共查询到20条相似文献,搜索用时 218 毫秒
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1.55微米波段GaAs基近红外长波长材料在光纤通讯,高频电路和光电集成等领域有潜在的应用价值。本文用分子束外延方法研究了GaAs基异变InAs量子点材料的生长,力图实现在拓展量子点发光波长的同时保持或增加InAs量子点的密度。在实验中,首先优化了In0.15GaAs异变缓冲层的生长,研究了生长温度和退火对减少穿通位错的作用。在此基础上,优化了长波长InAs量子点的生长。最终在GaAs基上获得了温室发光波长在1491nm,半高宽为27.73meV,密度达到4×1010cm-2的InAs量子点。 相似文献
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通过优化分子束外延生长条件,得到室温发光在1300nm低密度的自组织InAs/GaAs量子点.使用极低的InAs生长速率(0.001单层/秒)可以把量子点的密度降低到4×106cm-2.这些结果使得InAs/GaAs量子点可以作为单光子源应用在未来的光纤基量子密码、量子通信中. 相似文献
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用X射线双晶衍射方法测定了自组织生长的InAs/GaAs量子点的摇摆曲线,根据Takagi-Taupin方程对曲线进行了拟合。在考虑量子点层晶格失配的情况下,理论曲线和实验曲线符合得很好,从而确定了量子点垂直样品表面的失配度,约为4~6%,这与宏观连续体弹性理论的预测相近。结合电镜、原子力显微镜的观察结果表明对子单层沉积方法获得的量子点层采用化合物构层进行拟合所得结果是合理的。 相似文献
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采用分子束外延(MBE)法,在优化Ge衬底退火工艺的基础上,通过对比在(001)面偏<111>方向分别为0°、2°、4°和6°的Ge衬底上生长的GaAs薄膜,发现当Ge衬底的偏角为6°时有利于高质量GaAs薄膜的生长;通过改变迁移增强外延(MEE)的生长温度,发现在GaAs成核温度为375℃时,可在6°偏角的Ge衬底上获得质量最好的GaAs薄膜。通过摸索GaAs/Ge衬底上InAs量子点的生长工艺,实现了高效的InAs量子点光致发光,其性能接近GaAs衬底上直接生长的InAs量子点的水平。 相似文献
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陈英鑫黄晓莹杨灼辉钟汉城宋长坤刘林喻颖余思远 《真空科学与技术学报》2023,(3):210-218
半导体量子点因其具有类原子的分立能级结构,可在三维方向上对载流子运动进行束缚,因此被认为是光发射器件(激光器、量子光源等)极具前景的有源物质之一。其器件的性能强烈依赖于量子点材料的品质、光场与量子点偶极子场的有效相互作用等。本文将从半导体InAs/GaAs自组织量子点的可控分子束外延生长调控技术出发,进一步探讨应用于光通信、片上光互联领域的量子点激光器,以及应用于光量子信息领域的高品质量子光源器件。 相似文献
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Issues related to the implementation of Pb-free electronic solders in consumer electronics 总被引:2,自引:0,他引:2
D. R. Frear 《Journal of Materials Science: Materials in Electronics》2007,18(1-3):319-330
Consumer electronic applications are the primary target of the Pb-free initiative and package assembly and performance is
affected by the move from eutectic Sn–Pb to Pb-free solder alloys. This paper outlines the key issues and mitigation possibilities
for package assembly using Pb-free solders: High temperature reflow, Interfacial reactions, and Reliability. At the high temperatures
required to reflow Pb-free alloys, moisture absorbed into the package can result in delamination and failure. The reaction
of the Pb-free solder with Ni and Cu metallizations results in interfacial intermetallics that are not significantly thicker
than with Sn–Pb but provide a path for fracture under mechanical loading due to the increased strength of the Pb-free alloys.
