缓冲层对铜催化生长碳管形貌和性能的影响

碳纳米管的生长通常使用Fe,Co,Ni作为催化剂,除此以外的一些过渡元素也能催化裂解生长碳管。其中用铜制备的碳管阈值电场低、发射电流密度大、发射均匀性好等等良好的场发射特性。铜与硅、或金属之间具有很强的的扩散特性,而碳管应用于场发射显示器必然使用玻璃、硅片作为衬底,所以需要一层缓冲层阻挡催化剂铜扩散入衬底。本文使用磁控溅射制备铜薄膜作为催化剂,化学气相沉积方法裂解乙炔生长碳管薄膜形成场发射阴极。并试验W,Ni,Cr和Ti作为铜薄膜的缓冲层,结果表明不同的金属阻挡特性不同,生长后碳管的形貌和特性都有差异。结果表明Ti和W能很好地阻挡铜的扩散,从而使铜催化裂解出附着性好、分布均匀、密度适中、场发射特性良好的碳管薄膜。对于Ni和Cr金属,由于生长的碳管与衬底结合差或者场发射能力差而不适合作铜的缓冲层。     

《电子显微学报》征稿简则

《电子显微学报》是中国物理学会主办的学术刊物，主要刊登电子显微学和其他新兴显微学的理论研究、仪器研制生产以及在生命科学、材料科学、纳米科技、医学、金属、地质、化工、半导体等应用方面的学术论文，及时反映我国显微学领域的最新科研成果。     

《电子显微学报》征稿简则

《电子显微学报》是中国物理学会主办的学术刊物,主要刊登电子显微学和其他新兴显微学的理论研究、仪器研制生产以及在生命科学、材料科学、纳米科技、医学、金属、地质、化工、半导体等应用方面的学术论文,及时反映我国显微学领域的最新科研成果。面向的读者是从事上述领域的科学工作者、工程技术人员与大专院校师生等。     

《电子显微学报》征稿简则

《电子显微学报》是中国物理学会主办的学术刊物,主要刊登电子显微学和其他新兴显微学的理论研究、仪器研制生产以及在生命科学、材料科学、纳米科技、医学、金属、地质、化工、半导体等应用方面的学术论文,及时反映我国显微学领域的最新科研成果。面向的读者是从事上述领域的科学工作者、工程技术人员与大专院校师生等。     

《电子显微学报》征稿简则

《电子显微学报》是中国物理学会主办的学术刊物,主要刊登电子显微学和其他新兴显微学的理论研究、仪器研制生产以及在生命科学、材料科学、纳米科技、医学、金属、地质、化工、半导体等应用方面的学术论文,及时反映我国显微学领域的最新科研成果。面向的读者是从事上述领域的科学工作者、工程技术人员与大专院校师生等。     

《电子显微学报》征稿简则

《电子显微学报》是中国物理学会主办的学术刊物,主要刊登电子显微学和其他新兴显微学的理论研究、仪器研制生产以及在生命科学、材料科学、纳米科技、医学、金属、地质、化工、半导体等应用方面的学术论文,及时反映我国显微学领域的最新科研成果。面向的读者是从事上述领域的科学工作者、工程技术人员与大专院校师生等。     

《电子显微学报》征稿简则

《电子显微学报》是中国物理学会主办的学术刊物，主要刊登电子显微学和其他新兴显微学的理论研究、仪器研制生产以及在生命科学、材料科学、纳米科技、医学、金属、地质、化工、半导体等应用方面的学术论文，及时反映我国显微学领域的最新科研成果。面向的读者是从事上述领域的科学工作者、工程技术人员与大专院校师生等。     

用金属有机化合物制备铁电薄膜：工艺及进展

本文概述了以金属有机化合物为原料制备铁电薄膜的工艺过程、特点，以及最新研究进展；着重介绍了金属有机物化学气相沉积，金属有机物热分解，以及溶胶一凝胶三种制备技术在铁电薄膜制备领域中的应用。     

《电子显微学报》征稿简则

《电子显微学报》是中国物理学会主办的学术刊物,主要刊登电子显微学和其他新兴显微学的理论研究、仪器研制生产以及在生命科学、材料科学、纳米科技、医学、金属、地质、化工、半导体等应用方面的学术论文,及时反映我国显微学领域的最新科研成果。面向的读者是从事上述领域的科学工作者、工程技术人员与大专院校师生等。《电子显微学报》为双月刊,国内外发行,是国家自然科学核心期刊,中国科技论文统计源期刊（中国科技核心期刊）,中国科学引文数据库（核心期刊）（CSCID）和中国学术期刊综合评价数据库的源期刊。《中国期刊全文数据库》、《中国学术期刊（光盘版）》全文收录,美国化学文摘CA和俄罗斯文摘杂志AJ收录。一、《电子显微学报》选用刊登下列未曾发表过的文章：     

