Package-related Failure Mechanisms and Attributes

[b]Package-relatedFailureMechanismsandAttributes[/b] ----------BallLifting Balllifting,isthedetachmentofaballbondfromthebondpadofasemiconductordevice. Seeseparatearticleonballlifting. BondShorting BondShortingisthepresenceofanunintendedelectricalconnectionbetweentwobonds.Theelectricalconnectionmaybeintheformofbondstouchingeachother,orstrayconductivematerialsbridgingonebondtoanother.Bondplacementproblemsinvolvingadjacentwedgebondswithlongtailsinadiewithtightly-packedbondpadsarethemostcommonformoftouchingbonds. Designrulesforbondpadsizeandspacing,bondsize,bondposition,andbonddeformationcaneasilypreventtouchingbonds.Dieattachmaterialthataccidentallyfallsordripsonthediesurface,orreachitinwhateverway,canbridgeonebondtoanother.Straywiresthatsomehowgetintohermeticpackagescanalsobridgeonebondtoanother.Eutecticflakesorballsfromhighlyoxidizedeutecticdieattachmaterialcangetlooseinsidethepackageandlikewiseactasbridgesbetweenbonds.Aluminumsqueeze-outsaroundthewedgebondscanalsogetlooseandshortbonds. BrandFailureAttributes Poormarkabilityistheconditionwhereinthepackageisdifficultorimpossibletomarkorbrandcorrectlyand/orthemarkorbrandonthepackageexhibitsinsufficientpermanence.Inkmarkabilityproblemsareoftenduetotheinabilityoftheinktoadheretothesurfaceofthepackage.Lasermarkabilityproblemsareoftenduetoimproperbrandingequipmentset-up,butmaysometimesbeduetotexturalproblemsonthesurfaceofthepackageaswell. Pooradhesionofinkmarksorbrandsonthepackageisusuallycausedbythepresenceofathinfilmorlayerofforeignmaterialonthepackagesurface.Forinstance,packageswithexcessiveamountsofmoldreleaseagentontheirsurfacesarelikelytoexhibitpoormarkability.Itmayalsobeduetotheuseofanincorrect,incompatible,orexpiredink. Poorlasermarkabilityisusuallycausedbywronglaserbrandingsettings.Packageswithtexturalproblemsordefectsmaylikewiseexhibitpoorcontrastafterlasermarking.Forexample,reworkedpackagesthathaveundergonesandblastinggenerallyexhibitillegiblemarks. Contamination,External Externalcontaminationisthepresenceofaforeignmaterial,whetherattachedorunattached,anywhereontheexternalportionsofthepackageandleads.Thecriteriaforrejectingexternalcontaminationdependsonitslocation,extent,andcomposition.Somecontaminantsarerejectedbecauseitresultsincosmeticfailure,whileothersarerejectedbecauseofthereliabilityriskinvolved,mainlywithregardtoleadcsolderabilityissues,aswellaselectricalleakabetweenpins

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