Reliability Analysis and Life Prediction of Solder Joints for Avionics Devices With Immersion Cooling

In this study, a reliability analysis and life prediction of solder joints for avionics devices with immersion cooling under random vibration by considering the effect of coupled electrical-thermal-mechanical fields were conducted. A comparison of mechanical performance and fatigue life between different avionics server module structures with variable inlet Reynold number (Re) is carried out by using the 3-D numerical simulation. The simulation results showed that the value of maximum temperature, maximum thermal stress, and maximum equivalent plastic strain of the printed circuit board (PCB) assembly for designs A and B was decreased gradually as inlet Re increased, and the discrepancy of maximum temperature and maximum equivalent plastic strain for solder joints between designs A and B was increased. However, the discrepancy of maximum thermal stress was kept at about 4%. Under the condition of random vibration with or without temperature, the dangerous solder joint with the largest equivalent plastic strain is located at the corner of the outer edge of the solder joint array. The discrepancy of maximum von Mises stress, maximum equivalent plastic strain, and maximum total deformation for the most critical solder joints between designs A and B was about 8.5%, 9.2%, and 8.2%, respectively. Increasing inlet Re has a great influence on the fatigue life of dangerous solder joint, which increases by 110 and 72 h for designs A and B, respectively. However, the fatigue life of design B was always smaller than that of design A, and the relative difference was kept at about 54% with inlet Re increase. It can be concluded that the use of a flow distributor can enhance the mechanical performance of the PCB assembly and extend the fatigue life of dangerous solder joint.