粉末冶金法制备AlSiC电子封装材料及性能

采用粉末冶金法制备了一定粒径分布的SiC颗粒体积分数不同的AlSiC电子封装复合材料。实验结果表明:材料微观组织致密,颗粒分布均匀。复合材料的平均热膨胀系数、热导率和弯曲强度都随SiC含量的增加而降低,抗弯断口以脆性断裂为主要断裂模式。     

热循环对SiCp/Al复合材料性能影响的研究

SiCp/Al复合材料具有可调的热膨胀系数(CTE)、高热导率、低密度和良好的尺寸稳定性等优异性能,广泛应用于航空航天、军用电子等封装领域,由于SiCp/Al复合材料制成的组件工作环境较为苛刻,温度变化对其影响值得探讨。文章研究了热循环对SiCp/Al复合材料的CTE、热导率和弯曲强度的影响,并对其热膨胀行为作了分析。实验结果表明,热循环能有效降低SiCp/Al中的热残余应力,其热性能比铸态明显改善,弯曲强度有所降低;在低温阶段,经退火处理和退火处理+热循环处理后SiCp/Al的CTE基本重合,在高温阶段,经退火处理+热循环处理后的SiCp/Al具有更低的CTE。     

电子封装用AlSiC复合材料热导率影响因素探讨

采用模压成型和真空压力浸渗工艺制备了高体积分数SiC增强Al基复合材料(AlSiC)。物相和显微结构研究结果表明,此种方法制备的AlSiC复合材料,组织致密且大小两种粒径的SiC颗粒均匀分布于Al基质中,界面结合强度高;SiC增强颗粒与Al基质界面反应控制良好,未出现Al4C3等脆性相。在此基础上,研究了基体金属、粘结剂用量、粗细SiC颗粒比例对复合材料热导率的影响。结果表明,以1A90高纯铝为基体的复合材料的热导率高于以6061铝合金为基体的复合材料的热导率;粘结剂用量减少时,复合材料热导率提高;当SiC体积分数一定时,AlSiC复合材料的热导率随增强体中粗颗粒SiC比例增大而增大。     

SiCp/Al复合材料在电子封装应用中的基础研究

采用挤压铸造方法,制备了高体积分数的SiC增强铝基复合材料。经扫描电镜分析,复合材料颗粒分布均匀,材料组织致密。通过改变铝合金成分与SiC含量,SiCp/Al复合材料材料热膨胀系数介于(6.9~9.7)106℃1之间可调,热导率大于120 W/(m·℃),材料的比强度、比模量高。对材料表面涂覆性能进行了可行性研究,得到了实用的Ni和Cu镀层。     

SiC增强Al基复合材料的制备和性能

采用模压成型和真空压力浸渗工艺制备了高体积分数SiC增强Al基复合材料(AlSiC)。物相和显微结构研究结果表明,此种方法制备的AlSiC复合材料,组织致密且大小两种粒径的SiC颗粒均匀分布于Al基质中,界面结合强度高;SiC增强颗粒与Al基质界面反应控制良好,未出现Al4C3脆性相。对Al4C3相形成机理进行了分析,指出6061铝合金中的Si元素和真空压力浸渗工艺条件有利于防止脆性相Al4C3的形成。热性能测试结果表明,随温度升高,复合材料热膨胀系数先增大后减小,315℃附近出现最大值。所获得复合材料的平均热膨胀系数为7.00×10-6℃-1,热导率为155.1W/mK,密度为3.1g/cm3,完全满足高性能电子封装材料的要求。     

SiC质量分数对超声辅助激光熔化沉积AlSi30基复合材料组织和性能的影响

采用超声波辅助激光熔化沉积法制备SiC_p/AlSi30复合材料，研究SiC质量分数对铝基复合材料相组成、微观组织及力学性能的影响规律。当SiC的质量分数小于10%时，液态铝合金与SiC颗粒之间未发生界面反应，陶瓷颗粒保持原始的形态。当SiC的质量分数达到15%时，部分SiC颗粒与熔融的铝合金反应形成了针状的Al₄SiC₄。SiC增强相的加入促进了硅相的非均匀形核，导致初生硅尺寸的细化。由于高硬度增强相的加入和晶粒细化的共同作用，质量分数10%碳化硅颗粒增强AlSi30复合材料的力学性能得到提高，其显微硬度与未增强的AlSi30合金相比提高了25.3%。此外，质量分数10%SiC_p/AlSi30的摩擦因数和磨损率与超声波辅助激光熔化沉积法制备的纯AlSi30合金相比分别降低了19%和25%,复合材料磨损性能得到提高。     

碳化硅纳米线的形貌和微结构TEM表征

由于SiC纳米线优越的力学、热学及电学性能和高的物理、化学稳定性、热导率、临界击穿电场、电子饱和迁移率等特性，一维SiC纳米线在高温、高频、大功率和高密度集成电子器件等方面具有巨大的应用潜力；也可作为塑料、金属和陶瓷等复合材料的增强相，同时也是人们研究低维材料的物理、力学性能与尺寸效应的典型材料。     

