机械背钻孔制作技术研究浅谈简

PCB制造过程中镀通孔可当作是线路来看,某些镀通孔端部的无连接,这将导致信号的折回,共振也会减轻,可能会造成信号传输的反射、散射、延迟等,给信号带来“失真”的问题,通过背钻技术,对减少孔链路损耗越有利和更能保证信号的完整性。文章主要介绍了机械背钻和背钻孔镀铜控制两个方面的制作经验,以供同行业参考。     

三角形谱啁啾光纤光栅在光栅传感系统中的应用

利用三角形谱啁啾光纤布拉格光栅（T-CFBG）的反射和时延特性,提出了一种新的基于相位检测的FBG解调方案。该方案由光强来确定传感器光栅反射波长的相位延迟角范围,由相位检测来确定在该范围的相位延迟角大小,两者结合给卅传感光栅的反射波长,因此具有更高精度和更大波长检测范围。实验制作了宽带宽具有三角形反射谱的T-CFBG,并对其用于传感解调予以了模拟分析。     

光模块中刚柔线路板电连接宽带阻抗匹配研究

文章分别对光收发组件中50 Ω柔性线路板和50 Ω刚性线路板,以及25Ω柔性线路板和50Ω刚性线路板间的电互连阻抗匹配进行了设计、仿真与实验验证.对于50 Ω_50 Ω刚柔板的高频连接,通过对其返回路径的通孔位置优化设计,使反射损耗Su在高频段降低约11％,插入损耗S21减小190％;对于25 Ω_50 Ω刚柔板的高频连接,提出新的优化方式:在硬板信号线的金手指上做通孔设计,并提取该结构的寄生参数,构建电路模型.该结构大幅提高了连接处容性阻抗,降低了阻抗失配,使得S11在高频段降低约38.2％,S21减小约34％.提出的柔性线路板与刚性线路板的电互连方式,能实现传输线间的阻抗匹配,减小信号反射和插入损耗,提高光模块传输质量,对于光器件的接入具有较大应用价值.     

导通孔设计对高速信号完整性的影响

当今的高速数字电路设计中,印制板上传输线轻微的不连续问题都必须认真对待,特别是被广泛使用的导通孔。随着频率的增长和信号上升沿的变陡,导通孔带来的阻抗不连续会引起信号的反射,严重影响系统的性能和信号完整性。文章用全波电磁仿真软件HFSS,对多种导通孔结构进行了全面的研究。通过建模仿真,分析了导通孔直径,导通孔长度和多余的导通孔短柱几种关键设计参数对信号完整性的影响。此研究对高速数字设计者深入理解导通孔设计有一定意义。     

差分过孔的高频特性仿真分析

为满足差分过孔在高速PCB中低反射、高传输和阻抗稳定的设计要求,提出了短柱和非功能焊盘的优化设计方法,并给出了建模仿真与理论分析。采用HFSS软件对12层PCB中差分过孔进行三维建模与仿真,并使用ADS软件对仿真结果进行了眼图分析,结果表明:钻除短柱可以有效改善差分过孔的高频传输特性,其中信号反射的能量减少了79.1%,传输的能量增加了82.1%;移除非功能焊盘可以进一步改善差分过孔的高频特性,其中反射的能量减少了14.46%,传输的能量增加了14.13%。     

基于Anand模型的柔性直流输电用IGBT模块焊接应力变形分析

IGBT模块直接覆铜(DBC)基板与底板进行回流焊接过程中,由于材料热膨胀系数不匹配,会产生较大翘曲与残余应力,影响模块可靠性.针对某柔性直流(VSC-HVDC)输电用大功率IGBT模块,基于有限元法,根据实际真空回流焊温度曲线,对比分析了Al2O3/Cu、AlN/AISiC和Si3N4/AlSiC 3种陶瓷衬板与底板组合的焊接翘曲变形与残余应力分布.结果 表明相对于Cu底板,采用AlSiC底板能有效降低底板翘曲与残余应力.相较于Si3N4陶瓷衬板,AlN陶瓷衬板与AlSiC底板的热膨胀系数匹配度更高,焊接后翘曲与残余应力最小.测试结果表明,AlN/AlSiC组合的仿真与实测变形量基本一致,测量范围内长边和短边方向误差分别为5.9％和5.6％.     

