by the area of each element. By solving the above two configurations, the maximum temperature of the element is obviously reduced. The equal power density layout makes the maximum temperature lower, which is better than simulated annealing algorithm in theory. The difference between the two kinds of optimization is that the equal power density changes the distance between the elements, while the latter only changes the position, and the result of the former is better.
【学位授予单位】：南京大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN41

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