双层叠轧铜箔的组织性能和表面形貌特征及形成机理

发布时间：2018-05-18 22:19

本文选题：铜箔 + 双层叠轧　；参考：《北京科技大学》2015年博士论文

【摘要】：通过某些常规成形方法制备出具备晶粒尺寸多级多尺度结构或两表面不同粗糙度结构的金属材料,使其不同部位满足不同使用工况的要求或具有不同的功能,是提高金属材料综合性能的一种有效途径。已有研究表明,控制不同区域晶粒的变形程度呈梯度变化是获得晶粒尺寸梯度结构的主要办法,设计两表面上的摩擦润滑条件不同是获得两表面不同粗糙度结构的主要途径。但迄今为止,未见有塑性加工方法直接制备同时具有梯度组织和两表面不同粗糙度结构材料的相关报道。因此,本课题组提出了“采用双层叠轧法直接制备兼具梯度组织和两表面不同粗糙度结构材料”的思路,以期短流程、高效地开发出一种综合性能优异的金属材料。而研究双层叠轧材料的微观组织和表面形貌特征,了解微观组织和表面形貌的形成机理,弄清微观组织和表面粗糙度的影响因素及规律,则是正确设计叠轧工艺,实现上述思路,制备出兼具梯度组织和两表面不同粗糙度结构的高性能金属材料的关键科学问题。本论文以广泛应用于电子领域的金属纯铜为对象,利用双层叠轧成形纯铜箔材,系统研究了双层叠轧铜箔的微观组织和表面形貌特征及形成机理,分析了微观组织、表面形貌与叠轧铜箔性能之间的内在联系,所得结果为开发及应用兼具梯度组织和两表面不同粗糙度结构的高性能纯铜箔材奠定了实验和理论基础。研究工作主要取得了以下创新性结果：开发了兼具厚度方向非对称梯度组织和两表面不同粗糙度结构的纯铜箔材。以厚度50μm的双层叠轧铜箔为例,其光面粗糙度Rz为0.061μm,毛面粗糙度Rz为1.095μm,满足与挠性印刷电路板基板粘结时对铜箔表面粗糙度的要求,有望省略传统铜箔生产工艺中的单面毛化处理；厚度方向上从光面至毛面,铜箔晶界间距平均值先由2.3μm增加至7.4μm,然后又降低到3.6μm；相比于相同压下率的单层轧制铜箔,叠轧铜箔的耐弯折疲劳寿命提高15%以上。揭示了双层叠轧铜箔非对称梯度组织及两表面相异织构的形成机理。铜带两侧不同的轧制压应力和剪切应力,以及非对称的变形渗透作用是影响不同区域晶粒尺寸、导致叠轧铜箔非对称梯度组织形成的主要原因。光面侧的强压缩和剪切变形条件有利于促进晶粒向铜型织构取向集中,毛面侧的叠合摩擦变形条件更有利于促进晶粒通过位错滑移的方式向黄铜型织构取向集中,并且该作用强于机械孪生方式对晶粒向黄铜型织构取向转动的促进作用。基于金属流动和变形力学理论,建立了双层叠轧铜箔毛面粗糙度的形成模型,揭示了毛面的形成机理。由于金属以沿轧制方向流动为主,在被闭合双合油(或空气)压力的作用下,两层叠合面之间的初始微坑首先发生沿轧制方向的连通合并,逐步形成稳定的密闭微坑；随着稳定密闭微坑体积不断压缩、流体压力不断增大,微坑凹陷显著变深；同时由于变形区内金属应力变形的特点,微坑更容易沿宽度方向连通合并,使得叠合面上的微坑发展成为具有一定宽度方向伸展的凹陷纹和凸起纹。阐明了粗糙度与位错密度对双层叠轧铜箔表面功函数和耐蚀性能的共同影响作用。粗糙度主要影响叠轧铜箔表面功函数的均匀性,位错密度增大对叠轧铜箔表面功函数降低的贡献明显大于表面粗糙度增大。对于厚度大于110μm的叠轧铜箔,两表面的功函数都在4.4eV以上,此时耐蚀性能主要受粗糙度影响,光面耐蚀性能优于毛面；对于厚度小于70μm的叠轧铜箔,两表面的功函数都在4.1eV以下且均发生晶间腐蚀,此时耐蚀性能主要受位错密度影响,毛面耐蚀性能优于光面。发现了双层叠轧铜材拉伸断裂的厚度效应。随着厚度的减小,叠轧铜材表面硬化层所占厚度比例增大,芯部韧性层对延续铜材整体拉伸变形的作用不断减弱,因而断口中韧窝和韧窝凹坑数量和尺寸都明显减少,断后伸长率显著降低。
[Abstract]:It is an effective way to improve the comprehensive performance of metal materials by using some conventional forming methods to prepare metal materials with multilevel multi-scale structure of grain size or different roughness structure of two surface, so that different parts meet the requirements of different operating conditions or have different functions. The main way to obtain grain size gradient structure is that the degree of grain deformation is gradient, and the main way to obtain the different roughness on the surface of the two surface is the main way to obtain the different roughness structure on the two surface. But so far, no plastic processing method has been produced directly with the gradient and two surface different roughness structure. As a result, we put forward the idea of using double layer rolling method to direct the preparation of structure materials with gradient and two surface roughness, in order to develop a kind of metal material with excellent comprehensive performance in a short process. The formation mechanism of microstructures and surface morphology and the understanding of the influencing factors and rules of the microstructure and surface roughness are the key scientific problems in the correct design of the rolling process and the realization of the above ideas, and the preparation of high performance metal materials with both gradient and two surface roughness structures.
In this paper, the microstructure and surface morphology characteristics and formation mechanism of double folded rolled copper foil are systematically studied by using the pure copper foil which is widely used in the field of electron. The internal relations between the microstructure, the surface morphology and the properties of the rolled copper foil are analyzed. The results are both for development and application. The experimental and theoretical basis of the high performance pure copper foil with the gradient structure and the two surface roughness structure has been established, and the following innovative results have been obtained.
