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倒装芯片封装中的下填充工艺可以有效地提高封装连接的可靠性,因而得到了广泛应用。含有硅填料的环氧树脂是常用的下填充胶料,在下填充流动过程中表现出明显的非牛顿流体特性。利用Fluent软件对具有非牛顿流体特性胶料的下填充过程进行了三维数值模拟。采用流体体积比函数(VOF)对流动前沿界面进行追踪,再用连续表面张力(CSF)模型来计算下填充流动的毛细驱动力,并用幂函数本构方程来体现下填充胶料的非牛顿流体特性。通过数值模拟,获得了下填充流动前沿位置随时间变化的数据,这些数据与实验结果有较好的吻合度。该数值方法可较好地预测具有非牛顿流体性质胶料的下填充过程。
Underfill technology in flip-chip packaging can effectively improve the reliability of the package connection, which has been widely used. Epoxy resins containing silicon fillers are commonly used underfill compounds that exhibit significant non-Newtonian fluid properties during underfill flow. The Fluent software was used to simulate the process of underfilling with non-Newtonian fluid. The fluid frontier interface was tracked by the fluid volume ratio function (VOF), and then the capillary driving force of the underfilled flow was calculated by the continuous surface tension (CSF) model. The power function constitutive equation was used to represent the non-Newtonian fluid characteristic. Through the numerical simulation, the data of the position of the front of filling flow with time are obtained. These data are in good agreement with the experimental results. This numerical method can better predict the underfill process with non-Newtonian fluid.