不同尺寸对FCBGA元器件焊点可靠性有限元分析

Finite Element Analysis on Soldered Joint Reliability of FCBGA Device with Different Dimensions

采用有限元法对FCBGA器件焊点尺寸和焊点间距进行了优化模拟。研究发现,元器件整体的最大应力集中在阵列最拐角焊点的上表面上,该部位可能成为焊点裂纹的发源地。对焊点最大应力节点进行时间历程处理,发现应力松弛现象严重,且应力值随着温度循环加载具有累积迭加的趋势。焊点优化结果显示,焊点高度对应的应力值曲线具有明显的单调递减特性。模拟的焊点直径值和实际情况吻合,同时发现焊点直径为0.02mm时对应的应力值最小。焊点间距曲线单调性表现为单调递增性,因此,可以根据应力最小的原则来选择焊点尺寸。

The finite element method is used to simulate and optimize the size and the space of the FCBGA（flip chip ball grid array） package of soldered joints. Results indicate that the maximum stress concentrates on the top surface of the outmost corner of the soldered joint where the potential initial crack may appear. It is found that the stress relaxation is obvious and the trend of stress accumulated enhancement exists with the temperature cycling loaded. Results from dimension optimizing of soldered joints show that the stress will decrease monotonously with the height of the soldered joint. Numerical results are in accord with the experiment, and the optimum diameter of the solder joint is 0. 02 mm with a lowest stress value. Meanwhile, the stress will increase monotonously with the space of solder joints. The dimension of soldered joints can then be determined based on the least stress rule.