1 1 1 lock-in thermography - fraunhofer iisb · due to improper bond wire process parameters 1...
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F R A U N H O F E R I N S T I T U T E F O R I N T E G R AT E D S Y S T E M S A N D D E V I C E T E C H N O L O G Y
LOCK-IN THERMOGRAPHY Non-destructive localization of electric active defects
Description of lock-in thermography analysis
• Detecting of failed power electronic devices such as IGBT, MosFETs, diodes and
resistors
• Analysisofshortcircuits,ESDdefects,oxidedamages,edgeterminationdefects,
avalanchebrakedown,whiskersandelectricalconductivecontamination
• HighsensitivityforhotspotdetectionwithaheatdissipationintheμWrange
• 2D/3Ddefectlocalizationforfurtherdestructiveanalysistoidentifythefailure
mechanism
Special features
• MeasurementvoltagefrommVupto10kV
• Decapsulationofmoldcompoundsaswellassiliconegels
• Chemicalremovalofchiptopsidemetallizationandcontactsforinstancebond
wiresandribbonsoutofdifferentmaterials
• Followupinvestigationssuchascrosssections,scanningelectronmicroscopy,
microsectionswithfocusedionbeam
• Interpretationoftestresultsandfailuremechanisms
• Consultancyonthedifferentinvestigatedfailuremodesforinstancechipdamage
duetoimproperbondwireprocessparameters
1 Lock- In Thermo graphy
in act ion
Fraunhofer Institute for
Integrated Systems and
Device Technology IISB
Landgrabenstraße 94
90443Nürnberg
Germany
Contact:
AdamTokarski
Phone: +4991123568157
Fax: +499112356812
adam.tokarski@iisb.fraunhofer.de
www.iisb.fraunhofer.de
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Analysis principle
• Thedeviceundertestispulsedwiththerectangularvoltageby
arbitrarylock-Infrequency(typical:1to25Hz)
• Electricaldefectdissipatethermalpower
• Thermalpowerheatsupthesurface
• Measurementofinfraredsignalwithinfraredcamera
• Acquisitionofamplitudeimageaswellasresultingtime
dependentstepresponse(phaseimage)
Advantages
• Differentialmeasurementprinciple
• Bestsuitedfordifferentemissioncoefficientsofthe
devicesurfacematerials
• Noinfluenceoftheambient(temperature,reflections)
• Threedifferentzoomlensestoinvestigatestructuresfrom
completepowermoduletosingleIGBTcells
Application example
• Afterfabrication,apowermodulefailedthefinalelectricalqualitytest(e.g.
gate-emitterleakagecurrent)
• Lock-inthermographyhelpstodetectwhichsemiconductorisresponsible
fortheleakagecurrentanddetermindstheexactpositionofthedefecton
the device
• Nextstepconsistsofremovingbondwiresandaluminium-metalizationof
thesemiconductorfollowedbyasecondlock-inthermographyanalysisto
getthemicroscalelocationofthedefect
• Anadditionalinvestigationcanbeafocusedionbeaminvestigationwith
scanningelectronmicroscopytodetectthecauseoffailure(e.g.damaged
gatestructure)
2 Opt i ca l Micro scopy of IGBT
3 Lock- In Thermo graphy Ampl i tude of IGBT
4 Lock- In Thermo graphy Phase of IGBT
Demolded dev ice Topography
Cross sect ion Focused ion beam
Power modul
Lock- in overv iew
2 3 4
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