Next Generation Device Attachment Thermal Interface Material

TECHNOLOGY AREA(S): Sensors
OBJECTIVE: Develop a high-conductance, device attach thermal interface material (TIM) for use in high power density applications such as the interface between a GaN Power Amplifier and heat spreader or carrier.
DESCRIPTION: Current thermal management of solid state power amplifiers (SSPAs) in space is limited in its ability to spread power densities from the channels of active Power Amplifier devices (PA) to the large area thermal radiators required for ultimate rejection of heat to space. Current power densities at the bottom of the PA device can exceed 62 W/cm2 and are expected to climb to values >1488 W/cm2 in the next 5-6 years. At these expected power densities, it is apparent that current state of the art solders used at this interface will no longer be acceptable due to the need for higher performance.

The Device Attachment TIM shall provide a heat transfer coefficient >1340 W/cm2-C over an area of 0.3 cm x 0.3 cm. The TIM shall provide sufficient attachment with high thermal performance to survive various environments it will be subjected to through the satellite mission, including dynamic loads, large diurnal variations, and thermal cycles. The high thermal conductance is required in a space environment (vacuum and no gravity), as well as on Earth in any orientation with respect to gravity for ground testability. The TIM shall meet performance over an operating temperature range of 0°C to 150°C and must survive a temperature range of -60°C to 150°C. Please be sure to address the thermal induced stress on the heat spreader after thermal cycles in a specific application as this will vary depending on the mission. In addition, the TIM shall not require significant cure time or any harsh processing environments that would damage the device, unit or system (including temperatures over 250 °C). The TIM shall be free of potential workmanship issues to avoid (or at least limit) the thermal vacuum testing required for recurring, standard designs.

Proposers are highly encouraged to team with systems integrators and payload providers to ensure applicability of their efforts and to provide a clear transition path.
PHASE I: Develop concepts to provide a robust, reliable TIM that has the potential to provide a heat transfer coefficient >1340 W/cm2-C. Demonstrate by analysis and/or test the feasibility of such concepts to meet all requirements stated above.
PHASE II: Optimize and fully demonstrate a TIM capable of providing an effective heat transfer coefficient >1340 W/cm2-C. Perform thermal performance testing and thermal cycling to confirm all above requirements have been met under both on-orbit and ground test environments to verify susceptibility of debonds at large temperature variations and power densities. Perform testing on a large number of samples to verify robustness and that the TIM is independent of workmanship issues.
PHASE III: This research would benefit all military and commercial satellite programs, including MILSATCOM and global positioning satellite programs. TIMs are required for all high power electronic components used on aerospace systems.
REFERENCES: 1. Gilmore, D. G., Spacecraft Thermal Control Handbook Volume I: Fundamental Technologies, 2nd Ed, The Aerospace Press, El Segundo, CA, 2002.; 2. Liu, J., T. Wang, B. Carlberg, and M. Inoue, "Recent Progress of Thermal Interface Materials," ESTC (2008), 2nd, pp. 351-358, 1-4 Sept. 2008; 3. Hansson, J., Ye, L., Rhedin, H., Liu, J., “A Review of Recent Progress of Thermal Interface Materials: From Research to Industrial Applications,” IMAPS Nordic Annual Conference 2016 Proceedings, June 5-7, 2016.; 4. "Spacecraft Thermal Control Workshop Proceedings," Aerospace Corporation, March 20-22, 2018 (available directly from Aerospace Corporation at stcw.mailbox@aero.org)KEYWORDS: 1 Thermal Management
2 GaN Power Amplifier
3 Thermal Interface
4 High Power
5 Solder
6 Die Attach