| With the development of communication technology, the application of high frequency technology is constantly emerging. The electronic components and the mobile terminal equipments are developing to the directions of miniaturization, integrating, surface modularization, multi-dimension and multi-functionalization and so on. Choosing suitable dielectric material and using multilayer structure design for the electronic devices become to the main approach to meet the development tendency. Therefore, the low temperature co-fired ceramic technology has been developed. In this technology, the lamination and co-firing processes are two main steps in the manufacturing of multilayer ceramic devices and ceramic package substrates and the results of them directly affect the final quality of products. Therefore, the lamination and co-firing processes become the hot research pots at home and abroad.In this paper, the cordierite nano-powders prepared by sol-gel method are mixed with Bi2O3additives under the existing achievements of our research team and the cordierite green tapes with certain strength and good flexibility are cast according the mature slurry formula firstly. On this basis, the properties of cordierite ceramic tapes are studied. The results showed that the cordierite ceramic tapes can be sintered at900℃and it meets the co-firing temperature demand of the low temperature co-fired ceramics and low melting metals. The main crystalline phase of cordierite ceramic tapes sintered at900℃is a-cordierite and the sintered tapes have good density (the shrinkage and density are36.67%and2.358g/cm3, respectively), low dielectric constant(ε=3.4993;2GHz) and low dielectric (tgδ=0.0063;2GHz) and satisfy the requirements of multilayer ceramic devices and ceramic packing substrates in high frequency.Then, with the cordierite tapes prepared as matrix material, the lamination of cordierite tapes is studied by adhesive based lamination method and cold press lamination method, respectively. The results show that10layers of cordierite ceramic tapes can be laminated under2MPa with a dwell time of2min with PVA as adhesive by adhesive based lamination method. Similarly,10layers of cordierite ceramic tapes can also be laminated under8MPa with a dwell time of5min by cold press lamination method. The main influencing factors on the adhesive based lamination method are adhesive concentration, pressure and so on. The effect of sintering temperature on the joining of cordierite ceramic tapes is not obvious. The main influencing factors on the cold press lamination method are pressure, dwell time, the layers of tapes and so on. The effect of the layers of cordierite ceramic tapes on the joining of cordierite ceramic tapes is not obvious as well and the sintering temperature mainly affects the density of the laminated samples after sintering. The advantages of adhesive based lamination method are that the cordierite ceramic tapes can be laminated under low pressures and temperatures. The shortcomings of the displacement of cordierite ceramic tapes caused by the unequilibrium pressures and the uncontrolled mass flow in the traditional thermo-compressive lamination method are avoided. Therefore, the obvious deformation of the structures is reduced and it is suitable for the manufacturing of the fine and complex devices. However, the cordierite ceramic tapes shall have a certain amount of porosity. The concentration of the PVA solvent shall also be controlled to meet the need of lamination. The adhesive method is not fit to the lamination of high numbers of cordierite ceramic tapes. Otherwise, the precision of lamination will not be guaranteed. As to the cold press lamination, the cordierite ceramic tapes can be laminated at ambient temperature. Compared to the adhesive based lamination, it needn’t to have certain porosity for the cordierite ceramic tapes. Moreover, the process is simple and more layers of cordierite ceramic tapes can be laminated. However, due to certain pressures are needed in the lamination process and if the pressure applied is not equilibrium, a degree of deformation is easily to occur. In the adhesive based lamination, the joining of cordierite ceramic tapes is relied on the capillary forces of the melts of adhesive substances occurred in the sintering process. However, the joining of cordierite ceramic tapes is depended on the good elastic-plastic, the rearrangement of cordierite ceramic particles under pressures, the viscosity flow of liquid glass composition and so on.In the following, the co-firing behavior of cordierite ceramic tapes and Ag-Pd conductive metal is investigated. The Ag-Pd conductive metal sintered at different temperatures has different surface morphologies. The best morphology appears in the sample that sintered at900℃. On this condition, the particle size of Ag-Pd is smaller and the particles appear to be spherical. The particle distribution is uniform and the coverage to the cordierite ceramic tapes is compact. There is good co-firing compatibility between the cordierite ceramic tapes and Ag-Pd conductive metal in the co-firing process. Under900℃, the area of co-firing interface is very dense and no pores and cracks present are detected. Moreover, each element is evenly distributed and no chemical reaction occurs. All these characteristics can ensure the high frequency application of cordierite ceramic tapes in the fields of multilayer ceramic devices and ceramic packing substrates.At last, a new pressure assisted measure is designed to solve the problems such as deformation in the sintering process of the samples of lamination and co-firing. The samples are covered with Al2O3powders and then sintered in a furnace under the pressures of blocks. Al2O3powders used in the design have good fluidity under the pressures of blocks and the samples can be closely pressured all the time. Therefore, the contraction of cordierite ceramic tapes is confined and the deformation of the samples is reduced. Moreover, the surface smoothness of the structure is also guaranteed. |
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