【作者】 汪冬梅；

【导师】 郑治祥； 吴玉程；

【作者基本信息】 合肥工业大学 ， 材料学， 2019， 博士

【摘要】 高体积分数SiC_p/Al复合材料因具有高导热、低热膨胀系数以及低密度等优点,特别是其具有的性能可设计性,使其在高密度、大功率、高频率集成电路及器件等领域备受瞩目,成为电子封装领域极具前景的最新型材料。但电子信息产业的迅猛发展对该新型电子封装材料的综合性能提出了越来越高的要求。本论文基于无压熔渗技术,以降低界面热阻提高复合材料热导率为出发点,对复合材料中SiC与SiC之间、SiC与Al之间的界面进行优化设计,制备出具有三维互穿结构的高体积分数3D-SiC/Al-Si-Mg互穿复合材料。制备用SiC粉体原料经过了圆整纯化处理以降低SiC晶体结构和几何外形等缺陷对后续所制备的SiC/Al复合材料性能影响。SiC坯体成形所用粘结剂聚碳硅烷（Polycarbosilane,PCS）高温热裂解生成SiC分布在SiC颗粒表面又可以在高温烧结SiC预制件时充当固相助烧剂。主要研究结果如下:（1）采用高Si含量的Al-15Si-10Mg合金无压熔渗未氧化的3D-SiC预制件,成功制备了具有三维互穿结构的高导热、低热膨胀3D-SiC/Al-Si-Mg复合材料。复合材料中SiC相和Al合金相分布均匀,生成有害产物Al₄C₃的界面反应得到了有效控制。SiC含量为67 vol%的3D-SiC/Al-Si-Mg互穿复合材料密度为3.01 g/cm³（相对密度99.2%）,热导率为224.5 W/（m·℃）,热膨胀系数（RT～300℃）为7.04×10^-6℃^-1,抗弯强度为277 MPa。T6处理能够进一步提升其性能,复合材料的热导率达到233.6 W/（m·℃）,热膨胀系数（RT～300℃）为7.03×10^-6℃^-1,抗弯强度为288 MPa。（2）低且可剪裁热膨胀系数的电子封装材料可以获得与用作芯片或基片材料比较精准的热匹配,这样可以减轻或消除微电子系统中因温度波动引起相邻元件之间产生热应力导致的机械故障,因而保证了系统工作的可靠性和稳定性。本论文采用Al-15Si-10Mg合金和粒径为F220、F800及F1000的SiC粉体无压熔渗制备出热膨胀系数低且可剪裁的高体积分数多粒径（双粒径和三粒径）分布的3D-SiC/Al-Si-Mg互穿复合材料,研究了SiC粒径分布与3D-SiC/Al-Si-Mg互穿复合材料的热导率和热膨胀系数之间的关系。优化的多粒径分布的3D-SiC/Al-Si-Mg互穿复合材料显示出比单粒径分布的3D-SiC/Al-Si-Mg互穿复合材料更好的综合性能。SiC含量为73vol%,具有F220和F800双粒径的3D-SiC_F220/800/Al-Si-Mg互穿复合材料获得最高热导率值233.2 W/（m·℃）和抗弯强度283 MPa以及较低的热膨胀系数（RT～300℃）6.32×10^-6℃^-1。在3D-SiC预制件中使用更细小的F1000 SiC微粉因更易团聚导致其不能很好地填充进SiC网络的自由间隙空间,这会引起后续无压熔渗制备的3D-SiC/Al Al-Si-Mg复合材料中出现较多的组织缺陷,如不均匀的微观组织结构、过量Mg₂Si脆性相的形成以及更多孔隙的存留,从而导致复合材料强度和热导率的减弱。SiC含量为79vol%且含有F220、F800和F1000三种粒径的3D-SiC_{F220/800/1000}/Al-Si-Mg互穿复合材料的热膨胀系数低至5.68×10^-6℃^-1,与用作芯片的半导体材料的热膨胀系数极为接近。（3）基于热弹性理论建立了一个适用于三维互穿结构复合材料热膨胀系数计算的新理论模型,该模型计算的3D-SiC/Al-Si-Mg热膨胀系数值与实验测量的热膨胀系数数据相吻合。（4）3D-SiC/Al互穿复合材料中SiC与Al合金的界面结合以及界面结构和组成等界面特性在决定材料热物理性能和力学性能方面有着重要作用。本论文分别采用两种成分的Al-15Si-10Mg和Al-9Si-6Mg合金无压熔渗进未经氧化或经1000～1200℃预氧化的3D-SiC预制件中,制备出系列3D-SiC/Al-Si-Mg互穿复合材料,研究了复合材料界面调控机理。结果表明:两种Al合金制备的三维互穿复合材料均能获得较理想的界面结构和优良的热物理性能和力学性能。采用高Si含量的Al-15Si-10Mg合金熔渗进未经氧化3D-SiC预制件制备的3D-SiC/Al-Si-Mg互穿复合材料界面通过原子匹配直接结合;3D-SiC预制件的预氧化对复合材料热膨胀系数的影响可忽略不计,但使得热导率及抗弯强度均有所弱化。采用低Si含量的Al-9Si-6Mg合金熔渗进预氧化3D-SiC预制件中制备的3D-SiC/Al-Si-Mg互穿复合材料界面属于反应键合界面;界面反应产物AlN和MgAl₂O₄与SiC具有较好的亲和性,并且有效隔离了液态Al与SiC防止有害相Al₄C₃的形成;1000℃预氧化的预制件制备的3D-SiC/Al-Si-Mg互穿复合材料中形成了厚度约为200 nm的界面区域,该复合材料的综合性能优异,热导率为219.5W/（m·℃）,热膨胀系数（RT～300℃）为7.66×10^-6℃^-1,抗弯强度达到318 MPa。更多还原

【Abstract】 High volume fraction SiC_p/Al composites have attracted considerable attention in application researches of high-density,high-power,high-frequency integrated circuits and become highly promising candidates for electronic packaging due to their excellent comprehensive properties of high thermal conductivity,low thermal expansion coefficient,low density,and especially their performance designability.However,the increasing development of microelectronic systems in the miniaturization,integration and high performance imposes ever more demanding requirements on the composite.In this thesis,the high SiC volume fraction 3D-SiC/Al-Si-Mg