Detection of broadband signals in frequency and time dispersivechannels

A major problem for active sonar systems operating in shallow water is reverberation. High time-bandwidth waveforms and coherent matched filtering are often used to improve detection performance in reverberation. However, an active sonar echo undergoes distortion during the two-way propagation and reflection from the target. As a result, the full performance gain is not achievable, and this approach is severely limited. In this case, more robust detectors are needed. We evaluate the detection performance of several commonly used detectors in an ideal nondistorting channel, a fast-fading distortion (FFD) channel, and a channel with time-spreading distortion (TSD). We examine the robustness of the various detectors by evaluating the performance in the case of mismatch between the detector and the channel parameters. Studying the relation between the FFD model and the TSD, we show that, under certain conditions, the TSD and FFD channels have an equivalent effect on the waveform     

Exponential parameter estimation an the presence of knowncomponents and noise

In the determination of the natural modes of an electromagnetic scatterer, the measured time series will contain desired information, noise, and quite often known transient components introduced by the excitation source or measuring equipment. This paper describes a linearly constrained total least squares (LCTLS)-Prony method for extracting the exponential model parameters from observed transient data. For such problems, the TLS criterion yields better parameter estimates than LS. Moreover, the incorporation of known signal information via constraints leads to even greater improvements in performance. Mathematical connections between LCTLS-Prony and a TLS variation of time series deflation (TSD) are used to derive constraints for higher order excitation poles. Also, we use TSD concepts to derive numerically superior data transformations For LCTLS. Simulation studies involving idealized test data and synthetic scattering response data of a perfectly conducting sphere demonstrate the advantages of the method     

n型4H-SiC材料中位错的电学特性研究

研究位错的电学特性对于研究器件可靠性具有重要意义.文章利用拉曼散射技术在室温条件下研究了n型4H-SiC材料中位错电学特性.结果表明:螺型位错(TSD)、刃型位错(TED)的电子浓度均高于无位错区,且TSD电子浓度高于TED.结合位错结构分析认为:TED中心的半原子面存在不饱和Si键,该键通过吸附电子使其饱和并达到稳定状态,因此TED中心俘获了比无位错区更多的电子;TSD结构中,位错区域原子间的拉应力导致该区域Si原子电负性增高,因而俘获电子形成比无位错区高的电子分布.     

环氧塑封料中填充剂的作用和发展

环氧塑封料占据整个半导体封装市场的90％左右,而填充剂含量占环氧塑封料的60％～90％,因此填充剂的性能直接影响环氧塑封料的加工性能、机械性能、导热性能和半导体器件的封装工艺性能、导热性能、可靠性能等。另外,当今社会电子技术日新月异,集成电路正向着超大规模、超高速、高密度、大功率、多功能、绿色环保化的方向发展,因此对环氧塑封料的性能要求愈来愈高,相应的填充剂性能也有了许多新的要求,并且也出现了许多新型填充剂。文中详细地介绍了环氧塑封料中填充剂的作用,各种填充剂对环氧塑封料和封装器件的性能影响以及环氧塑封料中填充剂的分类和发展。     

New hybrid electronic molding compounds

This paper describes the performance characteristics of a new class of electronic molding compounds for semiconductor encapsulation. These new materials are identified as silicone-epoxy hybrid polymers. They were evaluated by testing integrated circuits molded in the hybrid system and comparing these results with those obtained with current state-of-the-art commercial silicone and epoxy molding compounds. Results are given for long-term life testing under environmental conditions of high temperature/high humidity and salt atmosphere. Temperature humidity bias data on linear integrated circuits tested by a semiconductor manufacturer are also presented. The effects of temperature and humidity on the molded plastic as measured by moisture absorption and dimensional stability are shown.     

