Mechanics Simulation Analysis Of Plate Bending For Multilayer Ceramic Capacitors

Multi-layer ceramic capacitors(MLCC)are one of the most widely used passive components in aerospace,automotive,marine,information and other fields due to their small size,high capacity,high stability and easy installation.At present,there are a lot of research results combining experimental and EDA(Electronic Design Automation)simulation on the electrical properties of MLCCs,but the research on their mechanical properties is still dominated by the experimental approach,which has the problems of difficult quantitative analysis and unknown failure mechanism,and lacks the guidance and supplement of simulation methods.In this thesis,the equivalent simulation model for MLCC plate bending test is established by means of simulation,and the application scope of different equivalent simulation models is discussed.The influence of MLCC type difference and size difference on the stress state of MLCC in plate bending test is calculated.The causes of failure of specific MLCC and specific failure modes are analyzed.The influence of installation angle and flexible electrode on the force state of MLCC in plate bending test is studied.The main contents and conclusions include :(1)The equivalent modeling of MLCC board bending test is studied.It is found that the friction coefficient between the indenter and PCB has little effect on the capacitor side displacement solution;after the number of mesh nodes reaches160,000,the simulation results are basically independent of the number of meshes.Three equivalent modeling approaches are proposed: no simplified model,material homogenization equivalent model and main structure layer substitution equivalent model.The calculation quantity of the three models decreases in order,and the calculation accuracy can meet the demand of engineering applications.(2)Simulation analysis of plate bending is carried out for different types and sizes of MLCC.The larger the aspect ratio and the smaller the thickness of MLCC,the larger the stress-strain value under the same bending condition and the lower the strength of MLCC,which makes it more prone to failure.The 135 degree tensile stress is the main cause of 45 degree crack failure in capacitor ceramic bodies commonly seen in plate bending.The reverse bending situation is relatively safer and less prones to 45 degree cracking caused by the same,tensile stress as forward bending.(3)Simulation analysis is performed for two MLCC failure prevention means: the installation form perpendicular to the bending direction and the MLCC with flexible ends.It is found that the stress-strain value of each MLCC type increases and then decreases as the rotation angle increases.When installed perpendicular to the bending direction,the stress-strain value of smaller size MLCCs(0603,0805,1206)decreases more significantly,while the risk of failure of larger size MLCCs(1210,1812)with welded ends increases.For a 20 ?m thick flexible layer,it can absorb a large amount of deformation,largely reduce the stress-strain value of the MLCC,which makes it possible to withstand greater bending depth;Flexible layer of 20 ?m thickness or more can further reduce the stress-strain value of the MLCC,but its effect is limited.