## ANSYS的QFN电子元器件结构优化设计

QFN Electronic Component Structural Optimization
Abstract
Establishing 1/4 model for the study of QFN package, Anand model was constructed using solder Sn3.0Ag0.5Cu constitutive equations, finite element analysis and simulation by ANSYS software, determined under thermal cycling conditions location key pad and its analysis of stress and strain, and compared different forms when QFN solder joint reliability. The results showed that: under thermal cycling conditions, the maximum stress of QFN solder electronic components located at the corner of the upper surface of the solder joint position, the position of joints most likely to fail. Pin design is superior reliability without retracting have retracted pin design; when using non-design pin is retracted, due to increase solder thickness and central heat pad welding area are cumulative plastic work influence, can improve reliability of solder joints; change of fillet weld height and length had no significant effect on the accumulation of plastic work, that no significant effect on the reliability of solder joints. 源￥自%六:维;论-文'网=www.lwfree.cn
Keywords: QFN package; finite element analysis; plastic work; reliability

1.1 电子封装发展与演变趋势    1
1.2 QFN电子封装    2
1.3 研究意义    2
1.4 国内外研究发展现状    3
1.5 本章主要内容    4

2.1 有限元法的基本思想    6
2.2 有限元建模方法及步骤    6
2.3 ANSYS软件介绍    7
2.4 ANSYS有限元分析主要流程    8
2.5 本章小结    8

3.1 QFN封装模型    9
3.2 模型简化    9
3.3 单元选取与材料参数    10
3.4 Anand粘塑性本构模型方程    10
3.5 模型建立与边界条件    11
3.6 热循环温度载荷施加    12
3.7 本章小结    12

4.1 QFN关键焊点的确定    13
4.2 关键焊点应力应变分析    14
4.3 关键焊点失效原因    15
4.4 本章小结    16

5.1 引脚形态优化设计    17
5.2钎料厚度的影响    19
5.3 散热焊盘焊接面积的影响    20
5.4 焊脚高度的影响    22
5.5 焊点长度的影响    23
5.6 本章小结    25

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