Optimal structure of sensor systems composed of nonidentical sensors

The sensor system has two types of contradictory failures; a fail-dangerous failure and a fail-safe failure. A method of obtaining the optimal structure is developed for the sensor system which is composed of general components. The optimal structure minimizes an expected damage, considering all possible boolean structures including noncoherent systems. A simple optimality criterion is obtained and several properties of the optimal structures are derived; a noncoherent structure can be optimal in some cases. A simple systematic search algorithm can be used effectively to determine the optimal system. Analytic solutions are obtained for systems composed of identical components. Illustrative examples are given.     

Adhesion evaluation on low-cost alternatives to thermosetting epoxy encapsulants

The thermosetting epoxy curing systems have been widely used as encapsulants in the electronic packaging industry. With the continual evolving of electronic product markets, material suppliers have been challenged to provide more options to meet the requirements of advanced, yet cost effective, packaging solutions. In this paper, two low-cost alternative materials have been investigated experimentally regarding their adhesion and reliability performance, and these have then been compared with the thermosetting epoxy systems. One of the materials is thermoplastic bisphenol A epoxy/phenoxy resin, and the other is an interpenetrating polymer network composed of an epoxy curing component and a free radical polymerizable component. Some formulations of the materials being studied could exhibit excellent adhesion, durability and application reliability. While reworkability is expected for these materials, they are promising as cost effective encapsulants for electronic packaging, and may be applied with appropriate processing techniques.     

Optimization of Epoxy-Barium Titanate Nanocomposites for High Performance Embedded Capacitor Components

One of the most promising avenues to meet the requirements of higher performance, lower cost, and smaller size in electronic systems is the embedded capacitor technology. Polymer-ceramic nanocomposites can combine the low cost, low temperature processability of polymers with the desirable electrical and dielectric properties of ceramic fillers, and have been identified as the major dielectric materials for embedded capacitors. However, the demanding requirements of mechanical properties and reliability of embedded capacitor components restrict the maximum applicable filler loading (<50vol%) of nanocomposites and thereby limit their highest dielectric constants (<50) for real applications. In this paper, we present a study on the optimization of the epoxy-barium titanate nanocomposites in order to obtain high performance, reliable embedded capacitor components. To improve the reliability of polymer-ceramic nanocomposites at a high filler loading, the epoxy matrix was modified with a secondary rubberized epoxy, which formed isolated flexible domains (island) in the continuous primary epoxy phase (sea). The effects of sea-island structure on the thermal mechanical properties, adhesion, and thermal stress reliability of embedded capacitors were systematically evaluated. The optimized, rubberized nanocomposite formulations had a high dielectric constant above 50 and successfully passed the stringent thermal stress reliability test. A high breakdown voltage of 89MV/m and a low leakage current of about 1.9times10^-11A/cm² were measured in the large area thin film capacitors     

环氧树脂灌封材料的增韧研究

抗冲击精密电子元器件用灌封材料往往需要具有好的韧性.在综合考虑灌封材料力学性能与灌封工艺性的基础上,采用自制带液晶基团聚酯型环氧树脂对环氧树脂E-51进行了增韧改性研究.结果表明,优化配方的增韧型环氧树脂灌封材料在保持自身较高压缩强度的同时,抗冲击强度提高了4.1倍,且具有良好的灌封工艺性,其在25℃条件下的适用期(凝...     

单层圆片带引线元件的片式化实现

介绍了在单层陶瓷圆片的基础上实现单层陶瓷圆片带引线元件的片式化。即将陶瓷芯片夹于上下连体扁平引线中间并焊接,模塑环氧树脂封装,再分割切开引线,使切开后的扁平引线贴在外壳表面,得到了用单层圆片制成的片式结构元件。已开发出CCH单层塑封型片式高压瓷介电容器、CCF单层塑封型片式交流瓷介电容器、ZVD单层塑封型片式氧化锌压敏电阻器产品,其结构坚固牢靠、防潮性能好、散热性能好、可靠性高,适应用于SMT生产。     

Autonomic Healing of Epoxy Vinyl Esters via Ring Opening Metathesis Polymerization

