【作者】 李志刚；

【导师】 树学峰；

【作者基本信息】 太原理工大学 ， 固体力学， 2009， 博士

【摘要】 高密度集成电子技术的迅速发展对电子封装可靠性的要求日趋提高。高聚物电子封装材料在回流焊过程中的“popcorn”失效严重影响了产品的合格率,是电子封装领域关注的热点之一。本文利用非线性材料有限变形的基本理论对“popcorn”失效进行了弹-塑性分析和数值计算。本文的主要工作及获得的结果如下:1.对方形扁平封装(QFP)、球栅阵列封装(BGA)等封装器件中常用的GR9810和KL-G900HC高聚物材料进行了热分析实验。测得两类典型材料的热膨胀系数与玻璃态转化温度。为采用有限变形孔穴不稳定理论对“popcorn”失效研究提供了必要的实验支持。2.利用孔穴不稳定增长问题的基本理论,对七类具有典型储能形式的高聚物材料的“popcorn”失效进行了弹性分析。推导了各材料中的孔穴增长与湿热应力之间的解析关系。对解析关系的数值分析发现是否发生“popcorn”失效与储能函数的形式紧密相关。对于发生失效的高聚物材料,讨论了“popcorn”失效的极限载荷与极限孔穴率与本构模型中的各储能项之间的关系。对于利用弹性稳定性理论分析不发生失效的高聚物材料,我们补充极限伸长的失效准则,分析了其“popcorn”失效的可能性。3.考虑了温度变化对高聚物材料体积的影响,将材料的不可压缩假定修正为可压缩假定,推导了各类典型储能材料与温度相关的广义σ?f解析关系。由实验测得的热膨胀系数分析了考虑可压缩假定下“popcorn”失效的极限载荷与极限孔穴率。4.针对“popcorn”失效问题,对具有各典型储能形式高聚物材料的孔穴增长行为进行了弹-塑性稳定性分析。推导了考虑弹-塑性特点时孔穴增长规律的控制方程组。分析了考虑高聚物材料的弹-塑性特性的“popcorn”失效问题并与弹性分析的结果进行了对比。本文二、三、四、五章的工作是对现有的“popcorn”失效理论研究工作的系统化。第六章的工作是“popcorn”失效问题理论研究工作的进一步深入。另外本文的工作对类橡胶材料孔穴不稳定增长与空穴突然生成问题的理论研究工作的统一具有促进意义,使有限变形的稳定性理论应用到了更广泛的工程实际中。更多还原

【Abstract】 The rapid development of high-density integrated electronic technology sets a higher request to reliability of electronic packing. During the solder-reflow process, popcorn failure of plastic electronic packages has a strong impact on proportion of qualified products, which is one of the hottest research points. In this paper, elasto-plastic analysis of popcorn failure was made and the numerical results were given by using nonlinear materials’finite deformation theory. The main results contain as follows:1. Thermal analysis of polymer materials(GR9810 and KL-G900HC) used in package devices such as QFP, BGA etc. was carried out. The coefficients of thermal expansion and glass transition temperature were obtained, which provide necessary lab support for applying finite deformation theory about unstable void growth to analyze popcorn failure.2. Popcorn failure about seven kinds of typical polymer materials which have different strain energy functions under elastic stage was analyzed according to finite deformation theory about unstable void growth. Analytical relationships were gained between void growth and the sum of the vapor pressure and thermal stress. Numerical analyses show that popcorn failure is related to stored energy function closely. The relations between critical values and energy storage forms were discussed when popcorn failure occurred. If popcorn failure didn’t happen, we added failure criterions of ultimate elongation to discuss the probability of popcorn failure.3. The assumption of materials’ incompressibility was revised to compressibility when the effect of temperature change on the volume of polymer materials was taken under consideration, and the generalized temperature-dependent relationship forσ?f was given. Critical traction and void growth for popcorn failure were discussed by measurement of thermal expansion coefficient.4. In view of the problem of popcorn failure, the void growth behavior of polymer materials which have typical strain energy functions respectively was analyzed according to by using elasto-plastic stability theory. The governing equations of void growth considering elasto-plastic property were given. The elasto-plastic analysis and elastic analysis of popcorn failure about polymer materials was carried out.The chapter 2 to chapter 5 of this paper make the present theoretical research on popcorn failure systematic. The chapter 6 makes theoretical research on popcorn failure further. In addition, this paper can promote harmonization of theories research on void formation and growth, and bring stability theory of finite deformation into boarder use in engineering.更多还原