高体积分数SiCp/2024Al基复合材料添加Ti-6Al-4V中间层激光焊接特性

高体积分数SiCp/2024Al基复合材料由于大量增强相颗粒的存在,在熔化焊接过程中Al基体极易与SiC颗粒反应,生成Al4C3金属间化合物,严重降低焊缝的力学性能。以Ti-6Al-4V金属薄片作为中间层填充材料,采用氩气作为保护气体,对SiC体积分数为45%的SiCp/Al基复合材料进行激光焊接,分析SiCp/Al基复合材料的焊接特性。结果表明,填充钛合金材料进行CO2激光焊接时接头组织致密,结合较好,在焊缝组织中获得了以Ti3Al为基体、Ti5Si3和TiC等反应产物为增强相的焊缝组织,所获得的最高抗拉强度为母材的50%左右。     

热处理对SiCp／Al尺寸稳定性的影响

采用真空压力浸渗技术制备了两种不同体积分数的SiCp／Al复合材料,研究了热处理工艺对复合材料尺寸稳定性的影响,并对其影响因素进行了分析。结果表明：残余应力的存在对复合材料的尺寸稳定性有着重要的影响;退火和固溶时效处理能提高复合材料的尺寸稳定性,与铸态相比,在100MPa下复合材料的残余应变降低了60％,而淬火处理对复合材料的尺寸稳定性不利。     

中科院物理所成功研制6英寸碳化硅单晶衬底

碳化硅(SiC)单晶是一种宽禁带半导体材料,具有禁带宽度大、临界击穿场强大、热导率高、饱和漂移速度高等诸多特点,被广泛应用于制作高温、高频及大功率电子器件。此外,由于SiC和氮化镓(GaN)的晶格失配小,SiC单晶是GaN基LED、肖特基二极管、MOSFET、IGBT、HEMT等器件的理想衬底材料。为降低器件成本,下游产业对SiC单晶衬底提出了大尺寸的要求,目前国际市场上已有6英寸(150mm)产品,预计市场份额     

不同WC含量下WC/Cu复合材料弹性模量实验研究

为了研究数字图像相关方法运用于小试样下WC/Cu复合材料弹性模量测定的准确性,采用粉末冶金法制备出了WC含量不同的WC/Cu复合材料,对试件表面用白漆配合碳粉方法进行制斑,并在万能材料试验机上进行拉伸实验,用CCD相机记录其散斑图。对记录的散斑图进行相关运算,并通过畸变校正理论校正位移计算结果,计算出小应变范围内WC/Cu复合材料的应力应变曲线,得到弹性模量;与传统电测方法结果进行对比,数据吻合较好。结果表明,采用数字图像相关方法和小试件制斑方法运用于WC/Cu复合材料弹性模量的测定是较为精确可靠的。     

天然鲜胶乳制备蒙脱土/NR纳米复合材料的结构与性能

采用多溶剂分散法制备片层尺寸达微、纳米级蒙脱土,并与天然鲜胶乳混合制备蒙脱土/天然橡胶复合材料,用扫描电镜研究蒙脱土结构及其在复合材料中的分布,并测定其力学性能.结果表明,通过多溶剂分散法可制备片层厚度为100nm～200nm的蒙脱土;在蒙脱土填充量为7%时,复合材料500%定伸应力从6.96MPa提高到11.22MPa;加入2%蒙脱土,复合材料拉伸强度从17.71MPa提高到21.01MPa;在4%填充量下,拉伸强度达23.56MPa,体现蒙脱土纳米增强效应.材料扯断伸长率随蒙脱土填充量增加而下降的幅度小,复合材料保持高弹性.复合材料硬度在蒙脱土填充量为8%时达到稳定值.上述结果表明,天然鲜胶乳可与蒙脱土直接复合,制备高性能天然橡胶复合材料.     

SiCp/A390复合材料中析出相的形貌及界面结构演变

采用快速凝固的A390铝合金粉体和SiC颗粒,通过粉末冶金法+热挤压工艺制备了SiCp/A390复合材料,并对复合材料进行了T6处理,利用扫描电镜(SEM)、透射电镜(TEM)及高分辨透射电镜(HRTEM)对复合材料时效过程中第二相的析出形貌及界面结构进行了表征,测定了复合材料的力学性能,探讨了析出相的演变规律、析出相与基体的界面结构及其对力学性能的影响.结果表明:SiCp/A390复合材料经固溶+时效处理后,合金元素从基体中析出形成GP区,然后转变为颗粒状的δ″相.随着时效时间的延长,这些颗粒状δ″相继续长大成δ′相和δ相;同时,时效析出相与基体之间界面结构随时效时间的延长发生着转变,其转变规律为:完全共格界面GP区→共格界面的δ″相→半共格界面δ′相→非共格界面δ相;SiCp/A390复合材料的抗拉强度随着时效时间延长先增加后降低,在时效6h时,复合材料的力学性能达到最大值.     

