共查询到20条相似文献,搜索用时 125 毫秒
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基于SEM的MLCC端电极焊接失效分析 总被引:1,自引:0,他引:1
针对多层陶瓷电容器端电极锡镀层的可焊性失效问题,运用扫描电子显微镜(SEM)分析了锡镀层的微观结构,并用能谱仪对其进行成分分析,找出了失效的主要原因:可焊性变差样品的端电极表面锡镀层出现因氧化产生的异常区域,以至于器件的可焊性变差.并通过后期的可焊性实验验证了分析的结果,找出了端电极焊接失效的原因,并提出了应对端电极氧化问题的改进措施.根据分析提出了改进意见,较好地解决了器件的焊接失效问题. 相似文献
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稀土对表面组装用Sn2.0Ag0.7CuRE钎料合金组织与性能的影响 总被引:10,自引:1,他引:10
对真空条件下制备的Sn2.0Ag0.7CuRE钎料合金显微组织、力学及物理性能进行了研究。结果表明:当稀土(RE)的添加量小于0.1%(质量分数)时,RE均匀地分布在钎料合金中,除铺展面积和延伸率与Sn37Pb钎料相当外,Sn2.0Ag0.7CuRE钎料合金的拉伸强度和导电性能均高于传统的Sn37Pb钎料;当RE添加量达到0.5%时,钎料合金中出现了明显的梅花状和点状RE化合相且弥散分布于晶界和相界附近,且拉伸强度、延伸率和铺展面积都出现了不同程度的下降。从综合性能和制造成本考虑,真空条件下制备Sn2.0Ag0.7CuRE钎料合金,RE的添加量应不大于0.1%。 相似文献
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含稀土Sn-Zn-Bi系无铅钎料润湿性能的研究 总被引:7,自引:0,他引:7
通过向Sn-Zn-Bi系钎料合金中添加适量合金元素Ga,Cu和La,制备了对Cu母材具有较好润湿性能的Sn-8.9Zn-2.7Bi-1.0Ga-0.5Cu-0.2La无铅钎料,其润湿角为25.1°。同时,还研究了无铅钎料中稀土元素La以及合金元素Ga的微量变化对钎料的润湿性及与母材金属结合界面组织结构的影响。研究发现,La和合金元素Ga的含量对Sn-Zn-Bi系无铅钎料润湿性能有较大影响,适量添加无论是在空气中还是在氮气保护下,均可以改善钎料的润湿性。 相似文献
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稀土元素在LD30铝合金真空钎焊中的作用 总被引:4,自引:1,他引:4
研究了添加La和Ce的Al-Si基钎料真空钎焊LD30铝合金接头的力学性能,微观组织形貌和EDS,并与未添加稀土元素的Al-Si基钎料真空钎焊接头进行对比。结果表明,添加稀土元素的LD30铝合金真空钎焊接头抗拉强度为288MPa,达母材抗拉强度的97.6%,明显高于未添加稀土的LD30合金真空钎焊接头。其机制在于La,Ce能够明显提高Al-Si基钎料与LD30铝合金的润湿性能,改善LD30铝合金真空钎焊接头焊缝及其基体中杂质元素的分布,促进钎料和母材中各元素的均匀扩散,从而提高真空钎焊接头的力学性能。 相似文献
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K. N. Nishchev V. V. Eliseev L. A. Emikh M. I. Novopoltsev N. E. Fomin V. A. Yudin A. N. Afanas’ev-Khodykin 《Polymer Science Series D》2012,5(3):195-198
Heat removal from electronic components in power electronic devices is provided owing to heat-spreading bases. The findings
of our studies show that the efficiency of heat removal first of all depends on the quality of joints between electronic components
and the base; a good quality is reached by soldering electronic elements to the nickel coating deposited on the base with
a sublayer made of a matrix alloy and by selecting a particular solder and flux that improve the flowing of the solder. 相似文献
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The SnPb molecule has been identified in a Knudsen effusion mass spectrometry experiment. The direct dissociation reaction and two isomolecular exchange reactions involving the Sn(2) and Pb(2) molecules have been studied, in the 1426-1705 K range of temperatures, using both second and third law procedures. The D(degree)0(SnPb,g) has been derived, for the first time, as (122.6+/-4.0) kJ mol(-1). Density functional and ab initio calculations up to the coupled clusters level of theory were also performed. In addition, the anion dissociation energy D(degree)0(SnPb(-),g) of (179.2+/-4.2) kJ mol(-1) was determined using the D(degree)0(SnPb,g) mass spectrometric value derived in this investigation and literature data. 相似文献
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Kai Zhang Sander Oldenhof Yiming Wang Jan H. van Esch Eduardo Mendes 《Angewandte Chemie (International ed. in English)》2020,59(22):8601-8607
Supramolecular assemblies are promising building blocks for the fabrication of functional soft devices for high‐tech applications. However, there is a lack of effective methods for large‐scale manipulation and integration of nano‐sized supramolecular structures on soft substrate. Now, functional soft devices composed of micellar filaments and hydrogels can be created through a versatile approach involving guided dewetting, transfer‐printing, and laser‐assisted patterning. Such an approach enables unprecedented control over the location and alignment of the micellar filaments on hydrogel substrates. As examples, freely suspended micellar fishnets immobilized on hydrogels are formed, showing the capability of trapping and releasing micro‐objects and the piconewton force sensitivity. By incorporating responsive moieties into hydrogels, shape‐morphing actuators with micelle‐controlled rolling directionality are constructed. 相似文献
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Periodic soft nanostructures are building blocks for small devices. However, mechanical failure in the form of structure buckling or distortion from their original shape is often reported when the dimension of these soft structures were reduced to below submicron scale. Such a phenomenon seriously limits a reliable impact of these nanostructures to greater applications. Current understandings of buckling of soft 2-D nanostructures are limited. The substrate for these soft nanostructures is usually very compliant. Neighboring nanostructures could interact through the deformation of the substrate. We analyze the collective buckling of a two-dimensional array of nanoscale columns with their lower ends built into an elastic substrate. Buckling of these nanostructures is mathematically described by an eigenvalue problem. Numerical analyses show patterned collapse for these 2-D nanostructures, qualitatively matching reported experimental findings. Our efforts are useful toward the understanding and manufacturing of many two-dimensional nanoscale features. 相似文献
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William J. Plumbridge 《Monatshefte für Chemie / Chemical Monthly》2005,136(11):1811-1821
Summary. For environmental reasons, lead has to be removed from solder alloys used for interconnection purposes in electronics equipment.
