The cosmic rays (mainly atmospheric neutrons) in high-altitude areas are strong

and under the combined action of voltage and temperature stress

it will lead to a decrease in the operational reliability of the key component of the flexible DC converter valve-insulated gate bipolar transistor (IGBT). A neutron beam on the atmospheric neutron irradiation spectrometer is used to conduct accelerated life tests on 4.5 kV IGBT chips. The failure mechanism of IGBT chips is simulated and analyzed

and the distribution type under voltage

temperature

and neutron irradiation stress is studied. The failure rate and mathematical model at an altitude of 4500 meters are analyzed. The research results indicate that the peak electric field shifts from the front to the back

leading to an electric field increase at the N-drift region/N+ buffer layer interface

triggering an avalanche doubling effect at the interface

which leads to chip burnout. Under the effects of voltage

temperature

and neutron irradiation stress

the life distribution of IGBT chips is exponential. The failure rate increases as the temperature decreases. When the temperature and neutron flux are constant

the relationship between the failure rate and voltage is as follows: λ=αeβ/U (α > 0

β < 0). The chip failure rate has a cutoff at lower applied voltage value. The failure rate of the 4.5 kV/5000 A IGBT module at 2200 V at a working junction temperature of 90 ℃ is 98.7 FIT. The research results of this paper will support the design of high-voltage flexible DC transmission projects in high-altitude areas.