表面贴装封装发光二极管的结构设计

为了提高表面贴片封装(SMD)发光二极管(LED)封装结构的封装效率,根据LED的光学结构和性质,建立了简化的SMD LED封装结构模型,并实现了LED封装结构的连续自动生成、仿真和优化。仿真结果表明:在色温相同的条件下,光通量和辐射通量呈线性关系,侧壁的改变会造成白光光通量先增加后减少的趋势。通过对3款不同侧壁张角的LED进行测试,测试结果与仿真结果光通量趋势相同,并得到了对于这种封装方式的最佳侧壁张角为60°的结论,验证了仿真的正确性。     

超声显微检测技术在电子封装中的应用与发展

超声显微检测技术应用于电子封装领域始于上世纪80年代,如今已是检测电子封装可靠性和完整性的重要手段,被广泛应用到了电子封装的缺陷检测和精密测量等方面。针对电子封装的超声显微检测存在回波重叠、信噪比低等问题,近年来,发展了许多时频分析方法,用于获得优于常规方法的纵向分辨率,即实现超分辨率。本文首先介绍了超声显微检测的发展历史,对其检测原理和分辨率理论进行了简述;其次,综述了超声显微检测技术在电子封装中的主要应用与发展现状;然后,对超声显微检测的超分辨率成像方法进行了综述,分别介绍了基于小波分析的反卷积、连续小波变换和稀疏表示在实现超分辨率时的原理及适用场景;最后,探讨归纳了电子封装超声显微检测的主要研究方向及难点。     

边缘重构对锯齿型石墨烯纳米带电子输运的影响

实验研究表明石墨烯纳米带中广泛地存在边缘结构重构且稳定的边缘缺陷结构.本文采用第一性原理的计算方法研究了锯齿型石墨烯纳米带中边缘结构重构形成的两种不同缺陷结构对材料电子输运性能的影响.研究发现两种缺陷边缘结构对稳定纳米尺度位型结构和电子能带结构具有显著影响,它使得费米能级发生移动并引起了共振背散射.两种边缘缺陷重构均抑制了费米能级附近电子输运特性并导致不同区域的电子完全共振背散射,电导的抑制不仅与边缘缺陷结构的大小有关,它更取决于边缘缺陷重构位型引起的缺陷态的具体分布和电子能带的移动.     

基于图像数据封装包文的数据采集方法

针对如何在工业应用中找到一种实现周期更短和更低成本的图像数据采集方法进行了研究。通过分析以太网帧格式和JPEG图像数据特点,给出了一种对JPEG图像帧进行分片并对分片进行数据封装的方法,在此基础之上实现了基于图像数据封装包文的数据采集设计。最后在FPGA环境中对该设计进行了实现,此实现成功应用到了工程项目当中。实践表明,基于图像数据封装包文的数据采集方法能够在不添加外置存储器等复杂器件的情况下实现稳定的、实时的JPEG图像数据采集。     

不同封装方式对肖特基二极管高频性能的影响

肖特基二极管是太赫兹接收机的关键器件,通过在高频下对不同封装形式的肖特基二极管进行建模仿真,研究不同封装方式对肖特基二极管性能的影响。首先通过建立肖特基二极管的仿真模型,在高频结构仿真软件HFSS中对肖特基二极管在0~120GHz频段进行仿真,得到该肖特基二极管的S参数,并对S参数仿真结果和实测结果进行对比,证明了该二极管模型的准确性。然后分别建立肖特基二极管的普通封装模型和肖特基二极管的倒装芯片(flip-chip)封装模型,并对这两种封装模型进行仿真,得到其在两种不同封装结构下的S参数,进而对两种不同封装方式的S参数的-3dB带宽以及相位一致性进行对比分析。最终,对应用于太赫兹波段的肖特基二极管由于封装不同而带来的带宽以及相位的区别及其成因进行分析,论证了flipchip封装更适合应用于太赫兹波段的肖特基二极管,与普通封装相比,该封装在高频下对肖特基二极管的电性能有比较大的改进。     

基于预应力的超低温漂光纤光栅封装技术实验研究

提出了一种基于预应力的超低温漂光纤光栅封装方法并进行了实验测试,通过分析光纤光栅的应力和温度交叉作用的原理,结合硬铝材料和石英管材料不同的膨胀系数,在光纤光栅上施加预应力的结构来解决光纤光栅温度补偿问题;通过设计和制作含预应力的封装结构产生负温度效应的方法,使封装的光纤光栅实现光纤光栅中心波长超低温度漂移。实验结果表明:在温度为20～80℃的测试范围内,这种封装结构可实现光纤光栅0.0002nm/℃的超低温度漂移,而且具有良好的稳定性和一致性。     

SEM扫描云纹法的相移技术研究

提出一种扫描电镜(SEM)扫描云纹法的相移新技术,通过SEM系统控制电镜电子束扫描线移动,对获取的云纹图像实现0-2π范围内的四步相移,从而获得了更高的位移测量灵敏度。同时对SEM扫描云纹法的测量原理以及相移实验技术的原理进行了详细的阐述。并将该技术应用到电子封装试件栅的相移分析中。实验结果证明了该方法的可行性,该方法为微米云纹法的条纹处理提供了一种新途径。     

