Abstract: To investigate the effects of atmospheric neutron radiation effects on a system-in-package (SiP) device, single event upset (SEU) and single event functional interruption (SEFI) were focused on in the experiment. Correlations between these effects and experimental parameters were found and the reasons for these correlations were analyzed. The accelerated irradiation experiment of a SiP device was conducted based on the atmospheric neutron irradiation spectrometer. The experiment observed the effects of SEU and SEFI caused by neutrons. SEUs are found in the static random access memory (SRAM) module of the digital signal processor (DSP) and the block random access memory (BRAM) module inside the field programmable gate array (FPGA). SEFI errors are primarily program crashes and DSP state machine freezes. The SEU cross section caused by neutrons was calculated, and the effects of process nodes and neutron beam energy spectrum on the SEU cross section were analyzed. As the process node decreases from 40 nm to 28 nm, the U-SEU cross section reduces by 73%. Thermal neutrons significantly impacts the SEU cross section of SRAM. After filtering thermal neutron components from the neutron beam, the SRAM SEU cross section decreases by 28.8%. The experimental results were analyzed through simulations performed using GEANT4, a particle transport and interaction modeling software. The simulated results provide essential insights into the underlying mechanisms contributing to the lower SEU cross section observed in the experimental. The soft error rate at New York sea level was calculated, revealing that the BRAM inside the FPGA was the most SEU-sensitive module, with a soft error rate of 766.8 FIT/Mb due to high-energy neutrons (E＞1 MeV). This finding emphasizes the necessity for error correction codes (ECC) or redundancy techniques to mitigate potential SEUs in critical memory devices. No SEUs are found in DDR2 SDRAM, CLB, or ROM inside the FPGA. This resilience may stem from architectural design or test capacity. The DSP is found to be the most SEFI-sensitive module. Overall, the experimental data serve as a critical resource for guiding the design and development of SiP devices with improved resistance to neutron-induced radiation effects. The insights derived from this study are invaluable for advancing the reliability and performance of semiconductor devices operating in neutron radiation environments.