Speaker
Description
This presentation addresses the main architecture and technological investigations performed in the frame of a new power supply for solid state power amplifiers compatible with baseplate reference temperature of 85°C. This power supply module has been studied by Thales Alena Space Belgium R&I department, supported by an ESA contract (ESA AO/1-10209/20/NL/CLP).
Main mechanical and thermal design difficulties and technological choices linked to high temperature aspects are presented as well as thermal vacuum tests and comparison with predicted temperatures.
In a telecommunication satellite, this power supply unit (PSU) is functionally located between the antenna (containing the solid state power amplifiers, “SSPA”) and the electrical power system (EPS). Its main goal is to provide several adjustable power sources for the SSPA system as well as required auxiliary supplies. This unit is composed of several power modules, each one capable of providing 1kW. Depending on satellite architecture, this PSU could be located close to the antenna, possibly in a location regulated at higher temperature than usual for that kind of power supply unit.
Indeed, maximum reference temperature could reach 85°C at thermal reference point. This has a strong impact, especially on electronic components and materials (solder joints, PCBs…), and made this module a good candidate for investigating the different technologies linked to higher temperature.
In order to limit the impact of this increase of reference temperature, the technology selection objectives are to minimize the thermal path between the dissipative components and the heatsink and to use “high temperature” compatible components and materials.
In that frame, components were selected based on their ability to work at high temperature with a minimum rating of 125°C. COTS components (compatible with automotive standards) were used for cost optimization as well as space grade components when required (need of radiation hardened for example).
For the power part of the modules, an Insulated Metal Substrate (IMS) technology combined with classical PCB was selected. The key advantage of this architecture is to combine thermal performance of the IMS substrate and the capability of the PCB for the use of components like Ball Grid Array (BGA) for GaN transistors control and driving.
A thermal gap filler has been used between the IMS and the structure allowing to have a good thermal path while dealing with the different mechanical tolerances.
Moreover, particular care has been taken to define assembly processes of the components on the IMS and PCB. Analysis and tests have been performed to assess reliability of solder joint connections submitted to high temperature and thermal cycling.
A thermal model of the module has been build and analysis were made in order to assess the compliance of the architecture with the requirements.
Finally, an EM model of one module has been manufactured and tested in TVAC conditions. This allowed to compare predicted temperatures with measurements.
Tests performed on the EM model and on its technological constituents allowed to reach a TRL level of 4 at the end of this project confirming the possibility to use associated technological building blocks for future developments.