The reliability issues discussed include thermomechanical fatigue, mechanical shock, electromigration and whiskering. The
Pb-free alloys tend to improve thermomechanical fatigue and electromigration performance but are detrimental to mechanical
shock and whiskering. Design trade-offs must be made to successfully implement Pb-free alloys into consumer applications. 相似文献
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Syahira Annuar Mohd Hamdi King-Ning Tu 《Science and Technology of Advanced Materials》2013,14(1):693-703
AbstractThe high performance and downsizing technology of three-dimensional integrated circuits (3D-ICs) for mobile consumer electronic products have gained much attention in the microelectronics industry. This has been driven by the utilization of chip stacking by through-Si-via and solder microbumps. Pb-free solder microbumps are intended to replace conventional Pb-containing solder joints due to the rising awareness of environmental preservation. The use of low-volume solder microbumps has led to crucial constraints that cause several reliability issues, including excessive intermetallic compounds (IMCs) formation and solder microbump embrittlement due to IMCs growth. This article reviews technologies related to 3D-ICs, IMCs formation mechanisms and reliability issues concerning IMCs with Pb-free solder microbumps. Finally, future outlook on the potential growth of research in this area is discussed. 相似文献
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Michael Osterman Abhijit Dasgupta 《Journal of Materials Science: Materials in Electronics》2007,18(1-3):229-236
The transition from lead (Pb) bearing solder to Pb-free solder has arisen in response to government restrictions on the use
of lead (Pb) by the European Union. As a result, electronic manufacturers have sought a material comparable to the conventional
63Sn37Pb solder that has been traditionally used to assemble electronic hardware. Based on extensive review of various solder
combination, the majority of electronic manufacturers appear to be adopting a tin–silver–copper (SAC) solder as a popular
Pb-free solder replacement. Significant investments have been made by many researchers to characterize the material behavior
and durability of this solder system. While the exact composition of the SAC solder is still in question, it now appears that
the 96.5Sn3.0Ag0.5Cu (SAC305) solder is gaining wider acceptance as the favored Pb-free replacement, for surface mount assemblies
that are going to be subjected predominantly to cyclic thermal environments. This paper presents a review of our current understanding
of the life expectancy of Pb-free SAC solder interconnects for electronic hardware. To this end, the paper focuses on material
characterization of SAC solder, as well as its temperature cycling and vibration fatigue reliability. From this review, SAC
solder interconnects are shown to be suitable for providing adequate life expectancies for temperature cycling in electronic
hardware. However, it is clear that there are differences between SAC and the conventional Sn37Pb solder, that need to be
understood in order to design reliable electronic hardware. 相似文献
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Iver E. Anderson 《Journal of Materials Science: Materials in Electronics》2007,18(1-3):55-76
The global electronic assembly community is striving to accommodate the replacement of Pb-containing solders, primarily Sn–Pb
alloys, with Pb-free solders due to environmental regulations and market pressures. Of the Pb-free choices, a family of solder
alloys based on the Sn–Ag–Cu (SAC) ternary eutectic (T
eut. = 217°C) composition have emerged with the most potential for broad use across the industry, but the preferred (typically
near-eutectic) composition is still in debate. This review will attempt to clarify the characteristic microstructures and
mechanical properties of the current candidates and recommend alloy choices, a maximum operating temperature limit, and directions
for future work. Also included in this review will be an exploration of several SAC + X candidates, i.e., 4th element modifications
of SAC solder alloys, that are intended to control solder alloy undercooling and solidification product phases and to improve
the resistance of SAC solder joints to high temperature thermal aging effects. Again, preliminary alloy recommendations will
be offered, along with suggestions for future work. 相似文献
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《Materials Science & Technology》2013,29(3):257-273
AbstractSince 2006 and the implementation of environmental regulations, the electronic industry has moved to Pb-free solders. Harsh environment industries that were exempted from the regulations will soon have to follow suit. However, a suitable replacement solder for use in harsh environments still has to be validated and reliability models are yet to be established. In this review, research that led to the selection of currently used Pb-free alloys and the continuing search for high reliability alloys are described. Sn pest and Sn whiskers, potential major threats for electronics operating in harsh environments, are highlighted. This review also focuses on the microstructure, mechanical properties and deformation mechanisms of Pb-free alloys. Emphasis is placed on Sn–Ag–Cu alloys, now considered to be the alloys of choice for replacement of Sn–Pb solders. The reliability of Pb-free electronic assemblies is studied, focusing on thermal fatigue, believed to be the main source of failure through creep–fatigue mechanisms. The validity of models for Pb-free solder joints life time prediction is assessed and the lack of cohesiveness among the available reliability data is examined. 相似文献
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Lead-free Solders in Microelectronics 总被引:91,自引:0,他引:91
