Simulation Study Of The Rf Mlcc Environmental Stress And Its Reliability

RF MLCC is widely used in a variety of RF circuit. The product technology,technical level and reliability of RF MLCC are backwardness at home, and RF MLCChas not produced and supplied on large scale, current products are mainly imported, butthe high end military products are embargoed for domestic market. So it is urgent to setup the corresponding failure mechanism analysis and reliability research technology.Environmental stress is one of fatal aspects which affect the reliability of RFMLCC. In this paper, the relationship between the environmental stress and the failureof electronic device was analyzed, and the common methods to research the reliabilityfor MLCC were illustrated. Then, the impacts of temperature and frequency on thefailure of RF MLCC were simulated using numerical method, and the ways to improveits reliability were proposed. Numerical method takes less times and lower costcompared with physical experiment, can get good enough results, and the value ofthermal stress of RF MLCC is difficult to be showed in physical experiment, whenthermal shocks are applied. The simulation included the temperature shocks and theanalysis of frequency characteristics, the affects of inner electrode structure, thethickness of Argentine electrode and material parameters on the reliability of RF MLCCwere also discussed.First of all, the theoretical models were established and the simulation programswere designed using finite element method, which would show the distribution ofthermal stress on RF MLCC, then the thermal stresses were simulated for differentinner electrode, terminal electrode height and ceramic materials RF MLCC, whenthermal shocks were applied. The free meshing and mapped meshing were combined inthe simulation, and the abnormal grids were eliminated, then the sparse local grids wererefined several times, which made all SEPCs were kept less than 2%. The resultsshowed where were the brittle parts in RF MLCC due to the thermal stresses, and theaffects of the thermal cycling times, inner electrode structure, the thickness of Argentineelectrode and material parameters on the thermal stress of RF MLCC were also displayed.Five three dimensional models were established using Ansoft HFSS software, andthe frequency characteristics of RF MLCC were discussed within its working frequency,then frequency characteristics were compared between the float inner electrode RFMLCC and normal inner electrode RF MLCC, when the thickness of Argentineelectrode changed in the range of 10 20 micros, the trends in the frequencycharacteristics were analyzed. The results showed as follows: For the floatinner electrode RF MLCC, S11 was less than 20 dB in a large frequency range, S12approached to 4dB, Z11 and Z12 neared 5dBand 0dB respectively, when the frequencygreater than 1GHz, its frequency characteristics were much better than normalinner electrode RF MLCC. The frequency characteristics of RF MLCC were constant inits working frequency range, when the thickness of Argentine electrode changed from10 micros to the 20 micros.The environmental stress and the reliability of RF MLCC were simulated andresearched in this paper, the works in which provided a theoretic basis for the analysisof the failure of RF MLCC, the optimization of the structure and the improvement thereliability of RF MLCC, the results had theoretical and practical significance.