A new series of alloys, mainly based upon tin, and often containing copper and silver, has been evolved by empirical reasoning.
A more theoretical approach is now being pursued, using thermodynamic principles, to produce the second generation of solder alloys.
The paper outlines the soldering process, the requirements of solder alloys, and the various mechanisms (such as overload,
fatigue, creep, and thermomechanical fatigue) that are potential causes of failure in service. It also describes from the
manufacturing and the performance perspectives, the physical and mechanical properties necessary for reliable solder joints.
These include conductivity, melting point, strength, ductility, and thermal stability of microstructure. The challenging question
is posed as to how can thermodynamics contribute to prescribing and developing an improved series of alloys? 相似文献
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William J. Plumbridge 《Monatshefte für Chemie / Chemical Monthly》2005,53(6):1811-1821
For environmental reasons, lead has to be removed from solder alloys used for interconnection purposes in electronics equipment.
A new series of alloys, mainly based upon tin, and often containing copper and silver, has been evolved by empirical reasoning.
A more theoretical approach is now being pursued, using thermodynamic principles, to produce the second generation of solder alloys.
The paper outlines the soldering process, the requirements of solder alloys, and the various mechanisms (such as overload,
fatigue, creep, and thermomechanical fatigue) that are potential causes of failure in service. It also describes from the
manufacturing and the performance perspectives, the physical and mechanical properties necessary for reliable solder joints.
These include conductivity, melting point, strength, ductility, and thermal stability of microstructure. The challenging question
is posed as to how can thermodynamics contribute to prescribing and developing an improved series of alloys? 相似文献
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Fabrication of microfluidic systems in poly(dimethylsiloxane) 总被引:40,自引:0,他引:40
McDonald JC Duffy DC Anderson JR Chiu DT Wu H Schueller OJ Whitesides GM 《Electrophoresis》2000,21(1):27-40
Microfluidic devices are finding increasing application as analytical systems, biomedical devices, tools for chemistry and biochemistry, and systems for fundamental research. Conventional methods of fabricating microfluidic devices have centered on etching in glass and silicon. Fabrication of microfluidic devices in poly(dimethylsiloxane) (PDMS) by soft lithography provides faster, less expensive routes than these conventional methods to devices that handle aqueous solutions. These soft-lithographic methods are based on rapid prototyping and replica molding and are more accessible to chemists and biologists working under benchtop conditions than are the microelectronics-derived methods because, in soft lithography, devices do not need to be fabricated in a cleanroom. This paper describes devices fabricated in PDMS for separations, patterning of biological and nonbiological material, and components for integrated systems. 相似文献
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PDMS微流体系统的加工制作 总被引:1,自引:0,他引:1
目前,微流体装置越来越多地应用到分析系统、生物医学、化学等基础研究领域。传统的微流体系统制作方法是对玻璃和硅片进行刻蚀。用软刻法制作PDMS(Poly(dimethylsiloxane):聚二甲基硅氧烷)微流体装置比传统的制作方法更快速,成本更低廉,并且对于通道的密封也不需要玻璃或硅芯片键合密封等复杂工艺。这类软刻法的核心技术是快速原样制作法和复制压模技术。相对于微电子加工工艺,软刻法制作过程不需要超静环境,化学家和生物学家可在普通的实验室实现加工制作。本文介绍了PDMS微装置在分离和生物材料模式化等方面的应用。 相似文献
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Lead free solders are increasingly being used in electronic applications. Eutectic Sn-Cu solder alloy is one of the most favored lead free alloys used for soldering in electronic applications. It is inexpensive and principally used in wave soldering. Wetting of liquid solder on a substrate is a case of reactive wetting and is accompanied by the formation of intermetallic compounds (IMCs) at the interface. Wettability of Sn-0.7Cu solder on metallic substrates is significantly affected by the temperature and the type of flux. The wettability and microstructural evolution of IMCs at the Sn-0.7Cu solder/substrate interfaces are reviewed in the present paper. The reliability of solder joints in electronic packaging is controlled by the type and morphology of interfacial IMCs formed between Sn-0.7Cu solder and substrates. The formation and growth mechanisms of interfacial IMCs are highlighted. Mechanical behavior of bulk solder alloy and solder joint interfaces are analyzed. The characteristics of the IMCs which have marked effect on the mechanical properties and fracture behavior as well as reliability of solder joints of the alloy are discussed. An attempt has also been made to discuss the effect of cooling rate and strain rate on shear strength, tensile properties and creep resistance of the solder alloy. It is recommended that future work should focus on evolving a standard procedure involving sequential assessment of wetting behavior, evolution of IMCs and mechanical properties. 相似文献