Practically all microelectronic assemblies in use today utilize Pb–Sn solders for interconnection. With the advent of chip scale packaging technologies, the usage of solder connections has increased. The most widely used Pb–Sn solder has the eutectic composition. Emerging environmental regulations worldwide, most notably in Europe and Japan, have targeted the elimination of Pb usage in electronic assemblies, due to the inherent toxicity of Pb. This has made the search for suitable “Pb-free” solders an important issue for microelectronics assembly. Approximately 70 Pb-free solder alloy compositions have been proposed thus far. There is a general lack of engineering information, and there is also significant disparity in the information available on these alloys. The issues involved can be divided into two broad categories: manufacturing and reliability/performance. A major factor affecting alloy selection is the melting point of the alloy, since this will have a major impact on the other polymeric materials used in microelectronic assembly and encapsulation. Other important manufacturing issues are cost, availability, and wetting characteristics. Reliability related properties include mechanical strength, fatigue resistance, coefficient of thermal expansion and intermetallic compound formation. The data available in the open literature have been reviewed and are summarized in this paper. Where data were not available, such as for corrosion and oxidation resistance, chemical thermodynamics was used to develop this information. While a formal alloy selection decision analysis methodology has not been developed, less formal approaches indicate that Sn-rich alloys will be the Pb-free solder alloys of choice, with three to four alloys being identified for each of the different applications. Research on this topic continues at the present time at a vigorous pace, in view of the imminence of the issue. 相似文献
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Rare-earth additions to lead-free electronic solders 总被引:5,自引:0,他引:5
The research in lead(Pb)-free solder alloy has been a popular topic in recent years, and has led to commercially available
Pb-free alloys. Further research in certain properties to improve aspects such as manufacturability and long term reliability
in many Pb-free alloys are currently undertaken. It was found by researchers that popular Pb-free solders such as Sn–Ag, Sn–Cu,
Sn–Zn and Sn–Ag–Cu had improved their properties by doping with trace amounts of rare earth (RE) elements. The improvements
include better wettability, creep strength and tensile strength. In particular, the increase in creep rupture time in Sn–Ag–Cu–RE
was 7 times, when the RE elements were primarily Ce and La. Apart from these studies, other studies have also shown that the
addition of RE elements to existing Pb-free could make it solderable to substrates such as semiconductors and optical materials.
This paper summarizes the effect of RE elements on the microstructure, mechanical properties and wetting behavior of certain
Pb-free solder alloys. It also demonstrates that the addition of RE elements would improve the reliability of the interconnections
in electronic packaging. For example, when Pb-free-RE alloys were used as solder balls in a ball grid array (BGA) package,
the intermetallic compound layer thickness and the amount of interfacial reaction were reduced. 相似文献
18.
The dominant materials used for solders in electronic assemblies over the past 60 years have been Pb–Sn alloys. Increasing pressure from environmental and health authorities has stimulated the development of various Pb-free solders. One of the most promising replacements is eutectic or near-eutectic Sn–Ag–Cu alloys produced by electrodeposition. In this study, simple and “green” Sn–Cu-citrate solutions with suspended Ag particles have been developed and optimized for electrochemical composite deposition of eutectic and near-eutectic Sn–Ag–Cu solder films. Different plating conditions, including solution concentration, current density, agitation and additives, are investigated by evaluating their effects on plating rate, deposit composition and microstructure. 相似文献
19.
The preparation of solder joints in electronic applications is not easy because the solder is soft and often surrounded by hard and brittle materials. Smearing, scratching, and structural changes caused by the preparation as well as destruction of the specimens during preparation due to their filigree geometries make the procedure demanding. A sequence has been developed that enables the preparation of soft solder under these difficult circumstances. The preparation and the development of the phases found in solder is explained step by step and illustrated with examples. 相似文献
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Karl J. Puttlitz George T. Galyon 《Journal of Materials Science: Materials in Electronics》2007,18(1-3):331-346
The European Union enacted legislation, the ROHS Directive, that bans the use of lead (Pb) and several other substances in electronic products commencing July 1, 2006. The legislation recognized that in some situations no viable alternative Pb-free substitute materials are known at this time, and so provided exemptions for those cases. It was also recognized that certain electronic products, specifically servers, storage and storage array systems, network infrastructure equipment and network management for telecommunication equipment referred to as high-performance electronic products, perform tasks so important to modern society that their operational integrity had to be maintained. The introduction of new and unproven materials posed a significant potential reliability risk. Accordingly, the European Commission (EC) granted an exemption permitting the continued use of Pb in solders, independent of concentration, for high-performance (H-P) equipment applications. This exemption was primarily aimed at assuring that the reliability of solder joints, particularly flip-chip solder joints is preserved. Flip-chip solder joints experience the most severe operating conditions in comparison to other applications that utilize Pb in electronic equipment. This paper briefly describes the solder-exempted H-P electronic products, their capabilities, and some typical tasks they perform. Also discussed are the major attributes that differentiate H-P electronic equipment from consumer electronics, particularly in relation to their operational and reliability requirements. Interestingly, other than the special solder exemption accorded to H-P electronic equipment, these products must meet all the other requirements for ROHS compliancy. The EC was aware that issues would surface after the legislation was enacted, so it created the Technical Advisory Committee (TAC) to review industry-generated requests for exemptions. The paper discusses three exemption requests granted by the EC that are particularly relevant to H-P electronic products. The exemptions allow the continued use of lead-bearing solder materials. 相似文献