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1、BGAVoid气泡问题解读SourcesofVoidsN2(g)Chamber2Pressure=P2P1>P2LN2N2(g)Chamber1Pressure=P1Moltensolder在锡球生产过程中,会使用两个压力不同的Chamber,上方镕解槽C的压力大于下方冷却槽,并借着压力差使镕融的锡从Chamber1被挤压到Chamber2滴落,并在Chamber2冷却成形在溶融的锡中,所有的气泡都会因为浮力而悬浮在镕融的表面上,所以在溶融液中是没有气泡的镕融且未含气泡的锡在冷却阶段随着时间变成球形锡球生产的方式SourcesofVoidsPackagesideFluxPack
2、agesidePackagesidePackagesidePackagesideBoardsidePasteBoardsideBoardsidePackagesideBubblePackageside芯片植球的过程芯片Mount在主板上的过程有机会消散掉三明治结构让气泡无法散去IPC-7095B对锡球的描述TypeA:Void(s)withintheball(packagelevel)asreceived.TypeB:Void(s)attheball/packagesubstrateinterfaceasreceived.TypeC:Void(s)withintheballaf
3、terboardlevelassemblyprocess.TypeD:Void(s)attheball/packagesubstrateinterfaceafterboardlevelassemblyprocess.TypeE:Void(s)attheball/boardsubstrateinterfaceafterboardlevelassemblyprocess.VoidsclassificationinIPC-7095BMacrovoidsarethemostwidelyoccurringvoidsinsolderjoints.Thesearecausedbyvolati
4、lecompoundsthatevolveduringthesolderingprocesses.Thesemacrovoidsgenerallydonotaffectthesolderjointreliabilityunlesstheyarepresentatinterfacialregionsinthesolderjointswherecrackstypicallypropagate.Macrovoids是最常在锡球中广泛出现的Void,导因是挥发性的成分在焊接过程中释出的气体.这类的Void并不会影响锡球的可靠度,除非是在出现在交界面上的Void,因为这类的Void通常会
5、使裂痕增长PlanarMicrovoidsareaseriesofsmallvoids,inrelativelythesameplane,locatedattheinterfacebetweenthePCBLandsandthesolder.ThesearecausedbycoppercavesunderImAg-surface-finishcoatedlands.Theydonotaffectinitialproductquality,butcanaffectlongtermsolderjointreliability.PlanarMicrovoids是位在同一平面的一系列小
6、气泡,且通常座落在PCB面与Solder之间.这通常来自于化银板表面处理上的铜的孔洞.虽然不会影响初期的产品质量但是却会对solder的寿命产生影响(化银板容易有微气泡)ShrinkageVoidsarecausedbytheshrinkageduringsolidification,mostlyforSACandotherlead-freesolders.Theydonotgenerallyappearnearthesolder-to-PCBlandinterfaceanddonotimpairthesolderjointreliability.ShrinkageVoids导
7、因于固化过程的收缩,常出现于Sn-Ag-Cu等无铅锡球上.这些Void不会出现在锡球跟PCB的接面上,且不会损害锡球的可靠度VoidsclassificationinIPC-7095BMicroviaVoidsarecausedbythepresenceofmicroviasdesignedinthePCBlands.LargeMicroviaVoids,iflocatedinsolderjointsinhighstressareasofapackage,canimpactsolderjoi
