LTCC厚膜的受约束烧结致密化行为及连续介质力学理论模拟

发布时间：2018-03-19 06:38

  本文选题：LTCC厚膜　切入点：受约束烧结　出处：《合肥工业大学》2015年博士论文　论文类型：学位论文

【摘要】：由于受约束烧结问题的普遍性和实用性,对烧结体受约束烧结致密化行为的研究具有重大的应用价值和科学意义。近年来,LTCC厚膜材料逐渐成为电子元器件和集成电路领域内应用最为广泛的材料,但是对LTCC厚膜材料的受约束烧结致密化行为缺乏系统的理论研究。连续介质力学烧结理论能够实现对受约束烧结致密化行为的预测和模拟,得到了越来越多的关注。本文以LTCC厚膜材料为研究对象,通过原位光学膨胀仪观测系统,研究了多种约束条件下LTCC厚膜的烧结致密化行为。基于连续介质力学烧结理论,成功地使用垂直烧结方法测定了LTCC厚膜材料各向同性及各向异性的烧结参数,并根据测定的烧结参数对基板约束LTCC厚膜的烧结致密化行为进行了分析和预测。研究了多种约束烧结条件下LTCC厚膜内部显微结构的演变规律。本文的主要结论如下：(1)通过对流延工艺的探索和尝试,成功使用银峰(YF)低介微波陶瓷粉体和浩普(HP)铁氧体粉体制备出了厚度可控、一致性好、致密的LTCC厚膜材料。并可通过工艺参数的调控,制备出不同厚度的厚膜。搭建了原位光学膨胀仪,并结合垂直烧结样品台及石英摇摆臂测定了多种形式的受约束LTCC厚膜材料的烧结致密化行为。(2)采用薄膜悬挂垂直烧结方法,分别测定了几种LTCC厚膜材料,DuPont 951 tape(DU),Ferro A6M tape(FE)和YF厚膜的单轴粘度。通过研究发现,受到自身重力影响,垂直烧结的LTCC厚膜在垂直方向上的烧结致密化行为会受到细微的影响,但是其内部微结构仍然能保持各向同性。LTCC厚膜的单轴粘度随相对密度的增加呈现出非线性增长,在低密度范围内增长缓慢,在较高密度范围内则增长迅速。通过对比研究发现,实验测定的厚膜的单轴粘度与Raj模型预测的结果具有很好的一致性。通过In (Ep)与1/T之间的Arrhenius方程,求解出了DU厚膜的单轴粘度激活能,其数值290±47kJ/mol。(3)为测定LTCC厚膜材料的各向异性烧结参数,设计了单轴加载烧结实验,对垂直烧结的FE厚膜施加单轴载荷,并通过调节单轴载荷的大小,实现了FE厚膜在单轴方向上的零收缩烧结。研究发现单轴载荷可以明显改变加载方向上厚膜材料的烧结致密化行为,但是对厚膜整体的烧结致密化过程影响不大。通过对单轴加载FE厚膜显微结构的研究发现,厚膜内的气孔在烧结过程中会逐渐沿着单轴加载方向取向,而且气孔的取向程度随着单轴载荷的增大而逐渐增加。根据厚膜单轴零收缩烧结所对应的边界条件简化了各向异性连续介质力学方程,成功得到适用于计算厚膜各向异性的烧结参数的公式,并计算出在单轴零收缩条件下FE厚膜的单轴粘度和粘性泊松比系数。通过与各向同性烧结参数的对比发现,单轴零收缩烧结LTCC厚膜的单轴粘度明显增大,同时粘性泊松比系数随密度增加而逐渐下降。(4)研究了硬质基板约束FE厚膜的烧结致密化行为。由于基板的约束力,在烧结过程中FE厚膜在基板平面方向上的烧结致密化过程被抑制,只能在厚度方向上产生烧结收缩,在烧结后样品的密度低于自由烧结厚膜。在烧结过程中厚膜内出现了明显的各向异性微结构,随着密度的增加气孔会逐渐沿着平行于基板的方向取向。通过阿伦尼乌斯公式(Arrhenius)和主烧结曲线(MSC)两种方法研究了硬质基板约束的FE厚膜的烧结激活能。使用阿伦尼乌斯方法求得自由烧结厚膜的烧结激活能为530±30kJ/mol,而基板约束厚膜的烧结激活随着密度而逐渐降低,由640 kJ/mol逐渐下降至359kJ/mol。而使用主烧结曲线方法求得的自由烧结厚膜烧结激活能为510 kJ/mol,基板约束厚膜烧结激活能为440kJ/mol。通过对比发现,硬质基板约束厚膜的烧结激活能明显低于自由烧结厚膜。我们分别使用各向同性及各向异性连续介质力学本构方程对硬质基板约束厚膜的烧结致密化行为进行预测和模拟。通过对比实验测定和理论预测的结果发现,各向异性连续介质力学方程能更准确地预测出受约束厚膜在较高的密度范围内(75%)的烧结致密化行为。(5)通过对柔性基板约束HP厚膜研究发现,在烧结过程中厚膜会产生向上的翘曲变形。与硬质基板约束的厚膜相比,柔性基板通过翘曲释放了一部分基板约束力,厚膜的烧结致密化过程受到的抑制作用减弱,烧结后厚膜的密度更高。使用各向同性连续介质力学方程预测了受约束厚膜的致密化速率,与实验测定的结果对比后发现两者在低密度区能保持较好的一致性,但是随着密度的增加,两者之间的差异逐渐增大。通过分析了柔性基板约束HP厚膜的显微结构发现,厚膜内的气孔存在明显的梯度分布,气孔率在远离基板的位置逐渐降低。通过柔性基板的翘曲变形求解出了作用于厚膜上的基板约束力,并与各向同性连续介质力学预测的结果对比后发现,各向同性模型预测出的基板应力明显低于实际测定的应力。
[Abstract]:Because of the universality and practicability of constrained sintering problem, has great application value and scientific significance to study on the sintered constrained sintering densification behavior. In recent years, LTCC material has gradually become electronic components and integrated circuits in the field of the most widely used materials, but the lack of systematic theoretical research of constrained sintering behavior the densification of LTCC thick film material. To achieve the forecast and Simulation of constrained sintering densification behavior of sintered continuum mechanics theory, has attracted more and more attention. This paper research on the LTCC thick film material, by in situ optical dilatometer observation system, studied the Sintering Densification behavior of LTCC thick film multi constraints under the sintering theory. Based on continuum mechanics, the successful use of the vertical sintering method of sintering parameters of LTCC thick film material isotropy and anisotropy