摘要
目前微电子球栅阵列尺寸封装(BGA／CSP)正成为高端IC封装的主流技术。而焊点可靠性问题是发展BGA／CSP技术需解决的关键问题之一。实践证明热作用是芯片封装组件失效破坏的主导因素，因此热循环条件下的焊点可靠性研究有着非常重要的意义。为此，本文基于大型商用有限元软件ANSYS，对BGA／CSP形式的封装进行模拟，并在此基础上对多种情况进行对比分析，以此来评价各种因素对其可靠性的影响，从而来提高该封装的可靠性。本文又在焊点本构模型的构建方面作了一个尝试，以此为能对焊球找到一种更好的描述奠定基础。
本文首先对芯片封装及其可靠性分析方法及现状进行了概述，并对相关理论方法作了介绍。随后，通过参数化编程建立典型结构的BGA／CSP形式封装的三维模型，对此进行了应力、应变分析，并作了寿命预测。接着，又在上述分析的基础上，比较了同种封装的不同模型(如条形模型，1／4模型，1／8模型)、相同焊球材料的不同本构模型、不同寿命预测模型、不同焊球尺寸及网格密度等方面对寿命预测的影响。最后本文综合了两种典型的焊球本构方程构建了新的本构模型，再通过不同算法(如最小二乘法、遗传算法、试凑法)对焊球材料进行了曲线拟合，并对此作了比较分析。
本文针对相关问题，通过FORTRAN语言和ANSYS软件自带的程序设计语言(APDL)作了二次开发，编写了相关程序，从而能够更方便、更高效地利用ANSYS有限元软件来实现芯片封装的模拟分析。
At present, BGA/CSP is becoming the mainstream of the advanced IC package technology. Its development is based upon the solution of the reliability of solder ball, which is one of the key problems. It is proved that thermal fatigue is the main cause of the invalidity of the package. Therefore, it is significant to research the reliability of solder ball under the thermal cycle. In this paper, BGA/CSP is simulated and analyzed as implemented in the ANSYS finite element simulation software tool to evaluate the affect on its reliability; the constitutive model of the solder ball is constructed tentatively to find a better description for the solder ball.
First, the paper discusses briefly the IC package technology, the reliability analysis methodologies and the current situation of the IC package. Second, it eonstructs a typical BGA/CSP 3D model by programming the APDL code, then analyzes its life prediction. Third, it analyzes different influences upon the life predication by comparing different models of the same package, different constitutive models of the same solder ball's materials, different life prediction models, different solder ball dimensions, different mesh density etc. Finally, it compares some popular constitutive models of the solder ball materials, and constructs an integrated constitutive model by different curve fits.
The paper makes a "second exploitation" of ANSYS for solving certain problems through FORTRAN and APDL programming in order to apply the ANSYS finite element simulation software tool more conveniently and effectively to the simulation analysis of the IC package.
引文
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