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1、印刷电路板在回焊过程中变形的建模与仿真摘要在 SMT 中，回焊是非常重要的工站。在回焊过程中受到热冲击已成为印刷电路板(简称为 PCB)组件生产过程中产生缺陷的主要原因之一。PCB 组件组成材料不同，热膨胀系数等热性能参数相差较大，容易产生翘曲变形等缺陷，造成元器件和 PCB 之间的电气和物理连接失败，导致整个 PCB 组件失效。而由于传统的 ,经反复试验、反复调整来改进回焊工艺的方法既费时又耗费大量实验经费，不能适应当前电子产品更新速度快、竞争日益激烈的需求，在这一背景下，焊接工艺的建模与仿真、预测与控制研究引起了广泛的关注。模拟仿真可以识别在回焊过程中的温度变化以及确定其对生产质量的影响;
2、对回焊温度曲线的设定使设计者根据 PCB 热分布重新排布组件从而使产品设计达到最优化。本文利用有限元法对 PCB 组件在回焊过程中的受热进行分析，建立瞬态温度场和应力场模型。用 ANSYS 软件对 PCB 组件在回焊过程中由于受热产生的热机械反应进行了模拟和建模，得出了温度场以及应力场的分布。由于 PCB 组件组成材料的热物理性能不同，以及经过不同的温区加热，模拟了不同时刻整个 PCB 组件的温度场分布。建立了一个贴装了 3 个 PLCC 的 4 层 PCB 板物理简化模型，模拟了在三种约束条件下，该组件在回焊过程中受热冲击时，产生的热应力及热变形。选取 PCB 上 3 个点，得到了在三种约束
3、下面位移和离面位移的位移量，即在底面对角两点约束下面位移和离面位移的位移量最大;底面 4 顶点约束下面位移和离面位移的位移量其次;底面两对边约束下面位移和离面位移的位移量最小。通过仿真可对回焊温度曲线进行优化，使得 PCB组件得到比较均匀的温度场分布，并调整对 PCB 的约束，使得变形最小化。关键词:回焊;热应力; 建模;温度场;仿真;,1Modelling and simulating for PCB Deformed in refolw solderingAbstract of thesisReflow soldering is very important technics in SMT
4、. Thermal impact to PCBA during reflow soldering is considered one of the main drivers for manufacturing defects. The materials making up a PCBA is various, and the thermal property of the materials is also different ,this may cause some defects for example wargpage. Excessive warpage in the PCB may
5、 result in gaps forming between the module leads and the molten solder on the solder pads, then the failure of electronically and physical connection lead to PCBAs defect. The traditional approach of experimentally analysing production defects would be costly and virtually impossible, and cant reach
6、 the demand of the producer for the fast renovation and the acute competition. An alternative to this approach is to derive computational and numerical models that encapsulate representations of the key process physics, so that effect analysis of the pertinent process variables may be examined. The
7、application of the modelling and simulation to a sample PCBA has been carried out to explore how undue variations in the reflow temperature can be minimized by a number of different strategies. It has been shown that simple movements of components can have quite beneficial effects on the overall pro
8、cess thermal history of the PCB.The paper use finite element analysis method analysis the thermal impact of PCBA during the reflow soldering ,and building the temperature and stress distribution model. The paper model and simulate the thermal warpage of PCBA during reflow soldering , get the tempera
9、ture and stress distribution of PCBA. This paper simulate the temperature distribution of PCBA under the condition of the material making up PCBA is different ,and PCBA will go through different oven section, building a simple physical model of a 4-layer PCB with 3 PLCCs to simulate the thermal stre
10、ss and warpage of PCBA under three constrained conditions, when the PCBA go through the oven sections. Compared the surface displacement and the Zaxis displacement of three points on the PCB under the three constrained condition to get the result of following. The thermal warpage happened under the
11、constrained conditions of the two points on the cross were constrained is large than that happened under the constrained conditions of the four points were constrained . the constrained conditions of the two sides were Simulation warpage is constrained. Optimize and the temperature minimized by adju
12、sting,the temperature figure is attainable through the distribution of PCBA is more uniform, also the constrained condition. KEYWORD: refolw soldering; thermal stress; modeling temperature field; Simulation;2目录摘要 . 1Abstract . 1目 录 . 2第一章 绪论 .31. 课题背景意义 . 32. 国内外研究概况 . 33. 研究思路及方法 . 4第二章 PCB 组件概述 . 52.1 PCB 简介 . 52.1.1 PCB 的分类 . 52.1.2 PCB 的材料组成 .