新型低阻抗、可复位的过电流保护器POLYSWITCH TSM600-400

泰科电子旗下的Raychem电路保护部宣布推出低阻抗、可复位的过电流保护器件P o l y S w i t c hTSM600-400,用于通信基础设施各项应用的过电流保护。该器件符合有害物质限制使用标准(R o H S),可帮助通信设备满足目前全球适用的电信标准,还可用于符合国际电信联盟(ITU-T)K.21和K.21建议标准的通信系统。表面贴装式P o l y S w i t c hTSM600-400器件具有小尺寸和低阻抗的特点,设计用于高密度多端口线卡和其它空间有限的通信网络设备。TSM600-400器件在一个单一包装中采用了两个配对的低阻抗PPTC部件,因此具有高平衡阻抗的特点。…     

能带匹配对β-FeSi2(n)/ c-Si(p)太阳能电池转化效率的影响

运用AFORS-HET软件对TCO/β-FeSi2(n)/a-Si(i)/ c-Si(p)/ μc-Si(p )型太阳能电池各层结构之间的能带匹配进行了模拟。模拟结果表明,透明导电氧化膜与n型层间的能带匹配对太阳能电池的转化效率、开路电压和填充因子有较大影响,可以通过能带匹配有效地提高太阳能电池的转化效率。导带补偿会阻碍少数载流子的输运,界面态会加快少数载流子在界面的复合,降低导带失配,从而有利于提高太阳能电池的转化效率。衬底与背场的界面电场可以提高太阳能电池的转化效率。     

铟泰公司推出Indium5．PAT无铅焊膏

电子装配工业需要的设备越来越小，但要求功率更大、能力更好、可靠性更高。需要的产品重量轻，体积小，但又必须便于携带，坚固耐用。制造商必须面对一个事实，即这些高密度互联设备的输入和输出数目越来越多，使互联部位出现空洞的可能性也随之增大。对于采用底板内微通孔设计的BGA／CSP元件来说，空洞是一个关系到可靠性的严重问题。为了解决这一问题，需要新的焊膏技术。铟泰公司与主要的PCB装配顾客合作制成了Indium5．1AT无铅焊膏。     

多层微波集成电路中微带线层间互连仿真

针对多层微波集成电路设计的微带线层间互连问题,介绍了垂直通孔互连、垂直带条互连和层耦合过渡互连三种高性能的互连方法,并且采用三维电磁仿真软件HFSS对这三种互连结构进行了建模和仿真.仿真结果表明,垂直通孔互连和垂直带条互连在0.1~25 GHz的频宽范围内,回波损耗S11<-20 dB,插入损耗S21>-1 dB,互连性能优良,而层耦合过渡互连在20~68 GHz内回波损耗S11<-20 dB,插入损耗S21>-1 dB,具有在毫米波频段实现互连的潜力.     

Design Tables for a Class of Optimum Microwave Bandstop Filters (Correspondence)

Element value tables for optimum microwave bandstop filters consisting of quarter-wave spaced shunt open-circuited stubs are given. Both the stubs and the connecting unit elements contribute to the attenuation response. The tables give element values for 0.01dB, 0.10 dB, and 0.25 dB ripple Chebyshev designs with up to twenty-three elements, and for bandwidths between 30 percent and 150 percent.     

Open- and short-circuit terminated series stubs in finite-widthcoplanar waveguide on silicon

Open- and short-circuit terminated series stubs in finite-width coplanar waveguide (FCPW) fabricated on high-resistivity Si are experimentally characterized over the frequency range of 2-40 GHz. In coplanar waveguide (CPW), these stubs are typically placed in the center conductor, but in FCPW, the stubs may also be placed in the ground planes resulting in novel circuit elements with characteristics that make the stubs useful for matching circuits and filters. Equivalent circuit models for the stubs are presented, and it is shown that when the stub is in the ground plane the resonant frequency is equal, the inductance and resistance is halved, and the capacitance is double the values of the same stub in the center conductor. Furthermore, it is shown that by varying the stub position in the ground plane, higher Q stubs can be obtained     

Efficient object-oriented integration and regression testing

This paper presents a model, a strategy and a methodology for planning integration and regression testing from an object-oriented model. It shows how to produce a model of structural system test dependencies which evolves with the refinement process of the object-oriented design. The model (test dependency graph) serves as a basis for ordering classes and methods to be tested for regression and integration purposes (minimization of test stubs). The mapping from unified modeling language to the defined model is detailed as well as the test methodology. While the complexity of optimal stub minimization is exponential with the size of the model, an algorithm is given that: computes a strategy for integration testing with a quadratic complexity in the worst case; and provides an efficient testing order for minimizing the number of stubs. Various integration strategies are compared with the optimized algorithm (a real-world case study illustrates this comparison). The results of the experiment seem to give nearly optimal stubs with a low cost despite the exponential complexity of getting optimal stubs. As being a part of a design-for-testability approach, the presented methodology also leads to the early repartition of testing resources during system integration for reducing integration duration     