interpenetrating composites with high thermal conductivity and low thermal expansion were prepared by pressureless infiltration technique,by optimizing the interfaces between SiC and SiC as well as between SiC and Al in the composite and reducing the interfacial thermal resistance of the composites.SiC powders were modified to reduce the influence of such as SiC crystal defects and its irregular geometric shape on the properties of the resulited 3D-SiC/Al-Si-Mg composite.In the preparation of 3D-SiC preforms through SiC powders coated with polycarbosilane（PCS）,PCS plays different roles in either forming or sintering process.In the forming process,PCS acts as a binder and SiC particles are bonded together.In the sintering process,PCS is converted into SiC by high temperature pyrolysis to act as a solid sintering aid and the SiC particles are sintered into 3D-SiC preforms.（1）A high thermal conductivity（TC） and low thermal expansion coefficient（CTE） 3D-SiC/Al-Si-Mg IPC with three dimensional mutually interpenetrated structure has been successfully constructed using excessive Si content Al-15Si-10Mg alloy pressurelessly infiltrated into unoxidized 3D-SiC preform.The results showed that both SiC ceramic and Al alloy phases distribute evenly and form a three-dimensional mutually interpenetrated structure in the obtained interpenetrating composite.No clear brittle and harmful Al₄C₃ phase was found in the composite.The obtained interpenetrating composite contains 67vol%of SiC and has the properties of a density of 3.01 g/cm³,a relative density of 99.2%,a thermal conductivity of 224.5 W/（m·℃）,a thermal expansion coefficient（RT～300℃） of 7.04×10^-6℃^-1 and a bending strength of 277 MPa.T6 treatment further improved the overall performance of the composite having the properties of a thermal conductivity of 233.6 W/（m·℃）,a thermal expansion coefficient（RT～300℃） of 7.03×10^-6℃^-1 and a bending strength of 288 MPa.（2）Mechanical failure of components used in microelectronic systems is attributed to thermal stress involving temperature fluctuations,which can be eliminated by matching the CTE of the component parts.Low thermal expansion coefficient and high thermal conductivity 3D-SiC/Al-Si-Mg IPCs with monomodal or multimodal SiC distribution were fabricated by pressurelessly infiltrating Al-15Si-10Mg into high loading 3D-SiC preforms made from either a single size of SiC particle or mixed SiC particles with different sizes of F220,F800 and F1000 mesh,respectively.The effect of monomodal and multimodal SiC distribution on the thermal conductivity,thermal expansion coefficient and bending strength of the interpenetrating composites were carefully studied.3D-SiC/Al-Si-Mg IPCs with optimized multimodal SiC distribution showed better comprehensive properties than 3D-SiC/Al-Si-Mg IPCs with monomodal SiC distribution.The highest thermal conductivity of 