FEM modeling of temperature distribution of a flip-chip no-flow underfill package during solder reflow process
FEM modeling of temperature distribution of a flip-chip no-flow underfill package during solder reflow process
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DOI：
10.1109/tepm.2004.830505
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发表时间：
2004
影响因子：
--
通讯作者：
Zhuqing Zhang;S. Sitaraman;C. Wong
中科院分区：
文献类型：
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作者：
Zhuqing Zhang;S. Sitaraman;C. Wong
有机基板上的倒装芯片依靠底部填充来重新分配热机械应力，从而提高焊点的可靠性。然而，传统的倒装芯片底部填充工艺涉及多个工艺步骤，已成为倒装芯片工艺的瓶颈。发明无流底填充是为了简化倒装芯片底填充工艺，降低封装成本。无流底填充工艺要求底填充具有较高的固化延迟，以避免在焊料回流之前凝胶化，从而确保焊料互连。因此，无流动倒装芯片封装在回流焊过程中的温度分布对于高组装成品率是非常重要的。采用有限元方法对倒装芯片无流底填充封装在回流焊过程中的温度分布进行了数值模拟。利用差示扫描量热法得到的自催化反应模型，建立了底填固化动力学模型。为了将底填土的固化动力学纳入有限元模型，采用迭代和循环程序，提出了两种方法。研究了封装层和底部填充层的温度分布。讨论了底部填充圆角的存在和切屑尺寸对底部填充层温差的影响。此外，还评估了底填固化动力学对模拟结果的影响。
Flip chip on organic substrate has relied on underfill to redistribute the thermomechanical stress and to enhance the solder joint reliability. However, the conventional flip-chip underfill process involves multiple process steps and has become the bottleneck of the flip-chip process. The no-flow underfill is invented to simplify the flip-chip underfill process and to reduce the packaging cost. The no-flow underfill process requires the underfill to possess high curing latency to avoid gelation before solder reflow so to ensure the solder interconnect. Therefore, the temperature distribution of a no-flow flip-chip package during the solder reflow process is important for high assembly yield. This paper uses the finite-element method (FEM) to model the temperature distribution of a flip-chip no-flow underfill package during the solder reflow process. The kinetics of underfill curing is established using an autocatalytic reaction model obtained by DSC studies. Two approaches are developed in order to incorporate the curing kinetics of the underfill into the FEM model using iteration and a loop program. The temperature distribution across the package and across the underfill layer is studied. The effect of the presence of the underfill fillet and the influence of the chip dimension on the temperature difference in the underfill layer is discussed. The influence of the underfill curing kinetics on the modeling results is also evaluated.