Damage Path Simulation of Solder Joints in QFP
Damage Path Simulation of Solder Joints in QFP
复制标题
QFP 焊点的损伤路径模拟
DOI：
10.1115/ipack2005-73297
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
Kuniaki Takahashi
中科院分区：
文献类型：
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作者：
M. Mukai;K. Hirohata;H. Takahashi;T. Kawakami;Kuniaki Takahashi
焊点疲劳寿命预测是可靠性电子封装研究的重要领域之一。电子封装发展的最新趋势表明，正在向更小的焊点和更大的封装尺寸转变，现场条件下的温度变化也变得更大。随着焊点可靠性设计的日益严格，对焊点裂纹扩展的估计也变得与对裂纹萌生的估计一样重要。本文研究了一种基于有限元分析的无几何裂纹模型的裂纹扩展估计方法，以确保其在电子封装设计中的实际应用。在建立锡铅焊料损伤模型的基础上，对四方扁平封装(QFP)焊点损伤路径模拟方法进行了验证。在海鸥翼型焊点的情况下，疲劳裂纹通常从焊料圆角的上表面开始，并在与外部引线的界面附近扩展。显然，损伤路径的扩展与实际热循环试验中观察到的裂纹扩展行为具有很好的一致性。同时还模拟了外引线尖端和焊料圆角上表面的损伤路径扩展，最终在外引线和印刷电路板之间的缝隙处将两条损伤路径结合起来。当疲劳裂纹从两个或多个区域萌生时，本方法的优势尤为明显。根据本研究的结果，基于本方法的焊点裂纹扩展的估计是令人满意的工程目的。版权所有©2005由ASME
Fatigue life prediction of solder joints is one of the most important areas of research in the development of reliable electronic packages. Recent trends in electronic package development indicate a shift toward smaller solder joints and larger package sizes, and temperature changes under field conditions are also becoming greater. Since reliability design of solder joints has become severer, the estimation of the crack propagation is becoming important like the estimation of the crack initiation. In the present study, a new method of estimating the crack propagation, which is based on finite element analysis without geometrical crack model, was examined, in order to ensure suitability for practical use in electronic package design. On the basis of a damage model assumed for Sn-37Pb solder, the new method called ‘damage path simulation’ was verified for solder joints in QFP (Quad Flat Package). In the case of solder joints of the gull-wing type, fatigue cracks are commonly initiated from the upper surface of the solder fillet, and propagated in the vicinity of the interface with the outer lead. It was clear that the extension of the damage path showed good agreement with the behavior of crack propagation observed in the actual thermal cycle tests. Damage path extension from a pointed end of outer lead is also simulated simultaneously with that from the upper surface of the solder fillet, and both damage paths were finally combined at a gap between outer lead and printed circuit board. The advantage of the present method is especially evident when the fatigue cracks were initiated from two or more regions. From the results of this study, it was concluded that the estimation of the crack propagation in solder joints based on the present method is satisfactory for engineering purposes.Copyright © 2005 by ASME