《电子显微学报》征稿简则

《电子显微学报》是中国物理学会主办的学术刊物,主要刊登电子显微学和其他新兴显微学的理论研究、仪器研制生产以及在生命科学、材料科学、纳米科技、医学、金属、地质、化工、半导体等应用方面的学术论文,及时反映我国显微学领域的最新科研成果。面向的读者是从事上述领域的科学工作者、工程技术人员与大专院校师生等。     

Characterization of plastic encapsulant materials as a baseline for quality assessment and reliability testing

This paper discusses the assessment of chemical and physical properties of nine encapsulant materials and the tests which may be used to characterize the encapsulants and to confirm that the encapsulants are of consistent quality. The tests include glass transition temperature, coefficient of thermal expansion, filler content, moisture absorption, and ionic content.     

Analytical equations for predicting the thermal properties of isotropic conductive adhesives

This paper investigates a set of theoretical equations for analyzing the thermal properties of isotropic conductive adhesives (ICAs) containing several types of Cu filler particles. The thermal conductivity of ICAs containing randomly dispersed filler particles can be simulated well by Bruggeman’s equation for spherical particles and by Kanari’s equation for flake particles. The effect on the thermal conductivity of any residual voids can be taken into account in the analysis by the additional application of Bruggeman’s or Kanari’s equations with the appropriate shape factor. The linear thermal expansion coefficient of the ICAs was analyzed using Schapery’s scheme. The thermal expansion coefficients of ICAs with 40–50 vol.% of filler particles range between Schapery’s upper and lower limits. As the particle size of the filler decreases, the thermal expansion coefficient starts to approach the lower limit at a lowr volume fraction of the filler particles. The transition behavior of the thermal expansion coefficient is related to the characteristics of the network structure formed by percolating the filler particles.     

电子封装用SnAgCuGa钎料的改性

针对SnAgCu钎料存在的熔点偏高、润湿性较差等不足,研究了不同Sb含量对SnAg3.5Cu0.7Ga1钎料性能的影响。结果表明,随着Sb含量的增加,SnAg3.5Cu0.7Ga1钎料的固液相线呈增长趋势,但均低于230℃;Sb含量添加0.5%时,SnAg3.5Cu0.7Ga1合金在240℃无卤素松香助焊剂下润湿性变化不大,当Sb含量达到1.0%以上时,SnAg3.5Cu0.7Ga1合金的润湿性随着Sb含量的增加而提高。添加少量的Sb可以提高SnAg3.5Cu0.7Ga1无铅钎料的抗氧化性,随着Sb含量的增加,产生裂纹时的循环次数依次增加,可以提高钎焊铜合金接头的热疲劳强度。     

Discrete phase method study of ball grid array underfill process using nano-silica filler-reinforced composite-encapsulant with varying filler loadings

Advanced composite-encapsulant with reinforced solid inorganic fillers dispersed in the epoxy resin is regarded as a revolutionary effort in promoting the reliability of electronic device. While various researches have been conducted to study the preparation, chemical and thermomechanical properties of composite-encapsulant using filler-reinforcement, there is however no work found on the visualization aspect of the encapsulant flow progression and filler distribution in the encapsulant. In this paper, the underfilling rheology for encapsulation process of ball grid array (BGA) will be investigated using mono-dispersed nano-silica (SiO₂) composite-encapsulant. The filler loadings will be varied in the range of 2–25 wt% (weight percent) for optimization purpose. Eventually this work is aimed to provide an in-depth understanding on the impact of the amount of nano-silica fillers being added in the epoxy resin. Finite volume method (FVM) based numerical simulation using discrete phase model (DPM) will be used in this paper. The simulation works reported that the increase in filler loadings of composite-encapsulant effectively lengthen the underfilling process by up to 22% together with a decrease in average encapsulant's pressure. Furthermore, the flow profiles revealed an asymmetry flow front that is prone to form at high filler loadings. This subsequently leads to issues associated to filler's accumulation and swirling. Given these issues, the optimization of filler loadings in composite-encapsulant is of prime importance. Accordingly, this study recommended the usage of 15 wt% of nano-silica composite-encapsulant that balances between the relatively lower filling time and with reduced issues relating to filler accumulation and swirling while preserve the improvement in reliability upon the fillers additive. Additionally, the simulation of dispersed particle in continuous fluid phase using DPM had decisively proven its mettle and is hopefully will pioneer a new viable numerical tool in the nano-filler composite polymer study of electronic packaging in near future.     

