Package-relatedFailureMechanismsandAttributes
----------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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