Thermomechanical Related Failures in IGBT Based Power Converters
Translated title
Termomekanisk Relaterede Fejlmekanismer i IGBT Baserede Effektkonvertere
Author
Østergaard, Lotte Haxen
Term
4. term
Education
Publication year
2014
Submitted on
2014-06-04
Pages
90
Abstract
Dette projekt undersøger, hvordan IGBT-baserede strømomformere ældes ved hjælp af accelererede tests. IGBT (Insulated Gate Bipolar Transistor) er en type effektswitch-transistor, som ofte bruges i kraftmoduler. Simulationer af varmeoverførsel i strømmodulet viser, at gentagne tænd/sluk-cyklusser (power cycling) giver cykliske temperaturændringer. Disse temperaturudsving skaber mekaniske spændinger ved grænseflader mellem forskellige materialer, hvilket kan føre til termo-mekaniske fejl. Projektet undersøger flere af disse fejlmekanismer. Metalliseringsmønstrene på halvlederchips bliver analyseret med scanning elektronmikroskopi (SEM) og fokuseret ionestråle (FIB) fræsning. Nedbrydning i chips og ledninger vurderes ved præcise elektriske målinger med firepunkts-probing. Derudover undersøges ledningernes kornstruktur ved mikrosektionering. Samlet gør metoderne det muligt at kortlægge, hvor og hvordan strømmodulet nedbrydes.
This project examines how IGBT-based power converters age using accelerated testing. An IGBT (Insulated Gate Bipolar Transistor) is a type of power switching transistor commonly used in power modules. Simulations of heat flow in the module show that repeated on/off operation (power cycling) causes cyclic temperature changes. These thermal cycles create mechanical stresses at the interfaces between different materials, which can lead to thermo-mechanical failures. The study investigates several of these failure mechanisms. The metal layers on the semiconductor chips are inspected with scanning electron microscopy (SEM) and focused ion beam (FIB) milling. Degradation in the chips and wires is assessed with precise electrical measurements using four-point probing. The wire grain structure is also examined by micro-sectioning. Together, these methods make it possible to map how and where the power module degrades.
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