【作者】 窦刚；

【导师】 周东祥；

【作者基本信息】 华中科技大学 ， 微电子学与固体电子学， 2013， 博士

【摘要】 高频无线通信技术的高速发展，对电子元器件微型化、集成化及高性能化的要求越来越高，对电子封装技术也提出了更高的要求。低温共烧陶瓷（Low TemperatureCo-fired Ceramic, LTCC）技术为实现元器件的小型化和高密度封装提供了可能，是实现高频应用领域中元器件与基板高度集成的最有前景的技术。随着LTCC陶瓷和浆料低温烧结的深入研发，LTCC基板在芯片封装中的应用日渐广泛，因此，加速LTCC基板材料的研究不仅具有社会效益，还可以为今后电子元件的设计与研发提供更好的平台，带来经济效益。本论文主要研究了应用于LTCC基板的硅酸盐材料体系的微波介电性能，并对其介电性能和烧结温度进行了改善，制备出了适用于LTCC基板的性能优秀的微波介质陶瓷；探究了硅酸盐基微波陶瓷材料的介电损耗特性以及对其微波介电性能进行改善的过程中，损耗对微波介电性能的影响；分析了低温烧结中的液相烧结机理和硅酸盐微波介质陶瓷与银电极的化学兼容性；研究了硅酸盐基微波陶瓷材料的改性机理，并与实验数据作对比分析。硅酸盐陶瓷是无机非金属类材料中的重要组成部分，其微波介电性能大多极其优良，在微波介质陶瓷领域内的应用极广，其中Mg₂SiO₄和Zn₂SiO₄在所有已报道的微波陶瓷材料中都具有非常突出的高品质因数，但是它们极高的烧结温度和较差的热稳定性严重限制了它们作为LTCC基板材料在实际中的应用。根据Lichnetecker定则，选取具有正温度系数τf=+859ppm/°C的CaTiO₃材料与硅酸盐陶瓷进行复合，得到的复合陶瓷具有可调的τf值。当CaTiO₃的加入量从6.0mol%增加到10.0mol%时，（1-x）Mg₂SiO₄-xCaTiO₃陶瓷的谐振频率温度系数τf从-27.1增加到14.2ppm/°C。当x=0.08和0.09时，（1-x）Mg₂SiO₄-xCaTiO₃陶瓷有接近于零的τf值（-3.0和6.8ppm/°C）。与Mg₂SiO₄-CaTiO₃的Q×f值相比，当CaTiO₃的加入量从0mol%增加到7.0mol%时，（1-x）Zn₂SiO₄-xCaTiO₃陶瓷的τf值从-61.0增大到28.6ppm/°C，当x=0.05时，（1-x）Zn₂SiO₄-xCaTiO₃陶瓷的τf值为0.8ppm/°C。Zn₂SiO₄-CaTiO₃陶瓷的Q×f值的大小和变化趋势与之相近。同时，在实验结果的分析讨论过程中，还发现了CaTiO₃的加入对陶瓷材料的烧结温度有一定的降低效果。针对硅酸盐复合陶瓷的烧结温度高于950°C这一不利因素，首先采用Li⁺替代Zn₂SiO₄中Zn_<sup>2+的方法来降低陶瓷的烧结温度，研究了离子替代后陶瓷的微波介电性能，探讨该方法降低陶瓷烧结温度的可行性，并通过掺杂CaTiO₃对离子替代后陶瓷的τf进行了优化研究。研究发现，通过Li⁺对Zn_<sup>2+进行离子替代后，Li₂yZn_（2-y）SiO₄（y=0.5,0.8,1）陶瓷的Q×f值明显下降，烧结温度明显降低，当y=1时，降温达到最佳状态。掺杂CaTiO₃可使离子替代后陶瓷的τf在包含0的很大范围内可调。当x=0.17时，（1-x）Li₂ZnSiO₄-xCaTiO₃陶瓷有接近于零的τf值（-1.3ppm/°C），但是陶瓷的烧结温度仍远高于950°C。最后，只能采用添加低温烧结助剂的方法将复合陶瓷的烧结温度成功的降低到950°C以下，满足其在LTCC中应用的基本要求：当ZB玻璃的加入量为25.0wt.%时，0.75Li₂ZnSiO₄-0.25CaTiO₃陶瓷的微波介电性能为：r=9.5，Q×f=11,800GHz，τf=-5.2ppm/°C；当BLB的加入量为12.0wt.%时，0.91Mg₂SiO₄-0.09CaTiO₃陶瓷的微波介电性能为：r=7.7，Q×f=11,300GHz，τf=-5.0ppm/°C；当Li₂CO₃-H₃BO₃的加入量为4.0wt.%时，0.95Zn₂SiO₄-0.05CaTiO₃陶瓷的微波介电性能为：r=7.1，Q×f=26,300GHz，τf=-4.5ppm/°C。研究还表明0.95Zn₂SiO₄-0.05CaTiO₃复合陶瓷与Ag电极可以实现共烧。论文最后结合具体实验数据，从正价阳离子取代、掺杂CaTiO₃相、加入烧结助剂和改变烧结温度四个方面探讨了相对介电常数、介电损耗和谐振频率温度系数改性的基本理论。研究结果表明：微波陶瓷的相对介电常数随陶瓷单位体积内离子电价的升高和偶极子数量的增多而变大。对基板材料而言，低价态离子置换高价态离子，通过微孔降低材料的致密度等都会减小陶瓷的相对介电常数。多晶陶瓷作为主要的微波陶瓷，其衰减常数γ与损耗有关，微波陶瓷中所存在的非完整性因素如晶界、缺陷、杂质、气孔和裂纹等，是造成材料损耗的主要原因。Lichnetecker（李赫德捏凯）对数混合定则是针对多相共存复合微波介质陶瓷的微波介电性能的重要公式，对复合陶瓷的相对介电常数，介电损耗和谐振频率温度系数的改性机理都有指导意义。同时，经过研究发现，关于晶粒增大、晶界减少，陶瓷的Q×f值应该增大的理论，在陶瓷材料晶粒增大到某一程度以上或者陶瓷发生过烧而出现晶粒异常增大时，是与实验事实相违背的，即晶粒大小和晶界变化与陶瓷Q×f值的变化规律仅在某一晶粒粒度范围内才是符合实验事实的。粉末烧结由于在烧结过程中系统的自由能减小，有自动发生的趋势，烧结系统表面和界面自由能以及晶格歧变能的降低是烧结的主要推动力。在一定烧结温度下，液相的多少及分布对材料的烧结致密化起决定性作用。通过在不同烧结时期对烧结过程进行合理的选择和干预可使晶粒大小比例合理、均匀，减少气孔，有利于微波陶瓷材料介电性能的优化。更多还原

【Abstract】 The rapid progress of high-frequency wireless communication technology,increasingly high demand for the miniaturization, integration and high-performance ofelectronic components, also put forward higher requirements for the electronic packagingtechnology. LTCC technology provided the realization of the miniaturization andhigh-density packaging of the components, which is the most promising technology toachieve the integration of electronic components and the substrate in the field of highfrequency applications. With the in-depth research and development of low-temperaturesintering of LTCC ceramic and electrode paste, the LTCC substrate is increasinglywidespread application in the electronic