Research On Stress Simulation Method Of Device Structure And Stress Reliability Of Microstrip Isolator

With the development of miniaturization and integration of electronic devices, stress simulation gets more and more widespread applications in structure optimization and process improvement. Due to the increasingly extreme application environment and complicated process of devices, in order to make simulation more close to experiment, the research of simulation methods, including initial stress loading, intrinsic stress simulation and so on, becomes very significant.In this paper, firstly it introduces the mainly technical features of finite element software Ansys and simulation process of structure analysis, and discusses the key steps of simulation process which have a great influence on the simulation results. Then the fatigue analysis model of solder is analyzed. And the technical features, merits and demerits of known simulation method of devices structure residual stress are discussed.In order to analyze the influence of initial stress on stress distribution in structure simulation, simulation method of stacked structure initial stress loading is studied. Based on the technical features of presently known initial stress loading methods, combined with structural features of stacked structure, a new loading method of two steps is obtained, and applied to the aspects of microstrip isolator welding residual stress loading. The loading result shows that the initial stress distribution is in accord with the distribution of welding residual stress, so the method is usable.To simulate the temperature shock process, simulation method of microstrip isolator temperature shock is studied. According to marerial features of each part in microstrip isolator, the approprate volume model and material model are established. Combined with structure characteristics of isoaltor, 1/2 3-D model is used as the temperature shock simulation model, by discussed the simulation results of complete 3-D model, 1/2 3-D model and 2-D model. According to the temperature shock test conditions, two different boundary constraints are proposed and simulated. After analysis of simulation results the vertexs constraint of underside is adopted. By comparing the simulation results of two different loading methods of temperature shock load, the temperature shock load is straightly applied to all nodes of microstrip isoaltor model. The simulation error of temperature shock using the above studied method is assessed, and the eror is 6.49%.After simulating temperature shock process, stress reliability of microstrip isoaltor is studied. Stress distribution of microstrip isoaltor under temperature shock is analysed, and the influence of each part on microstrip isolator stress reliability is studied. The results reveal that first 5 shocks in 100 temperature shocks is primary period of stress accumulation, ferrite substrate and solder are maximum stress parts. According to material properties and process features of each part, the fracture of ferrite substrate is the major reason to cause microstrip isolator stress failure in temperature shock, and some measures are provided for improving microstrip isolator reliability.Because viod is one of the main defects in welding process, the influence of voids in solder on microstrip isolator is studied. Formation mechanism of voids in solder is analysed, and voids modeling method is studied. From the aspects of void area, position and distance, the influence of voids in solder on microstrip isolator is researched by 14 different void models. Research results indicated that the influence of voids on ferrite substrate reliability is negligible, and when the stress of void position or the area of void increases, the fatigue life of solder could be reduced.In order to get the residual stress distribution of devices structure, simulation method of device structure residual stress is studied. Based on the presently known simulation methods of films’ residual stress, combined with process features of Si/SiO2/Si3N4 structure, an “equivalent reference temperature” technique is used to obtain the simulation distribution of residual stress.Simulation methods of Si/SiO2/Si3N4 structure residual stress, stacked structure initial stress and microstrip isolator temperature shock are provied, and stress reliability of microstrip isolator is analysed. It can supply theoretical basis for improving microstrip islator.