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1、ProcessDevelopmentAndCharacterizationOfTheStencilPrintingProcessForSmallApertures12Dr.DarylSantosandDr.RitaMohanty1SUNYBinghamton,Binghamton,NewYork,USA2SpeedlineTechnologies,Franklin,Massachusetts,USAAbstractTheconsumer’sinterestforsmaller,lighterandhigherperformanceelectronicsproductshasinc
2、reasedtheuseofultrafinepitchpackages,suchasFlipChipsandChipScalePackages,inprintedcircuitboard(PCB)assembly.Theassemblyprocessesfortheseultrafinepitchpackagesareextremelycomplexandeachstepintheassemblyprocessinfluencestheassemblyyieldandreliability.Generallyspeaking,end-of-lineSMTdefectscanbe
3、greatlyinfluencedbythestencilprintingoperation.Theimportanceofthestencilprintingprocessprogressivelyincreasesasthepitchandthepackagesizedecreases.Athoroughunderstandingofbasicstencilprintingprincipleswouldfacilitatethedesignofprinters,stencilsandpastes,andwouldultimatelypermittheextensionofre
4、liableprinttechniquestotheultrafineprintarena.Stencildesignandstencilfabricationtechniquesarecriticalfactorsthataffectthestencilprintingprocess.Thisworkcomparesthestencildesignelements,suchasaperturewalltaperandaperturewallfinishthatplayamajorroleintheprintperformanceofthesmallapertures.Desig
5、nedexperimentsareperformedtodeterminethe‘optimum’levelofaperturetaperandaperturewallfinish.Thestudyalsocomparesthreemajorstencil-manufacturingtechniques(chemicaletching,lasercuttingandelectroforming)forsmallapertureprinting.Fromtheknowledgegathered,guidelinesarebeingdevelopedforthestencildesi
6、gnandthestencilprintingprocessforsmallapertures.IntroductionTheneedformorereliable,lighterandsmallerproductshasincreasedtheuseofFlipChip(FC’s),ChipScalePackagesTM(CSP’s),Micro-BGA( BGA),and0201sintheelectronicsindustry.Asidefromthenewer01005componentsthatarestartingtoreceiveattention,theafore
7、mentionedcomponentsarewidelyusedincellularphones,personaldigitalassistants1(PDAs),camcorders,etc.,wherereliabilityisofmainconcern.Thequalityofthesolderjointsaffectsthereliabilityofthesepackages,especiallywheretheyaresubjectedtoveryharshcondit