The pure copper foil with the thickness direction asymmetric gradient and the two surface roughness structure is developed. With the thickness of 50 m thickness double layer rolled copper foil, the surface roughness Rz is 0.061 mu m and the surface roughness Rz is 1.095 mu m. It is expected to meet the requirements of the surface roughness of the copper foil when bonded to the flexible printed circuit board substrate. It is hopeful to save the tradition. In the production process of copper foil, the average value of the grain boundary between the copper foil and the surface of the copper foil is increased from 2.3 mu m to 7.4 u m in the direction of thickness, and then to 3.6 mu m, and the bending fatigue life of the rolled copper foil is increased by more than 15% compared to the single rolled copper foil with the same pressing rate.
The formation mechanism of asymmetric gradient and two surface texture of double folded rolled copper foil is revealed. The different rolling compressive stress and shear stress on both sides of the copper strip and asymmetric deformation permeability are the main reasons that affect the grain size of different regions and lead to the formation of asymmetrical gradient of the rolled copper foil. The shear deformation conditions are beneficial to promote the orientation of the grain to copper texture orientation, and the overlapping friction deformation conditions on the surface side of the wool side are more conducive to promoting the orientation of the brass texture orientation through dislocation slip, which is stronger than the mechanism of mechanical twins to promote the direction of the brass texture.
Based on the theory of metal flow and deformation mechanics, the formation model of the coat roughness of double folded rolled copper foil was established, and the formation mechanism of the wool surface was revealed. The initial micro pit between the two laminates was first connected along the rolling direction, as the metal was mainly flowing along the rolling direction and under the action of closed double oil (or air) pressure. At the same time, stable closed micro pits are gradually formed. With the steady compression of the stable closed micro pits, the pressure of the fluid is increasing, and the micro pits sag is greatly deepened. At the same time, the micro pits are more easily connected along the width direction because of the metal stress and deformation in the deformation zone, which makes the micro pits on the overlapped surface develop into a certain width direction. The depressions and protruding lines.
The effect of roughness and dislocation density on the surface work function and corrosion resistance of double rolled copper foil has been clarified. The roughness mainly affects the uniformity of the surface work function of the rolled copper foil. The contribution of dislocation density to the decrease of the work function of the surface of the rolled copper foil is obviously greater than that of the surface roughness. For the stacked rolling, the thickness is more than 110 mu. For copper foil, the work function of the two surface is above 4.4eV, and the corrosion resistance is mainly influenced by the roughness at this time, and the corrosion resistance of the surface is better than that of the wool surface. For the rolled copper foil with thickness less than 70 mu, the work function of the two surface is below 4.1eV and the intergranular corrosion occurs, and the corrosion resistance is mainly affected by the dislocation density, and the corrosion resistance performance of the wool surface is superior to the light. Noodles.
The thickness effect of the tensile fracture of the double layer rolled copper material was found. With the decrease of thickness, the thickness ratio of the hardened layer on the surface of the rolled copper increased, and the effect of the ductile layer on the whole tensile deformation of the copper material continued to decrease, so the number and the scale of the dimple and dimple pit in the fracture decreased obviously, and the elongation at the end of the fracture decreased significantly.
【学位授予单位】：北京科技大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TG335.58

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