焊膏助焊剂固有特性造成的空洞

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VoidCausedbytheInherentCharacteristicsofSolderPasteFluxVoidisthepresenceofairbubbleinasolderjoint,whichaffectsthemechanicalstrength,thermalconductivityandelectricalpropertiesofthesolderjoint.UnderthesamePCBanddeviceconditions,somesolderingmaterialsarepronetovoidformation,whilesomesolderpastesexhibitexcellentpropertiesforcontrollingsolderjointvoid.Fluxchangesduringthesolderingprocessisaverycomplexprocessinvolvingavarietyofphysicalandchemicalchanges,thefluxformuladeterminesthesolderingeffectandcharacteristics.Duringtheweldingprocess,thefluxremovesmetaloxidesfromtheweldendsurfacetogeneratewaterandgasificationtoformvoid;theorganicacidsinthefluxesterifytogeneratewaterandgasificationtoformvoid;andtheorganicmatterinthefluxcrackstoformvoid.Basicreactionprinciple(a)

weldingprocessfluxtoremovetheweldendfacemetaloxidelayer,generatingmetalsaltsandwater.2RCOOH+SnO=(RCOO)2Sn+H2O↑2HBr+CuO=CuBr2+H2O↑(b)Fluxorganicacidlipidationduringsolderingtoformwatervapourescapes.RCOOH+R'OH=RCOOR'+H2O↑(c)

Insufficientfluxactivityduringthesolderingprocess,unabletoeffectivelyreducethesurfacetensionoftheliquidsolder,thefluxintheorganiccrackingofwatervapourproducedbywatervapouriswrappedupinthesolderjointtoformvoid.RelationshipbetweenfluxcharacteristicsandvoidrateVoidrateinthesolderjointiscloselyrelatedtotheactivityofthesolderpaste,Figure1solderjointbubblesandfluxactivityrelationshipshowsthatthefluxactivityisinverselyproportionaltothebubblesinthesolderjoint-thehigherthecontentoftheactiveagent,thelowertherateofvoidinthesolderjoint.Figure1:Solderpasteactivityandsolderjointvoidraterelationship.Solderpastefluxviscosityandsolderjointvoidrateisalsoinverselyproportionaltotherelationship,Figure2:asthefluxviscosityincreases,theamountofairbubblesinthesolderjointdecreased.Figure2:Relationshipbetweensolderpasteviscosityandsolderjointvoidrate.SolderpastefluxboilingpointandthebubblecontentinthesolderjointisalsoinverselyproportionaltotherelationshipinFigure3:thehighertheboilingpointoftheflux,thesmallertheholeinthesolderjoint.Figure3:Relationshipbetweensolderpastefluxboilingpointandsolderjointvoidrate.ThehighcontentofFluxactiveagentinthesolderpasteisconducivetocontrollingthebubblecontentinthesolderjoint,buttheresidueofactiveagentwillcorrodethesolderjoint,whichisunfavourabletothereliabilityoftheproduct.Highfluxviscosityisconducivetoreducingthevoidwithinthesolderjoint,buthigherviscosityisunfavourabletotheprintingofsolderpasteandaffectstheprintedproduct.Inaddition,theboilingpointofthefluxalsoaffectsthebubblecontentwithinthesolderjoint.Selectionoffluxwithahighboilingpointcancontrolthebubblecontentinthesolderjoint,suchasresin-basedfluxandhighboilingpointorganicsolvents;resindecompositionintoorganicacidsathightemperaturesiseasytoobtaintheeffectofahighboilingpoint,buttheresindecompositionwillbringthenegativeeffectoftoomuchresidue.FitechFluxFWF-5100,producedbyShenzhenFitechCo.,Ltd,is