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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WhataretheFactorsInfluencingSolderPastePrintingFactortwo:
SolderpasteSolderpasteisastablemixtureconsistingofasolderalloypowder,viscousflux,andsomeadditives,withacertainviscosityandgoodthixotropy.Ithasacertainviscosityatroomtemperature,whichcanmountthecomponentsinitially.Whenheatedtoacertaintemperature,theflux
andothersubstancesarevolatilized,andthealloypowdermeltsintoaliquidform.
Bytheeffectsofsurfacetensionandwettability,thesolderpastefillspadstoconnectthepadsandcomponents,formingfirmsolderjoints.
ThesolderpasteisprintedontothePCBsthroughthestencilaperturesbyasqueegeeutilizingthethixotropypropertyofthesolderpaste.Whenthesolderpasteisunderacertaintemperatureandshearforce,theviscositydropsrapidly,allowingthesolderpastetopassthroughtheapertures.Aftertheshearforceisremoved,thesolderpasteviscosityreturnstonormal.Solderpasteisashear-thinningmaterial.Whenshearstressispresent,theviscositywilldecrease.
Solderpasteshouldbestoredatlowtemperaturesandusedwithinthevalidityperiod.Thesolderpasteisusedinacycleatroomtemperature.Afterthesolderpastereachesroomtemperature,thesolderpastecontainercanbeopenedtopreventwatervaporfromcondensing,andthenthesolderpasteisstirredtomeettheprintingrequirements.Afterconductinganumberofexperiments,thesolderpastewastakenoutoftherefrigeratorandplacedataroomtemperatureof25°C.Thecorrespondingroomtemperaturecouldbereachedafter4hours.Atthesametime,thesolderpastewasrewarmedandtheviscositywasmeasured.Whenthestirringtimeis60-130seconds,theviscosityofthesolderpastemeetstherequirements.Thereisapositivecorrelationbetweenambienttemperatureandsolderpastemixingtimeandrewarmtemperature.Thegeneraltrendisthatthelowertheambienttemperature,thelongerthestirringtimeisrequired,andviceversa.Throughrelevantexperiments,aquestionnaireformixingtimeandambienttemperaturewasfinallydetermined,helpingpeopletoidentifywhethertheviscositymeetstheprintingrequirements.Generallyspeaking,theviscosityofsolderpastecanalsobedeterminedbyvisualinspectionifadedicatedsolderpastemixerisnotavailable.Themanufacturercanstirthesolderpastewithatoolfor30seconds,thenstirupapartofthesolderpasteandletitdripspontaneously.Ifthesolderpastedoesnotdrop,itistoosticky.Ifitfallscontinuously,itistoothin.
Fitech
isasemiconductorsolderR&Dandproductioncompanywith20yearsofexperience.Fitechhasacompletesetofsolderpastedevelopmentandinspectionequipment,
includingtheequipmenttomeasurethesolderpasteviscosityandthixotropy,whichensuresthe
productqualitycanmeetuserneeds.Factorthree:
PCBprintedcircuitboardsThestraightnessofthePCBboardisoneoftheimportantfactorsaffectingthequalityofsolderpasteprinting,especiallythelargePCboard,whichneedstobesupportedbyaspecialstenciltoavoidthewarpingofPCBsandthechangesintheamountofsolderpasteprinting.ThewarpingofthePCBsaffectsthesolderpastereleaseratio.
Therefore,itisnecessarytoreasonablydesigntheprintingstencilofthePCBstoensureitsstraightnessandsolderpasteprintability.
Factorsfour:
Adjusting
theprintingparametersTheadjustmentofprintingprocessparametersisimportant,includingprintingspeed,squeegeeangle,pressure,meshandPCBseparationspeed,etc.Thefastersqueegeespeedcausefastersolderpasterollsandlowerviscosity,whichisbeneficialtothefillingofthesolderpaste.However,thehighsqueegeespeedleadstoshortsolderfillingtime.Therefore,thepressureofthesqueegeeshouldbeappropriate.Ifitistoolarge,thesqueegeeandthestencilwillbedamaged,andthesurfaceofthestencilwillbestuckwiththesolder.Ifitistoosmall,aninsufficientvolumeofsolderpastewillbedepositedontothepads.DuringthesortingprocessofthestencilandthePCBs,duetothefrictionofthesidewallofthestencilandthebondingeffectofthesolderpaste,theflowvelocityatthesidewallofthestencilislowerthantheseparationspeednearthecenteroftheapertures,resultinginresidualsolderpasteonthesidewallanddecreaseinsolderreleaseratio.Thesmallerthesqueegeeangle,thegreaterthedownwardpressureonthesolder,anditisnoteasytoscrapethesolderpasteonthemeshsurface.Iftheangleistoolarge,thesolderpastecannotberolled,whichnegativelyaffectsthereleaseofthesolderpaste.Generally,theautomaticprintingmachineisabout60°.
SolderPasteInspectionAfterthesolderpasteprintingiscompleted,itisnecessarytojudgetheprintingquality.Theinspectionisgenerallycarriedoutthroughspecialequipment,anditisusuallyrequiredtodetectwhetherthesolderpasteheight,volume,size,deviation,andthree-dimensionalshapemeettherequirements.Theheight,area,andvolumeinIPC7527requiretheamountofsolderpastetoaccountfor75%to125%ofthecalculatedamountofthestencil.However,solderpasteprintingforfine-pitchdevicesrequiresstrictcontrolinactualproduction.
ConclusionTherearemanyfactorsaffectingsolderpasteprinting.Thisarticlemainlydiscussesthefactorsthataffectsolderpasteprinting,suchasstencils,solderpaste,PCBs,printingparameteradjustment,etc.Variousdefectsintheprocessareanalyzedandsol
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