packaging. To accelerate the study of LTCCsubstrate and antenna materials not only socially, but also thought to improve the designand development of electronic components in the future a better platform to bringeconomic benefits. In this thesis, the microwave dielectric properties of the silicatematerial system applied to the LTCC substrate were studied, and improved theirmicrowave dielectric properties and sintering temperature, prepared excellent LTCCsubstrate and microwave antenna ceramics; discuss the effects of intrinsic loss related tothe crystal structure and extrinsic loss due to the preparation process on the microwavedielectric properties of the silicate ceramic; analysed the low-temperature sinteringmechanism of liquid-phase sintering, and explored the compatibility of the system withAg; explore the dielectric loss characteristics of silicate base microwave ceramic materialand the silicate base microwave ceramic material modification theory, discussed themodification theory of the dielectric constant and dielectric loss, and compared with theexperimental data analysis.Silicate ceramics is a important part of inorganic non-metallic materials, theirmicrowave dielectric properties are extremely good, applied extremely extensive inmicrowave dielectric ceramics domain, such as: Mg₂SiO₄and Zn₂SiO₄have the extremelyprominent high quality factor in all the microwave ceramic material have been reported.But their extremely high sintering temperature and poor thermal stability severely limitthem as LTCC substrate materials in the practical application. According to theLichnetecker rule, in this paper we select CaTiO₃with positive temperature coefficient τf=+859ppm/°C as a compensation function material to get adjustable τfvalue. When the addition amount of CaTiO₃increase from6.0to10.0mol%, the τfvalues of the（1-x）Mg₂SiO₄-xCaTiO₃composite ceramic increase to14.2from-27.1ppm/°C. When x=0.08and0.09, the （1-x）Mg₂SiO₄-xCaTiO₃ceramic samples have close to zero τfvalues-3.0and6.8ppm/°C. Compared with the Q×f values of Mg₂SiO₄-CaTiO₃ceramics, the Q×fvalues and changing trends of Zn₂SiO₄-CaTiO₃ceramics are the same. When the additionamount of CaTiO₃from0increases to7.0mol%, the τfvalues of （1-x）Zn₂SiO₄-xCaTiO₃composite ceramic increase to28.6from-61.0ppm/°C. When x=0.05, the （1-x）Zn₂SiO₄-xCaTiO₃has close to zero τfvalue is0.8ppm/°C. And in the process of the analysis ofexperimental results, we find the addition of CaTiO₃has certain effect of low sinteringtemperature.According to the restriction condition the silicate ceramic sintering temperature arehigher than the LTCC ceramic sintering temperature of950°C, first use of Li+alternativeZn_<sup>2+to reduce the sintering temperature, and research the microwave dielectric propertiesof the ceramic after ion substitution, to explore the feasibility of the ways to reduce thesintering temperature and research theτfthrough doping CaTiO₃. Studies have found thatafter Li+alternative Zn_<sup>2+, the Q×f values of Li₂yZn_（2-y）SiO₄（y=0.5,0.8,1） and sinteringtemperatures are fall, especially when y=1. When x=0.17,（1-x）Li₂ZnSiO₄-xCaTiO₃ceramic samples has