锡膏印刷对回流焊接成功率的影响

深圳市福英达工业技术有限公司/一站式锡膏解决方案供应商ImpactofsolderpasteprintingonthesuccessrateofreflowsolderingAccordingtostatistics,inthePCBdesigniscorrect,componentsandprintedboardqualityisguaranteedunderthepremiseofsurfaceassemblyqualityproblemsinnearly70%isoutofthesolderpasteprintingprocess.Printingpositioniscorrectornot(printingaccuracy),theamountofsolderpaste,theamountofsolderisuniform,whetherthegraphicofthepasteisclear,thereisnosticking,PCBsurfaceisstainedbythesolderpaste,etc.,aredirectlyaffectingthequalityofPCBassemblywelding.Therearemanyfactorsthataffectthequalityofprinting,themainfactorsinclude:Stencilquality:stencilprintingiscontactprinting,sothethicknessandopeningsizeofthestenciltodeterminetheamountofsolderpasteprinting.Toomuchsolderpastewillresultinbridging,whiletoolittlepastewillresultininsufficientsolderorfalsesoldering.Theshapeofthestencilopeningandthesmoothnessoftheopeningalsoaffectthereleasequality.Theopeningofthestencilmustbeflareddownward,otherwisethesolderpastewillbebroughtoutfromthechamferoftheflarewhendemolding.Printingprocessofsolderpaste:Theviscosity,printability(rollability,transferability),thixotropy,andservicelifeatroomtemperatureofthesolderpastewillallaffecttheprintingquality.Iftheprintabilityofthesolderpasteisnotgood,inseverecases,thesolderpastejustslidesonthestencil,inwhichcaseitisimpossibletoprintthesolderpasteatall.Printingprocessparameters:Solderpasteisanon-Newtonianfluidwithviscosity.Whenthesqueegeeadvancesataspecificspeedandangle,itexertsacertainpressureonthesolderpaste,pushingittorollinfrontofthesqueegee,thusinjectingtherequiredpressureintothestencil.Thestickyfrictionofthepastecreatesshearwherethesqueegeemeetsthestencil,andthisshearhelpsthepastetobeinjectedsmoothlyintothestencil.Therearecertainmutualconstraintsbetweensqueegeespeed,squeegeepressure,stencilangleandpasteviscosity,soonlythecorrectcontroloftheseparameterscanensuretheprintingqualityofthepaste.Forexample,toomuchsqueegeepressurewillleadtopastepatternsticking,andtoofastprintingspeedwilleasilyleadtoinsufficientamountofpaste.Failuretoremovethesolderpasteleftatthebottomofthestencilintimemayresultinsolderpastecontaminationofareasoutsidethepadduringprinting,andallthesefactorsmayleadtosolderingdefectssuchasbridging,virtualsolderingandsolderbeads.EquipmentAccuracy:Whenprintinghigh-densityfine-pitchproducts,theprintingaccuracyandrepeatprintingaccuracyoftheprintingmachinewillalsoplayarole.Iftheprintingmachineisnotequippedwithavisualalignmentsystem,evenifthemanualgraphicalignmentisveryaccuratewhenthePCBpadgraphicsandstencilmeshgraphicscompletelyoverlap,butstillcannotsolvetheproblemofPCBprocessingerrors. Theuseofrecycledsolderpaste,managementandenvironmentalfactors:environmentaltemperature,humidityandenvironmentalhygienehaveanimpactonthequalityofsolderjoints.Recycledsolderpasteandnewsolderpasteshouldbestoredseparately,highambienttemperaturewillreducetheviscosityofthepaste,humidityistoohighwhenthepastewillcoefficientofmoistureintheair,humidityistoosmallwillacceleratethesolventevaporationinthepaste,theenvironment,dustmixedintothep