SMT缺陷及防范措施概述

SMTdefectsandcountermeasureSMT缺陷及防范措施2020/5/191IdentifySMTdefectsIdentifytheSMTdefectsaccordingtoIPC-A-610(Rev:D)根据IPC-A-610(Rev:D)确定缺陷．Thisstandardisacollectionofvisualqualityacceptabilityrequirementsforelectronicassemblies.IPC-A-610是关于电子组装外观质量验收条件要求的文件．2020/5/192Majorcontributortodefects缺陷的主要分布Source:MPM’sAuser’sguidetomorePreciseSMTprinting2020/5/193Knowthecommondefect了解常见缺陷类型Analysizethepossiblecause分析可能的原因Countermeasureforthedefects基于以上原因采取的对策LearningObjectives学习目的2020/5/194•Chipcomponentsstandingonaterminalend(tombstoning).片式元件末端翘起（墓碑）Tombstoning/立碑2020/5/195Countermeasure/对策Mechanism:Surfacetensionincomponentterminalisuneveninreflow.原理:在回流过程中零件两末端的表面张力不均衡.1.Componentterminalheatdistributedunevenly零件两末端受热分布不均衡.Insufficientsoaktime:Reflowprofileoptimization.保温区时间太短:优化回流曲线参数.2.PCBPaddesignissue(thepadsdistanceistoobig):improvePCBpaddesign.PCB焊盘 设计 领导形象设计圆作业设计ao工艺污水处理厂设计附属工程施工组织设计清扫机器人结构设计 问题(焊盘间距太大):改善PCB焊盘设计.Tombstoning/立碑2020/5/196Countermeasure/对策3.Componentterminaloxidizationorcontamination:SolderabilitytestifnecessaryandRTVthedefectmaterial.元件末端氧化或者受污染:根据情况做可焊性实验并且退还缺陷物料.4.Printingmisalignment:adjustprintingmachineparameters.丝印偏位:校正丝印机的参数.5.Placementmisalignment:OptimizetheP&Pmachineparameters.贴片偏位:优化贴片机的参数.6.Stencilaperturedesignissue:studyandimprovetheaperturedesign.钢网开孔的设计问题:研究并且改善开孔设计.Tombstoning/立碑2020/5/197•Asolderconnectionacrossconductorsthatwasjoined.焊锡在导体间非正常连接.•Solderhasbridgedtoadjacentnon-commonconductororcomponent.焊锡桥连到相邻的非导体或元件.Solderbridge/桥联2020/5/198Countermeasure/对策　1.Screenprintingissue/丝印问题:a)PasteheightoutofUCL:Adjusttheprintertocontrolthepasteheight.锡膏高度超出控制上线:校正丝印机,控制锡膏高度.b)Pasteprintingmisalignmentorbridging:Finetuneprintingmachine./锡膏印刷偏位或者桥联:优化丝印机.c)Icicleprinting:Finetuneprintingmachineorchangetolowerviscositypaste.丝印拉尖:优化丝印机或者使用低粘性的锡膏.d)Solderpastecollapse:changetohigherviscositypaste./锡膏塌陷:使用高粘性的锡膏.e)Nonstandardstencilapertureopening:Studyandimprovetheaperture./不标准的钢网开孔:研究并改善开孔.Solderbridge/桥联Icicleprinting丝印拉尖Pastecollapse锡膏塌陷Bridging桥联Misalignment印刷偏位2020/5/199Countermeasure/对策2.Pick&Placement/贴片a)Componentplacingmisalignment:FinetunetheP&Pmachine.元件贴片偏位:优化贴片机的参数.b)Highpressureforplacement:reducepressuretopropervalue.贴片压力过大:减少压力到适当的参数.3.Wavesoldering/波峰焊a)Lowconveyorramp:Raisetheconveyorrampperactualstatus.传送带角度过小:根据实际情况加大传送带角度b)Lessfluxonboard:Increasethefluxsprayvolumeonboardbeforegoingthroughwavesoldering.板上的助焊剂较少:波峰焊接之前加大助焊剂的喷射量Solderbridge/桥联2020/5/1910Componentdamaged(Nicks,cracks,orstressfractures)/元件损坏Nicks,cracks,orstressfractures.缺口，裂纹，压痕2020/5/1911Countermeasure/对策1.Rawmaterialdamaged:purgethebatchmaterial./来料损坏:清除这批来料.2.DamagedduringSMTprocess(Fixtureormachinetouchit):Investigateandtakecorrectiveactionsfornonstandardoperation.