简介:近几年,电子产品朝轻,薄,短,小化迅速发展,印制线路板也随着这股潮流朝向高密度封装方向发展。尤其是积层板总数的增加和导通孔以及连接盘的小径化也日益显著。对于积层线路板而言,用来加工层间连接的盲通孔(BVH)的激光方法取决于导通孔和连接盘径。激光器分为CO2激光和UV-Yag激光两种。导通孔径为60μm以上时,则一般用CO2激光加工。由于铜在CO2激光的波长(9.3μm~10.3μm)领域中的吸收比很低,因此"保形法"(在表面铜箔上,蚀刻出需要的加工孔径(开铜窗),再以激光打掉树脂)成为了现在的主流。然而,由于保形法需要蚀刻开铜窗,因此增加了形成图形的工序,而且导通孔的定位取决于下层的定位标记,容易发生错位。随着积层板层数的增加,导通孔和连接盘的小径化发展,越来越需要提高加工速度和定位精度。因此,同时对铜和树脂进行加工的"直接钻孔法"开始被关注。直接钻孔法是根据格柏数据进行导通孔的定位,因此,即使导通孔/连接盘径越趋小型化,也不会发生错位,是一种能够推进多层化,高密度化的先端技术。本文讲述了以直接钻孔法形成高可靠度导通孔时所需的技术和药品。
简介:TheproblemsofcharacteristicpolynomialassignmentinFomasini-Marchesini(F-M)modelⅡof2-Dsystemsareinvestigated.Thecorrespondingclosed-loopsystemsdescribedbyF-MmodelIIareobtainedviathestatefeedback.Usingthealgebraicgeometrymethod,thecharacteristicpolynomialassignmentinthedosed-loopsystemsisdiscussed.Intermsofthetheoryofalgebraicgeometry,theproblemofcharacteristicpolynomialassignmentistransferredtotheonewhetherarationalmappingisonto.SufficientconditionsforalmostarbitraryassignmentcoefficientsofcharacteristicpolynomialinF-MmodelⅡof2-Dsystemsviastatefeedbackarederived,andtheyareavailableformulti-inputcases.Italsohasbeenshownthatthismethodcanbeappliedtoassignthecharacteristicpolynomialwithoutputfeedback.Thesufficientconditionsforalmostarbitraryassignmentcoefficientsofcharacteristicpolynomialofmulti-input2-DsystemsdescribedbyF-MmodelⅡwithoutputfeedbackareestablished.
简介:ThekeyprobleminunstructuredP2Psystemishowtocontrol'Flood'.Somestudiesfocusonconstructingmoreefficienttopologywhileothersfocusonbetterqueryalgorithms.ThispaperpresentsHICUS(HierarchicalInterest-drivenCommunity-basedUnstructuredSystem)motivatedbyabasicthought-whethertheresourcescorrelatewithtopologydistinguishesstructuredandunstruc-turedP2Pessentially.Byintroducinghierarchical'interest',HICUSorganizesaquasi-structuredtopologythroughapuredistributedway,andprovidesanewplatformforqueryalgorithms.Westudytheprocedureandperformanceoftopologyorganization,andthesimulationsshowthatHICUSformsasmall-worldwhichcansignificantlyimprovetheroutingefficiency.
简介:AnewschemebasedonSOA-MZIforall-optical2Rregenerationisproposed.Thecharacteristicsofgainandswitchingwindowofthisdeviceareinvestigatedindetail.Numericalsimulationresultsindicatethatthenonlineargaincompression,thetimedelaybetweentheinputopticalsignalandthewidthoftheopticalpulseareessentialparametersforagoodperformanceofall-optical2Rregeneration.
简介:ReactiveionetchingcharacteristicsofGaAs,GaSb,InPandInAsusingCl2/Arplasmahavebeeninvestigated,itisthat,etchingratesandetchingprofilesasfunctionsofetchingtime,gasflowratioandRFpower.Etchratesofabove0.45μm/rinand1.2μm/rinhavebeenobtainedinetchingofGaAsandGaSbrespectively,whileveryslowetchrates(<40nm/rin)wereobservedinetchingofIn-containingmaterials,whichwerelinearlyincreasedwiththeappliedRFpower.EtchedsurfaceshaveremainedsmoothoverawiderangeofplasmaconditionsintheetchingofGaAs,InPandInAs,however,werepartlyblackenedinetchingofGaSbduetoaroughappearance.
简介:Theneedforwide-bandclockanddatarecovery(CDR)circuitsisdiscussed.A2Gbpsto12Gbpscontinuous-rateCDRcircuitemployingamulti-modevoltage-controloscillator(VCO),afrequencydetector,andaphasedetector(FD&PD)isdescribed.Anewautomaticfrequencybandselection(FBS)withoutexternalreferenceclockisproposedtoselecttheappropriatemodeandalsosolvetheinstabilityproblemwhenthecircuitispoweringon.Themulti-modeVCOandFD/PDcircuitswhichcanoperateatfull-rateandhalf-ratemodesfacilitateCDRwithsixoperationmodes.TheproposedCDRstructurehasbeenmodeledwithMATLABandthesimulatedresultsvalidateitsfeasibility.
简介:这篇文章集中于识别分享文件对等(P2P)(例如BitTorrent(BT))在一个树桩网络的边阶的交通。由分析应用程序的协议和交通,一个单身的用户的分享文件的P2P交通与极大地不同,这被发现传统并且另外的P2P(例如QQ)申请在深奥远程主机和遥远的端口的分发的交通。因此,一个方法基于远程主机(RHD)的组件和遥远的港口(RPD)的组件被建议识别象BT一样交通。这个方法仅仅在一个树桩网络依靠每台用户主机的流动信息,并且没有包收费载重需要被监视。在间隔,为并发的传播控制协议的立刻的RHD和为每台主机的用户数据包协议流动通过由每流动的远程主机属于的树桩网络组织流动分别地是计算的。在给定的条件上,立刻的RPD通过由遥远的港口组织流动修改立刻的RHD被计算。一位主人是否一直在使用象BT一样应用,能为时间的一个时期从立刻的RHD或平均RHD被推出。基于交通,特征是对比基于内容的方法识别变化多端的分享文件的P2P交通合适的更多的建议方法。试验性的结果证明这个方法与高精确性是有效的。