The recent commercial availability of silicon carbide power semiconductor devices are theoretically capable of operating at temperatures well beyond the limits of silicon devices and have generated an interest in developing high temperature capable packaging solutions to match. In this work, the performance and reliability of a number of commercially available silicon carbide power MOSFET dies from multiple vendors was determined for die temperatures up to 350°C. Although these results have demonstrated a number of aging effects and very high on-state resistances at high temperatures, it appears that these devices can perform reliably even in air atmospheres for 100 hours or more at 350°C. In addition, commercially available DBC type ceramic-based substrates have been evaluated for their thermal cycling performance and candidate high temperature capable die attach materials including silver sinter paste and tin and gold-tin pre-form based transient liquid phase types have also been evaluated. These results have demonstrated that the active metal brazed substrates, both copper and aluminium variants, in conjunction with the silicon carbide dies and silver sinter die attach may serve as the basis for high temperature power modules, and may be operated reliably in thermal cycled applications and in air atmospheres up to 300°C. Due to large threshold voltage shift of the SiC MOSFETs at these temperatures, it may be necessary to implement a negative gate bias capability.
This work has been carried out under the Innovate UK supported project HITEC, led by Prodrive and also including The University of Warwick, GE Aviation Systems, Ricardo, TT Electronics Semelab, Diamond Hard Surfaces and GaN Systems.
Rapid Ag/Sn/Ag transient liquid phase bonding for high-temperature power devices packaging by the assistance of ultrasound
