深圳市福英達(dá)工業(yè)技術(shù)有限公司/一站式錫膏解決方案供應(yīng)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