在SMT流程中损坏(夹具和设备接触):调查分析并且对不规范的操作作出矫正行动.3.Fastcoolingrateonreflowprocess:Controlthecoolingratetobelow4degreepersecond.在回流过程中冷却速率过快:控制冷却速度使斜率保持在每秒4度以下.Typicalreflowprofile/回流曲线典例:Componentdamaged(Nicks,cracks,orstressfractures)/元件损坏2020/5/1912Misalignment偏位2020/5/1913Countermeasure/对策1.P&Pmachinefunctionunstable:FinetunetheP&Pmachine.贴片机性能不稳定:优化贴片机性能参数.a)FinetuneX,Ydata/调整X,Y坐标b)Optimizepickandplacementparameters./校正吸料和贴片的参数.2.Componentterminationoxidization:Solderabilitytestifnecessary.Purgethefailedmaterial/元件末端氧化:可焊性实验,清除不合格的来料.3.Operatortouchthecomponentpriortoreflow:Standardizetheoperatorhandling(documentcontrol)/在回流炉前目检操作员碰到贴片元件:标准化操作员操作(文件控制)4.Airflowrateinthereflowovenissohighthatthecomponentsaremoved.回流炉内空气流量太高以致吹偏了元件.Misalignment偏位2020/5/1914Componentleadlifted元件引脚翘高Oneleadorseriesofleadsoncomponentisoutofalign-mentandfailstomakecontactwiththeland.元件一个或多个引脚变形不能与焊盘正常接触．2020/5/1915Componentleadlifted元件引脚翘高Countermeasure/对策1.Componentleadbentbeforeplacement:Sortthedefectivepartandreturnittovendor.贴片前元件引脚变形:挑选出缺陷元件,退回供应商．2.Manualplacementtheloosepart:Inspectthepartbeforepassittoreflow.手放散料:回流前目检．2020/5/1916Solderball锡珠Solderballsarespheresofsolderthatremainafterthesolderingprocess.Solderballsviolateminimumelectricalclearance.焊锡球是焊接后形成的呈球状焊锡.Solderfinesaretypicallysmallballsoftheoriginalsolderpastemetalscreensizethathavesplatteredaroundtheconnectionduringthereflowprocess.焊锡残渣是在回流中形成的小的球状或不规则状焊锡球.2020/5/1917Solderball锡珠Countermeasure/对策1.StencilAperturedonotfocustopad:improvestencilapertureopening.钢网开孔没有对准焊盘中心:改善钢网开孔.2.Printingmisalignment:Finetuneprintmachine.丝印偏位:调整丝印机状态.3.Excesspaste:Cpkcontrol.多锡:Cpk控制.4.DampPCB:BakethePCBbeforeloadingittoSMT.PCB焊盘受潮:SMT组装流程之前烘烤PCB.6.Stencilpolluted:cleanthestencil.钢网脏污:清洗钢网.7.Profilerampupistoofast:Optimizereflowprofile.回流曲线升温速度过快:优化回流曲线.8.Pasteoxidized:exchangewithfreshsolderpaste.锡膏氧化:更换新锡膏.9.Chipwaveorsolderwaveheightistoohighcausedexcesssoldertotopside:adjustthewavesolderingheighttoproperlevel(wavesolder).波峰高度设置的太高致使多余的焊锡到顶面:校正波峰焊设置到适当的高度(波峰焊接).2020/5/1918Non-Wetting,Dewetting/虚焊，半润湿•Solderhasnotwettedtothelandorterminationwheresolderisrequired.　虚焊:需要焊接的引脚焊盘不润湿．•Soldercoveragedoesnomeetrequirementsfortheterminationtype.•Dewettingasaconditionresultswhenmoltensoldercoatsasurfaceandthenrecedestoleaveirregularly-shapedmoundsofsolderthatareseparatedbyareasthatarecoveredwithathinfilmofsolderandwiththebasismetalorsurfacefinishnotexposed.半润湿:熔化的焊锡浸润表面后收缩,留下一焊锡薄层覆盖部分区域,焊锡形状不规则.2020/5/1919Non-Wetting,Dewetting/虚焊，半润湿1.Poorsolderabilityofcomponentorpad./元件或焊盘可焊性太低Rootcause:a)OlddatecomponentorPCB./陈旧元件或PCB板b)ContaminationoroxidationoncomponentorPCB.元件或焊盘污染或氧化Action:Purgethematerialforfurtherdisposition./清除来料2.Thepasteoutofitslifetime:/锡膏超出有效期Scrapthelotpasteandreplaceitwithfreshone　报废有问题的锡膏更换新锡膏2020/5/1920Coldsolder/冷焊•Incompletereflowofsolderpaste.　