close to zero τfvalue-1.3ppm/°C. But the sintering temperatures aremore than950°C. At last, we successfully reduced the sintering temperature of threecomposite ceramics by means of adding low melting point mixed oxideBi2O₃-Li₂CO₃-H3BO₃（BLB）, Li₂CO₃-H3BO₃and zinc boron （ZB） glass as lowtemperature sintering additives to950°C below, meeting the basic requirements of theapplication of LTCC, and a deep research on the relations of sintering additives additionand microwave dielectric properties: When the addition amount of ZB glass is25.0wt.%,the microwave dielectric properties of the0.75Li₂ZnSiO₄-0.25CaTiO₃ceramic samplesarer=9.5, Q×f=11,800GHz, τf=-5.2ppm/°C; when the addition amount of BLB is12.0wt.%, the microwave dielectric properties of the0.91Mg₂SiO₄-0.09CaTiO₃ceramicsamples arer=7.7, Q×f=11,300GHz, τf=-5.0ppm/°C; when the Li₂CO₃-H3BO₃quantityadded to4.0wt.%, the microwave dielectric properties of the0.95Zn₂SiO₄-0.05CaTiO₃ceramic samples arer=7.1, Q×f=26,300GHz, τf=-4.5ppm/°C. We also found that0.95Zn₂SiO₄-0.05CaTiO₃composite ceramic and Ag electrode have good chemicalcompatibility, can be co-fired, they can be used as the LTCC materials in the microwaveantenna and substrate. The paper studied the modified theory of the silicate base microwave ceramicmaterials, discussed the modification theory of relative dielectric constant, dielectric lossand resonance frequency temperature coefficient, and compared with the experimentaldata analysis. From the positive valence cations replace, doping new phase, add sinteringadditives and change the sintering temperature four aspects made a thorough research tomicrowave ceramic material modification theory, obtained some research achievements.Finally, powder sintering principle are discussed. The results show that the unit volumeinside ion electricity price is higher, more dipoles, the microwave ceramic relativedielectric constant is bigger, high ion replacement low state ion, the craft on the graingrowth fully, density as far as possible to achieve saturation, and improve the materialdensity is effective methods of relative dielectric constant improvement. Forpolycrystalline ceramics, attenuation constant γ related to the loss caused by grainboundary, void, dislocation, periodic defect, impurity atom and vacancy. Lichnetecker ruleis an important formula for microwave dielectric properties of multiphase coexistencecomposite microwave dielectric ceramics, has the guidance meaning to the dielectricproperty modification mechanism of composite ceramic. Sintering mechanism of thesintering process has automatic happen trend, from the view of thermodynamics point,powder sintering is the reducing process of system free energy, the reducing of free andlattice variable energy is the main driving force of sintering. The distribution of liquidphase under the sintering temperature will play a decisive role to material sinteringdensification. In different sintering period, reasonable choice sintering process can makethe grain size reasonable proportion, uniform, reduce porosity, be helpful for the materialdielectric performance optimization of microwave ceramic.更多还原