The　new　energy　vehicle　industry　has　entered　a　new　stage　of　accelerated　development,　and　the　safety　and　requirements　of　new　energy　vehicles　have　become　higher　and　higher.　As　one　of　the　core　components　of　new　energy　vehicles,　IGBT　(Insulated　Gate　Bipolar　Transistor)　determines　the　conversion　efficiency　and　reliability　of　the　vehicle.　However,　defects　such　as　voids　and　delamination　in　the　solder　layer　of　the　IGBT　power　module　may　cause　the　junction　temperature　of　the　module　to　be　too　high,　resulting　in　a　reduction　in　the　energy　conversion　efficiency　of　the　chip　or　failure.　Due　to　the　requirements　of　high　reliability　and　long　life,　it　is　necessary　to　conduct　all　inspections　of　automotive-grade　IGBT　modules,　which　requires　that　the　inspection　must　be　carried　out　in　a　non-destructive　manner.　In　this　paper,　a　temperature　field　model　is　first　established　to　analyze　the　effect　of　the　void　ratio　at　different　positions　of　the　solder　layer　defect　on　the　maximum　junction　temperature.　Then,　starting　from　the　ultrasonic　interface　propagation　theory,　without　considering　the　attenuation　of　ultrasonic　energy,　the　ultrasonic　propagation　mathematical　model　of　the　IGBT　multilayer　structure　is　established　to　predict　the　amplitude　and　phase　of　the　ultrasonic　waves　at　different　interfaces　of　the　IGBT.　Finally,　the　defects　of　IGBTs　were　detected　by　ultrasonic　scanning　microscope　and　the　prediction　model　was　verified.　This　paper　has　a　certain　reference　value　for　the　defect　detection　of　IGBT　power　modules.　©　2022　IEEE.