CryoGaNIC

What will power electronics for the electric aviation of tomorrow look like?

This is exactly where CryoGaNIC comes in: the aim of the project is to develop a novel, highly reliable GaN power module that can be cooled cryogenically from both sides while meeting the stringent requirements of future aviation. 

Within the project, the Chair of Power Electronics at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) is working together with its partners, TU Chemnitz and Fraunhofer IISB, to develop an innovative module concept, with a particular focus on the reliability of packaging and interconnection technology under extreme operating conditions. 

The Next Generation  

Cooling with cryogenic media at temperatures below −150 °C (123 K) offers enormous potential. GaN power semiconductors, in particular, exhibit significantly improved conduction characteristics at very low temperatures. This enables previously unattainable efficiencies as well as a substantial increase in the gravimetric power density of power electronic converters—both of which are decisive levers for the electrification of aviation. 

New Challenges 

At the same time, these extremely low temperatures pose entirely new challenges for power electronics.

The main issues are: 

• Unknown material behavior: Many materials used today (substrates, solders, dielectrics, etc.) have so far been insufficiently characterized in the cryogenic temperature range. 
• Thermomechanical stress due to temperature cycles: Large temperature swings cause high mechanical loads. In combination with altered material behavior, this leads to new failure mechanisms and a considerable need for reassessment of reliability. 
• New requirements for cooling concepts: Cryogenic cooling media differ significantly in their thermophysical properties from water or air. Powerful, novel, and above all safe cooling architectures are therefore required. 
• Increased insulation requirements: Cryogenic conditions further raise the demands on insulation systems—particularly in combination with the reduced air pressure at cruising altitude. 
  

To fully exploit the advantages of the module concept at the overall system level, CryoGaNIC is also accompanied by a coherent integration approach. The focus is on double-sided cooling, the connection of the DC link, and the management of high currents at system level, which are made possible by the new module layout. 

This highly demanding requirement profile is addressed within the project by the three project partners with an innovative module design, accompanied by renowned associated industrial partners. 

Reliability is King 

The high reliability and lifetime requirements in aviation demand comprehensive lifetime assessment of the cryogenically cooled half-bridge developed in the project, both through lifetime tests and lifetime simulations. This task is carried out by Fraunhofer IISB in the CryoGaNIC project. 

In doing so, Fraunhofer IISB makes a key contribution to the realization of reliable cryo-cooled power electronics for aviation. By considering lifetime aspects in the early phase of the half-bridge development, it becomes possible to incorporate lifetime findings into the module design at an early stage (design-for-reliability), thereby significantly reducing both time-to-market and development costs in the future.

For this purpose, the power module developed in the project, as well as early prototypes and sub-groups, will be tested in an active load cycle test (“Power Cycling Test” – PCT) and in a passive load cycle test (“Temperature Shock Test” – TST). Based on the findings, a lifetime digital twin will be developed for both tests. 

This project is funded under the Aviation Research Program (LuFo VII-1). 

https://luftfahrtforschungsprogramm.de/ 

Project Partners 

Professorship Materials and Reliablility of Microsystems, University of Technology Chemnitz 
https://www.tu-chemnitz.de/etit/wetel/forschung/index.php.en 

Cryogenic Power Electronics, Chair of Power Electronics, Universität Erlangen-Nürnberg (Website available only in German) 
https://www.lee.tf.fau.de/forschung/extreme-anforderungen-und-einsatzbedingungen/kryogene-leistungselektronik/

Packaging & Reliability, Fraunhofer IISB 
https://www.iisb.fraunhofer.de/en/research_areas/packaging_reliability.html