were determined, and According to the Sintering Densification behavior of sintering parameters on the determination of substrate bound LTCC thick film was analyzed and predicted. On the evolution of LTCC thick film microstructures of various constraints sintering conditions. The main conclusions of this paper are as follows: (1) through the exploration of the casting process and try to use the peak (YF) with low dielectric constant microwave ceramic powder and hope (HP) ferrite powders were prepared with controllable thickness, good consistency, LTCC thick film material dense. And through the control of process parameters, preparation of thick film with different thickness. Built in situ optical dilatometer, and various forms of the Sintering Densification behavior of constrained LTCC thick film material was measured with vertical sintering sample stage and quartz. The swing arm (2) by film hanging vertical sintering method, several kinds of LTCC thick film materials were determined, DuPont 951 tape (DU), Ferro A6M tape (FE) YF thick film and uniaxial viscosity . through the study found that, by their own gravity, sintering densification behavior of LTCC thick vertical sintering in vertical direction is affected by the subtle effect, but its microstructures can still maintain uniaxial viscosity of isotropic.LTCC thick film with the increase of relative density is nonlinear growth, slow growth in the low density range in high density range, rapid growth. By comparison, the prediction of thick film experimental determination of uniaxial viscosity and Raj model results have good consistency. The In (Ep) and Arrhenius 1/T equation, solved the uniaxial viscosity of DU thick film activation energy, the value of 290. 47kJ/mol. (3) for anisotropic sintering parameters determination of LTCC thick film material, the design of single axial loading sintering experiment, FE thick film on vertical sintering applied uniaxial load, and by adjusting the uniaxial load size, to achieve the FE Zero shrinkage sintering of thick film in uniaxial direction. The study found that a single axle load can significantly change the loading direction on thick film material sintering densification behavior, but has little effect on the whole of the thick film sintering process. Through the study of uniaxial loading of FE thick film microstructure, porosity in thick film will gradually along the axis the loading direction in the sintering process, and the degree of orientation hole increases with uniaxial load increasing gradually. According to the corresponding thick film uniaxial zero shrinkage sintering boundary conditions simplified anisotropic continuum mechanics equation, successfully obtained for Sintering Parameter Calculation of thick film anisotropy formula, and calculated in the single axis under the condition of zero shrinkage of FE thick film uniaxial viscosity and viscous coefficient of Poisson's ratio. By comparing with the isotropic sintering parameters, uniaxial uniaxial zero shrinkage of sintered LTCC thick film 绮樺害鏄庢樉澧炲ぇ,鍚屾椂绮樻，

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