Research On The LTCF Material And Passive Chip Elements

The technology of LTCF (Low Temperature Co-fired Ferrite) materials and elements can satisfy the requirements of miniaturization, low weight and high integration developments of modern electronic systems and become the major and key technology for passive integration.This paper focused the theoretical investigations on low temperature co-fired ferrite and correlative elements. Firstly, the sintering and transfering kinetics of the ferrite were analyzed to give directions to density the ferrite under low sintering temperature. Then the mixed-oxide method and sol-gel method were adopted to produce the ZL120 NiCuZn ferrite. In this process, effects of compositions, procedure methods and additives on sintering behaviors and magnetic properties of the ferrite had been investigated. Then, the HFSS and ADS softwares had been adopted to optimize the structure of the multilayer chip inductor, multilayer chip capacitor and multilayer chip filter. By using the produced NiCuZn ferrite and the LTCC technical line, we developed high performance multilayer chip inductors and multilayer chip filters.In the process of the ferrite research, the influences of compositions on the sintering behaviors, microstructures and magnetic properties of the ferrite were first investigated. It was confirmed that 10mol% CuO content was appropriate to give attention to both low-fired characteristic and good magnetic properties of the NiCuZn ferrite. Then the influences of V₂O₅, SiO₂ and Bi₂O₃ additives on the densification behaviors and magnetic properties of the ferrite were studied. Subsequently, on the base of V₂O₅ and Bi₂O₃ additives, WO₃ and Co₂O₃ additives were also added to further improve Q-factor. Finally, the optimal additives were chosen as 1wt%Bi₂O₃ + 0.2wt%Co₂O₃ to obtain the ZL120 NiCuZn ferrite. To compare with the mixed-oxide method, then the sol-gel method was adopted to produce the ZL120 NiCuZn ferrite. It was found that nanocrystalline ferrite particles enhanced densification of the samples obviously due to high surface free energy. Furthermore, higher Q-factor could be obtained due to no sintering aids added.In the process of the LTCC elements research, the Ansoft-HFSS and Agilent-ADS softwares were adopted to design, emulate and optimize the multilayer chip inductor and capacitor firstly. Effect of model parameters on the properties of the inductor were studied, and the calculated formula between inductance (L_eff) and circles (N) was deducted, which was L_eff=116.25×N^1.67nH. Subsequently, based on the investigations of multilayer chip inductor and capacitor, we designed and emulated a kind of anti-EMI LTCC filter. Finally, the prepared ZL120 NiCuZn ferrite was chosen to produce the LTCC chip inductor and filter by adopting LTCC technical line. It was confirmed that the produced inductance value was lower than the forecast, which was mainly due to debasement of the permeability. The insertion loss of the LTCC filter was close to the forecast and meet the request.