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摘要三文封装作为当今较为先进的电子封装形式之一，具有重量轻、体积较小以及封装效率高等优点。但是随着封装集成密度的增加使得模型结构内容易产生较多的热量，于是对于封装失效问题的分析开始进行人们的研究中。通过大量的数据表明，热循环作用是影响封装失效的主要原因，对热循环条件下焊点的可靠性研究有着十分深远的影响。然而基于三文封装中焊点的尺寸结构较小，实现起来具有一定的难度。因此，采用有限元模拟的方法对其进行模拟研究是如今较为有效的研究方法。39791
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本文运用ANSYS软件建立了三文封装模型，并基于Generalized Garofalo（Secondary）稳态模型本构方程，对三文封装器件的整体结构进行加载温度循环载荷。通过热循环模拟实现了对三文封装结构模型的焊点力学性能分析，明确了三文封装中最易发生疲劳破坏的焊点部位及该焊点的最高危区域。并且通过研究，得到了在热循环载荷下，钎料焊点在不同时间的应力应变分布规律。
本文将在模型结构进行蠕变应变的模拟分析过程中从焊点直径大小、焊点形状以及焊点的材料这三个方面来对焊点进行研究。从各种情况下模拟研究的结果表明，无论改变任何条件，焊点的上表面始终是应力应变发生的集中区域，也是焊点出现裂缝并发生断裂的根源地。各种拉伸以及弯曲变形的发生都是由于各组成部分材料的线膨胀系数不相互匹配引起的。因此，焊点对于整个结构起到了至关重要的影响和作用。
当单从剪切应力和Von Mises应力这两种应力方面的最小原则考虑时，选用尺寸大小为0.5mm × 0.328mm的大焊点最为合适的。焊点形状对整体结构模型的影响作用并不是很大，因此在一定情况下，对结构进行蠕变应变的模拟分析时，可以适当忽略焊点的形状因素。在整体结构的模型当中，三文封装结构的可靠性在很大程度上也是会受到焊点的材料影响。在研究分析的三种材料中，Sn3.0Ag0.5Cu有着最好的性能，这和里面Cu以及Ag成分含量较少有一定联系。这些基于蠕变应变的分析结果与实际电子应用元器件的试验数据结果的变化趋势相一致。
毕业论文关键词：三文封装结构；有限元法；蠕变应变；可靠性
The finite element analysis of 3D package
Abstract
3D package is one of the advanced electronic packaging now, it has lots of characteristics such as light weight, small volume and high encapsulation efficiency. But with the increase of package density makes more easier to generate more heat per unit volume, people pay more attention to the failure problem of package gradually. Through a lot of practice proved that the thermal effect is affecting the packaging, the main reasons for the failure of the reliability of solder joints under thermal cycle study plays a very important role. However, due to small size of welds in the 3D package, it is very difficult to realize. Therefore, adopting the method of finite element simulation to analyze is the more effective study method.
In this paper, the 3D packaging model is established by ANSYS software, it analyzes on the overall structure of the 3D packaging device loading temperature cycle load , which is based on the Generalized Garofalo (Secondary) static model equation. By thermal cycle simulation implements the analysis of 3D model of solder joint mechanical properties, it determines the most likely to happen in 3D packaging area of solder joint and the solder joint fatigue damage of the most dangerous area. By the study, it obtained the distribution rule of solder solders’ stress and strain at different times when the structure under thermal cycle load.
In the simulation analysis of creep strain, the passage analyze the solder joints from three aspects, such as the solder joints’ diameter, shape and material.The simulation results show that under any conditions, the stress and creep strain concentrate area is the top-surface of solder joints. The root causes of land is also the solder joints’ top-surface. The morph of stretch and bending is caused by linear expansion coefficient of each components’ material. So, the solder joints play an important role in the whole structure.
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