On account of its thinner display module and accurate local dimming ability, the Mini-LED technology has become a popular research direction in display field. Aiming at the lighting-off phenomenon through the light board aging process, the reason and mechanism of the lighting-off phenomenon is explored beginning with the manufacture process of the LED board. Based on the FEM simulation method, combined with the manufacture process and the structure of the Mini-LED light board, the simulation model is established reasonably, and the temperature simulation results showed the error of the model is within 5% compared with the measured results. In order to get the thermal stress field of the light board under extreme situation, the simulation result of the light board temperature field under high temperature operation is imported into the mechanics simulation. Compared with the measured results, the simulation result of the maximum chip thrust is between the upper quartile and the lower quartile, and is bigger than the average value of the measured results, which show the simulation is accord with the actual situation. The solder paste is developed based on the simulation, and the result shows that the probability of the light-off phenomenon is reduced to under 1×10-5 from 113×10-4 when the maximum chip thrust is increased by 15%, which shows the improvement effect is obvious.