7-1第七讲 smt表面安装技术(2-缺陷)

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1、2021/6/291SMTdefectsandcountermeasureSMT缺陷及防范措施2021/6/292IdentifySMTdefectsIdentifytheSMTdefectsaccordingtoIPC-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．2021/6/29

2、3Majorcontributortodefects缺陷的主要分布Source:MPM’sAuser’sguidetomorePreciseSMTprinting2021/6/294Knowthecommondefect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2021/6/295•Chipcomponentsstandingonaterminalend(tombstoning).片式元

3、件末端翘起（墓碑）Tombstoning/立碑2021/6/296Countermeasure/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(th

4、epadsdistanceistoobig):improvePCBpaddesign.PCB焊盘设计问题(焊盘间距太大):改善PCB焊盘设计.Tombstoning/立碑2021/6/297Countermeasure/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:adjustprin

5、tingmachineparameters.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2021/6/298•Asolderconnectionacrossconductorsthatwasjoined.焊锡在导体间非正常连接.•

6、Solderhasbridgedtoadjacentnon-commonconductororcomponent.焊锡桥连到相邻的非导体或元件.Solderbridge/桥联2021/6/299Countermeasure/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:Finetunep

7、rintingmachine./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.Sol

8、derbridge/桥联Icicleprinting丝印拉尖Pastecollapse锡膏塌陷Bridging桥联Misalignment印刷偏位2021/6/29