A materials system for autonomic healing of epoxy vinyl esters is demonstrated. The system is comprised of wax microspheres containing Grubbs' catalyst and microcapsules containing exo‐dicyclopentadiene (DCPD) embedded together in an epoxy vinyl ester matrix. Healing is triggered when damage in the form of a crack ruptures the microcapsules, causing DCPD to be released into the crack plane where it comes in contact and mixes with the catalyst microspheres initiating ring opening metathesis polymerization (ROMP). The chemical compatibility of the catalyst with the matrix is investigated and wax protection of the catalyst via microspheres of a sufficient size (34–98 μm) is shown to provide a suitable barrier for protecting the catalyst from free radicals generated in situ during the curing of the epoxy vinyl ester resin. Wax protection of the catalyst also allows uninhibited curing of the matrix to proceed at room temperature. Concentration of self‐healing components is varied with a view towards optimization of the recovery of virgin mechanical properties. Efficient self‐healing is observed with microspheres that are smaller than those used in previous polymer matrices. Significant recovery of virgin mechanical properties is observed within 2.5 min of healing time at room temperature and the mechanical properties of healed samples after 24 h of healing time match those of existing ROMP‐based self‐healing systems.     

Redundancy optimization for series-parallel multi-state systems

This paper generalizes a redundancy optimization problem to multi-state systems, where the system and its components have a range of performance levels-from perfect functioning to complete failure. The components are: (1) chosen from a list of products available in the market; and (2) characterized by their nominal performance level, availability and cost. System availability is represented by a multi-state availability function, which extends the binary-state availability. To satisfy the required multi-state system availability, the redundancy for each component can be used. A procedure which determines the minimal-cost series-parallel system structure subject to a multi-state availability constraint is proposed. A fast procedure is developed, based on a universal generating function, to evaluate the multi-state system availability. Two important types of systems are considered and special operators for the universal generating function determination are introduced. A genetic algorithm is used as an optimization technique. Examples are given     

活性酯固化环氧基高介电常数覆铜板的研制简

当前各界对于天线设计的重点在于小型化、结构简单化及多频或宽带。高介电常数基板可以缩小微波辐射波长,达到天线小型化的目的。采用活性酯作为环氧树脂的固化剂,活性酯固化剂分子中有两个或多个具有较高活性的酯基,可以同环氧树脂进行固化反应。在同环氧树脂反应时形成不含仲醇羟基的网架,所以固化后的环氧树脂具有低的介电损耗和吸水率。采用高介电常数填料作为功能填料。研制的高介电常数覆铜板具有低的热膨胀系数、低的介电损耗和低的吸水率。     

Adhesion Enhancement Between Electroless Copper and Epoxy-based Dielectrics

The adhesion between electrolessly deposited copper and an epoxy-containing dielectric material has been investigated. In particular, the role of mechanical anchoring and chemical bonding in these systems has been examined. The contribution of each of these mechanisms to adhesion has been identified. Probelec, a phenolic-novolac epoxy polymer, and Avatrel, an addition polymerized norbornene polymer with an epoxy side-group, have been tested in this study. Traditional swell and etch treatments have been used to enhance mechanical anchoring through pore-type roughness development on the phenol-novolac epoxy, but were found to be ineffective in roughening the Avatrel surface. The critical difference between the two polymers is the epoxy-backbone (for the phenolic epoxy) versus the epoxy side-group (for the norbornene backbone polymer). In order to create roughness on the Avatrel surface, a novel technique utilizing a blend of Avatrel and Probelec was investigated. This technique created pore-type roughness and enhanced mechanical anchoring on the Avatrel surface. ${rm NH}_{3}$ plasma treatments were utilized to enhance the chemical bonding contribution to adhesion and produce surfaces with peel strengths of 0.15–0.25 N/mm with minimal roughness generation. Finally, a combined wet-chemical and plasma treatment protocol was investigated to enhance chemical bonding and mechanical anchoring on the same surface. Samples with adhesion greater than 0.5 N/mm with roughness less than 50 nm were produced with both Avatrel and Probelec. Through the use of a combined wet-chemical and plasma-surface treatment the polymer surface has been optimized for adhesion while minimizing roughness.      

