本文選題：熱設(shè)計 + PCB布局�。� 參考：《南京大學(xué)》2015年碩士論文

【摘要】：電子設(shè)備在進行一段時間工作之后會產(chǎn)生功耗,溫度也將保持在一定的范圍值內(nèi)。如果這些熱量不能夠及時有效的排出,則會使得電子電路板的溫度持續(xù)保持很高的數(shù)值,有些元件對溫度十分敏感,當(dāng)溫度超過元件的額定值,元器件將失效,這被稱作熱損。熱損壞已經(jīng)成為電子產(chǎn)品的重要因素之一,并且隨溫度的增加,電子產(chǎn)品的失效率表現(xiàn)出指數(shù)增長[1]。因此對PCB進行熱設(shè)計研究具有重要意義。在電子電路熱設(shè)計方面,很多研究大部分以控制工藝為主,本文主要以PCB板級進行布局研究,即對于元件在PCB板上的排列位置,并不涉及具體元器件的工藝參數(shù)、PCB參數(shù)等。此外,提出等功率密度思想進行合理的布局,同時對等間距和常用的模擬退火算法進行布局相比較,結(jié)果表明等功率密度得到的溫度最大值最低。并最后對等功率密度的優(yōu)化結(jié)果進行了分析。本論文以下述內(nèi)容方式進行研究熱設(shè)計。緒論重點部分進行了國內(nèi)外在熱設(shè)計研究現(xiàn)狀方面分析,指出PCB溫升主要原因是功耗密度增大,影響功率密度增大的原因大致分為：芯片尺寸變小、PCB集成度高、封裝參數(shù)等。所以對PCB進行熱設(shè)計的主要原則是降低功耗密度。在進行電路板熱設(shè)計方面,涉及PCB板材料參數(shù)、芯片封裝參數(shù)、工藝條件等,總結(jié)主要從板級、封裝級和系統(tǒng)級三個方面進行設(shè)計。在熱設(shè)計中應(yīng)用的理論是熱力學(xué)和流體力學(xué),PCB上元件因其自身存在電阻而產(chǎn)生熱耗,能量通過傳導(dǎo)、對流、輻射等形式進行流動。元件熱量傳導(dǎo)給PCB板、對流到相鄰元件和輻射到附近元件。理論得出的方程往往是高階的,方程求解很難。本論文運用有限差分法將連續(xù)方程進行離散化處理求解方程。PCB設(shè)計中熱問題主要因素是芯片封裝參數(shù)、PCB板參數(shù),論文系統(tǒng)闡述了芯片封裝技術(shù)、封裝熱參數(shù)、PCB板、PCB熱參數(shù)等關(guān)鍵因素,并給出在設(shè)計中散熱器選擇和元件設(shè)計應(yīng)該遵循的原則。最后部分以面積為5cm×5cm的PCB板、元件的面積為1cm×1cm為對象,研究布局對元件溫度的影響。首先PCB板上的元件等間距分布,以第二章的熱設(shè)計理論基礎(chǔ)進行建立數(shù)學(xué)模型,通過有限差分法首先分析每個電子元件在等間距分布狀態(tài)下的溫度。在此基礎(chǔ)上應(yīng)用等功率密度分布進行布局和常用的模擬退火算法進行布局優(yōu)化,等功率密度度即每個元件功率除以元件所占的面積相等。經(jīng)過求解以上兩種布局,結(jié)果元件最高溫度都明顯得到了降低。其中等功耗密度布局使得最高溫度降低的更大,這在理論上是優(yōu)于模擬退火算法布局。兩種優(yōu)化區(qū)別在于,等功率密度改變了元件之間的距離,而后者僅僅是變換了位置,進而前者優(yōu)化的結(jié)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.
【學(xué)位授予單位】：南京大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TN41

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