An innovativesensitivetestmethodisdevelopedtodetectsolderjointcrackingforhighpowerLED packages.Themethodisbasedontransientthermalanalysisandcanfullyreplacethestilldominating light-on test.Forexperimentalapplicationofthemodel,testgroupsofLEDpackagesweresolderedwith two differentleadfreesolders(SnAgCu305andInnolotFL-640)onAluminumInsulatedMetalSubstrate (Al-IMS) andexposedtotemperaturecycles.Transientthermalmeasurementswereperformeddirectly afterassemblyandafterspecific cyclenumbers.Afterdataprocessingtheincreaseoftherelativethermal resistance betweentheinitialsignalat “0” cyclesand “n” cyclesisobtainedandcorrelatedwithcracksin the solderjointbycrosssections.BasedontheCADandmaterialdataoftheLEDpackagea finite element (FE) modelissetup.Thetime-resolvedtemperaturecurvesareproperlyreproducedbytransientthermal simulation. Themeasured “0” cyclecurvesare fitted usingtheFEmodelbyadjustingafewmaterial parameterswithintheirallowedtolerancerange.Aparametersensitivityanalysisisperformed.The impact ofacrackinthesolderjointbetweenpackageandprintedcircuitboard(PCB)onthetime resolvedtemperaturecurveissimulated.Thesimulatedcrackpropagatesfromthecornerofthepackage to itscenter.Theexperimentalmeasuredcurvesarereproduced.Basedonthesimulationafailurecriteria is defined, representingacracklengthbetween20%and30%ofthesolderjointarea,andWeibullcurves are calculated.AhighercreepresistanceforthetestgroupsolderedwithInnolotFL-640comparedtothe test groupsolderedwithSAC305isobserved.
Analysis of Solder Joint Reliability of High Power LEDs by Transient Thermal Testing and Transient Finite Element Simulations
CONTI, FOSCA
2015
Abstract
An innovativesensitivetestmethodisdevelopedtodetectsolderjointcrackingforhighpowerLED packages.Themethodisbasedontransientthermalanalysisandcanfullyreplacethestilldominating light-on test.Forexperimentalapplicationofthemodel,testgroupsofLEDpackagesweresolderedwith two differentleadfreesolders(SnAgCu305andInnolotFL-640)onAluminumInsulatedMetalSubstrate (Al-IMS) andexposedtotemperaturecycles.Transientthermalmeasurementswereperformeddirectly afterassemblyandafterspecific cyclenumbers.Afterdataprocessingtheincreaseoftherelativethermal resistance betweentheinitialsignalat “0” cyclesand “n” cyclesisobtainedandcorrelatedwithcracksin the solderjointbycrosssections.BasedontheCADandmaterialdataoftheLEDpackagea finite element (FE) modelissetup.Thetime-resolvedtemperaturecurvesareproperlyreproducedbytransientthermal simulation. Themeasured “0” cyclecurvesare fitted usingtheFEmodelbyadjustingafewmaterial parameterswithintheirallowedtolerancerange.Aparametersensitivityanalysisisperformed.The impact ofacrackinthesolderjointbetweenpackageandprintedcircuitboard(PCB)onthetime resolvedtemperaturecurveissimulated.Thesimulatedcrackpropagatesfromthecornerofthepackage to itscenter.Theexperimentalmeasuredcurvesarereproduced.Basedonthesimulationafailurecriteria is defined, representingacracklengthbetween20%and30%ofthesolderjointarea,andWeibullcurves are calculated.AhighercreepresistanceforthetestgroupsolderedwithInnolotFL-640comparedtothe test groupsolderedwithSAC305isobserved.Pubblicazioni consigliate
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