The reliability of solder joints in board-level packaging has always been a research focus, but there is still insufficient research on board-level vibration reliability at service temperatures. This paper investigated the dynamic characteristics and fatigue life of printed circuit board (PCB) assemblies under different fastening methods (with or without plain washer) and board thicknesses in thermal environments. Firstly, effective finite element models were established for diverse PCB fastening methods and thicknesses at 24 °C and 60 °C, and these models were verified by modal experiments. Then, modal analysis and harmonic response analysis were conducted to investigate the effect of PCB fastening methods and thickness on the inherent characteristics of PCB assemblies. Finally, the stresses of solder joints were analyzed by isothermal random vibration simulations, and the three-band method was applied to predict the vibration fatigue life of the solder joints. The results show that the board fastening method and thickness significantly affect the inherent characteristics and vibration reliability of PCB assembly. The addition of plain washers increases the fastening area. At 24 °C and 60 °C, the increase in fastening area and board thickness cause higher natural frequency of the system, lower displacement amplitude and solder stresses, which improve the fatigue life of the solder joints under random vibration loading. The application of the plain washers and the increase in PCB thickness improve the solder joints fatigue life by 8.5 % and 66.7 %, respectively, at 24 °C, and by 6.6 % and 66.5 %, respectively, at 60 °C. In addition, as the temperature rises, the improvement effects of PCB fastening methods and thickness on the fatigue life of solder joints diminish, especially for the case with adding plain washers. This research has important guiding significance for the reliability design of PCB assemblies.