Stub-Loaded Long-Wire Monopoles Optimized for High Gain Performance

A technique to realize stub-loaded monopoles with enhanced gain performance is introduced in this paper. The omnidirectional high gain is achieved by combining an electrically long monopole with stubs attached at optimal locations along the antenna. In general, the lengths of the stub-loaded monopoles presented in this paper are significantly longer than conventional quarter-wave monopoles. Long wires alone do not provide the desired gain and VSWR performance; the stubs connected to the long monopole are vital in realizing simultaneous high gain and low VSWR at the intended operating frequency. A genetic algorithm (GA) is employed to optimize the locations and lengths of each of the stubs required to meet the design objectives. The results of this work show that between 11 and 12 dBi of gain can be obtained when the stub-loaded monopoles are placed over an infinite ground plane, whereas 8 dBi is obtained for one example when sited over a finite ground plane. A prototype of an optimized stub-loaded monopole was fabricated and tested. Excellent agreement was achieved between the measured and simulated results.     

Stripline Triplexer for Use in Narrow-Bandwidth Multichannel Filters (Short Papers)

Design techniques and equivalent circuits are presented for constructing a printed-circuit narrow-bandwidth complementary triplexer filter. The techniques and circuits described allow the construction of contiguous-band multichannel filters using printed circuits with no shorted stubs. A unit was designed and constructed to give a three-percent relative bandwidth for each separate channel. The agreement between theory and experiment was in the range of measurement accuracy.     

Ladder-shaped network for ESD protection of millimetre-wave CMOS ICs

A compact ladder-shaped electrostatic discharge (ESD) protection circuit is presented for millimetre-wave integrated circuits (ICs) in CMOS technology. Multiple shorted shunt stubs form a ladder network together with series stubs as ESD protection that discharges current/voltage pulses caused by an ESD event, while at the same time the network is embedded as part of the matching circuit for a normal operation. A 60 GHz low-noise amplifier using a 90 nm CMOS process is demonstrated with the proposed ESD protection methodology that introduces less than 1 dB insertion loss. Owing to the ESD current distribution through multiple shorted stubs, the proposed methodology is useful to millimetre-wave ICs with advanced CMOS technology that suffers from higher sheet resistance of the metal layers.     

A Superconducting Microstrip Ultra-Wideband (UWB) Bandpass Filter at VHF-Band

A compact superconducting ultra-wideband filter with a passband from 125 to 260 MHz is demonstrated. The filter consists of ten shunt short-circuited stubs separated by connecting lines. The short-circuited stubs are grounded via a grounding strip that is attached to the box wall by a number of SiAl bonding wires. The filter is realized on two 2 in YBCO/LaAlO₃ substrates, which are connected by two bonding wires. The measured results demonstrate an insertion loss of less than 0.08 dB and a return loss of better than 21 dB without tuning. Furthermore, the experimental results of the filter are in good agreement with the simulated ones.     

Knowledge-Based Artificial Neural Network Models for Microstrip Radial Stubs

Radial stubs are a superior choice over low characteristic impedance rectangular stubs in terms of providing an accurate localized zero-impedance reference point and maintaining a low input impedance value over a wide frequency range. In this paper, knowledge-based artificial neural networks are used to model the microstrip radial stubs. Using space-mapping technology and Huber optimization make the neural network models for radial stubs decrease the number of training data, improve generalization ability, and reduce the complexity of the neural network topology with respect to the classical neuromodeling approach. The neural networks are developed for design and optimization of radial stubs, which are robust both from the angle of time of computation and accuracy.     

Miniaturized ring coupler of arbitrary reduced size

A simple and successful method for miniaturizing a ring coupler is proposed. The size of the ring coupler is reduced by connecting multiple open stubs on the inside of the ring. There is no need of any lumped element, via hole or wire bond, but only microstrip lines. The reduced size is arbitrary and the results of the miniaturized ring coupler coincide with that of the traditional one.     

Compact microstrip bandpass filter with two transmission zeros using a stub-tapped half-wavelength line resonator

A compact microstrip bandpass filter is developed using a half-wavelength (/spl lambda//2) transmission line resonator with a pair of tap-connected open-ended stubs. Such paired stubs with total length of about /spl lambda//2 constructs an equivalent line resonator. Together with two separated /spl lambda//4 line resonators, the three transmission poles can be achieved inside the passband. Meanwhile, two stub lengths are adjusted slightly longer and shorter than /spl lambda//4 to realize the two transmission zeros at both low and high rejection bands. Further, the long tapped-stub is kept wider than its short counterpart to improve the low rejection behavior. A filter sample is designed and fabricated to provide an experimental verification on the proposed filter.