In this research, finite-element analysis and failure analysis were performed to analyze delamination failure in quad flat no-lead (QFN) packages. Although a QFN is a traditional package and represents mature technology, the reliability standards of QFNs in automotive applications have become strict. The quality requirements of QFNs are increasing and require that no delamination or voids occur inside the package during the reflow process and precondition tests. Therefore, interfacial delamination is still a critical reliability issue for QFNs. Delamination failure weakens the internal structural strength of a QFN and affects the product reliability. In the interface delamination, initially generated small voids gradually expand due to hygromechanical stress during the moisture sensitivity level test. In addition, moisture penetration into the package can result in not only electrical failure but also chemical reactions that lead to corrosion. In this study, delamination occurs on the interface between the Cu pad and molding compound during the precondition tests. The available evidence indicates that the bonding strength between Ag plating on the Cu pad and molding compound is weak. Most delamination failure sites are located in the area of Ag plating according to scanning acoustic tomography (SAT) observations. To accurately predict the delamination failure in QFNs, the shear force on the molding compound/Ag plating and molding compound/Cu is combined with finite element modeling. Parametric analysis is conducted to determine the optimal design of the geometric structure in the QFN to combat delamination failure. This investigation can help improve the product reliability by preventing delamination failure in the QFN package through the analysis of the physics of failure (PoF).

中文翻译：

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结合实验和仿真方法预测四方扁平无铅封装中的脱层失败

在这项研究中，进行了有限元分析和失效分析，以分析四方扁平无引线（QFN）封装中的分层失效。尽管QFN是传统封装并代表着成熟的技术，但QFN在汽车应用中的可靠性标准已经变得严格。QFN的质量要求不断提高，并且要求在回流焊工艺和前提条件测试期间，包装内不会出现分层或空洞。因此，界面分层仍然是QFN的关键可靠性问题。分层失败会削弱QFN的内部结构强度，并影响产品的可靠性。在界面分层中，最初产生的小空隙在湿度敏感度测试过程中由于湿度机械应力而逐渐膨胀。此外，水分渗入包装中不仅会导致电气故障，还会导致化学反应，从而导致腐蚀。在这项研究中，在前提条件测试期间，在铜垫和模塑料之间的界面上发生了分层。现有证据表明，Cu垫上的Ag镀层与模塑料之间的结合强度很弱。根据扫描声波断层扫描（SAT）的观察，大多数脱层失败部位都位于Ag镀层区域。为了准确地预测QFN中的分层失败，将模塑料/镀银和模塑料/铜上的剪切力与有限元建模相结合。进行参数分析以确定QFN中的几何结构的最佳设计，以解决分层失败的问题。