Jiang Qian, Deshpande Abhishek Nitin, Dasgupta Abhijit
Center for Advanced Life Cycle Engineering (CALCE), Mechanical Engineering Department, University of Maryland, College Park, MD 20742, USA.
Materials (Basel). 2021 Oct 11;14(20):5973. doi: 10.3390/ma14205973.
Heterogeneous integration is leading to unprecedented miniaturization of solder joints, often with thousands of joints within a single package. The thermomechanical behavior of such SAC solder joints is critically important to assembly performance and reliability, but can be difficult to predict due to the significant joint-to-joint variability caused by the stochastic variability of the arrangement of a few highly-anisotropic grains in each joint. This study relies on grain-scale testing to characterize the mechanical behavior of such oligocrystalline solder joints, while a grain-scale modeling approach has been developed to assess the effect of microstructure that lacks statistical homogeneity. The contribution of the grain boundaries is modeled with isotropic cohesive elements and identified by an inverse iterative method that extracts material properties by comparing simulation with experimental measurements. The properties are extracted from the results of one test and validated by verifying reasonable agreement with test results from a different specimen. Equivalent creep strain heterogeneity within the same specimen and between different specimens are compared to assess typical variability due to the variability of microstructure.
异构集成正导致焊点前所未有的小型化，通常在单个封装内有数千个焊点。此类SAC焊点的热机械行为对组装性能和可靠性至关重要，但由于每个焊点中少数高度各向异性晶粒排列的随机变化导致显著的焊点间变异性，其热机械行为可能难以预测。本研究依靠晶粒尺度测试来表征此类多晶焊点的力学行为，同时已开发出一种晶粒尺度建模方法来评估缺乏统计均匀性的微观结构的影响。晶界的贡献用各向同性内聚单元进行建模，并通过一种逆迭代方法来识别，该方法通过将模拟结果与实验测量结果进行比较来提取材料特性。这些特性从一个测试结果中提取，并通过与不同试样的测试结果进行合理比较来验证。比较同一试样内和不同试样间的等效蠕变应变不均匀性，以评估由于微观结构变化导致的典型变异性。