High‐Strength Laminated Copper Matrix Nanocomposites Developed from a Single‐Walled Carbon Nanotube Film with Continuous Reticulate Architecture

A critical challenge in nanocomposite fabrication by adding SWCNTs as reinforcement is to realize an effective transfer of the excellent mechanical properties of the SWCNTs to the macroscale mechanical properties of the matrix. Using directly grown SWCNT films with continuous reticulate structure as the template, Cu/SWCNTs/Cu laminated nanocomposites are fabricated by an electrodepositing process. The resulting Cu/SWCNTs/Cu laminated nanocomposites exhibit extremely high strength and Young's modulus. The estimated Young's modulus of the SWCNT bundles in the composite are between 860 and 960 GPa. Such a high strength and an effective load‐transfer capacity are ascribed to the unique continuous reticulate architecture of SWCNT films and the strong interfacial strength between the SWCNTs and Cu matrix. Raman spectroscopy is used to characterize the loading status of the SWCNTs in the strained composite. It provides a route to investigate the load transfer of SWCNTs in the metal matrix composites.     

Analysis of copper grains in damascene trenches after rapid thermal processing or furnace anneals

The microstructures of Cu lines in damascene trenches annealed at temperatures from room temperature to 425°C using both rapid thermal processing (RTP) and furnace annealing were investigated using an array of characterization techniques including transmission electron microscopy (TEM), focused ion beam, scanning electron microscopy (SEM), and electron backscatter diffraction-orientation-imaging microscopy (EBSD-OIM). It was found that the final grain sizes strongly depend on the annealing process used; RTP generated larger grains than furnace annealing. The Cu line electrical resistance correlated with grain size differences observed for RTP and furnace anneals. The ramping rate, not the annealing time, played the critical role in the grain growth process. In either case, a high density of Σ3 coincident site lattice (CSL) twin boundaries was observed in the Cu lines. Forty-five percent of the grain boundaries measured were found to be Σ3 CSL twins, which are differentiated from random high-angle boundaries by having preferred electrical and diffusion properties. The minimum feature dimension of width or height of the damascene trenches limited the average grain size. Prior to the trench height limitation, the average grain size increased linearly with the trench width. The Cu (111) texture became stronger as the trench width increased up to 0.5 μm; for wider trenches, the texture did not increase further.     

The structural,optical, and electrical properties of vacuum evaporated Cu-doped ZnTe polycrystalline thin films

We have studied the structural, optical, and electrical properties of thermally evaporated, Cu-doped, ZnTe thin films as a function of Cu concentration and post-deposition annealing temperature. X-ray diffraction measurements showed that the ZnTe films evaporated on room temperature substrates were characterized by an average grain size of 300Å with a (111) preferred orientation. Optical absorption measurements yielded a bandgap of 2.21 eV for undoped ZnTe. A bandgap shrinkage was observed for the Cu-doped films. The dark resistivity of the as-deposited ZnTe decreased by more than three orders of magnitude as the Cu concentration was increased from 4 to 8 at.% and decreased to less than 1 ohm-cm after annealing at 260°C. For films doped with 6–7 at.% Cu, an increase of resistivity was also observed during annealing at 150–200°C. The activation energy of the dark conductivity was measured as a function of Cu concentration and annealing temperature. Hall measurements yielded hole mobility values in the range between 0.1 and 1 cm²/V·s for both as-deposited and annealed films. Solar cells with a CdS/CdTe/ZnTe/metal structure were fabricated using Cudoped ZnTe as a back contact layer on electrodeposited CdTe. Fill factors approaching 0.75 and energy conversion efficiencies as high as 12.1% were obtained.     

SiCp/6061Al复合材料激光表面熔化及合金化显微组织与耐蚀性

为提高颗粒增强铝基复合材料耐蚀性，对ＳｉＣｐ／６０６１Ａｌ复合材料进行激光表面熔化和激光表面合金化。结果表明：激光表面熔化后，因熔化层中形成大量耐蚀性低的针状Ａｌ_４Ｃ_３相及Ａｌ_４ＳｉＣ相而使激光表面熔化层耐蚀性降低，以Ｎｉ－Ｃｒ－Ｂ粉末为原料对ＳｉＣｐ／６０６１Ａｌ复合材料进行激光表面合金化后，合金层耐蚀性明显提高。     

Evaluation of the nanoindentation behaviors of SiGe epitaxial layer on Si substrate

In this paper, ultra-high vacuum chemical vapor deposition (UHV/CVD) was employed to synthesize silicon-germanium (SiGe), and sequence to endure annealing treatment. Morphological characterization, roughness, and microstructural morphology were observed by means of scanning electron microscopy (SEM), atomic force microscopy (AFM), and transmission electron microscopy (TEM). The elements distribution, crystallographic, and nanomechanical behavior were carried out using energy-dispersive X-ray spectroscopy (EDS) mapping technique, X-ray diffraction (XRD), and nanoindentation technique.The annealing treated SiGe leads to the 2D germanium segregation on the surface. The phenomenon is interpreted in terms of dislocation-induced structural changes in annealing treatment. Thus, the dislocation propagation in the microstructure was observed. Subsequently hardness and elastic modulus were increased because of a comparatively unstable microstructure after annealing treatment.