大功率LED散热用高导热硅脂的研制

以二甲基硅油为基础油,通过添加不同粒径和含量的Al、Cu、Ag、AlN、SiC和石墨,制备了单一填料的单组分以及两种填料大小搭配的二元混合导热硅脂,研究了硬脂酸表面处理、填料种类、大小及比例对导热硅脂热导率的影响,得到了以下结果:硬脂酸处理能提高单组份Al、AlN硅脂的导热性能,但不适用于提高含石墨、SiC、Cu的硅脂的性能;填料填充的最佳比例在0.55~0.60之间;以Ag微粒作为第二填料增强Al和AlN为主填料的硅脂时,对导热率的增强效果高于AlN和Cu、Ag/AlN二元混合硅脂热导率5.5W·m-1·K-1。将制备的导热硅脂用于LED散热,结果表明自制导热硅脂实际散热效果优于市购热界面材料。     

Dependence of Flip Chip Solder Reliability on Filler Settling

Thermomechanical reliability of solder joints in flip-chip packages is usually analyzed by assuming a homogeneous underfill ignoring the settling of filler particles. However, filler settling does impact flip chip reliability. This paper reports a numerical study of the influence of filler settling on the fatigue estimation of flip-chip solder joints. In total, nine underfill materials ( 35 vol% silica filler in three epoxies with three filler settling profiles for each epoxy) are individually introduced in a 2-D finite element (FE) model to compare the thermal response of flip chip solder joints that are surrounded by the underfill. The results show that the fatigue indicators for the solder joints (inelastic shear strain increments and inelastic shear strain energy density) corresponding to a gradual, nonuniform filler profile studied in this paper can be smaller than those associated with the uniform filler profile, suggesting that certain gradual filler settling profiles in conjunction with certain resin grades may favor a longer solder fatigue lifetime. The origin of this intriguing observation is in the fact that the solder fatigue indicators are a function of the thermal mismatch among the die, substrate, solder, and underfill materials. The thermal mechanics interplayed among these materials along with a gradual filler profile may allow for minimizing thermal mismatch; and thus lead to lower fatigue indicators.      

Piezoresistive Materials from Directed Shear‐Induced Assembly of Graphite Nanosheets in Polyethylene

A three‐dimensional conductive nanocomposite with an ordered conductive network and low percolation threshold has been successfully prepared by blending graphite nanosheets (GNs) with polyethylene on a two‐roll mill. The conductive nanosheets orient intensively in the composite, leading to highly anisotropic properties. The nanocomposite with the fraction of conductive nanosheets closest to the percolation threshold possesses a sharp positive pressure coefficient of resistivity, in which the abrupt transition can be attributed to compressive‐stress‐induced deformation of the conductive network. Such piezoresistive effects depend strongly on filler morphology, filler spatial arrangement, and filler concentration.     

Effects of ${hbox{CNT/BaTiO}}_{3}$ Composite Particles Prepared by Mechanical Process on Dielectric Properties of Epoxy Hybrid Films

A new type of composite filler mechanically treated with multi-walled carbon nanotubes (MWNTs) and (BT) particles was prepared to produce higher dielectric properties in the composite. The hybrid film fabricated by incorporating these composite fillers in an epoxy matrix had a high dielectric constant and similar dielectric loss as compared to the composite which contained neat BT particles. The dielectric properties of these hybrid films were found to be dependent on both the content of MWNTs and mechanical processing time. Results suggest that this novel hybrid film composed of the composite filler and the epoxy matrix can be used for embedded capacitor material.     

Improving the electrical conductivity of composites comprised of short conducting fibers in a nonconducting matrix: The addition of a nonconducting particulate filler

The addition of a second discontinuous filler (silica fume) that is essentially nonconducting to a composite with a comparably nonconducting matrix (cement) and a conducting discontinuous filler (carbon fibers) was found to increase the electrical conductivity of the composite when the conducting filler volume fraction was less than 3.2%. The maximum conducting filler volume fraction for the second filler to be effective was only 0.5% when the second filler was sand, which was much coarser than silica fume. The improved conductivity due to the presence of the second filler is due to the improved dispersion of the conducting filler. The silica fume addition did not affect the percolation threshold, but the sand addition increased the threshold.     

Fill pattern and particle distribution of underfill material

Underfills can dramatically improve flip chip reliability. However, the fillers used in some underfills can be dispersed unevenly, causing less than optimal reliability. In this study, underfill dispensing was conducted using various fill patterns. Experimental results show that particle settling occurs during the curing process, rather than during dispensing, and is affected by the difference between filler and matrix densities and underfill viscosity. Particle migration is a secondary mechanism, which causes uneven filler distribution. A vertically oriented transfer molding machine could help to mitigate settling.