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High temperature die-attach materials for aerospace power electronics: Lifetime tests and modeling

Hochtemperatur Halbleiteranbindungen für Luft- und Raumfahrt Leistungselektronik: Lebensdauertests und Modellierung
: Hutzler, Aaron; Tokarski, Adam; Schletz, Andreas


Institute of Electrical and Electronics Engineers -IEEE-:
IEEE Aerospace Conference 2015 : 7-14 March 2015, Big Sky, MT, USA
Piscataway, NJ: IEEE, 2015
ISBN: 978-1-4799-5379-0 (Print)
8 S.
Aerospace Conference <2015, Big Sky/Mont.>
Fraunhofer IISB ()
wide bandgap; SiC; silicon carbide; die attachment; die-attach; lifetime; active power cycling; environmental testing; high temperature testing

Increasing the temperature in power electronic applications usually causes a decreasing lifetime and reliability. This study shows that packaging materials and technologies, such as silver-sintering or gold germanium solders combined with silicon-carbide devices, can easily deal with temperatures above 200 °C/392 °F. Furthermore, lifetime tests (active power cycling) with 300 devices offered more cycles to failure at 120 °C/248 °F heat sink temperature than at 40 °C/104 °F (same ΔT) for silver-sintered samples and goldgermanium solders. SAC305 and tin-lead solders were also tested for comparison but could not withstand the harsh conditions. The samples were silicon carbide diodes attached to copper-ceramic-substrates (DBCs). For testing, the devices were heated up by current to ach ieve a 130 K temperature swing at different coolant temperatures (250 °C/482 °F maximum temperature). The reason behind the higher lifetime at elevated temperatures is the increasing ductility over temperature. The materials capability against thermomechanical stress is better at higher temperatures, while creep effects are not dominating. This effect can be used especially for high temperature application with extraordinary requirements on lifetime and reliability. Analytical models based on stress strain calculations can explain this material behavior. Together with an in-situ measurement of the thermal impedance the models can predict the lifetime consumption of the application and thereby upcoming maintenance.