Thermal-mechanical analysis of system-level electronic packages for space applications

Abstract

A position sensitive radiation sensor is being designed in conjunction with a field programmable gate array (FPGA) in order to further harden space flight computers against cosmic radiation. The system functionality is such that it requires a stack of PCB's that power and support the radiation sensor. The stacked architecture introduces limitations in terms of mechanical stability that must be addressed. Mechanical characterization of system electronics must be performed in order to ensure that a new system will not fail under normal operation. This is especially true for systems subjected to harsh environments such as space flight. System level packaging must be employed in order to prevent damaging these systems. Factors such as weight constraints, system architecture, mechanical, and thermal loading must be considered, especially in space applications. During development of the sensor, different test beds were employed in order to characterize the radiation sensor and it's supporting electronic systems. The most common preliminary tests are high altitude balloon tests which allow the sensor to experience cosmic radiation at high altitudes, consistent with space flight operations. Each balloon test has mechanical and thermal criteria that must be met in order to survive flight. These criteria include resistance to vibration loading, as well as the ability to maintain system operational temperatures inside a payload as it ascends through the atmosphere. Finite element analysis (FEA) was used to evaluate primary system architecture, system support structures, as well as the flight payload in order to determine if the system would survive preliminary, and future, testing. System level architecture and test payloads were designed using SolidWorks cad software. ANSYS FEA software was used to create thermal models which accurately simulated convective cooling through the atmosphere, and solar radiation loading on the exterior of the payload. Vibration models were performed in order to find the natural frequencies of the subsystem, as well as characterize the response to applied vibrations. Conclusions from each model show that the system will survive expected test loading at a wide range of vibration frequencies, and maintain a thermally stable environment in order to prevent damage to the internal electronic systems.