PCB表面处理复合工艺

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PCBSurfaceTreatmentCompositeProcess-ImmersionGold+OSPThePCBsurfacetreatmentcompositeprocess-ImmersionGold+OSPisaprocesscombinationcommonlyusedinthemanufactureofhigh-endelectronics.ThiscombinationprocesscombinesasinkerplatewithanOSP(OrganicSolderabilityPreservatives)processtoachieveabetteroverallresult.Theintermetalliccompound(IMC)inthesolderjointofthesinkerplategrowsonthenickellayer,whilethemechanicalstrengthofthenickel-tinintergranulesisslightlyweakerthanthatofthecopper-tinintergranules.Theproblemofinsolubleblackdiscswithhighphosphoruscontentprocessescanariseintheimmersedgoldprocess,whichisadifficultproblemtosolve.However,thesunkengoldprocessstilloffersmanyadvantages,suchasaflatpadsurface,theoxidationresistanceandlowresistivitypropertiesofgold,andawideprocesswindow.ApplicationofcompositeprocessesInordertocombinemechanicalstrengthwithotheradvantages,thesmartphonemanufacturingindustrycommonlyusesacompositeprocess,i.e.asinkgoldboard+BGAareapadsusingtheOSPprocess.ThisprocessallowstheBGAsolderjointstobegrowndirectlyontothecopperfoiltoensuretheirmechanicalstrength.Thecompositeprocessisarelativelycomplexmanufacturingprocess,initiallyusedinhigh-endsmartphones,andisgraduallybecomingrecognisedandpopularinthemanufacturingofhigh-endelectronics.Figure1.PCBsurfacetreatmentcompositeprocess:Applemobilephonemotherboard;wheretheBGApadsareOSPprocessandotherareasofthepadssurfacetreatmentENIGGiovannieffectandinsolublegoldsurfacesinthesinkerprocessAftertheuseofthegoldsinkingprocess,theporesonthegoldsurfacemayexposethenickellayer,whichcanleadtotheGalvanicEffectinacorrosiveenvironment,resultinginthedissolutionofnickel(goldascathodeandnickelasanode).Thedissolutionofnickelcanleadtothesimultaneousreductionanddepositionofcopperionsinsolutiononthegoldsurface,resultinginadarkeningofthegoldskinfilmoreventheappearanceofmetalliccopper.Oncecopperispresentonthesurfaceaftersinkingthegold,theoxidisedcopperwillcausethepadstorefusetosolderandthustheproblemofthegoldsurfacenotdissolving.Thisisadetailthatneedsattention.Insummary,electrolessnickel-goldpadshaveaflatsurface,aresuitableforclosepitchprocessrequirements,canbebakedandcleaned,andhaveawideprocesswindow.ThegoldsurfacecanbeusedasacontactsurfaceorWirebondsubstrateandthenon-oxidisingpropertiesofgoldgivetheimmersedgoldboardgoodsolderability.CommondisadvantagesoftheimmersiongoldprocessHowever,therearealsosomecommondefectsinelectrolessnickel-goldboards,includingblackpansduetoabnormalcontrolofthesinkprocess(solderdrops,insufficientstrengthofsolderjoints),inclusionsoforganicmatterinthegoldlayerduetothesinkprocess(refusaltosolder,poorsoldershrinkage),thingoldlayersduetoabnormalcontrolofthehighphosphoruscontentprocess(refusaltosolder,soldershrinkage,padsnotgold),residualplatingsolutionduetoabnormalPCBprocesses(refusaltosolder,soldershrinkage,foreignmatter(contamination),poorcontrolofthesinkingprocessleadingtooxidationandcontaminationofthenickellayer(goldpeeling,solderrejection,shrinkage),abnormalcontrolofthesi