焊锡回流不完全2020/5/1921Coldsolder/冷焊Countermeasure/对策1.Peaktemperatureistooloworreflowtime(dwelltime)isnotenough:Re-setuptheprofiletofulfillthepastespecorcustomerprovidedspec.requirement.回流峰值温度太低或者回流时间不够:重设温度曲线图.Typicalreflowprofile:/典型的回流曲线2020/5/1922Time时间Temp.温度230°C250°Ctc1–smallSMDtc1–mediumSMDtc3–largeSMD20°C20°CPeak:230–250°CColdsolder/冷焊2020/5/1923Coldsolder/冷焊Countermeasure/对策2.Thecomponentinsomelocationcoveredwithreflowpallet(Peaktemperatureistooloworreflowtime(dwelltime)isnotenough):EnlargethepalletopenwindowforthedefectlocationstoreducetheΔT.某些元件位置被回流托盘遮挡造成该点峰值温度太低或回流时间不足:对缺陷位置放大托盘的开口从而减少温差（ΔT）.2020/5/1924Solderhole/锡洞•Blowholes,pinholes,voids吹孔,针孔,空洞2020/5/1925Solderhole/锡洞Countermeasure/对策1.Insufficientpreheat:Reflowprofileoptimize.预热时间不足:优化回流曲线设置.2.Rampupistoofast:Re-setupthereflowprofiletomakeitoptimize.升温速率太快:重设回流曲线图使之最优化.3.Excessfluxinsolderpaste:properlytoincreasepreheattimeandtemperature.锡膏助焊剂含量过多:适当增加预热时间和温度值.4.DampPCB:BakethePCBbeforeloadingittoSMT.PCB受潮:SMT组装前烘烤PCB板.5.Componentfeetoxidation:BakeitbeforeSMTorrequirevacuumpackingonincomingmaterial.元件脚氧化:烘烤或者来料真空包装.6.Attachedfluxresidueoncomponentfoot:Sortoutthedefectpart.元件脚有助焊剂残渣:挑选出缺陷来料.2020/5/1926DisturbedSolder/焊锡紊乱•Disturbedsolderjointcharacterizedbystresslinesfrommovementintheconnection.在冷却时受外力影响,呈现紊乱痕迹的焊锡2020/5/1927DisturbedSolder/焊锡紊乱Countermeasure1.Optimizereflowsolderingprofileespeciallyforcoolingzone.优化冷却区回流曲线2.ConveyorshakinginPCAcoolingdownphase:Repairtheconveyorperactualstatus.冷却阶段传送带震动:根据实际情况调校传送带．2020/5/1928SolderProjections/锡尖Solderprojectionviolatesassemblymaximumheightrequirementsorleadprotrusionrequirements.焊锡毛刺违反组装的最大高度要求或引脚凸出要求.Solderprojectionviolatesminimumelectricalclearance.焊锡毛刺违反最小电气间隙.2020/5/1929SolderProjections/锡尖Countermeasure1.Lessfluxonboard:Increasethefluxsprayrateonboardbeforegothroughwavesoldering(wavesolder).助焊剂不足:增加助焊剂的喷射量2.Lowconveyorramp:Raisetheconveyorrampperactualstatus(wavesolder).传送带角度过小:根据实际情况校正传送带角度3.Excesspreheattemperatureandtime(fluxdryoff):Optimizewavesolderingprofile.(Wavesolder)预热过度（助焊剂过度挥发）:优化波峰曲线(波峰焊)4.Causedbyrework:Standardizeoperatorhandlingandenhancevisualinspection.返修中产生:规范员工操作加强目检.2020/5/1930NoSolder/无锡Nosoldertothelandorterminationwheresolderisrequired.　焊点无锡2020/5/1931NoSolder/无锡Countermeasure/对策1.Missingprinting/漏印Rootcause:a)Stencilaperturewasjammed./钢网堵孔b)Highviscosityofsolderpaste./锡膏粘性过高Action:a)Cleanstencil;/清洗钢网b)Replacetherecycledpastewithfreshone./更换新锡膏c)Printingmachineparameteradjustment./校正丝印机参数2.Poorsolderabilityofcomponentorpad./元件或焊盘可焊性太低Rootcause:a)OlddatecomponentorPCB./陈旧元件或PCB板b)ContaminationoncomponentorPCB./元件或焊盘受污染Action:Purgethematerialforfurtherdisposition./清除来料3.Insufficientfluxvolume:increasefluxsprayrate(wavesolder).