233.2 W/（m·℃）and bending strength of 283 MPa as well as lower thermal expansion coefficient of 6.32×10^-6℃^-1 were obtained for the bimodal 3D-SiC_F220/800/Al-Si-Mg IPC having a total 73% volume fraction of F220 and F800 SiC.The use of finer F1000 SiC particles in the high loading 3D-SiC preforms could lead to finer SiC particles not well filling in the free space left by coarse SiC network and the forming of agglomerates,which result in the microstructural nonuniformity,excessive Mg₂Si and retained pores in the prepared interpenetrating composites causing the weakening of strength and thermal conductivity of the interpenetrating composites.A significant reduction in thermal expansion coefficient（RT～300℃） of 5.68×10^-6℃^-1 was achieved with trimodal 3D-SiC_{F220/800/1000}/Al-Si-Mg interpenetrating composite having a total 79% volume fraction of F220,F800 and F1000 SiC.（3）A new theoretical model to calculate the thermal expansion coefficient of 3D interpenetrating composite based on the thermal elasticity has been proposed which fits well with the experimental thermal expansion coefficient data of the interpenetrating composites.（4）The interfacial characteristics of the 3D-SiC/Al IPCs,including interfacial bonding between SiC reinforcement and Al alloy in composites as well as the structure and composition of interface,carry a great weight in determining the thermophysical and mechanical properties of the composite.Interface in the 3D-SiC/Al-Si-Mg IPC was modificated by using two different kinds of aluminum alloy Al-15Si-10Mg and Al-9Si-6Mg to infiltrate into the 3D-SiC preforms either unoxidized or preoxidized in air at 1000℃,1100℃ and 1200℃ for 2 h,respectively.The results showed that desired interface can be achieved in both interpenetrating composites made with those two aluminum alloys,as demonstrated by their excellent comprehensive properties.When the Al-15Si-10Mg alloy with excessive Si content is used for infiltration,interface in 3D-SiC/Al-Si-Mg IPC fabricated with the unoxidized 3D-SiC preform is directly bonded through atomic matching without any interfacial reaction.The pre-oxidation of3D-SiC preforms has negligible effect on the thermal expansion coefficient of composites,but the thermal conductivity and bending strength are weakened.When the Al-9Si-6Mg alloy with a lower Si content is used for infiltration,interface zone with a thickness around 200 nm forms in the 3D-SiC/Al-Si-Mg IPC fabricated with the 3D-SiC preform preoxidized at 1000℃.The reaction-bonded interface is composed of AlN and MgAl₂O₄,which have better interfacial affinity with SiC and can isolate SiC effectively from liquid Al against the formation of detrimental Al₄C₃ phase.The composite has the properties of a thermal conductivity of 219.5 W/（m·℃）,a thermal expansion coefficient（RT～300℃） of 7.66×10^-6℃^-1 and a bending strength of 318 MPa.更多还原