The application of modal effective mass for PCB friction lock compliance against spacecraft launch random vibration spectrum

Modern spacecraft design requires high density, low mass, modular electronic system architectures. This format often utilises a common backplane with Printed Circuit Boards (PCBs) interconnects. Adaptable electronic systems, such as modular Data Acquisition (DAq) systems, allow for configuration via insertion and removal of modules to meet the mission requirements. Common methods to mechanically fix the PCB to the chassis are by using stand-offs, with the primary function to minimise displacement through structural rigidity and to provide strain relief to the electronic connectors. Other methods, such as PCB friction lock allow for strain relief, improved thermal grounding of the PCB to the chassis but also allows for easy insertion and removal of the PCBs. One disadvantage of this system is that the retention force of the PCB is carried by a friction lock device and under acceleration loads, typically experienced in the launch environment, may cause failure. This paper presents a method to establish compliance of PCB friction lock devices using modal Finite Element Analysis (FEA) to predict the resonant frequencies and their Mass Participation Factor (MPF). Using this data, it is proposed that the use of an adaptation of the Miles Equation along with an equivalent g-RMS estimation can be used to determine the Random Vibration Load Factors (RVLF). A comparison of the RVLF with the retention force of the friction lock device can then give insight to the friction joint compliance.