RF MLCC热应力分析

Analysis of Thermal Stress on RF MLCC

采用有限元方法,应用ANSYS软件,模拟不同内电极结构和不同端电极厚度的RFMLCC在热冲击时的热应力分布。模拟结果显示:端电极倒角处、银电极与内电极引出端的接触处所受vonmises热应力较大,是热应力下RFMLCC结构中最薄弱的部位;结构中的峰值热应力随温度循环次数的增加而增加,五次循环后的热应力约为首次循环的4.5倍;悬浮内电极结构银电极上的最大热应力远小于正常内电极结构;增加银电极厚度可以大大减小热应力,对于13层悬浮内电极结构的RFMLCC,银电极厚度增加一倍,其所受热应力最大值减少约50%。本次仿真结合了自由划分和映射划分,并且多次局部细化网格,消除了畸形网格,使得各次仿真的能量准则百分比误差均小于2%。为分析RFMLCC热失效机制、优化结构、提高其可靠性提供了理论依据。

Using finite element method and ANSYS software, the thermal stress distributions were simulated for RF MLCCs with different inner-electrodes and different terminal electrode thickneses, when thermal shocks were applied. The results showed that the vital von mises stresses were located in the fillets of the terminal electrodes and the contacts of Ag electrodes and inner- electrodes, which were the brittle parts in RF MLCC due to the thermal stresses. The peak stress on the RF MLCC rised with the increasing of the number of thermal cycles, and the peak stress in the fifth cycle was about 4.5 times as in the first cycle. The peak stress on the Argentine electrode in the inner floated struchture was much less than that on the normal inner-electrode. The magnitudes of thermal stresses decreased significantly with the increasing of the Ag electrode thickness, and the peak stress decreased by 50% as the Argentine electrode thickness doubled for a 13-layer floated inner-electrode RF MLCC. The free meshing and mapped meshing were combined in the simulation, and the abnormal grids were eliminated, with several times the sparse local grids refinement of to lower all SEPCs to less than 2%..Theresearch provided a theoretical basis for the analysis of the failure of RF MLCC, the optimization of the structure and the reliability improvement of RF MLCC.