助焊剂量不足:增加助焊剂喷射量(波峰焊接)4.Preheatexcess:lowerpreheattemperatureproperly(wavesolder).预热过度:适当降低预热温度(波峰焊)5.Chipwaveorsolderwaveheightislow:properheight(wavesolder).波峰高度过低:调整到适当高度(波峰焊)2020/5/1932InsufficientSolder/少锡Insufficientsolder焊锡不足2020/5/1933InsufficientSolder/少锡Countermeasure/对策1.Stencilaperturecloggingcauseincompletesolderprinting):Automaticormanualcleanthestencil.钢网孔堵塞导致锡膏不完全印刷:自动或者手工清洗钢网2.Noenoughsolderpastevolume(PasteheightunderLCL):VisualinspectionandCpkcontrol.锡膏量不足(锡膏高度在LCL以下):目检和Cpk控制3.Solderpasteprintmisalignment:Finetuneprintingmachine锡膏印刷偏位:校正丝印机使之最优4.PoorsolderabilityofcomponentorPCBpad:元件或PCB焊盘可焊性差a)Optimizereflowprofile.优化回流曲线b)Exchangethepoorsolderabilitycomponent.更换掉低可焊性元件5.Excessglueorgluemisalignment:Finetunescreenprint(wavesolder).点胶过多或点胶偏位:优化丝印参数6.Lessflux:Increasethefluxsprayonboardbeforeitpasswavesoldering(wavesolder).助焊剂不足:增加助焊剂的喷射量2020/5/1934•Solderfilletextendsontothetopofthecomponentbody.　焊锡接触元件体．ExcessSolder/多锡2020/5/1935ExcessSolder/多锡Countermeasure/对策1.Excesssolderpaste:锡膏量过多a).SolderpasteheightoutofUCL:Adjustprintingmachinetocontrolthepasteheight.锡膏高度超出UCL:校正丝印机控制锡膏高度b).Nonstandardofstencilapertureopening:standardizethestencilapertureopeningfordifferenttypecomponents.钢网开孔不标准:为不同类型的元件设置相应钢网的开孔标准2.Wavesoldering/波峰焊接a)Lowconveyerramp,longwavesolderingtime:Adjustconveyorrampangleto5~7degreeandsolderingtimeto3~5second.传送带角度过小,波峰焊接时间变长:校正传送带角度到5~7度,焊接时间3~5秒b)Highpreheattemperaturetodryofftheflux:Accordingtofluxspectocontrolthepreheattemperature,normallythePCBsurfacepreheattemperatureshouldbeunder100oC.高预热温度造成助焊剂过度挥发:按照助焊剂的规格控制预热温度,通常,PCB表面温度一般低于100oC2020/5/1936WrongOrientation/Polarity反向,极性反　Correctpolarity/　　正确的极性Wrongpolarity/极性反ThismarkisanodeoftantalumcapacitoronPCB.Thismarkisanodeoftantalumcapacitor.　Correctpolarity/　正确的极性Wrongpolarity/极性反Thismarkiscathodedirection.Thismarkiscathodedirection.WrongPolarity:/极性反2020/5/1937WrongOrientation/Polarity反向,极性反Correctdirection/正确的方向WrongOrientation/反向ThismarkisIC'sdirection.ThismarkisIC'sdirectiononPCB.WrongOrientation/反向:TheICispopulatedininversedirectiononthePCB./IC被反方向组装在线路板上2020/5/1938Countermeasure/对策1.Wrongplacementmachineprogram:Checkandcorrectthemachineprogram.贴片机程序错误:检查和更正机器程序2.Manualplacementinreversedirection:手工放置元件错误a)Avoidmanualplacementcomponents避免手工放置元件b)Needspecialinspectionforthemanualplacementpriortoreflow(documentcontrol).炉前需要特别检查那些手工放置的元件(文件控制)3.Disorderedorientationinthetray/reeloftheincomingmaterial:卷装或盘装来料元件的不规则放置．a)InspectbeforeloadingittoSMT.上料前检查来料b)Feedbacktovendortotakecorrectiveactions.反馈给供应商采取改善行动WrongOrientation/Polarity反向,极性反2020/5/1939a.Longlead/shortlead脚长/脚短b.Missingcomponent元件丢失c.Exposecopper露铜d.Surfacescratched外观划伤Countermeasure/对策Takecorrectiveactionandpreventiveactionafterinvestigated.调查后采取相应的改善措施和预防措施．Others其它2020/5/1940ThankyouTheEnd2020/5/1941