On testing trained vector quantizer codebooks

This paper discusses a criterion for testing a vector quantizer (VQ) codebook that is obtained by "training". When a VQ codebook is designed by a clustering algorithm using a training set, "time-average" distortion, which is called the training-set-distortion (TSD), is usually calculated in each iteration of the algorithm, since the input probability function is unknown in general and cumbersome to deal with. The algorithm stops when the TSD ceases to significantly decrease. In order to test the resultant codebook, validating-set-distortion (VSD) is calculated on a separate validating set (VS). Codebooks that yield small difference between the TSD and the VSD are regarded as good ones. However, the difference VSD-TSD is not necessarily a desirable criterion for testing a trained codebook unless certain conditions are satisfied. A condition that is previously assumed to be important is that the VS has to be quite large to well approximate the source distribution. This condition implies greater computational burden of testing a codebook. In this paper, we first discuss the condition under which the difference VSD-TSD is a meaningful codebook testing criterion. Then, convergence properties of the VSD, a time-average quantity, are investigated. Finally we show that for large codebooks, a VS size as small as the size of the codebook is sufficient to evaluate the VSD. This paper consequently presents a simple method to test trained codebooks for VQ's. Experimental results on synthetic data and real images supporting the analysis are also provided and discussed.     

高性能嵌入电容元件用的最佳环氧-钛酸钡纳米复合物

概述了旨在获得高性能和可靠的嵌入电容元件的最佳环氧-钛酸钡（BaTiO3）纳米复合物。为了在高填充量下改善聚合物-陶瓷纳米复合物的可靠性，采用仲橡胶处理的环氧进行环氧基体的改性，在连续的原环氧相（海洋）中形成隔离的柔性区域（岛屿）。系统地评估了海洋-岛屿结构对嵌入电容元件的热机械性质，附着性和热应力可靠性的影响。最佳的橡胶处理的纳米复合物组成具有50以上的高介质常数，成功地通过了严格的热应力可靠性试验。大面积的薄膜电容器测得89MV／m的高击穿电压和约为1．9×10^-11A／cm^2的低漏电流。     

塑封电子元器件破坏性物理分析方法

目前塑封电子元器件得到广泛的应用,但它本身的质量问题却使得关键系统和模块中很少采用塑封电子元器件,而作为验证电子元器件的设计、结构、材料和制造质量的破坏性物理分析至今还没有形成标准或方法,还不能有效地应用到塑封电子元器件的可靠性验证中。根据塑封电子元器件的特点和主要的缺陷形式,给出塑封电子元器件破坏性物理分析的参考方法,并为将来塑封电子元器件破坏性物理分析标准或方法的制定打下基础。     

基于改进遗传算法的双频滤波器自动设计

双频滤波器(Daul-band Filter)广泛应用于各类无线通信系统。采用K-Medoids聚类算法对种群进行分类,对选择、交叉和变异等环节进行算法改进,在不预先确定滤波器结构的情况下,对滤波器的结构和元件参数进行全局优化,自动配置滤波器内部结构及其元件参数,不依赖先验数据而获得最优解。通过C程序实现算法,并在Matlab软件中计算结果,用ADS验证了设计结果,证明了该方法适用于工程应用。     

环氧树脂对环氧模塑料(EMC)的性能影响分析

在环氧模塑料中,环氧树脂是环氧模塑料的基体树脂,也是环氧模塑料的主要原材料,起着将其他组分交联结合到一起的重要作用。环氧树脂作为环氧模塑料的胶粘剂,具有粘合性高、固化收缩率小、耐化学介质稳定性好、电绝缘性优良、工艺性能良好等特点。因此环氧树脂类型的选择及其性能对环氧模塑料的性能都有很大的影响。文章简单介绍了环氧树脂的分类、结构、作用及特点,主要探讨了不同结构环氧树脂对环氧模塑料的粘接性、稳定性、收缩率、电性能及机械性能等的影响。