高k介质栅材料电子辐照下的红外研究

本文研究了SiO_2/Si、SiNX/Si、Al_2O_3/Si这三种具有不同介电常数(k)栅介质材料结构在1.7 MeV电子辐照前后的傅里叶红外光谱。随着辐照剂量的增大,三种结构的吸收峰强度均随之减小,其振动模式受到影响。电子辐照SiO_2/Si结构后,振动吸收峰随着辐照剂量的增大,由Si-O-Si、Si-O键引起的伸缩振动吸收峰的位置向低波数移动。电子辐照SiNX/Si结构后,由Si-N键、Si-O键引起的伸缩振动吸收峰的位置向高波数移动。电子辐照Al_2O_3/Si结构后,由Al_2O_3的晶格振动,Al-O-Al键引起的伸缩振动吸收峰的位置向高波数移动。吸收峰的变化为电子辐照不同介质材料引入的缺陷提供了新的信息。     

光纤光栅边孔封装技术

提出了一种新型的光纤光栅压力增敏封装技术——边孔封装技术,它通过改变封装体的几何结构实现了高倍数的压力增敏效果,较大程度减小了压力增敏倍数对聚合物材料参量的依赖性。采用有限元理论建立了边孔封装结构的压力传感模型,分析了封装体几何结构变化对封装后压力灵敏度的影响。采用聚合物材料进行了封装制作实验,测量结果表明封装后光纤光栅的压力灵敏度为5251 pm/MPa,是封装前压力灵敏度的1750倍,并将交叉敏感问题改善了近三个数量级,可满足高精度水下压力测量的应用要求。     

后栅结构四针状纳米ZnO场致发射显示器的研制

为了解决二极结构FED驱动电压高的问题,设计制作了后栅式三极结构纳米ZnO场致发射显示器,进行了场致发射实验,验证这种结构的可行性。采用丝网印刷厚膜技术实现后栅极结构FED的制作,工艺简单,实现了较低电压的调制。对影响场致发射性能的栅极电压、阳极电压进行了分析讨论。将阴栅极板和荧光屏封装成5英寸三极结构的场致发射显示器,实现了稳定的场致电子发光显示。     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Hybrid Wavelength and Code Division Multiple Access in Optical Networks

A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Research on beamforming method for dual-line array with space mismatch between the two line arrays

The performance of port/starboard discrimination of dual-line array will be seriously degraded when the space between the two line arrays of the dual-line array is mismatched. The directivity function of the delay-sum and delay-subtract beamforming is deduced and the port/starboard discrimination of the delay-sum and delay-subtract beamforming is also studied both under the ideal status and the status under which the space between the two line arrays of the dual-line array is mismatched. Analysis results show the delay-subtract beamforming has better performance of port/starboard discrimination. At last, the sea trial results demonstrate the theoretical results.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Retrieval of ultraviolet skylight radiances and O3 slant column densities from balloon-borne limb spectrometer

With a novel light-weight and absolutely calibrated ultraviolet （UV） spectrometer, UV skylight radiances and O3 slant column densities are measured by balloon-borne limb measurements in Xinjiang area, China. UV skylight radiances measured at the height of 31 km are compared with the results from Modtran in the wavelength range from 290 to 420 nm. O3 slant column densities are derived from radiance spectra in the Huggins bands （320 - 335 nm） using differential optical absorption spectroscopy method. And the parameter exhibits a good correlation with the same value simulated by radiative transfer model （Tracy）. The O3 profile simultaneously measured by an O3 sonde is used as input in Tracy calculations. The O3 sonde is launched on the same balloon.     

Design optimization of highly sensitive LSPR enhanced surface plasmon resonance biosensors with nanoholes

For breaking through the sensitivity limitation of conventional surface plasmon resonance (SPR) biosensors, novel highly sensitive SPR biosensors with Au nanoparticles and nanogratings enhancement have been proposed recently.But in practice, these structures have obvious disadvantages.In this study, a nanohole based sensitivity enhancement SPR biosensor is proposed and the influence of different structural parameters on the performance is investigated by using rigorous coupled wave analysis (RCWA).Electromagnetic field distributions around the nanohole are also given out to directly explain the performance difference for various structural parameters.The results indicate that significant sensitivity increase is associated with localized surface plasmons (LSPs) excitation mediated by nanoholes.Except to outcome the weakness of other LSP based biosensors, larger resonance angle shift, reflectance amplitude, and sharper SPR curves' width are obtained simultaneously under optimized structural parameters.     

Polymer gratings based on photopolymerization for low-order distributed feedback polymer lasers

Novel polymer distributed feedback(DFB)gratings are fabricated based on photopolymerization to reduce lasing threshold of polymer lasers.A photopolymer formulation sensitive to 355-nm ultraviolet(UV)light is proposed for the fabrication of polymer gratings and it can be used to form polymer films by spin-coating process.A very low surface-relief depth ranging from 12.5 to about 1.0 nm has been demonstrated with a refractive-index modulation of about 0.012.The experimental results indicate that such polymer gratings have promising potentials for the fabrication of low-order DFB organic semiconductor lasers.