A lot of progress has been made over recent years in the development of high power semiconductors like gallium nitride (GaN) and Silicon Carbide (SiC) transistors, being considered as critical notably for space applications. As these technologies have developed, a parallel need has emerged for efficient thermal management techniques to fully exploit their potential.
Keeping the components as cold as possible has a huge impact on their performance and reliability, a complex task for electronic devices with increasing functionalities within decreased footprints, leading to greater power densities to handle. While 50% of electronics failures at least are related to thermal issues, effective thermal management is paramount to improve the devices mean time to failure and therefore the overall reliability, particularly in space products where systems have to operate for missions of up to 15 years without any chance of being repaired.
In this context, the HEATPACK project team developed critical technology building blocks for enabling high power components transformative packages with very low thermal resistance for space applications.
This includes Metal-Diamond-based composite materials for use as package baseplate, benefiting from Diamond’s outstanding thermal properties. Various metal-diamond composites, consisting of silver or copper matrix, were thus developed, with tailored properties for subsequent integration into power electronic packages.
A focus has also been put on improving the Thermal Interface Materials (TIM) connecting together the main elements of a packed device. These interfaces play an equally important role in the overall performance. Two products have been developed: a sintered silver paste, demonstrating very good thermal efficiency i.e. about two times better than the best soldering material currently in use, and an adhesive film, featuring thermally and electrically conductive properties with performances close to that of commercial references.
More advanced solutions have also been studied, such as active cooling of components through micro heat pipes integrated in silicon substrate. This procedure has been shown to be very effective, with performance levels that in theory are even better than those of the best existing bulk or composites materials. The project enabled a reliable manufacturing process to be put in place for this type of cooler, and to confirm that it operates correctly when a heat source is activated.
Precisely characterizing the thermal performance of these technologies remains a challenge, in this regard, a new method (FDTR) has been developed, including a dedicated test bench and associated analysis software. The instrument has been successfully implemented as its accuracy has been demonstrated on standard materials but as well on the ones developed within the consortium.
Ultimately, these building blocks have been combined to define two different high thermal efficiency packages. Electrical demonstrators have been produced in order to test the modules under representative conditions, confirming the potential of the technologies, especially the very good thermal performances achieved. Reliability tests finally allowed to assess the suitability of the solutions for use into space applications, making it possible to envisage an integration in flight model products in the short to medium term.