摘要焊点连接电子元器件并使其实现预定功能的重要单元。它同时起着机械支撑 和电气连接的作用。电子产品在使用的过程当中，断电通电以及温度的变化都会 导致元器件与焊点焊端、PCB 基板体积的变化，因为它们的热胀系数不相匹配， 在温度变化过程中会产生交变的应变和应力，在循环应力的作用下焊点的局部应 力的最大处会首先形成微裂纹，微裂纹渐渐发展形成宏观裂纹并且形成断裂面， 这就是焊点的热疲劳失效。随着不断深入的无铅化进程，军用的电子学产品的无 铅化组装也已经刻不容缓。对于无铅焊点热疲劳失效的问题，焊接材料的变化， 对军用品研制的单位来说有着十分重要的意义。焊点的热疲劳可靠性的问题历来 是电子封装研究的紧要方向之一。当前研究的关键主要聚集在焊点热循环应力- 应变的模拟技术上。72668

本文运用 ANSYS 软件构建出片式电阻器件的三维实体模型，针对材料、焊接 尺寸等影响因素，对无铅焊点的热疲劳可靠性进行了研究。通过建立三维模型并 定义边界条件与相应载荷，分析材料焊接部位附近的力学性能。基于 ANSYS 的分 析结果确定片式电阻器件在焊接部位最终出现裂的位置和最易形变的区域，发现 焊球随热载荷的变化而变化的焊点应力应变的分布规律。

论文有图 25 幅，表 4 个，参考文献有 60 篇。

毕业论文关键词： 有限元分析 应力应变 焊点可靠性

Thermal fatigue finite element analysis of lead free solder joints of chip resistance device

Abstract

Solder joint is an important element to connect the electronic components and make it realize the intended function。 It also plays the role of mechanical support and electrical connection。 Electronic products in use process, broken Diantong  and changes in temperature will lead to changes in components and solder terminal and PCB substrate volume, because of their thermal expansion coefficients do not match the, will produce alternating strain and stress in the process of temperature change, under cyclic stress of the solder joint local stress maximum will first of all, the formation of micro cracks, micro cracks gradually development form the macro crack and the formation of the fracture surface, this is thermal fatigue of solder joint failure。 With the continuous deepening of the lead-free process, the military electronics products lead-free assembly has no time to delay。 For lead-free solder joint thermal fatigue failure of the problem, the change of welding materials, the development of military supplies, the unit has a very important significance。 The thermal fatigue reliability of solder joints has always been one of the important directions in the research of electronic packaging。 The key of the current study is the simulation of the thermal cycling stress and strain of the solder joints。

Using ANSYS finite element software constructs the 3D solid model of chip resistor device, was studied by changing the spot of the material, and the height of component and substrate spacing, the reliability of solder joints, through load was applied to the 3D entity model, and analysis of the mechanical properties of solder joints, eventually find a chip resistor components to produce the crack location of solder joint and the most likely to produce areas of stress and strain。 By studying the distribution of the stress and strain of the solder joint in different time, we can find the solder joint loading at different time。

Key Words: Finite element analysis Stress strain Solder joint reliability

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